Article pubs.acs.org/JAFC
Cite This: J. Agric. Food Chem. 2018, 66, 1341−1348
Discovery of Glycosylated Genipin Derivatives as Novel Antiviral, Insecticidal, and Fungicidal Agents Qing Xia,† Jianyang Dong,† Ling Li,† Qiang Wang,† Yuxiu Liu,† and Qingmin Wang*,†,‡ †
State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, People’s Republic of China ‡ Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071, People’s Republic of China S Supporting Information *
ABSTRACT: A series of novel genipin glycoside derivatives incorporating 11 glycosidic moieties at either the 1 or 10 position of genipin were designed and synthesized. These compounds exhibited moderate to excellent inhibitory activities against tobacco mosaic virus. Especially, the in vitro and in vivo activities of compounds 6e, 7c, 7d, 7f, 7h, and 7i were comparable to that of ribavirin. In particular, compound 7c, the mannosyl derivative of genipin at the 10 position, showed the best activity. The series of genipin glycosyl derivatives also displayed fungicidal activities against 14 kinds of phytopathogenic fungi, especially for Rhizoctonia cerealis and Sclerotinia sclerotiorum. Moreover, compound 6h exhibited good insecticidal activity against diamondback moth; compounds 7b, 7c, and 7g exhibited moderate insecticidal activity against three kinds of Lepidoptera pests (oriental armyworm, cotton bollworm, and corn borer); and compound 7e showed excellent larvacidal activities against mosquito. KEYWORDS: natural products, geniposide, glycosylation, antiviral activity, biological activity
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INTRODUCTION Plant virus diseases replicate in host cells by hijacking the host cell metabolic machinery; therefore, it is extremely difficult to find an antiviral reagent that only inhibits viral functions but spares host cellular processes.1 The well-known plant virus tobacco mosaic virus (TMV) can infect members of 36 plant families and at least 400 individual species.2 It could lead to mosaic or leaf necrosis at harvesting time, causing significant yield losses in crop production worldwide.3 However, plants have established an excellent chemical defense system to selectively suppress pathogens by producing secondary metabolites with antimicrobial activities throughout their evolution. 4−6 Thus, it can be imagined that antiviral compounds would be produced in plants as part of their innate defense system, and the various secondary metabolites could be nontoxic to the host plants and could be screened as antiviral compounds with a selective target spectrum. Several secondary metabolites with antiviral activity against TMV have been separated and studied. Our group previously demonstrated that harmine, tetrahydroharmine, and their derivatives exhibited higher anti-TMV activity than the commercial antiviral agent ribavirin both in vitro and in vivo.7,8 We also found that gossypol Schiff base derivatives and a series of phenanthroindolizidine alkaloid derivatives exhibited excellent anti-TMV activity.3,9,10 Some other natural products have also been found to possess antiviral activity.11,12 However, there is still a lack of economically viable antiviral chemicals that could be available for application in agriculture; thus, further research for development of new natural antiviral products is needed. Glycoconjugation of natural products is a frequently used modifying method of plants during their biosynthesis and is also an important factor to determine their bioactivity and bioavailability. Ningnanmycin, a cytidine peptide type of antibiotic isolated from Streptomyces noursei var. xichangensis, © 2018 American Chemical Society
seems to be the most successful registered anti-plant virus agent; it has been demonstrated to induce tobacco systemic resistance against TMV via activating multiple plant defense signaling pathways.13−15 Yang et al.16 investigated the inhibitory effects of sulfated lentinan with different degrees of sulfation against TMV; mechanism studies indicated that sulfated lentinan induces systemic protection against TMV. Natural polysaccharides possess a broad spectrum of biological activities, limited side effects, and a relatively low toxicity and, thus, had attracted much attention in the field of biochemistry.17 Wu et al.18 found that the antiviral activity of polysaccharide peptide (PSP) was stronger than ningnanmycin, and the mechanism study showed that PSP could lead to an apparent oxidative burst in tobacco leaves and increase expression levels of PR-1a and PR-5, which then induced resistance responses of plants to TMV. In addition, chitosan, oligosaccharide, and laminarin could induce the generation of H2O2 and increase resistance responses of various plant seedlings.19−21 Some other natural glycosides and derivatives, such as pinoresinol glycosides,12 syringaresinol glycosides,12 and seco-pregnane steroid glycosides,1 also have anti-TMV activity. More than that, glycoconjugation is widely used to improve the water solubility22 and reduce toxicity23 of some natural products. Wang et al.24 designed and synthesized a series of phenanthroindolizidine alkaloid glycoconjugates to improve water solubility and molecule polarity, and the bioassay results showed that the introduction of sugar units successfully improved the antiviral activity of these glycoconjugates. Thus, the glycosylation of natural products and Received: Revised: Accepted: Published: 1341
December 13, 2017 January 6, 2018 January 7, 2018 January 31, 2018 DOI: 10.1021/acs.jafc.7b05861 J. Agric. Food Chem. 2018, 66, 1341−1348
Article
Journal of Agricultural and Food Chemistry
temperature. Then, the reaction mixture was filtrated through a pad of Celite. The filtrate was poured into cooled saturated NaHCO3 and extracted with Et2O 3 times. The combined organic phase was washed with brine, dried, and concentrated in vacuo. The residue was added into a solution of pyridinium p-toluenesulfonate (126 mg, 0.5 mmol) in EtOH (30 mL) and was stirred for 2 days at room temperature. Then, the reaction mixture was added to saturated NaHCO3 (30 mL) and concentrated in vacuo. The residue was extracted by Et2O 3 times, washed with brine, and dried. Flash chromatography of the residue with petroleum ether/EtOAc (2:1, v/v) gave compound 2 (1.45 g, 85%) as a colorless oil. The synthetic procedure for trichloroacetimidate donors 2,3,4,6tetra-O-acetyl-α-D-glucopyranosyl trichloroacetimidate (3a), 2,3,4,6tetra-O-acetyl-α-D-galactopyranosyl trichloroacetimidate (3b), 2,3,4,6tetra-O-acetyl-α-D-mannopyranosyl trichloroacetimidate (3c), 2,3,4-triO-acetyl-α-D-xylopyranosyl trichloroacetimidate (3d), 2,3,4-tri-Oacetyl-α-D-glucuronide methyl ester trichloroacetimidate (3e), 2,3,4tri-O-acetyl-α-L-rhamnopyranosyl trichloroacetimidate (3f), and 2,3,6,2,3′,4′,6′-hepta-O-acetyl-α-maltosyl trichloroacetimidate (3g) was performed according to the published literature.32−34 Synthesis of 3,4,6-Tri-O-acetyl-2-deoxy-2-trifluoroacetamido-β-Dglucopyranosyl Trichloroacetimidate (3h) (Figure 2). 1,3,4,6-TetraO-acetyl-2-amino-2-deoxy-β-D-glucopyranose hydrochloride (3ha) was synthesized as previously described.35 1,3,4,6-Tetra-O-acetyl-2-deoxy-2-trifluoroacetamido-β-D-glucopyranose (3hb): To a solution of compound 3ha (3.17 g, 8.26 mmol) in dichloromethane (25 mL) and pyridine (3.3 mL) was added trifluoroacetic anhydride (3.21 mL, 23.1 mmol) at 0 °C. After stirring for 1 h at room temperature, the solution was poured into ice−water. The organic phase was washed with water (25 mL), dried over anhydrous MgSO4, and concentrated in vacuo. The residue was added of Et2O to yield compound 3hb as crystals (3.45 g, 94%). 3,4,6-Tri-O-acetyl-2-deoxy-2-trifluoroacetamido-α-D-glucopyranose (3hc): To a solution of compound 3hb (3.45 g, 7.8 mmol) in tetrahydrofuran (THF, 20 mL) was added methylamine (1.53 mL, 9.7 M in EtOH, 14.8 mmol). After stirring for 8 h at room temperature, the solution was evaporated. The residue was extracted with chloroform and washed with 1 M aqueous HCl, saturated aqueous NaHCO3, and brine. After dried over MgSO4, the residue was concentrated to dryness and purified by silica gel column chromatography with petroleum ether/EtOAc (2:1, v/v) to afford pure compound 3hc (2.69 g, 86%) as a white amorphous powder. Trichloroacetonitrile (0.4 mL, 4.0 mmol) and 1,8-diazabicyclo[5,4,0]-7-undecene (30 μL, 0.2 mmol) were added to a solution of compound 3hc (0.4 g, 1.0 mmol) in dry dichloromethane (10 mL) at 0 °C. After the reaction was stirred for 5 h at room temperature, the solution was concentrated to dryness and purified by silica gel column chromatography with petroleum ether/EtOAc (4:1, v/v) to afford compound 3h (320 mg, 59%) as a colorless oil. Synthesis of 2,3,5-Tri-O-benzoyl-α-L-arabinofuranosyl Trichloroacetimidate (3i) (Figure 2). To a solution of L-arabinofuranose (5 g, 33.3 mmol) dissolved in MeOH (30 mL) at 0 °C was added acetyl chloride (0.75 mL, 10 mmol) dropwise. The mixture was stirred overnight before quenching with pyridine (20 mL). The solvent was co-evaporated with toluene to give a yellow oil. Then, the oil was diluted with pyridine (20 mL) at 0 °C; benzoyl chloride (15.4 mL, 133 mmol) was added; and the reaction mixture was stirred overnight at room temperature. Then, the mixture was diluted with water and extracted with dichloromethane 3 times. The combined organic phases were washed with water (30 mL), 3 N H2SO4 solution (30 mL), saturated NaHCO3 solution (30 mL), and brine (30 mL). The organic phase was dried, and the solvent was evaporated. The crude mixture was recrystallized from ethanol to give methyl 2,3,5-tri-O-benzoyl-1-αL-arabinofuranoside (3ib, 13.7 g, 86%) as colorless crystals. Compound 3ib (1 g, 2.1 mmol) was suspended in acetone (5 mL), and trifluoroacetic acid (30 mL) was added. The mixture was stirred at 50 °C for 6 h before concentration to dryness in vacuo. Then, the residue was purified on a silica gel column chromatography with petroleum ether/EtOAc (5:1, v/v) to give 3,5-di-O-benzoyl-Larabinofuranose (3ic, 466 mg, 46%) as a colorless oil.
derivatives seems to be a common and reasonable strategy to find new compounds possessing anti-TMV activity. Geniposide, an iridoid glycoside, is a primary component of Fructus gardenia. It has long been used as a traditional Chinese medicine, which is attributed to its anti-inflammatory, antioxidant, antitumor, and antihyperlipidemic characteristics.25−27 Xiao et al.28 obtained botanical extracts of F. gardenia and tested the inhibitory effect by passive activation of TMV in vitro; the results indicated that the extracts had great inhibitory effect on TMV. Lin et al.29 found that geniposide inhibited both enterovirus 71 (EV71) replication and viral internal ribosome entry site (IRES) activity; the mechanistic investigation suggested that the antiviral effect occurs by blocking viral protein translation. However, reports on the antiTMV activity of geniposide and derivatives are rather rare, and no examples are documented in recent literature. Therefore, in this work, a series of geniposide and genipin glycoside derivatives were designed and synthesized and their antiTMV activities were evaluated using both in vitro and in vivo test methods. Moreover, the synthesized derivatives were also investigated as potential fungicidal and insecticidal agents.
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MATERIALS AND METHODS
Synthetic Procedures. Genipin, ribavirin, carbendazim, chlorothalonil, ametryne, rotenone, and other reagents were purchased from commercial sources and were used as received. The melting points were determined using an X-4 binocular microscope melting point apparatus (Beijing Tech Instruments Co., Beijing, China). Reaction progress was monitored by thin-layer chromatography on silica gel GF254 with detection by ultraviolet (UV). 1H and 13C nuclear magnetic resonance (NMR) spectra were obtained with an Avance 400 MHz spectrometer (Bruker, Switzerland). Chemical shifts (δ) were given in parts per million (ppm) and were measured downfield from internal tetramethylsilane. High-resolution mass spectra (HRMS) were obtained with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer (Varian, Palo, Alto, CA, U.S.A.). Synthesis of Methyl (1R,4aS,7aS)-1-Hydroxy-7-((pivaloyloxy)methyl)-1,4a,5,7a-tetrahydrocyclopenta[c]pyran-4-carboxylate30 (1) (Figure 1). To a mixture of genipin (500 mg, 2.21 mmol), dichloromethane (22 mL), and pyridine (0.27 mL, 3.32 mmol) was added trimethylacetyl chloride (0.3 mL, 2.43 mmol) at 0 °C, and the reaction was stirred overnight at room temperature under a balloon of argon. The reaction mixture was then extracted by Et2O and washed with a saturated aqueous solution of NH4Cl, a 5% aqueous solution of CuSO4, and brine. The combined organic phase was concentrated in vacuo and purified by flash column chromatography with petroleum ether/EtOAc (5:1, v/v) to furnish compound 1 as a white solid (555 mg, 81%) (NMR and HRMS data in the Supporting Information). Synthesis of Methyl (1S,4aS,7aS)-1-(tert-Butyldimethylsilyloxy)-7hydroxymethyl-1,4a,5,7a-tetrahydrocyclopenta[c]pyran-4-carboxylate31 (2) (Figure 1). To a stirred suspension of genipin (1.13 g, 5 mmol) and silver nitrate (2.12 g, 12.5 mmol) in dimethylformamide (DMF, 30 mL) was slowly added tert-butyldimethylsilyl chloride (1.88 g, 12.5 mmol) at 0 °C. The reaction was stirred overnight at room
Figure 1. Reagents and conditions: (a) PivCl, pyridine, CH2Cl2, from 0 °C to room temperature, overnight; (b) TBSCl, AgNO3, DMF, from 0 °C to room temperature, overnight; and (c) catalyst PPTS, EtOH, 2 days. 1342
DOI: 10.1021/acs.jafc.7b05861 J. Agric. Food Chem. 2018, 66, 1341−1348
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Journal of Agricultural and Food Chemistry
Figure 2. Reagents and conditions: (a) TFFA, pyridine, CH2Cl2, from 0 °C to room temperature, 1 h; (b) MeNH2/EtOH, THF, 8 h; (c) CCl3CN, DBU, CH2Cl2, from 0 °C to room temperature, 5 h; (d) AcCl, MeOH, from 0 °C to room temperature, overnight; then BzCl, pyridine, from 0 °C to room temperature, overnight; (e) TFA/acetone, 50 °C, 6 h; and (f) CCl3CN, K2CO3, CH2Cl2, overnight. Biological Assay. The anti-TMV and fungicidal and insecticidal activities of the synthesized compounds were tested using our previously reported methods.36
Compound 3ic (260 mg, 0.56 mmol) was added to a solution of trichloroacetonitrile (170 μL, 1.69 mmol) and K2CO3 (200 mg, 1.4 mmol) in dichloromethane (5 mL). The mixture was stirred at room temperature overnight. Then, the mixture was filtered, and the filtrate was concentrated. Purification of the residue on column chromatography with petroleum ether/EtOAc (7:1, v/v) gave compound 3i as a white solid (125 mg, 37%). General Procedure for the Synthesis of Title Compounds 4a−4i and 5a−5i (Figure 3). Compound 1 or 2 (1 mmol) was added to a solution of compound 3 (1 mmol) in 3 mL of anhydrous dichloromethane, and the solution was stirred with activated 4 Å molecular sieves for 0.5 h under an atmosphere of argon at room temperature. The reaction mixture was then cooled to −30 °C, and trimethylsilyl trifluoromethanesulfonate (TMSOTf, 0.5 mmol) was added dropwise. After stirring at −30 °C for 3 h and then at room temperature for 0.5 h, the reaction mixture was quenched with Et3N and filtered through Celite. The filtrate was concentrated and purified by flash chromatography to afford compounds 4a−4i and 5a−5i. General Procedure for the Synthesis of Title Compounds 6a−6j (Figure 3). The compounds 4a−4i (1 mmol) were dissolved in dry MeOH (10 mL). Freshly prepared NaOMe/MeOH (0.5 M, 2 mL) was added, and the reaction was stirred at 50 °C for 3 h. The reaction mixture was neutralized with Amberlite IR 120 (H+) resin and filtered, and then the filtrate was evaporated. The residues were purified by column chromatography with CHCl3/MeOH to afford the desired products 6a−6j as solids. General Procedure for Synthesis Title Compounds 7a−7i (Figure 3). The compounds 5a−5i (1 mmol) were dissolved in dry MeOH (10 mL). Freshly prepared NaOMe/MeOH (0.5 M, 2 mL) was added, and the reaction was stirred at room temperature for 1 h. The reaction mixture was neutralized with Amberlite IR 120 (H+) resin and filtered, and then the filtrate was evaporated. The residues were dissolved in dry THF, and tetrabutylammonium fluoride (1 mL, 1 M THF solution) was added and reacted at room temperature for 0.5 h. The solution was then evaporated in vacuo, and the residue was purified by column chromatography with CHCl3/MeOH to afford the desired products 7a−7i as solids.
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RESULTS AND DISCUSSION Synthesis. We used the trichloroacetimidate method to create a glycosidic linkage between genipin and the mono- or disaccharide.37 A widely used Lewis acid BF3·Et2O was not efficient enough to afford the target products, which was probably because the hydroxyl groups of compounds 1 and 2 are less active. Therefore, a more effective catalyst TMSOTf was introduced to the condensation (Figure 3). The condensation of 2,3,4-tri-O-acetyl-α-L-rhamnopyranosyl trichloroacetimidate (3f) with genipin derivative 1 in the presence of TMSOTf gave compound 4f in 90% yield. However, there are two type of products (5f and 5i) when compound 3f coupled with compound 2. The mechanism for the process to generate disaccharide 5i has not been reported. We speculated that, during the condensation, the 2-acetyl group of compound 3f was displaced and the 2-hydroxyl of compound 3f was coupled with another trichloroacetimidate 3f to yield the product 5i. Acetyl and benzoyl groups are easy to deprotect using NaOMe/MeOH, while the deprotection of pivalic acyl needs stronger conditions. After screening the reaction conditions, 0.5 M NaOMe/MeOH at 50 °C was selected to be the best condition, which could produce the deprotected products 6a− 6j with favorable yield within 3 h. Phytotoxic Activity. Phytotoxic activity of compounds 6a−6j and 7a−7i against tobacco, rape, amaranth pigweed, barnyard grass, and hairy crabgrass was first tested. All of the tested compounds are safe to the test plant at 1.5 kg/ha. Antiviral Activity. The results of anti-TMV activities of 6a−6j and 7a−7i are listed in Tables 1 and 2. To make a judgment on the antiviral potency of the synthesized 1343
DOI: 10.1021/acs.jafc.7b05861 J. Agric. Food Chem. 2018, 66, 1341−1348
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Journal of Agricultural and Food Chemistry
Figure 3. Reagents and conditions: (a) TMSOTf, CH2Cl2, 4 Å molecular sieves, Ar, −30 °C for 3 h and then room temperature for 0.5 h; (b) 0.5 M NaOMe/MeOH, 50 °C, 3 h; (c) 0.05 M NaOMe/MeOH, 1 h; and (d) 1 M TBAF/THF, 0.5 h.
general, the in vitro anti-TMV bioassay demonstrated that 1OH glycosylated genipin (7) exhibited higher activity than 10OH glycosylated genipin (6). In Vivo Anti-TMV Activity. As a result of the in vitro antiviral activities against TMV, the in vivo antiviral activities of these compounds deserved to be exploited further. The results shown in Table 2 indicate that all of the glycosylated genipin derivatives exhibited better activities in vivo against TMV than geniposide 6a and compounds 6e, 7c, 7f, 7h, and 7i possess comparative in vivo anti-TMV activities to ribavirin. More importantly, compound 7f with α-L-rhamnopyranoside at the 10 position showed the same curative effect at 500 mg/kg
compounds, the commercially available plant virucide ribavirin was used as the control. All of the compounds were tested at both 500 and 100 mg/kg. In Vitro Anti-TMV Activity. The results shown in Table 1 indicate that some of these target compounds exhibited moderate to excellent inhibitory activities against TMV. Compound 7d exhibited comparative in vitro antiviral activity at 500 mg/kg to ribavirin, and the activity of compound 6e at 100 mg/kg (7.7%) was also close to ribavirin (7.3%). Especially, genipin 10-mannopyranoside (7c) possessed higher antiviral activity than ribavirin at both 500 and 100 mg/kg, thus emerging as a new lead compound for antiviral research. In 1344
DOI: 10.1021/acs.jafc.7b05861 J. Agric. Food Chem. 2018, 66, 1341−1348
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Journal of Agricultural and Food Chemistry Table 1. In Vitro Antiviral Activity of Compounds 6a−6j and 7a−7i against TMV compound
concentration (mg/kg)
inhibition rate (%)
compound
concentration (mg/kg)
inhibition rate (%)
ribavirin
500 100 500 500 500 500 500 100 500 500 500 500
38.2 7.3 0 0 11 5.4 31.4 7.7 22.6 7.1 0 0
6j 7a 7b 7c
500 500 500 500 100 500 500 500 500 500 500
19.5 27 19.6 39.8 18.5 36.2 20.8 29.7 18.4 32 25.3
6a 6b 6c 6d 6e 6f 6g 6h 6i
7d 7e 7f 7g 7h 7i
Table 2. In Vivo Antiviral Activity of Compounds 6a−6j and 7a−7i against TMV compound ribavirin 6a 6b 6c 6d 6e 6f 6g 6h 6i 6j 7a 7b 7c 7d 7e 7f 7g 7h 7i
concentration (mg/kg)
inactivation effect (%)
curative effect (%)
protective effect (%)
500 100 500 500 500 500 500 100 500 500 500 500 500 500 500 500 100 500 500 500 500 500 500
37.5 10.4 5.3 0 17.3 12.5 39.2 5.7 36.5 18 7.6 20.1 28.4 30.1 32 42.9 14.1 30.4 26.3 36 22.0 39.1 34.3
40 9.6 0 10.2 24.4 20.2 42.5 9.2 31.4 26.4 12.3 28.3 22.3 32.3 27.3 45.8 8.2 22.5 31.9 41.2 26.9 30.6 31.8
38.1 12.2 0 5.9 16 0 34.2 11.4 28.1 13.6 0 15.5 14 24.9 21.3 39.4 13.5 34.8 22.4 33.4 30.2 35 37.5
genipin 7 were higher than those of 10-OH glycosylated genipin 6 both in vitro and in vivo (Tables 1 and 2). That is, the hemiacetal hydroxyl at the 1 position of genipin was demonstrated to be the active functional group of genipin for the anti-TMV activities; thus, further derivatization for antiTMV lead compounds of genipin should be avoided at the 1 position of genipin. Fungicidal Activity. The fungicidal activities of compounds 6 and 7 against 14 kinds of phytopathogenic fungi at 50 mg/kg are listed in Table 3. Remarkably, the series of glycosylated genipin derivatives displayed satisfactory activities against Rhizoctonia cerealis (>60% inhibition rates at 50 mg/kg), and the inhibition rates of compounds 6b and 6j even exceeded 75% at 50 mg/kg. In addition, compounds 6b (53.6%) and 7a (60.7%) were more effective against Physalospora piricola at 50 mg/kg than other compounds. For Sclerotinia sclerotiorum, compounds 6f, 6g, 7a, and 7d exhibited higher inhibitory effects, especially genipin 1-xylopyranoside genipin (7d), which had a 77.3% inhibition rate. Insecticidal Activity. Insecticidal Activities against Lepidopteran Pests. The insecticidal activities of target compounds and the commercial natural insecticide rotenone against oriental armyworm (Mythimna separata), diamondback moth (Plutella xylostella), cotton bollworm (Helicoverpa armigera), and corn borer (Ostrinia furnacalis) are listed in Table 4. The results indicated that some of the target compounds showed satisfactory insecticidal activities against these lepidopteran pests. Although the antivirus activity of compound 6h was far less effective, the insecticidal activity of compound 6h against diamondback moth was much higher than those of other tested compounds, even at a lower concentration (70% fatal rate against diamondback moth at 100 mg/kg). Compounds 6c, 6g, and 7h also possess at least 70% fatality rate against diamondback moth at 200 mg/kg. The LC50 values of compounds 6c, 6g, 6h, and 7h were determined, which shows that compound 6h (LC50 value of 53.0 mg/kg, with a 95% confidence interval of 45.2−62.1 mg/kg) possesses similar values to commercial rotenone (LC50 value of 35.4 mg/ kg, with a 95% confidence interval of 22.2−56.4 mg/kg). The insecticidal activities of the target compounds against oriental armyworm, cotton bollworm, and corn borer are consistent with the antiviral activities; that is, 1-OH glycosylated genipin 7 is higher than 10-OH glycosylated genipin 6. Compounds 7b (100% against oriental armyworm, 75% against cotton bollworm, and 75% against corn borer), 7c (100% against oriental armyworm, 65% against cotton bollworm, and 70% against corn borer), and 7g (100% against
(41.2%) as ribavirin (40.0%), and compound 7h with a trifluoroacetamido glucopyranoside at the 10 position also had equivalent activity to ribavirin (39.1% for compound 7h and 37.5% for ribavirin at 500 mg/kg). In particular, genipin 10mannopyranoside (7c) showed the best in vivo activities (inactivation activity, 42.9%/500 mg/kg and 14.1%/100 mg/ kg; curative activity, 45.8%/500 mg/kg; and protective activity, 39.4%/500 mg/kg and 13.5%/100 mg/kg), all higher than those of ribavirin. In combination with the results of in vitro anti-TMV activities, compound 7c seems to be the best antiTMV compound among these glycosylated genipin derivatives, and the mannosylation at the 10 position of genipin significantly improved the anti-TMV activity. Similarly, Wang et al.24 also found mannopyranosyl (S)-antofine to be the best anti-TMV compound among the series of phenanthroindolizidine alkaloid glycoconjugates. In addition, the relationship between the positions of glycosyl substituents and anti-TMV activities were further confirmed. The anti-TMV activities of 1-OH glycosylated 1345
DOI: 10.1021/acs.jafc.7b05861 J. Agric. Food Chem. 2018, 66, 1341−1348
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Journal of Agricultural and Food Chemistry Table 3. Fungicidal Activity of Compounds 6a−6j and 7a−7i against 14 Kinds of Phytopathogens fungicidal activitya (%/50 mg/kg) b
compound
FC
carbendazim chlorothalonil 6a 6b 6c 6d 6e 6f 6g 6h 6i 6j 7a 7b 7c 7d 7e 7f 7g 7h 7i
