Idesia polycarpa (Salicaceae) leaf constituents and their toxic effect on Cerura vinula and Lymantria dispar (Lepidoptera) larvae

Subchronic Toxicity Evaluation of Idesia polycarpa Fruit Oil by 90-Day Oral Exposure in Wistar Rats

Idesia polycarpa, belonging to the Flacourtiaceae family, is a tall deciduous tree, widely distributed in some Asian countries. It is famous for its high yield of fruit known as oil grape, which is rich of linoleic acid and linolenic acid, and so on. To provide evidences for its safe use as food, subchronic toxicity of I. polycarpa fruit oil and no observed adverse effect level were performed in male and female specific pathogen-free Wistar rats. Based on the Organization for Economic Co-operation and Development guidelines, the oil was orally administered to rats by gavage at 0, 1.0, 2.0, and 4.0mL/kg.bw/day for 90 days, followed by a 28-day recovery period. The results showed that no sign of oil-related toxicity, clinically or histologically, was observed in both male and female rats. Although there was a slight increase or decrease in some indicators such as hematology, serum chemistry, and so on, those changes were all within the normal ranges, and as presented in the 90-day study, the oil exhibited no toxic effect compared to the control rats. I. polycarpa might be a potential excellent and healthy vegetable oil resource.

A Mechanism to Transform Complex Salicinoids with Caffeoylquinic Acids in Lepidopteran Specialist Herbivores (Notodontidae)

Larvae of the Salicaceae-adapted Notodontidae have developed a unique mechanism to metabolize the chemical defenses of their Salicaceae host plants. Salicinoids and salicortinoids are enzymatically transformed into salicyloyl, benzoyl and mixed salicyloyl-benzoyl quinates. The source of quinates and benzoates was previously unknown. To elucidate the origin of quinate and benzoate in the metabolic end-products, we fed Cerura vinula caterpillars with 13C-labelled poplar defense compounds. Caffeoylquinic acids (CQAs), such as chlorogenic acid, neochlorogenic acid and their methyl esters, were identified as the source of quinates in the caterpillar's metabolism. Benzoyl substituents in the quinate end-products were found to originate from compounds such as tremulacin or trichocarpin. Salicaceae-adapted Notodontidae caterpillars have the ability to overcome their host plant's chemical defense by metabolizing CQAs and salicinoids, both abundant defense compounds in Salicacea plants, by a strategy of transformation and recombination. We believe that our study opens up avenues for understanding salicortinoid biotransformation at the enzymatic level.

Reductive Conversion Leads to Detoxification of Salicortin-like Chemical Defenses (Salicortinoids) in Lepidopteran Specialist Herbivores (Notodontidae)

Lepidopteran specialist herbivores of the Notodontidae family have adapted to thrive on poplar and willow species (Salicaceae). Previous research showed that Cerura vinula, a member of the Notodontidae family occurring throughout Europe and Asia, uses a unique mechanism to transform salicortinoids, the host plant's defense compounds, into quinic acid-salicylate conjugates. However, how the production of this conjugates relates to the detoxification of salicortinoids and how this transformation proceeds mechanistically have remained unknown. To find the mechanisms, we conducted gut homogenate incubation experiments with C. vinula and re-examined its metabolism by analyzing the constituents of its frass. To estimate the contribution of spontaneous degradation, we examined the chemical stability of salicortinoids and found that salicortinoids were degraded very quickly by midgut homogenates and that spontaneous degradation plays only a marginal role in the metabolism. We learned how salicortinoids are transformed into salicylate after we discovered reductively transformed derivatives, which were revealed to play key roles in the metabolism. Unless they have undergone the process of reduction, salicortinoids produce toxic catechol. We also studied constituents in the frass of the Notodontidae species Cerura erminea, Clostera anachoreta, Furcula furcula, Notodonta ziczac, and Pheosia tremula, and found the same metabolites as those described for C. vinula. We conclude that the process whereby salicortinoids are reductively transformed represents an important adaption of the Notodontidae to their Salicaceae host species.

A peroxisomal β-oxidative pathway contributes to the formation of C6-C1 aromatic volatiles in poplar

Benzenoids (C6-C1 aromatic compounds) play important roles in plant defense and are often produced upon herbivory. Black cottonwood (Populus trichocarpa) produces a variety of volatile and nonvolatile benzenoids involved in various defense responses. However, their biosynthesis in poplar is mainly unresolved. We showed feeding of the poplar leaf beetle (Chrysomela populi) on P. trichocarpa leaves led to increased emission of the benzenoid volatiles benzaldehyde, benzylalcohol, and benzyl benzoate. The accumulation of salicinoids, a group of nonvolatile phenolic defense glycosides composed in part of benzenoid units, was hardly affected by beetle herbivory. In planta labeling experiments revealed that volatile and nonvolatile poplar benzenoids are produced from cinnamic acid (C6-C3). The biosynthesis of C6-C1 aromatic compounds from cinnamic acid has been described in petunia (Petunia hybrida) flowers where the pathway includes a peroxisomal-localized chain shortening sequence, involving cinnamate-CoA ligase (CNL), cinnamoyl-CoA hydratase/dehydrogenase (CHD), and 3-ketoacyl-CoA thiolase (KAT). Sequence and phylogenetic analysis enabled the identification of small CNL, CHD, and KAT gene families in P. trichocarpa. Heterologous expression of the candidate genes in Escherichia coli and characterization of purified proteins in vitro revealed enzymatic activities similar to those described in petunia flowers. RNA interference-mediated knockdown of the CNL subfamily in gray poplar (Populus x canescens) resulted in decreased emission of C6-C1 aromatic volatiles upon herbivory, while constitutively accumulating salicinoids were not affected. This indicates the peroxisomal β-oxidative pathway participates in the formation of volatile benzenoids. The chain shortening steps for salicinoids, however, likely employ an alternative pathway.

Drying methods and structure-activity relationships of hydroxycinnamic acid derivatives in Idesia polycarpa Maxim. Leaves

Idesia polycarpa Maxim. leaves are an excellent source of hydroxycinnamic acid derivatives and have drawn special attention due to their various biological activities. However, the effects of post-harvest treatment on the structure-activity relationships of hydroxycinnamic acid derivatives in leaves of I. polycarpa are still unknown. In the current study, we compared the contents of unstable compounds in leaves with four drying methods, namely sun-drying, freeze-drying, shade-drying, and oven-drying. We found that the four hydroxycinnamic acid derivative isomers of leaves were significantly affected after drying processing with four different drying methods. Consequently, the underlying mechanisms responsible for the variation of these compounds during the drying processes have been well elucidated: UV lighting induced the isomerization of 1-[(6'-O-(E)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (1) and 1-[(4'-O-(E)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (3) into 1-[(6'-O-(Z)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (2) and 1-[(4'-O-(Z)-p-coumaroyl)-β-d-glucopyranosyl]-oxy-2-phenol (4). Also, heat (exceeding 20 °C) led to the rearrangement of the (E/Z)-p-coumaric acid moiety of compounds 3 and 4, of which the 4-O-acylglucoses changed into the 6-O-acylglucoses to generate compounds 1 and 2, respectively. Interestingly, the hepatocyte-free fatty acid accumulation in OA-induced steatosis-conditioned HepG2 cells decreased by 65.00%, 10.69%, and 47.00%, respectively, following treatment with compounds 2, 3 and 4, and compound 1 presented no lipid-lowering activity. In addition, the bioactivities of compounds 2 and 4 were substantially enhanced by 58.42% and 25.33% with the sun-drying method compared to the freeze-dying methods. Our study suggests that sun-drying processing is the best method among the four drying processing methods of I. polycarpa Maxim. leaves.

Amelioration by Idesia polycarpa Maxim. var. vestita Diels. of Oleic Acid-Induced Nonalcoholic Fatty Liver in HepG2 Cells through Antioxidant and Modulation of Lipid Metabolism

Idesia polycarpa Maxim. var. vestita Diels (I. polycarpa) is well known as an edible oil plant which contains abundant linoleic acid and polyphenols. The objective of this study was to maximize the by-product of defatted fruit of I. polycarpa. We found that the fraction D of ethyl acetate extract (EF-D) contained more polyphenols, which contribute to its strong antioxidant activity by antioxidant assays (DPPH, ABTS, and FRAP). Meanwhile, EF-D showed a significant lipid-lowering effect on oleic acid- (OA-) induced hepatic steatosis in HepG2 cells through enhancing antioxidant activity, reducing liver damage, and regulating lipid metabolism, antioxidant, and inflammation-related gene expression. The SOD and T-AOC levels significantly increased, but the levels of MDA, AST, and ALT decreased obviously when treated with EF-D. In general, EF-D improved the antioxidant enzyme activities and decreased the hepatic injury activities. Besides, treatment with EF-D for NAFLD influenced lipid metabolism and inflammation by activating PPARα which was associated with the increased expression of CPT1 and decreased expression of SCD, NF-κB, and IL-1. Moreover, EF-D improved the oxidative stress system through activation of the Nrf2 antioxidant signal pathways and upregulated its target genes of HO-1, NQO1, and GSTA2. The results highlighted the EF-D from the defatted fruit of I. polycarpa regarding lipid-lowering, proving it to be a potential drug resource of natural products for treating the nonalcoholic fatty liver disease (NAFLD).

Anti-Influenza Virus Activity and Chemical Components from the Parasitic Plant Cuscuta japonica Choisy on Dimocarpus longans Lour

Dodder (Cuscuta spp.) is a parasitic weed damaging many plants and agricultural production. The native obligate parasite Cuscuta japonica Choisy (Japanese dodder) parasitizes Dimocarpus longans Lour., Ficus septica Burm. F., Ficus microcarpa L.f., Mikania micrantha H.B.K. and Melia azedarach Linn, respectively. Five Japanese dodders growing on different plants exhibit slightly different metabolites and amounts which present different pharmacological effects. Among these plants, a significant antiviral activity against influenza A virus (IAV) was found in Japanese dodder parasitizing on D. longans Lour. (CL). To further explore methanol extract components in Japanese dodder (CL), four undescribed aromatic glycosides, cuscutasides A–D (compounds 1–4) were isolated, together with twenty-six known compounds 5–30. The chemical structures of 1–4 were elucidated using a combination of spectroscopic techniques. The eighteen isolated compounds were evaluated for antiviral activity against IAV activity. Among them, 1-monopalmitin (29) displayed potent activity against influenza A virus (A/WSN/1933(H1N1)) with EC₅₀ 2.28 ± 0.04 μM and without noteworthy cytotoxicity in MDCK cells. The interrupt step of 29 on the IAV life cycle was determined. These data provide invaluable information for new applications for this otherwise harmful weed.

Evaluation of in vitro Antifungal Activity of Xylosma prockia (Turcz.) Turcz. (Salicaceae) Leaves Against Cryptococcus spp

Cryptococcus species are responsible for important systemic mycosis and are estimated to cause millions of new cases annually. The available therapy is limited due to the high toxicity and the increasing rates of yeast resistance to antifungal drugs. Popularly known as “sucará,” Xylosma prockia (Turcz.) Turcz. (Salicaceae) is a native plant from Brazil with little information on its pharmacological potential. In this work, we evaluated in vitro anticryptococcal effects of the leaf ethanolic extract of X. prockia and its fractions against Cryptococcus gattii and Cryptococcus neoformans. We also evaluated phenotypic alterations caused by ethyl acetate fraction (EAF) (chosen according to its biological results). The liquid chromatography–mass spectrometry (LC-MS) analysis of EAF demonstrated the presence of phenolic metabolites that belong to three structurally related groups as majority compounds: caffeoylquinic acid, coumaroyl-glucoside, and caffeoyl-glucoside/deoxyhexosyl-caffeoyl glucoside derivatives. The minimum inhibitory concentration (MIC) values against C. gattii and C. neoformans ranged from 8 to 64 mg/L and from 0.5 to 8 mg/L, for ethanolic extract and EAF, respectively. The EAF triggered an oxidative burst and promoted lipid peroxidation. EAF also induced a reduction of ergosterol content in the pathogen cell membrane. These effects were not associated with alterations in the cell surface charge or in the thermodynamic fingerprint of the molecular interaction between EAF and the yeasts evaluated. Cytotoxic experiments with peripheral blood mononuclear cells (PBMCs) demonstrated that EAF was more selective for yeasts than was PBMCs. The results may provide evidence that X. prockia leaf extract might indeed be a potential source of antifungal agents.

Isolation and purification of four phenolic glycoside isomers from the leaves of Idesia polycarpa Maxim. by high-speed counter-current chromatography and preparative high-performance liquid chromatography

We established an efficient method using high-speed counter-current chromatography (HSCCC) combined with preparative high-performance liquid chromatography (prep-HPLC) for isolating and purifying phenolic glycoside isomers. The method involves a rapid and sensitive ultra-performance liquid chromatography-under voltage(UPLC-UV) technique using a sub-2 μm core-shell particle column for qualitative and quantitative analysis of four phenolic glycoside isomers from Idesia polycarpa Maxim. leaves. The partially purified samples from ethyl acetate extraction of ethanol extracts of I. polycarpa Maxim. leaves were obtained by HSCCC with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water solution (3:5:3:5, v/v/v/v) to obtain fractions I and II, which contain two phenolic glycoside isomers. The two fractions were further isolated by prep-HPLC to yield compounds 1, 2, 3, and 4 with purities of 98.29%, 98.71%, 98.49% and 98.52%, and total recoveries of 93.5%, 72.2%, 75.5% and 88.3%, respectively. Compound 1 was first isolated from I. polycarpa Maxim., while compound 2 was reported to be a new phenolic glycoside, which is 1-[(6'-O-(Z)-p-coumaroyl)-β-D-glucopyranosyl]-oxy-2-phenol. The chemical structures of the four phenolic glycoside isomers were analyzed and confirmed by UPLC, UV, electrospray ionization mass spectrometry (ESI-MS), fourier transform infra-red (FT-IR), 1H-nuclear magnetic resonance (1H NMR), 13C-nuclear magnetic resonance (13C NMR) and 2D nuclear magnetic resonance (2D NMR) spectra. This study opens prospects for broad industrial applications of HSCCC/prep-HPLC for the isolation and purification of isomers.

A new phenolic glycoside from the Idesia polycarpa Maxim. leaves

Phytochemical investigation on the ethyl acetate extract of Idesia polycarpa Maxim. Leaves led to the isolation of four phenolic glycoside isomers (1-4). Compound 2 appeared to be new reported phenolic glycoside, while compound 1 was the first time isolated from the titled species. Their structures were established by IR, UV, HRESI-MS and 1D and 2D NMR spectroscopies analysis and comparison of spectral data with previously reported data. The compounds 3 and 4 showed stronger activity of scavenging the DPPH free radical than the other two compounds, while the compounds 1 and 2 showed a significant activity of scavenging the ABTS free radical. Compounds 2 and 4 exhibited stronger cytotoxicity against HepG2 cell lines compared to compounds 1 and 3. Moreover, compound 3 presented the highest cytotoxicity against MCF cell lines with IC₅₀ value of 37.17 ± 0.26 μg/mL than compounds 1, 2 and 4.