Bioaccessibility and Absorption Mechanism of Phenylethanoid

4 days ago - The human colon adenocarcinoma cell line Caco-2 was obtained from the Cell Bank of the Chinese Academy of Sciences (Shanghai, China). ...
2 downloads 4 Views 1MB Size
Subscriber access provided by UNIV OF DURHAM

Bioactive Constituents, Metabolites, and Functions

Bioaccessibility and absorption mechanism of phenylethanoid glycosides using simulated digestion/Caco-2 intestinal cell models Fei Zhou, Weisu Huang, Maiquan Li, Yongheng Zhong, Mengmeng Wang, and Baiyi Lu J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.8b01307 • Publication Date (Web): 24 Apr 2018 Downloaded from http://pubs.acs.org on April 24, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 37

Journal of Agricultural and Food Chemistry

1

Title

2

Bioaccessibility and absorption mechanism of phenylethanoid glycosides using

3

simulated digestion/Caco-2 intestinal cell models

4

Fei Zhou†, Weisu Huang‡, Maiquan Li†, Yongheng Zhong†, Mengmeng Wang†, Baiyi

5

Lu†*

6



7

Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture,

8

Key Laboratory for Agro-Products Nutritional Evaluation of Ministry of Agriculture,

9

Zhejiang Key Laboratory for Agro-Food Processing, Fuli Institute of Food Science,

10

College of Biosystems Engineering and Food Science, Zhejiang University,

11

Hangzhou, 310058, China

12



13

Hangzhou 310018, China

National Engineering Laboratory of Intelligent Food Technology and Equipment,

Department of Applied Technology, Zhejiang Economic & Trade Polytechnic,

14 15

* Corresponding author

16

Tel./fax: +86-0571-89882665.

17

E-mail address: [email protected].

18

Address: Yuhangtang Road 866#, Hangzhou 310058, Zhejiang, P. R. China.

1

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

19

ABSTRACT

20

Acteoside and salidroside are major phenylethanoid glycosides (PhGs) in

21

Osmanthus fragrans Lour. flowers with extensive pharmacological activities and poor

22

oral bioavailability. The absorption mechanisms of these two compounds remain

23

unclear. This study aimed to investigate the bioaccessibility of these compounds using

24

an in vitro gastro–intestinal digestion model, and to examine the absorption and

25

transport mechanisms of PhGs using the Caco-2 cell model. The in vitro digestion

26

model revealed that the bioaccessibility of salidroside (98.7±1.35%) was higher than

27

that of acteoside (50.1±3.04%), and the superior bioaccessibility of salidroside can be

28

attributed to its stability. The absorption percentages of total phenylethanoid glycoside,

29

salidroside and acteoside were 1.42–1.54%, 2.10–2.68% and 0.461–0.698% in the

30

Caco-2 model, respectively. Salidroside permeated Caco-2 cell monolayers through

31

passive diffusion. At the concentration of 200 µg/mL, the apparent permeability (Papp)

32

of salidroside in the basolateral (BL)-to-apical (AP) direction was 23.7±1.33 × 10−7

33

cm/s, which was 1.09-fold of that in the AP-to-BL direction (21.7±1.38 × 10−7 cm/s).

34

Acteoside was poorly absorbed with low Papp (AP to BL) (4.75±0.251 × 10−7 cm/s),

35

and its permeation mechanism was passive diffusion with active efflux mediated by

36

P-glycoprotein (P-gp). This study clarified the bioaccessibility, absorption and

37

transport mechanisms of PhGs. It also demonstrated that the low bioavailability of

38

acteoside might be attributed to its poor bioaccessibility, low absorption and P-gp

39

efflux transporter. 2

ACS Paragon Plus Environment

Page 2 of 37

Page 3 of 37

Journal of Agricultural and Food Chemistry

40

KEYWORDS

41

Total phenylethanoid glycoside; Acteoside; Salidroside; Bioaccessibility; Absorption

42

mechanism.

3

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

43

Page 4 of 37

INTRODUCTION

44

Acteoside (verbascoside) and salidroside (Fig. 1) are phenylethanoid glycosides

45

(PhGs) belonging to water-soluble polyphenolic compounds. The two compounds

46

have been detected in food and traditional Chinese medicine, such as Olea europaea

47

L. fruit, Osmanthus fragrans flower, Rhodiola rosea L., Cistanche deserticola Ma,

48

and Striga asiatica.1, 2 The total phenylethanoid glycoside (TPG) are abundant in O.

49

fragrans flowers3 with the contents of 92.66–130.57 milligrams of acteoside

50

equivalents (AE) per gram of dry weight (mg AE /g DW), and in particular 32.78–

51

71.79 mg/g DW for acteoside and 4.72–16.08 mg/g DW for salidroside,4 respectively.

52

Acteoside has anti-inflammatory, antioxidant and neuroprotective properties.1 It can PC12

cells

from

CoCl2-induced

damage3

53

protect

54

1-methyl-4-phenylpyridinium ion-induced apoptosis or necrosis.5 Salidroside has

55

anti-inflammation,6 antioxidation,7 antistress,8 anticancer9 and neuroprotective

56

effects.10-12 However, the oral bioavailability of acteoside is as low as 0.12%,13 and

57

32.1% for salidroside.14 Although acteoside and salidroside exhibit excellent

58

pharmacological activities, their bioavailability limits their wide application. This

59

poor bioavailability could be linked to the influence of several factors, such as

60

degradation in gastrointestinal tract, potential substrate for efflux transporters and

61

potential metabolism by microbiome. It has reported that the acteoside and salidroside

62

were unstable at high temperature, high pH and light exposure conditions in the

63

previous study.3 The degradation of acteoside and salidroside may occur in the

4

ACS Paragon Plus Environment

hypoxia

and

Page 5 of 37

Journal of Agricultural and Food Chemistry

64

gastrointestinal tract. Cardinali et al.15 found that verbascoside is remained at 53% in

65

vitro digestive conditions, and has low absorption of 0.1%.16 There is no more

66

information about the bioaccessibility, absorption and transport mechanism of TPG,

67

acteoside and salidroside.

68

In vitro digestion and Caco-2 cell monolayer models have been utilized to clarify

69

the effects of digestion and absorption on the bioaccessibility and bioavailability of

70

bioactive compounds, such as phenolic compounds.15, 17-19 Bioaccessibility is defined

71

as the relative amount of a food constituent, which released from the food matrix

72

during digestion and might pass through the intestinal barrier to be absorbed.20 In

73

general, the bioavailability of dietary compounds, such as phytochemicals, depends

74

on the digestive stability and efficiency of the transepithelial passage. Therefore,

75

bioaccessibility must be considered in bioavailability studies. The Caco-2 cell line,

76

which is derived from human colorectal carcinoma, expresses nutrient and drug

77

transporters, and thus is an appropriate model for use in the study of carrier-mediated

78

uptake and efflux mechanisms.21 Caco-2 cells can express ATP-binding cassette (ABC)

79

transporters, including P-glycoprotein (P-gp), multidrug resistance protein (MRP),

80

and breast cancer resistance protein (BCRP).22 These proteins reduce the

81

bioavailability by refluxing absorbed substrates into the intestinal lumen.23

82

This study aimed to investigate the bioaccessibility of TPG, acteoside and

83

salidroside using an in vitro gastro–intestinal digestion model, and to determine their

84

absorption and transport mechanisms using the Caco-2 cell monolayer model.

5

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

85

MATERIALS AND METHODS

86

Materials and Chemicals. Acteoside (purity = 99%), salidroside (purity = 98%),

87

verapamil hydrochloride (purity = 99%), Ko 143 (purity = 98%), and the chemicals

88

used in the in vitro digestion model (including α-amylase, pepsin, pancreatin, lipase,

89

bile salts, and uric acid) were purchased from Aladdin (Shanghai, China). MK 571

90

(purity = 98%) was purchased from Sigma–Aldrich (St. Louis, MO, USA). Formic

91

acid and HPLC-grade acetonitrile were obtained from Merck (Shanghai, China).

92

Other chemicals and reagents (analytical grade) were purchased from Sinopharm

93

Chemical Reagent Co. (Shanghai, China).

94

The human colon adenocarcinoma cell line Caco-2 was obtained from the Cell

95

Bank of the Chinese Academy of Sciences (Shanghai, China). Dulbecco’s modified

96

Eagle’s medium (DMEM) and porous polycarbonate cell culture Transwell® inserts

97

(pore size, 0.4 µm; diameter, 12 mm) were purchased from Coster (Corning

98

Incorporated, USA). Hank’s balanced salt solution (HBSS), 0.25% trypsin–

99

ethylenediaminetetraacetic acid (EDTA) solution and penicillin–streptomycin (10 000

100

IU/mL penicillin, 10 000 µg/mL streptomycin) were purchased from Solarbio (Beijing

101

Solarbio Science & Technology Co. Ltd., China). Fetal bovine serum (FBS) and Cell

102

Counting Kit-8 (CCK-8) were obtained from Gibco (Life Technologies Inc., USA)

103

and Nanjing Jiancheng Bioengineering Institute (Nanjing, China), respectively.

104

Total Phenylethanoid Glycoside Extraction. Dried O. fragrans var. thunbergii

105

flowers (Guilin, Guangxi, China) were extracted with 95% ethanol for 12 h at 20°C in

6

ACS Paragon Plus Environment

Page 6 of 37

Page 7 of 37

Journal of Agricultural and Food Chemistry

106

a material-to-solvent ratio of 1:10 (g:mL).3 The mixture was filtered by vacuum

107

pump (YuKang, Shanghai, China), and the filtrate was evaporated under a

108

vacuum (YaRong, Shanghai, China) at 40°C to dryness.

109

In Vitro Digestion. The in vitro digestion model was described in previous

110

reports with some modifications.4,

24, 25

111

described by Versantvoort et al.25 The digestion of samples was initiated through

112

the addition of 1 mL of PhGs (TPG, 10 mg/mL; acteoside and salidroside standard

113

solution, 1mg/mL) and 3 mL of saliva (mixture pH adjusted to 6.8), and incubation

114

for 5 min. Then, 6 mL of gastric juice was added, and gastric digestion was

115

simulated for 2 h (mixture pH adjusted to 2.0). Finally, intestinal digestion was

116

simulated for 2 h with 6 mL of duodenal juice and 3 mL of bile juice (mixture pH

117

adjusted to 6.8). All incubations were performed at 37°C in a shaking water bath.

118

The gastric and intestinal digestion samples were collected, respectively, and ethanol

119

was added to ensure enzyme inactivation.

Digestive juices were prepared as

120

The digestion mixtures were filtered using a vacuum pump by filter paper (30-50

121

µm), and the filtrates were concentrated to dryness and then diluted to 5 mL with

122

distilled methanol. A controlled trial without the prepared samples was conducted to

123

improve accuracy. All the processes were performed in triplicate. PhGs with high

124

retention rates were stable in gastrointestinal conditions, and the retention rate was

125

calculated as follows:    (%) =

ℎ   ℎ   × 100% ℎ   ℎ   7

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

126

To evaluate the bioaccessibility of PhGs, the intestinal digestion samples were

127

centrifuged at 10000 rpm for 30 min at 4 °C (H1850R centrifuge, Hunan, China) to

128

obtain the supernatants.26 The supernatants were concentrated to dryness and then

129

diluted to 5 mL with distilled methanol. The bioaccessibility was calculated as

130

follows:   (%) =

ℎ   ℎ      × 100% ℎ   ℎ  

131

Cell Culture and Cell Viability Assay. Caco-2 cells between passages 40 and

132

60 were cultured in DMEM, containing 100 U/mL penicillin, 100 µg/mL

133

streptomycin and 10% FBS in a humidified incubator with 5% CO2 at 37°C.27

134

Caco-2 cells at 80% confluence were treated with 0.25% trypsin–EDTA and seeded

135

on Transwell® inserts (1.12 cm2) at a density of 1 × 105 cells/cm2. The culture

136

medium was replaced every day, and Caco-2 cell monolayers were obtained for

137

experiments at least 21 days after seeding.28 The integrity of the cell monolayer was

138

checked before each experiment on the basis of transepithelial electrical resistance

139

(TEER), which was measured with a Millicell ERS electrode (Millipore Corp,

140

Billerica, MA, USA). Only cell monolayers with a TEER value of more than 300

141

Ω·cm2 were considered intact and were used for transport experiments.29

142

To identify the appropriate TPG, acteoside and salidroside concentrations that can

143

be used in transport experiments, cytotoxicity was analyzed through a cell viability

144

experiment. Cell viability was determined through Cell counting kit-8 (CCK-8)

145

method.30, 31 Caco-2 cells were seeded in 96-well plates at a density of 1 × 104

8

ACS Paragon Plus Environment

Page 8 of 37

Page 9 of 37

Journal of Agricultural and Food Chemistry

146

cells per well and a volume of l80 µL. The plates were cultured for 24 h, and 20

147

µL of sample was added to the experimental groups, whereas 20 µL of culture

148

medium was added to control groups. After 24 h of incubation, the culture

149

medium was replaced with 100 µL of medium containing 10 µL of CCK-8

150

solution, and the plates were incubated at 37°C for an additional 2 h.

151

Absorbance was measured at 450 nm using a Biotek microplate reader

152

(Winooski, VT, USA), and background absorbance was excluded by performing

153

blank corrections. Cell viability was expressed as the percentage of the

154

untreated group (control = 100%). In the cell viability assay, every sample was

155

tested with five replicates.

156

Transepithelial Transport Experiments. Experiments on the transport of TPG,

157

acteoside and salidroside across Caco-2 monolayers were performed in

158

accordance with previously reported method with some modifications.29 In

159

brief, cell monolayers were gently rinsed twice with HBSS (pH 6.8, 37°C) prior

160

to the experiments, and incubated with transport buffer for 30 min at 37°C. The

161

incubation medium was then aspirated.

162

For the experiment on transport from the apical (AP) side to the basolateral (BL)

163

side, 0.5 mL of HBSS containing TPG, acteoside or salidroside (100, 200, 300,

164

400 and 500 µg/mL) was added to the AP side, and 1.5 mL of HBSS was added

165

to the BL side. After 30, 60, 90, 120, 150 and 180 min of incubation at 37°C,

166

samples (0.4 mL) were collected from the BL side and replaced with the same

9

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

167

volume of HBSS. For the experiment on transport from BL to AP, 1.5 mL of

168

sample was added to the BL side, and 0.5 mL of HBSS was added to the AP

169

side. At the above time intervals, 0.4 mL of samples was collected from the AP

170

side and replaced with the same volume of HBSS. The acteoside and salidroside

171

concentrations in the samples were determined through the UHPLC–DAD analytical

172

methods. All incubations were performed in triplicate.

173

Inhibition studies were conducted using 100 µM verapamil (P-gp inhibitor), 100

174

µM MK571 (MRP2 inhibitor)32 or 10 µM Ko143 (BCRP inhibitor)33. The inhibitors

175

were added in the sample solution in the AP and BL sides. The transport study was

176

then conducted as described above.

177 178

Apparent permeability coefficients (Papp) were calculated using the following equatioin: !"" (⁄) = ($ ⁄ )(1⁄%&' )

179

Where, dQ/dt is the transport rate on the receiver side (µg/s); A is the membrane

180

surface area of the insert (1.12 cm2); and C0 is the initial drug concentration in

181

the donor compartment (µg/mL).

182 183

The efflux ratio (ER), which is the ratio of Papp (BL to AP) to Papp (AP to BL), was determined using the following equation: ( =

!"" ()  %) !"" (%  ))

184

Total Phenylethanoid Glycoside Content Determination. The TPG content was

185

determined using a method described by Zhou et al.3 The OFE was diluted with

10

ACS Paragon Plus Environment

Page 10 of 37

Page 11 of 37

Journal of Agricultural and Food Chemistry

186

methanol to a suitable concentration and added 200 µL per well to 96-well plates.

187

The absorbance of OFE was measured at 334 nm using a Biotek microplate reader

188

(Winooski, VT, USA), and the TPG content was expressed as micrograms of

189

acteoside equivalents (AE) per milliliters. The acteoside concentration range of the

190

calibration series was 0.5 to 200 µg/mL.

191

UHPLC–DAD Analysis. Samples were filtered through a 0.22 µm nylon syringe

192

filter (ANPEL, Shanghai, China) and were analyzed following a previously described

193

method34 with modifications using an Agilent 1290 UHPLC instrument (Agilent,

194

Waldbronn, Germany) equipped with autosampler, binary pump, column thermostat

195

and diode-array detector. Samples were separated on an Agilent ZORBAX

196

Eclipse XDB-C18 column (3.5 µm, 2.1 mm × 150 mm) at 25°C. The mobile

197

phase consisted of acetonitrile (solvent A) and water (containing 0.1% formic

198

acid, solvent B). A gradient program was used with the following profiles: 0–1

199

min, 6% A; 1–4 min, from 6% to 15% A; 4–8 min, from 15% to 20% A; 8–10 min,

200

from 20% to 30% A; 10–12 min, from 30% to 100% A; and 12–12.5 min, from 100%

201

to 6% A; 12.5–15 min, 6% A. The flow rate was 0.2 mL/min, and the injection

202

volume was 4 µL. The DAD detector was set from 190 nm to 400 nm.

203

Statistical Analysis. Values were reported as mean ± SD. Statistical analysis was

204

performed using SPSS 20.0. One-way analysis of variance was used to determine the

205

level of significance (p < 0.05).

206

RESULTS AND DISCUSSION

11

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Page 12 of 37

207

Digestive Stability and Bioaccessibility of TPG, Salidroside and Acteoside in

208

the In Vitro Digestion Model. The stability of PhGs after gastric and intestinal

209

digestion phases was evaluated on the basis of the remaining PhGs content. In the

210

gastric digestion phase, the retention rates of salidroside and acteoside (Fig. 2)

211

standards were 99.6% and 102%, respectively, indicating that PhGs are stable under

212

gastric digestion conditions. However, the retention rate of acteoside remarkably

213

dropped to 51.5%, and that of salidroside decreased to 99.8% in intestinal digestion.

214

Salidroside

215

phenylethanoid disaccharide with an ester linkage, which is easily destroyed.

216

Acteoside destabilizes under increasing pH.3,

217

likely decreased during intestinal digestion because of the elevated pH. The acteoside

218

retention rate in intestinal digestion is similar to that (53%) in olive mill wastewater.15

219

The OFE was analyzed by UHPLC–DAD (Fig. 3), and the TPG, salidroside and

220

acteoside contents in OFE were 117.23 µg AE/mL, 7.46 µg/mL and 76.61 µg/mL,

221

respectively.3 The retention rates of TPG, salidroside and acteoside in OFE (Fig. 2)

222

were 102%, 100% and 102% in gastric digestion phase, respectively, and the retention

223

rates of TPG, salidroside and acteoside in OFE dropped to 82.3%, 97.3% and 49.4%

224

in intestinal digestion, respectively. It indicated that TPG and acteoside in OFE were

225

less stable in intestinal digestion, and the retention rates of salidroside and acteoside

226

in OFE showed no significant differences with those of salidroside and acteoside

227

standards during digestion. In previous study, Jiang et al.4 reported that the retention

is

a phenylethanoid

monosaccharide,

35

whereas acteoside

is a

Therefore, acteoside concentration

12

ACS Paragon Plus Environment

Page 13 of 37

Journal of Agricultural and Food Chemistry

228

rates of TPG, salidroside and acteoside in O. fragrans var. thunbergii were 35.47%,

229

97.41% and 5.11% after intestinal digestion, respectively. The total phenylethanoid

230

glycoside extraction method and digestion samples were different from this study.

231

Also Jiang et al. did not adjust the pH of mixture during digestion. Those might lead to

232

lower retention rates of TPG and acteoside than those in this study.

233

Bioaccessibility includes digestive recovery, aqueous solubility in the intestinal

234

digesta and necessary degradation before absorption.15 The bioaccessibilities of TPG,

235

salidroside standard and acteoside standard were 80.9±2.92%, 98.7±1.35% and

236

50.1±3.04%, respectively, and had no significant difference with the retention rates in

237

intestinal digestion. This result indicated that higher amounts of salidroside than of

238

acteoside are available for absorption in the intestinal tract. Salidroside has better

239

bioaccessibility than acteoside because of its stability, and the bioaccessibilities of

240

TPG and acteoside were most impacted by poor stability rather than limited solubility

241

in the intestine.

242

Cytotoxicities of TPG, Salidroside and Acteoside to Caco-2 Cells. Cytotoxicities

243

of TPG in OFE, salidroside standard and acteoside standard (100, 200, 400, 600 and

244

800 µg/mL) were measured using the CCK-8 assay on Caco-2 cells. As shown in Fig.

245

4, the cell viabilities of salidroside treated cells were 105%, 108%, 109%, 102% and

246

97.1% corresponding to 100, 200, 400, 600 and 800 µg/mL. Cell viability higher than

247

90% indicates that compounds were nontoxic to cells at the indicated concentration.36

248

It suggested that salidroside was nontoxic to Caco-2 cells from 100 to 800 µg/mL. For

13

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

249

TPG and acteoside, the cell viabilities were more than 100% at the concentrations

250

lower than 600 µg/mL. However, the cell viabilities of TPG and acteoside decreased

251

to 79.4% and 80.0% at 800 µg/mL, respectively. TPG and acteoside showed

252

inhibitory effects on Caco-2 cells at 800 µg/mL. Therefore, the concentrations of TPG,

253

salidroside and acteoside less than 600 µg/mL were used in the following experiment.

254

Transport of TPG, Salidroside and Acteoside across Caco-2 Cells. TPG in OFE,

255

salidroside standard and acteoside standard absorption was investigated using the

256

Caco-2 cell model, and the TEER value of the Caco-2 cell monolayers was 357±22

257

Ω·cm2. PhGs transport in the AP-to-BL and the BL-to-AP directions was studied, and

258

absorptive Papp (AP to BL) and secretory Papp (BL to AP) permeabilities were

259

estimated. The transported amounts of 200 µg/mL TPG, salidroside and acteoside

260

linearly increased with time (Fig. 5). The Papp (AP to BL) of acteoside (Table 1) was

261

determined as 4.75 × 10−7 cm/s in 180 min, indicating poor permeability and

262

absorption.36 This result is slightly higher than the Papp (AP to BL) of acteoside (1.15 ×

263

10−7) from Cistanche deserticola across Caco-2 cells,37 but is considerably lower than

264

that of acteoside (1.67 × 10−6) from olive mill wastewater using the Ussing chamber

265

model,16 which is different from the model used in the present study. In this work, the

266

Papp (BL to AP) of acteoside (9.17 × 10−7 cm/s, Table 1) was 1.93-fold greater than its

267

Papp (AP to BL) value.

268

The Papp values (Table 1) of TPG and salidroside were higher than those of acteoside

269

in both the AP-to-BL and the BL-to-AP direction. The Papp (AP to BL) values of TPG

14

ACS Paragon Plus Environment

Page 14 of 37

Page 15 of 37

Journal of Agricultural and Food Chemistry

270

and salidroside were higher than that of acteoside, which were 13.2 × 10–7 and 21.7 ×

271

10–7 cm/s, respectively. This result indicated that TPG and salidroside are more easily

272

absorbed than acteoside. The ER of TPG and salidroside were 1.78 and 1.09,

273

respectively.

274

The effect of concentration on the transport of TPG, salidroside and acteoside

275

(100-500 µg/mL) was determined. As the concentration of acteoside increased from

276

100 µg/mL to 500 µg/mL, the transported amount of acteoside in the AP-to-BL

277

direction increased in a concentration-dependent manner without saturation (Fig. 6 c),

278

indicating that acteoside transport in the AP-to-BL direction mainly occurred through

279

passive diffusion. The Papp (AP to BL) values of acteoside at concentrations of 100

280

µg/mL to 500 µg/mL ranged from 4.26 × 10−7 cm/s to 6.48 × 10−7 cm/s (Table 1).

281

However, acteoside transport in the BL-to-AP direction was considerably faster than

282

that in the AP-to-BL direction, with saturation at concentrations higher than 400 µg/mL.

283

The Papp (BL to AP) values of acteoside were greater than its Papp (AP to BL) values at

284

different concentrations, with ER values of 2.00, 1.93, 1.94, 1.85 and 1.54 at 100, 200,

285

300, 400 and 500 µg/mL (Table 1), respectively. The Papp (BL to AP) of acteoside

286

decreased at the concentration of 500 µg/mL, suggesting the saturation of the

287

transported amount of acteoside in the BL-to-AP direction. Generally, ER values of

288

more than 1.5 indicate active efflux.38 The present result suggested that the permeation

289

mechanism of acteoside is passive diffusion with active efflux in the BL-to-AP

290

direction. Acteoside might be the substrate of one or more efflux transporters (P-gp,

15

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

291

MRP2 or BCRP).

292

Results of TPG transport were similar to that of acteoside. The Papp (AP to BL) values

293

were in a small range from 13.2 × 10–7 cm/s to 14.3 × 10–7 cm/s over 100 µg/mL to 500

294

µg/mL, and the ER values calculated as 1.85, 1.78, 1.77, 1.73 and 1.52 at 100, 200, 300,

295

400 and 500 µg/mL (Table 1), respectively. The transport mechanism of TPG is also

296

passive diffusion with active efflux. The transported amounts and Papp values of

297

salidroside in the AP-to-BL and BL-to-AP directions were similar over 100 µg/mL to

298

500 µg/mL (Fig. 6 b) with ER values of 1.07–1.15. Thus, the permeation mechanism

299

for salidroside may be passive diffusion without active efflux.

300

In addition, the absorption percentages of TPG, salidroside and acteoside were

301

1.42–1.54%, 2.10–2.68% and 0.461–0.698% across Caco-2 monolayers, respectively

302

(Table 2). In a previous study, approximately 0.1% of acteoside in olive mill

303

wastewater was absorbed.16 These conflicting results may be attributed to the

304

different absorption model (Ussing chamber), acteoside concentrations (100 µM) and

305

incubation times (60 min) used in the previous study.

306

Effect of Inhibitors on TPG, Salidroside and Acteoside Absorption. Three ABC

307

transporter inhibitors, namely verapamil (P-gp inhibitor), MK571 (MRP2 inhibitor)

308

and Ko143 (BCRP inhibitor) were used to identify the transporters involved in the

309

transport of TPG in OFE, salidroside standard and acteoside standard. Treatment with

310

verapamil, MK571 or Ko143 did not significantly affect on the Papp (AP to BL) and Papp

311

(BL to AP) values of salidroside (Fig. 7 b and Table 3). Similarly, MK571 and Ko143

16

ACS Paragon Plus Environment

Page 16 of 37

Page 17 of 37

Journal of Agricultural and Food Chemistry

312

did not significantly affect the Papp values of TPG and acteoside in both transport

313

directions. The addition of verapamil significantly decreased the Papp (BL to AP)

314

values of TPG and acteoside to 17.5 × 10–7 cm/s and 6.52 × 10−7 cm/s, respectively,

315

and significantly increased Papp (AP to BL) to18.8 × 10–7 cm/s and 6.76 × 10−7 cm/s

316

(Fig. 7 a, Fig. 7 c and Table 3), respectively. Verapamil inhibited the BL-to-AP efflux of

317

TPG and acteoside, and significantly increased their AP-to-BL influx. The ER values

318

of TPG and acteoside decreased to 0.932 and 0.964, respectively, indicating that TPG

319

and acteoside transport is mediated by P-gp. In other words, the transport mechanism

320

of TPG and acteoside is passive diffusion with active efflux mediated by P-gp.

321

In conclusion, the bioaccessibility, absorption and transport mechanisms of PhGs

322

were investigated. TPG, salidroside and acteoside exhibited bioaccessibilities of

323

80.9%, 98.7% and 50.1%, respectively, and absorption percentages of 1.42–1.54%,

324

2.10–2.68% and 0.461–0.698%, respectively. The transport experiment demonstrated

325

that the intrinsic permeability of salidroside is better than that of acteoside. The

326

permeation mechanism of salidroside is passive diffusion without active efflux, while

327

acteoside is the substrate of P-gp. This study demonstrated that the low bioavailability

328

of acteoside might be attributed to its poor bioaccessibility, low absorption and P-gp

329

efflux transporter.

330

AUTHOR INFORMATION

331

Corresponding author

332

* (B. L.) Tel./fax: +86-0571-89882665. E-mail: [email protected].

17

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

333

Funding

334

This study was supported by the National Major R & D Program of China (No.

335

2017YFD0400200), the Zhejiang Provincial Natural Science Foundation of China

336

(No. R15C200002), and the Special Project of Agricultural Product Quality Safety

337

Risk Assessment (No. GJFP2018015), Ministry of Agriculture, China.

338

Notes

339

The authors declare no competing financial interest.

340

REFERENCES

341

(1) Alipieva, K.; Korkina, L.; Orhan, I. E.; Georgiev, M. I., Verbascoside-a review of

342

its occurrence, (bio)synthesis and pharmacological significance. Biotechnol. Adv.

343

2014, 32, 1065-1076.

344

(2) Panossian, A.; Wikman, G.; Sarris, J., Rosenroot (Rhodiola rosea): Traditional use,

345

chemical composition, pharmacology and clinical efficacy. Phytomedicine 2010, 17,

346

481-493.

347

(3) Zhou, F.; Zhao, Y.; Li, M.; Xu, T.; Zhang, L.; Lu, B.; Wu, X.; Ge, Z., Degradation

348

of phenylethanoid glycosides in Osmanthus fragrans Lour. flowers and its effect on

349

anti-hypoxia activity. Sci. Rep. 2017, 7, 10068.

350

(4) Jiang, Y.; Mao, S.; Huang, W.; Lu, B.; Cai, Z.; Zhou, F.; Li, M.; Lou, T.; Zhao, Y.,

351

Phenylethanoid glycoside profiles and antioxidant activities of Osmanthus fragrans

352

Lour. flowers by UPLC/PDA/MS and simulated digestion model. J. Agric. Food

353

Chem. 2016, 64, 2459-2466.

18

ACS Paragon Plus Environment

Page 18 of 37

Page 19 of 37

Journal of Agricultural and Food Chemistry

354

(5) Sheng, G. Q.; Zhang, J. R.; Pu, X. P.; Ma, J.; Li, C. L., Protective effect of

355

verbascoside on 1-methyl-4-phenylpyridinium ion-induced neurotoxicity in PC12

356

cells. Eur. J. Pharmacol. 2002, 451, 119-124.

357

(6) Guan, S.; Feng, H.; Song, B.; Guo, W.; Xiong, Y.; Huang, G.; Zhong, W.; Huo, M.;

358

Chen, N.; Lu, J.; Deng, X., Salidroside attenuates LPS-induced pro-inflammatory

359

cytokine

360

Immunopharmacol. 2011, 11, 2194-2199.

361

(7) Yuan, Y.; Wu, S. J.; Liu, X.; Zhang, L. L., Antioxidant effect of salidroside and its

362

protective effect against furan-induced hepatocyte damage in mice. Food. Funct. 2013,

363

4, 763-769.

364

(8) Darbinyan, V.; Kteyan, A.; Panossian, A.; Gabrielian, E.; Wikman, G.; Wagner, H.,

365

Rhodiola rosea in stress induced fatigue — a double blind cross-over study of a

366

standardized extract SHR-5 with a repeated low-dose regimen on the mental

367

performance of healthy physicians during night duty. Phytomedicine 2000, 7,

368

365-371.

369

(9) Sun, K. X.; Xia, H. W.; Xia, R. L., Anticancer effect of salidroside on colon cancer

370

through inhibiting JAK2/STAT3 signaling pathway. Int. J. Clin. Exp. Pathol. 2015, 8,

371

615-621.

372

(10) Li, X.; Ye, X.; Li, X.; Sun, X.; Liang, Q.; Tao, L.; Kang, X.; Chen, J., Salidroside

373

protects against MPP+-induced apoptosis in PC12 cells by inhibiting the NO pathway.

374

Brain Res. 2011, 1382, 9-18.

responses

and

improves

survival

in

murine

19

ACS Paragon Plus Environment

endotoxemia.

Int.

Journal of Agricultural and Food Chemistry

Page 20 of 37

375

(11) Zhang, L.; Yu, H.; Zhao, X.; Lin, X.; Tan, C.; Cao, G.; Wang, Z., Neuroprotective

376

effects of salidroside against beta-amyloid-induced oxidative stress in SH-SY5Y

377

human neuroblastoma cells. Neurochem. Int. 2010, 57, 547-555.

378

(12) Zhang, L.; Ding, W.; Sun, H.; Zhou, Q.; Huang, J.; Li, X.; Xie, Y.; Chen, J.,

379

Salidroside protects PC12 cells from MPP+-induced apoptosis via activation of the

380

PI3K/Akt pathway. Food Chem. Toxicol. 2012, 50, 2591-2597.

381

(13) Wu, Y. T.; Lin, L. C.; Sung, J. S.; Tsai, T. H., Determination of acteoside in

382

Cistanche deserticola and Boschniakia rossica and its pharmacokinetics in

383

freely-moving rats using LC–MS/MS. J. Chromatogr. B 2006, 844, 89-95.

384

(14) Yu, S.; Liu, L.; Wen, T.; Liu, Y.; Wang, D.; He, Y.; Liang, Y.; Liu, X.; Xie, L.;

385

Wang,

386

chromatographic/electrospray ionization mass spectrometric method for the

387

determination of salidroside in rat plasma: Application to the pharmacokinetics study.

388

J. Chromatogr. B 2008, 861, 10-15.

389

(15) Cardinali, A.; Linsalata, V.; Lattanzio, V.; Ferruzzi, M. G., Verbascosides from

390

olive mill waste water: Assessment of their bioaccessibility and intestinal uptake

391

using an in vitro digestion/Caco-2 model system. J. Food. Sci. 2011, 76, 48-54.

392

(16) Cardinali, A.; Rotondo, F.; Minervini, F.; Linsalata, V.; D'Antuono, I.; Debellis,

393

L.; Ferruzzi, M. G., Assessment of verbascoside absorption in human colonic tissues

394

using the Ussing chamber model. Food Res. Int. 2013, 54, 132-138.

395

(17) Lee, H. J.; Cha, K. H.; Kim, C. Y.; Nho, C. W.; Pan, C. H., Bioavailability of

G.;

Wei,

W.,

Development

and

validation

20

ACS Paragon Plus Environment

of

a

liquid

Page 21 of 37

Journal of Agricultural and Food Chemistry

396

hydroxycinnamic acids from Crepidiastrum denticulatum using simulated digestion

397

and Caco-2 intestinal cells. J. Agric. Food Chem. 2014, 62, 5290-5295.

398

(18) Kosińska-Cagnazzo, A.; Diering, S.; Prim, D.; Andlauer, W., Identification of

399

bioaccessible and uptaken phenolic compounds from strawberry fruits in in vitro

400

digestion/Caco-2 absorption model. Food Chem. 2015, 170, 288-294.

401

(19) Moser, S.; Lim, J.; Chegeni, M.; Wightman, D. J.; Hamaker, R. B.; Ferruzzi, G.

402

M., Concord and niagara grape juice and their phenolics modify intestinal glucose

403

transport in a coupled in vitro digestion/Caco-2 human intestinal model. Nutrients

404

2016, 8, 414.

405

(20) Fernández-García, E.; Carvajal-Lérida, I.; Pérez-Gálvez, A., In vitro

406

bioaccessibility assessment as a prediction tool of nutritional efficiency. Nutr. Res.

407

2009, 29, 751-760.

408

(21) Pinto, M., Enterocyte-like differentiation and polarization of the human colon

409

carcinoma cell line Caco-2 in culture. Biol. cell 1983, 47, 323-330.

410

(22) Shen, C.; Chen, R.; Qian, Z.; Meng, X.; Hu, T.; Li, Y.; Chen, Z.; Huang, C.; Hu,

411

C.; Li, J., Intestinal absorption mechanisms of MTBH, a novel hesperetin derivative,

412

in Caco-2 cells, and potential involvement of monocarboxylate transporter 1 and

413

multidrug resistance protein 2. Eur. J. Pharm. Sci. 2015, 78, 214-224.

414

(23) Chan, L. M. S.; Lowes, S.; Hirst, B. H., The ABCs of drug transport in intestine

415

and liver: Efflux proteins limiting drug absorption and bioavailability. Eur. J. Pharm.

416

Sci. 2004, 21, 25-51.

21

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

417

(24) Huang, W.; Mao, S.; Zhang, L.; Lu, B.; Zheng, L.; Zhou, F.; Zhao, Y.; Li, M.,

418

Phenolic compounds, antioxidant potential and antiproliferative potential of 10

419

common edible flowers from China assessed using a simulated in vitro digestion–

420

dialysis process combined with cellular assays. J. Sci. Food. Agric. 2017, 97,

421

4760-4769.

422

(25) Versantvoort, C. H. M.; Oomen, A. G.; Van de Kamp, E.; Rompelberg, C. J. M.;

423

Sips, A. J. A. M., Applicability of an in vitro digestion model in assessing the

424

bioaccessibility of mycotoxins from food. Food Chem. Toxicol. 2005, 43, 31-40.

425

(26) Seiquer, I.; Rueda, A.; Olalla, M.; Cabrera-Vique, C., Assessing the

426

bioavailability of polyphenols and antioxidant properties of extra virgin argan oil by

427

simulated digestion and Caco-2 cell assays. Comparative study with extra virgin olive

428

oil. Food Chem. 2015, 188, 496-503.

429

(27) Zhang, B.; Zhu, X. M.; Hu, J. N.; Ye, H.; Luo, T.; Liu, X. R.; Li, H. Y.; Li, W.;

430

Zheng, Y. N.; Deng, Z. Y., Absorption mechanism of ginsenoside compound K and its

431

butyl and octyl ester prodrugs in Caco-2 cells. J. Agric. Food Chem. 2012, 60,

432

10278-10284.

433

(28) Bhattacherjee, A.; Hrynets, Y.; Betti, M., Transport of the glucosamine-derived

434

browning product fructosazine (polyhydroxyalkylpyrazine) across the human

435

intestinal Caco-2 cell monolayer: Role of the hexose transporters. J. Agric. Food

436

Chem. 2017, 65, 4642-4650.

437

(29) Zou, T. B.; Feng, D.; Song, G.; Li, H. W.; Tang, H. W.; Ling, W. H., The role of

22

ACS Paragon Plus Environment

Page 22 of 37

Page 23 of 37

Journal of Agricultural and Food Chemistry

438

sodium-dependent glucose transporter 1 and glucose transporter 2 in the absorption of

439

cyanidin-3-o-beta-glucoside in Caco-2 cells. Nutrients 2014, 6, 4165-4177.

440

(30) He, B.; Lin, P.; Jia, Z.; Du, W.; Qu, W.; Yuan, L.; Dai, W.; Zhang, H.; Wang, X.;

441

Wang, J.; Zhang, X.; Zhang, Q., The transport mechanisms of polymer nanoparticles

442

in Caco-2 epithelial cells. Biomater 2013, 34, 6082-6098.

443

(31) Ma, J.; Guan, R.; Shen, H.; Lu, F.; Xiao, C.; Liu, M.; Kang, T., Comparison of

444

anticancer activity between lactoferrin nanoliposome and lactoferrin in Caco-2 cells in

445

vitro. Food Chem. Toxicol. 2013, 59, 72-77.

446

(32) Xie, Y.; Duan, J.; Fu, Q.; Xia, M.; Zhang, L.; Li, G.; Wu, T.; Ji, G., Comparison

447

of isorhamnetin absorption properties in total flavones of Hippophae rhamnoides L.

448

with its pure form in a Caco-2 cell model mediated by multidrug resistance-associated

449

protein. Eur. J. Pharm. Sci. 2015, 73, 1-8.

450

(33) Wright, J. A.; Haslam, I. S.; Coleman, T.; Simmons, N. L., Breast cancer

451

resistance protein BCRP (ABCG2)-mediated transepithelial nitrofurantoin secretion

452

and its regulation in human intestinal epithelial (Caco-2) layers. Eur. J. Pharmacol.

453

2011, 672, 70-76.

454

(34) Zhou, F.; Peng, J.; Zhao, Y.; Huang, W.; Jiang, Y.; Li, M.; Wu, X.; Lu, B.,

455

Varietal classification and antioxidant activity prediction of Osmanthus fragrans Lour.

456

flowers using UPLC–PDA/QTOF–MS and multivariable analysis. Food Chem. 2017,

457

217, 490-497.

458

(35) D'Imperio, M.; Cardinali, A.; D'Antuono, I.; Linsalata, V.; Minervini, F.; Redan,

23

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

459

B. W.; Ferruzzi, M. G., Stability–activity of verbascoside, a known antioxidant

460

compound, at different pH conditions. Food Res. Int. 2014, 66, 373-378.

461

(36) Yee, S., In vitro permeability across Caco-2 cells (colonic) can predict in vivo

462

(small intestinal) absorption in man-fact or myth. Pharm. Res. 1997, 14, 763-766.

463

(37) Gao, Y.; Zong, C.; Liu, F.; Fang, L.; Cai, R.; Shi, Y.; Chen, X.; Qi, Y., Evaluation

464

of the intestinal transport of a phenylethanoid glycoside-rich extract from Cistanche

465

deserticola across the Caco-2 cell monolayer model. Plos One 2015, 10, e0116490.

466

(38) Artursson, P.; Karlsson, J., Correlation between oral drug absorption in humans

467

and apparent drug permeability coefficients in human intestinal epithelial (Caco-2)

468

cells. Biochem. Biophys. Res. Commun. 1991, 175, 880-885.

469

24

ACS Paragon Plus Environment

Page 24 of 37

Page 25 of 37

Journal of Agricultural and Food Chemistry

Figure Captions Figure 1. Chemical structures of (a) salidroside and (b) acteoside. Figure 2. Retention rates of TPG in OFE, salidroside in OFE, acteoside in OFE, salidroside standard and acteoside standard in the in vitro digestion model during the gastric and intestinal digestion stages. Retention rate is expressed as the percentage of the group before digestion (before digestion = 100%). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; *, p < 0.05 compared with the group before digestion. Figure 3. UHPLC–DAD spectrum of O. fragrans extracts at 280nm. Figure 4. Cytotoxicity of TPG in OFE, salidroside standard and acteoside standard on Caco-2 cells as determined using the CCK-8 assay. Data are presented as mean value ± SD (n = 5). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; *, p < 0.05 compared with the control group at the concentration of 0 µg/mL. Figure 5. Bidirectionally transported amounts (µg/cm2) of 200 µg/mL (a) TPG in OFE, (b) salidroside standard and (c) acteoside standard from 0 min to 180 min. Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side. Figure 6. Effect of concentration on the bidirectionally transported amounts (µg/cm2) of (a) TPG in OFE, (b) salidroside standard and (c) acteoside standard. Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side.

25

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Figure 7. Effect of inhibitors on the apparent permeability coefficients (Papp) of (a) TPG in OFE, (b) salidroside standard and (c) acteoside standard during transportation across Caco-2 cell monolayers. Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side; *, p < 0.05 compared with the control group.

26

ACS Paragon Plus Environment

Page 26 of 37

Page 27 of 37

Journal of Agricultural and Food Chemistry

Table 1. Effect of concentration on the apparent permeability coefficients (Papp) and efflux ratio (ER) of TPG in OFE, salidroside standard and acteoside standard across Caco-2 cell monolayers. Concentration (µg/mL) 100 200 300 400 500

TPG Papp (× 10-7 cm/s) AP to BL BL to AP a 13.2±2.46 24.3±3.69a* 13.2±0.259a 23.4±1.10a* 13.5±1.43a 23.9±2.70a* 13.5±1.52a 23.3±2.41a* 14.3±2.25a 21.7±2.21b*

ER 1.85 1.78 1.77 1.73 1.52

Salidroside Papp (× 10-7 cm/s) AP to BL BL to AP a 24.8±1.01 28.2±0.268a 21.7±1.38b 23.7±1.33b 20.1±2.46b 22.0±1.05b 19.4±1.60b 20.8±2.26b 19.4±1.72b 22.3±2.26b

ER 1.13 1.09 1.10 1.07 1.15

Acteoside Papp (× 10-7 cm/s) AP to BL BL to AP a 4.26±0.753 8.52±1.82a* 4.75±0.251a 9.17±0.708a* 4.97±0.676a 9.63±1.73a* 5.60±1.00a 10.4±0.984b* 6.48±1.19b 9.96±1.18b*

ER 2.00 1.93 1.94 1.85 1.54

Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side. Values marked by different superscript letters in a column are statistically different at the level p < 0.05. *, p < 0.05 compared with Papp (AP to BL).

27

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Table 2. Absorption percentages of TPG in OFE, salidroside standard and acteoside standard determined by Caco-2 intestinal cell model. Concentration (µg/mL) 100 200 300 400 500

Absorption percentage (%) TPG Salidroside Acteoside a b 1.42±0.112 2.68±0.388 0.461±0.0441c 1.42±0.238a 2.40±0.213b 0.503±0.102c 1.46±0.144a 2.17±0.138b 0.536±0.134c 1.46±0.192a 2.10±0.182b 0.607±0.0912c 1.54±0.256a 2.10±0.201b 0.698±0.113c

Data are presented as mean value ± SD (n = 3). Values marked by different superscript letters in a row are statistically different at the level p < 0.05. TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts.

28

ACS Paragon Plus Environment

Page 28 of 37

Page 29 of 37

Journal of Agricultural and Food Chemistry

Table 3. Effect of verapamil, MK571 and Ko143 on the apparent permeability coefficients (Papp) and efflux ratio (ER) of TPG in OFE, salidroside standard and acteoside standard across Caco-2 cell monolayers.

Groups Control Verapamil MK571 Ko143

TPG Papp (× 10 cm/s) AP to BL BL to AP 13.2±0.259 23.4±1.10 18.8±2.05* 17.5±2.63* 12.8±0.526 21.9±0.813 13.5±0.418 22.2±1.75 -7

ER 1.78 0.932 1.71 1.64

Salidroside Papp (× 10-7 cm/s) AP to BL BL to AP 21.7±1.38 23.7±1.33 22.3±0.961 22.6±1.29 23.6±0.770 24.4±0.836 22.5±0.758 23.3±0.929

ER 1.09 1.02 1.03 1.03

Acteoside Papp (× 10-7 cm/s) AP to BL BL to AP 4.75±0.251 9.17±0.708 6.76±0.170* 6.52±0.895* 5.11±0.148 10.2±0.528 4.99±0.118 9.38±0.560

ER 1.93 0.964 1.99 1.88

Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side; *, p < 0.05 compared with the control group.

29

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Figure 1. Chemical structures of (a) salidroside and (b) acteoside.

30

ACS Paragon Plus Environment

Page 30 of 37

Page 31 of 37

Journal of Agricultural and Food Chemistry

Figure 2. Retention rates of TPG in OFE, salidroside in OFE, acteoside in OFE, salidroside standard and acteoside standard in the in vitro digestion model during the gastric and intestinal digestion stages. Retention rate is expressed as the percentage of the group before digestion (before digestion = 100%). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; *, p < 0.05 compared with the group before digestion.

31

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Figure 3. UHPLC–DAD spectrum of O. fragrans extracts at 280nm.

32

ACS Paragon Plus Environment

Page 32 of 37

Page 33 of 37

Journal of Agricultural and Food Chemistry

Figure 4. Cytotoxicity of TPG in OFE, salidroside standard and acteoside standard on Caco-2 cells as determined using the CCK-8 assay. Data are presented as mean value ± SD (n = 5). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; *, p < 0.05 compared with the control group at the concentration of 0 µg/mL.

33

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Figure 5. Bidirectionally transported amounts (µg/cm2) of 200 µg/mL (a) TPG in OFE, (b) salidroside standard and (c) acteoside standard from 0 min to 180 min. Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side.

34

ACS Paragon Plus Environment

Page 34 of 37

Page 35 of 37

Journal of Agricultural and Food Chemistry

Figure 6. Effect of concentration on the bidirectionally transported amounts (µg/cm2) of (a) TPG in OFE, (b) salidroside standard and (c) acteoside standard. Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side.

35

ACS Paragon Plus Environment

Journal of Agricultural and Food Chemistry

Figure 7. Effect of inhibitors on the apparent permeability coefficients (Papp) of (a) TPG in OFE, (b) salidroside standard and (c) acteoside standard during transportation across Caco-2 cell monolayers. Data are presented as mean value ± SD (n = 3). TPG, total phenylethanoid glycoside; OFE, O. fragrans extracts; AP, apical side; BL, basolateral side; *, p < 0.05 compared with the control group.

36

ACS Paragon Plus Environment

Page 36 of 37

Page 37 of 37

Journal of Agricultural and Food Chemistry

TOC graphic

37

ACS Paragon Plus Environment