Relationship between the Acyl Chain Length of Paradol Analogues

Jun 8, 2014 - ABSTRACT: 6-Paradol is known to activate thermogenesis in brown adipose tissue (BAT), and paradol analogues with different acyl chain ...
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Relationship between the Acyl Chain Length of Paradol Analogues and Their Antiobesity Activity following Oral Ingestion Akinori Haratake, Daisuke Watase,* Shuichi Setoguchi, Kazuki Terada, Kazuhisa Matsunaga, and Jiro Takata Laboratory of Drug Design and Drug Delivery, Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan ABSTRACT: 6-Paradol is known to activate thermogenesis in brown adipose tissue (BAT), and paradol analogues with different acyl chain lengths possess different pungency thresholds. In this study, the influence of the acyl chain length on the antiobesity activity of the paradol analogues was investigated. The antiobesity activity of 6-paradol in mice fed a high-fat diet for 8 weeks was greater than that of dihydrocapsiate. A comparison of the antiobesity activities of zingerone and 6-paradol showed that the length of the acyl chain in the paradol analogue was important for strong activity. Furthermore, the antiobesity activities of 6-, 8-, and 12-paradol appeared to decrease in an acyl chain length-dependent manner. The mechanism of the antiobesity activity of 6-paradol was enhanced by increasing levels of energy metabolism in the BAT, as well as an increase in the expression of uncoupling proteins 1 via the activation of sympathetic nerve activity. KEYWORDS: antiobesity activity, paradol analogue, acyl chain, oral ingestion, uncoupling protein

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thermogenesis and energy expenditure,10 subsequent studies revealed this speculation to be unfounded.11,12 Furthermore, the results of a recent study revealed that UCP-3 does not play a role in any thermogenic process, although the results of the same study did indicate that novel UCPs were involved in attenuating the production of reactive oxygen species, particularly during fatty acid oxidation.13 The results of another recent study, however, showed that UCP-3 was not required for fatty acid oxidation or fatty acid anion export, but that it was essential for adaptation to fasting, where it may be involved in mitigating the formation of reactive oxygen species.14 Finally, the overexpression of UCP-3 in mice leads to decreased body mass despite higher food intake.15 Although the role of UCP-3 is currently unclear, evidence from the literature strongly suggests that an increase in UCP-3 expression leads to a reduction in body mass. In their recent review, Bonet et al.16 reported that dietary changes and chemicals including specific nutrients were strongly associated with BAT. There have been several reports in the literature suggesting that the activity of BAT was activated with dietary methionine restriction, dietary leucine restriction, high-fat diet, fucoxanthin, salmon protein hydrolysate, n-3 fatty acids of marine origin, and resveratrol. Furthermore, thermogenesis can be modified by macronutrient content in the different types of fat.17 It has also been reported that olive leaf extracts can exert beneficial antiobesity effects by regulating the expression of genes involved in adipogenesis and thermogenesis in the visceral adipose tissue of mice fed a highfat diet.18 Spices and their principal pungent components have been reported to provide several potential benefits to human

INTRODUCTION Obesity and related health issues represent a significant threat to human health in an increasing number of countries.1 Obesity is the outcome of a prolonged positive energy balance, which can be caused by reduced energy expenditure and/or excessive calorie intake. A negative energy balance is needed to produce weight loss and can be achieved by a reduction in calorie intake or increased energy expenditure. Several tools are available for the management of obesity, including caffeine, ephedrine, capsaicin, and green tea, and materials of this type have been proposed as parts of strategies for weight loss and weight maintenance because their intake can lead to an increase in energy and could therefore counteract the decrease in metabolic rate that occurs during weight loss.2 Brown adipose tissue (BAT) acts as a major defense mechanism against obesity in rodents and human infants, where it serves to increase energy expenditure through dissipation in the form of heat (thermogenesis).3 BAT tends to be localized in the intrascapular and paraspinal regions, and the amount present in rodents and humans appears to decrease as they develop from the neonatal to adult stage.4 Increases in thermogenesis in BAT occur in response to cold or calorie intake, whereas the ablation of BAT resulting from the use of a toxigene results in hyperphagia and obesity.5 The protein responsible for thermogenesis in BAT is uncoupling protein (UCP)-1,6−8 which is the major endogenous stimulator of thermogenesis, and β3-adrenergic receptor stimulation induces UCP-1 expression.7 Knockout of UCP-1 in mice leads to a decrease in oxygen consumption following treatment with a β3adrenergic receptor agonist and also leads to increased cold sensitivity.9 Two other UCPs, UCP-2 and UCP-3, are more widely expressed than UCP-1 and appear to play important roles in mitochondrial function in a limited number of tissues. Although it was initially thought that UCP-2 and UCP-3 might also allow tissues such as skeletal muscle to undergo © 2014 American Chemical Society

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February 21, 2014 June 4, 2014 June 8, 2014 June 8, 2014 dx.doi.org/10.1021/jf500873a | J. Agric. Food Chem. 2014, 62, 6166−6174

Journal of Agricultural and Food Chemistry

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namide (C18), are not pungent, although some of these analogues do enhance the secretion of adrenaline from the adrenal medulla in rodents in the same way as capsaicin.21,28 Vanillyl (Z)-9-octadecenamide (C18:1) possesses capsaicin-like biological and physiological properties without any noxious stimuli.29 Paradols are a series of phenolic ketones that are structurally related to gingerols and shogaols.30 Zingerone (Figure 1) is a 0paradol of paradol analogues and is the major pungent component of ginger.31 The oral administration of zingerone led to a significant reduction in the body weight and final parametrial adipose tissue weight in ovariectomized rats.31 6Paradol (Figure 1) is the characteristic pungent component of the extract of the seeds of Amomum melegueta Roscoe (zingiberaceae), which are also known as grains of paradise, and is the only naturally occurring member of the paradol series to have been isolated to date exclusive of zingerone, although there are strong indications that other paradols also exist in nature.30 Iwami et al.32 recently demonstrated that an extract from the grains of paradise and 6-paradol activated thermogenesis in BAT, which could open up new avenues for the regulation of weight loss and weight maintenance. Furthermore, Sugita et al.33 demonstrated that the oral ingestion of an extract of grains of paradise increased whole-body energy expenditure via the activation of BAT in human subjects. However, no studies have been reported in the literature to date pertaining to the antiobesity effects of 6-paradol following oral ingestion. Paradol analogues with different acyl chain lengths have been reported to have different pungency thresholds.30 With this in mind, it was envisaged that the length of the acyl chains in different paradol analogues, which is related to their pungency strength, could also be related to the strength of their antiobesity effect following oral ingestion.

health, including antiobesity activity. Capsaicin, which is the major pungent component of hot red pepper,19 has been reported to elevate body temperature,20 stimulate the secretion of catecholamines,21 promote energy expenditure,22 and suppress body fat accumulation23 in experimental animals. However, capsaicin is strongly pungent and neurotoxic,24 and high capsaicin concentrations can be damaging to human health. Capsinoids (i.e., capsiate, dihydrocapsiate (Figure 1),

Figure 1. Structures of the paradol analogues and dihydrocapsiate tested for their antiobesity effects.

and nordihydrocapsiate) are nonpungent analogues of capsaicin that are derived from CH-19 sweet pepper,25 and have been shown to increase oxygen consumption and suppress body fat accumulation in mice to the same extent as capsaicin.26,27 Capsaicin analogues bearing longer acyl chains than capsaicin, such as vanillyl tetradecanamide (C14) and vanillyl octadeca-

Table 1. Compositions (% wt) of the Different Diets Used in This Study diet groups high-fat ingredient AIN-93 mix milk casein L-cysteine maltodextrin corn starch α-corn starch sucrose soybean oil cellulose powder AIN-93G-MXa CaCO3 AIN-93-VMb choline bitartrate lard zingerone 6-paradol 8-paradol 12-paradol dihydrocapsiate total a

normal

control

zingerone

6-paradol

8-paradol

12-paradol

dihydro capsiate

AIN-93M

67.0 38.2 0.5 9.0

66.9 38.2 0.5 9.0

66.9 38.2 0.5 9.0

66.9 38.2 0.5 9.0

66.9 38.2 0.5 9.0

66.9 38.2 0.5 9.0

100.0 14.0 0.2

23.9 8.2 3.0 9.9 5.2 0.3 1.5 0.3

23.9 8.2 3.0 9.9 5.2 0.3 1.5 0.3

23.9 8.2 3.0 9.9 5.2 0.3 1.5 0.3

23.9 8.2 3.0 9.9 5.2 0.3 1.5 0.3

23.9 8.2 3.0 9.9 5.2 0.3 1.5 0.3

23.9 8.2 3.0 9.9 5.2 0.3 1.5 0.3

33.0

33.0 0.1

33.0

33.0

33.0

33.0

46.6 15.5 10.0 4.0 5.0 3.5 1.0 0.3

0.1 0.1 0.1 0.1 100.0

100.0

100.0

100.0

100.0

100.0

100.0

Mineral mix. bVitamin mix. 6167

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femoral muscles were collected and stored at −80 °C prior to being subjected to Western blotting for UCP-3. Immunoblotting. Mitochondria were isolated using the method reported by Hong et al.35 The protein contents were determined in triplicate using the Bradford method (Bradford reagent, Sigma-Aldrich, St. Louis, MO, USA). BAT and muscle protein (4 μg) samples were subjected to gel electrophoresis using sodium dodecyl sulfate 10% polyacrylamide mini-gels and electroblotted onto polyvinylidene difluoride. Blocked polyvinylidene difluoride (Blocking One, Nacalai Tesque, Kyoto, Japan; 4 °C, overnight) was probed with rabbit antiUCP-1 polyclonal antibody (Abcam, Cambridge, MA, USA) at a dilution of 1:100000, as well as rabbit anti-UCP-3 polyclonal antibody (Abcam) at a dilution of 1:5000. Horseradish peroxidase-conjugated mouse anti-rabbit IgG antibody (Cell Signaling Technology, Beverly, MA, USA) was used as the secondary antibody at a dilution of 1:50000. Each incubation was performed for 1 h at room temperature, with the resulting immune complexes being detected with Immunostar LD (Wako Pure Chemical Industries) and a Western blot imaging system (FluorChemQ, Palo Alto, CA, USA). The expression levels of UCP-1 and -3 have been shown as the ratio of the level of expression on the high-fat diet to the level of expression observed on the normal diet (mean ± SE). Pharmacokinetics. The pharmacokinetic properties of the paradol analogues and their metabolites were investigated following their oral administration to determine their active sites. At 8 weeks old, the rats were fasted for 14 h prior to the oral administration of olive oil (1 mL) containing zingerone or 6-, 8-, or 12-paradol (10 mg/kg). Three rats in each group were anesthetized with isoflurane, and samples (300 μL) of their blood were collected from their jugular vein using a heparinized needle and syringe at 0 (before administration), 0.25, 0.5, 1, 3, 6, and 24 h after oral administration. The samples were centrifuged, and the resulting plasma was harvested and frozen at −80 °C prior to its analysis. The plasma (50 μL) was incubated at 37 °C for 1 h with 50 μL of βglucuronidase. Each component was then collected by sequential extraction with 100 μL of methanol and 300 μL of n-hexane using a combination of vortexing and centrifugation. The hexane extract was then evaporated to dryness under a gentle stream of N2 gas to give a residue, which was dissolved in methanol and analyzed using an API4000 QTRAP LC-MS/MS system (Applied Biosystems API4000, Life Technologies, Carlsbad, CA, USA) and a Prominence UFLC system (Shimadzu) equipped with a reversed-phase C18 column (Capcell PAK C18 UG120, 3 μm particle size, 100 × 2.0 mm, i.d., Shiseido). The MS detector was equipped with an electrospray ionization source. Mass spectral data were obtained by electrospray in the positive ion mode. Quantization analyses were performed using the multiple reaction monitoring mode with an external standard. The following pairs of ions were monitored with values of 195 (Q1) and 137 (Q3) for zingerone; 279 (Q1) and 137 (Q3) for 6-paradol; 307 (Q1) and 137 (Q3) for 8-paradol; and 363 (Q1) and 137 (Q3) for 12paradol. The maximum concentration in the plasma (Cmax) and the time to reach Cmax (tmax) were recorded as observed. The area under the plasma concentration−time curve from 0 to 24 h (AUC0−24h) and the mean residence time (MRT) were calculated using the moment method.36,37 Measurement of Lipolysis. Mice at 8 weeks old were fed a highfat diet for 8 weeks. The mice were then sacrificed, and their epididymal adipose tissue was quickly collected. Isolated fat cells were obtained from the collected epididymal adipose tissue using the method of Rodbell.38 The fat cells (40 μL packed volume) were incubated at 37 °C for 1 h in 160 μL of Hanks’ buffer (pH 7.4) supplemented with 2.5% (w/v) bovine serum albumin (Rockland Immunochemicals, Gilbertsville, PA, USA), 6-paradol (concentration of 10−6, 10−5, or 10−4 M), and norepinephrine (NE, 0.1 μg/mL). The free fatty acids (FFAs) were extracted, and the amount of FFAs was determined using the method of Zapf et al.39 The amounts of FFAs are shown as microquivalents released per milliliter of packed fat cells per hour (mean ± SE). Statistical Analysis. All of the values have been expressed as the mean ± SE. Data were analyzed using Student’s t test or Tukey’s

In this study, the antiobesity activities of high-fat diets containing 6-paradol or zingerone were compared in mice. Furthermore, the antiobesity activities of a series of paradol analogues bearing acyl chains of different lengths were evaluated following their oral ingestion, and the antiobesity mechanism of 6-paradol was investigated.

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MATERIALS AND METHODS

Animals. Five-week-old C57BL/6J mice (male) were purchased from Clea Japan (Tokyo, Japan) and 5-week-old Sprague−Dawley rats (male) were purchased from Charles River Laboratories Japan (Kanagawa, Japan). The animals were housed in standard cages (345 × 403 × 177 mm) under controlled conditions (i.e., ambient temperature, 23 ± 2 °C; relative humidity, 60 ± 10%; 12 h light/dark cycle). The mice were given AIN-93 M (Oriental Yeast, Tokyo, Japan) and water ad libitum, whereas the rats received CE-2 (Clea Japan) and water ad libitum. All of the procedures used in the current study regarding the care and use of the animals were carried out on the basis of the regulations dictated by the Experimental Animal Care and Use Committee of Fukuoka University. Chemicals. Zingerone was purchased from Givaudan (Dubendorf, Switzerland). 6-, 8-, and 12-paradol (Figure 1) were synthesized from the reactions of vanillin (Tokyo Chemical Industry, Tokyo, Japan) with 2-nonanone (Wako Pure Chemical Industries, Osaka, Japan), 2undecanone (Wako Pure Chemical Industries), and 2-pentadecanone (Tokyo Chemical Industry), respectively, using the methods reported by Locksley and Rauney.30 Dihydrocapsiate was synthesized from vanillyl alcohol (Tokyo Chemical Industry) and methyl nonanoate (Tokyo Chemical Industry) according to the method described by Kobata et al.34 The compounds synthesized in this study were characterized by NMR spectrometry (JNM-A500, JEOL, Tokyo, Japan) at 500 MHz, and their purities were confirmed by element analysis (MICRO CORDER JM10, J-Science, Kyoto, Japan) with an absolute error of 2-fold greater than that of 6paradol, and zingerone also had a faster absorption rate (tmax; Table 4; Figure 5). It has been reported that the accelerated effect of lipid decomposition led to a decrease in the adipose tissue weight of rats treated with zingerone via a stomach tube for 72 days.31 However, 6-paradol did not have an effect on murine adiposities in the current study, as measured using the method of Han et al.31 (Figure 6). Although the differences observed between zingerone and 6-paradol could be related to differences in the animal species studied,31 it was speculated that they were most likely related to the active sites because of the differences in the physical properties of these compounds. The level of UCP-3 expression in the femoral muscle following the oral ingestion of 6-paradol was also investigated. No differences were observed in the food intakes between the high-fat control and 6-paradol groups (Table 5). Table 4 also shows the initial and final body weights of the mice fed the different diets, as well as their adipose tissue weight. These data show that the final body weight of the 6-paradol group was significantly lower than that of the high-fat control group (p < 0.01). The amounts of subcutaneous, epididymal, and perirenal fat in the 6-paradol group were also significantly lower than those found in the high-fat control group (p < 0.05, p < 0.01, and p < 0.05, respectively). Figure 7 shows the changes in the expression levels of UCP-3 protein in the femoral muscle mitochondria. The level of UCP3 protein expression in mice fed the high-fat diet with 6-paradol was about 1.5-fold greater than that of those given the normal diet (p < 0.05). In contrast, the level of UCP-3 expression in

a compound can be used to provide an index of its lipid solubility. The clogP values of 6-, 8-, and 12-paradol were 4.7, 5.5, and 7.2, respectively, with the increase in the clogP value reflecting the increase in lipid solubility of the compounds. This increase in lipid solubility was attributed to the increase in the length of the acyl chains of the paradol analogues, which reduced their solubility in the intestinal lumen, leading to a decrease in their bioavailability. These results clearly indicate that 6-paradol was effectively absorbed into the enterocyte following oral ingestion and, therefore, suggested that the difference in the absorption properties were related to the different effects of the paradol analogues. The effect of 6-paradol on norepinephrine-induced lipolysis is shown in Figure 6. The administration of NE at a

Figure 6. Effect of 6-paradol on lipolysis in fat cells derived from murine epididymal fat following oral ingestion of a high-fat diet for 8 weeks. Fat cells were incubated at 37 °C for 1 h with 6-paradol (10−6, 10−5, or 10−4 M) and/or norepinephrine (NE, 0.1 μg/mL). Data are shown as the mean ± SE (n = 4). (∗) p < 0.05; Student’s t test.

concentration of 0.1 μg/mL led to a significant increase in the amount of FFAs released by fat cells (p < 0.05). In contrast, 6-paradol at a concentration in the range of 10−6−10−4 M had no discernible effect on the release of FFAs from fat cells. It was previously reported that capsiate is readily broken down in the intestinal tract to yield vanillyl alcohol and a fatty acid,50 indicating that the active sites for the antiobesity effect of orally administered capsiate were located in the digestive canal prior to the small intestine. The bioactivity of capsaicin has been attributed to an increase in the secretion of catecholamine from the adrenal medulla, which occurs through the activation of the sympathetic nervous system,44 as well binding to and activating specific transient receptor potential channels within the gastrointestinal tract.51 The capsaicin-dependent selective activation of transient receptor potential channels in the upper gastrointestinal tract has been shown to trigger the 6172

dx.doi.org/10.1021/jf500873a | J. Agric. Food Chem. 2014, 62, 6166−6174

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Notes

Table 5. Food Intake and Body and Adipose Tissue Weightsa

The authors declare no competing financial interest.

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diet groups high-fat parameter n food intake (g/mouse/day) initial body wt (g) final body wt (g) subcutaneous fat (mg) epididymal fat (mg) perirenal fat (mg)

control

ABBREVIATIONS USED BAT, brown adipose tissue; UCP, uncoupling protein; Cmax, maximum concentration in plasma; tmax, time to reach Cmax; AUC0−24h, area under plasma concentration−time curve from 0 to 24 h; MRT, mean residence time; NE, norepinephrine; FFA, free fatty acid; LOD, limit of detection; LOQ, limit of quantitation; clogP, calculated logP

normal 6-pardol

9 1.96 ± 0.05

10 1.89 ± 0.02

10 2.14 ± 0.05

22.0 ± 0.7 33.4 ± 0.8 1105.9 ± 99.2 1387.4 ± 72.8 393.7 ± 36.5

21.9 ± 0.2 30.1 ± 0.5c 851.6 ± 65.6b 632.1 ± 134.9c 258.3 ± 51.9b

22.6 ± 0.4 27.9 ± 0.2 603.4 ± 48.9 669.3 ± 48.7 153.6 ± 16.5

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(1) Obesity: preventing and managing the global epidemic. Report of a WHO consultation. WHO Tech. Rep. Ser. 2000, No. 894, i−xii, 1− 253. (2) Diepvens, K.; Westerterp, K. R.; Westerterp-Plantenga, M. S. Obesity and thermogenesis related to the consumption of caffeine, ephedrine, capsaicin, and green tea. Am. J. Physiol. Regul. Integr. Comp. Physiol. 2007, 292, R77−R85. (3) Spiegelman, B. M.; Flier, J. S. Obesity and the regulation of energy balance. Cell 2001, 104, 531−543. (4) Himms-Hagen, J. Does brown adipose tissue (BAT) have a role in the physiology or treatment of human obesity? Rev. Endocr. Metab. Disord. 2001, 2, 395−401. (5) Lowell, B. B.; S-Susulic, V.; Hamann, A.; Lawitts, J. A.; HimmsHagen, J.; Boyer, B. B.; Kozak, L. P.; Flier, J. S. Development of obesity in transgenic mice after genetic ablation of brown adipose tissue. Nature 1993, 366, 740−742. (6) Lowell, B. B. Adaptive thermogenesis: turning on the heat. Curr. Biol. 1998, 8, R517−R520. (7) Lowell, B. B.; Spiegelman, B. M. Towards a molecular understanding of adaptive thermogenesis. Nature 2000, 404, 652−660. (8) Nicholls, D. G.; Locke, R. M. Thermogenic mechanisms in brown fat. Physiol. Rev. 1984, 64, 1−64. (9) Enerback, S.; Jacobsson, A.; Simpson, E. M.; Guerra, C.; Yamashita, H.; Harper, M. E.; Kozak, L. P. Mice lacking mitochondrial uncoupling protein are cold-sensitive but not obese. Nature 1997, 387, 90−94. (10) Wolf, G. The uncoupling proteins UCP2 and UCP3 in skeletal muscle. Nutr. Rev. 2001, 59, 56−57. (11) Erlanson-Albertsson, C. The role of uncoupling proteins in the regulation of metabolism. Acta Physiol. Scand. 2003, 178, 405−412. (12) Fink, B. D.; Hong, Y. S.; Mathahs, M. M.; Scholz, T. D.; Dillon, J. S.; Sivitz, W. I. UCP2-dependent proton leak in isolated mammalian mitochondria. J. Biol. Chem. 2002, 277, 3918−3925. (13) Affourtit, C.; Crichton, P. G.; Parker, N.; Brand, M. D. Novel uncoupling proteins. Novartis Found. Symp. 2007, 287, 70−80 (discussion 80−91). (14) Seifert, E. L.; Bezaire, V.; Estey, C.; Harper, M. E. Essential role for uncoupling protein-3 in mitochondrial adaptation to fasting but not in fatty acid oxidation or fatty acid anion export. J. Biol. Chem. 2008, 283, 25124−25131. (15) Clapham, J. C.; Arch, J. R.; Chapman, H.; Haynes, A.; Lister, C.; Moore, G. B.; Piercy, V.; Carter, S. A.; Lehner, I.; Smith, S. A.; Beeley, L. J.; Godden, R. J.; Herrity, N.; Skehel, M.; Changani, K. K.; Hockings, P. D.; Reid, D. G.; Squires, S. M.; Hatcher, J.; Trail, B.; Latcham, J.; Rastan, S.; Harper, A. J.; Cadenas, S.; Buckingham, J. A.; Brand, M. D.; Abuin, A. Mice overexpressing human uncoupling protein-3 in skeletal muscle are hyperphagic and lean. Nature 2000, 406, 415−418. (16) Bonet, M. L.; Oliver, P.; Palou, A. Pharmacological and nutritional agents promoting browning of white adipose tissue. Biochim. Biophys. Acta 2013, 1831, 969−985. (17) Rodriguez, V. M.; Portillo, M. P.; Pico, C.; Macarulla, M. T.; Palou, A. Olive oil feeding up-regulates uncoupling protein genes in rat brown adipose tissue and skeletal muscle. Am. J. Clin. Nutr. 2002, 75, 213−220.

Data are shown as the mean ± SE (n = 9 or 10). bp < 0.05. cp < 0.01, Student’s t test. a

Figure 7. UCP-3 protein expression levels in murine femoral muscles following the oral ingestion of 6-paradol for 8 weeks. Data are shown as the mean ± SE (n = 9). a, p < 0.05 versus normal; b, p < 0.05 versus control; Tukey’s multiple-range test.

the high-fat control group (1.1-fold) remained unchanged relative to the normal diet group, although it was significantly different from the 6-paradol diet group (p < 0.05). Although the role of UCP-3 remains unclear, it was concluded that the increase in UCP-3 expression was one of the mechanisms responsible for the antiobesity effects of 6-paradol. In summary, the antiobesity activities of orally ingested paradols with different acyl chain lengths were investigated. The effect of 6-paradol was stronger than that of the positive control dihydrocapsiate. Our results also showed that the length of the acyl chain of the paradol analogues had a significant impact on the strength of their antiobesity activity. Furthermore, a comparison of the antiobesity activities of 6-, 8-, and 12paradol revealed that the strength of their antiobesity activities was also related to the length of their acyl chain. On the basis of these results, it was concluded that the mechanisms of the antiobesity activity of 6-paradol involve increased energy metabolism in BAT, as well as an increase in UCP-1 protein expression, which occurred through the activation of the sympathetic nervous system.

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REFERENCES

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*(D.W.) E-mail: [email protected]. Phone: +81-92-8716631. Fax: +81-92-862-4431. 6173

dx.doi.org/10.1021/jf500873a | J. Agric. Food Chem. 2014, 62, 6166−6174

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dx.doi.org/10.1021/jf500873a | J. Agric. Food Chem. 2014, 62, 6166−6174