Isolation and identification of xanthotoxin (8-methoxypsoralen) and bergapten (5-methoxypsoralen) from celery infected with Sclerotinia sclerotiorum

Anti-Helicobacter pylori, anti-biofilm activity, and molecular docking study of citropten, bergapten, and its positional isomer isolated from Citrus sinensis L. leaves

Introduction

Citrus sinensis L. is a candidate plant with promising antimicrobial potential. In the current study, the phytochemical investigation of C. sinensis leaf extract led to the isolation of three coumarins, namely bergapten, xanthotoxin, and citropten.

Methods

The chemical structures of the isolated coumarins were elucidated using NMR and ESI-MS techniques. The total aqueous ethanol leaf extract and the isolated coumarins were evaluated for their antimicrobial effects against Helicobacter pylori using the MTT-micro-well dilution method and its anti-biofilm activity using MBEC assay, as compared to clarithromycin.

Results

The results showed that citropten scored the lowest MIC value at 3.9 μg/mL and completely inhibited the planktonic growth of H. pylori. In addition, it completely suppressed H. pylori biofilm at 31.25 μg/mL. These findings have been supported by molecular docking studies on the active sites of the H. pylori inosine 5'-monophosphate dehydrogenase (HpIMPDH) model and the urease enzyme, showing a strong binding affinity of citropten to HpIMPDH with seven hydrogen bonds and a binding energy of -6.9 kcal/mol. Xanthotoxin and bergapten showed good docking scores, both at -6.5 kcal/mol for HpIMPDH, with each having four hydrogen bondings. Furthermore, xanthotoxin showed many hydrophobic interactions, while bergapten formed one Pi-anion interaction. Concerning docking in the urease enzyme, the compounds showed mild to moderate binding affinities as compared to the ligand. Thus, based on docking results and good binding scores observed with the HpIMPDH active site, an in-vitro HpIMPDH inhibition assay was done for the compounds. Citropten showed the most promising inhibitory activity with an IC50 value of 2.4 μM. Conclusion: The present study demonstrates that C. sinensis L. leaves are a good source for supplying coumarins that can act as naturally effective anti-H. pylori agents.

Identification of lead chemotherapeutic agents from medicinal plants against blood flukes and whipworms

Schistosomiasis and trichuriasis are two of the most common neglected tropical diseases (NTD) that affect almost a billion people worldwide. There is only a limited number of effective drugs to combat these NTD. Medicinal plants are a viable source of parasiticides. In this study, we have investigated six of the 19 phytochemicals isolated from two Bhutanese medicinal plants, Corydalis crispa and Pleurospermum amabile, for their anthelmintic properties. We used the xWORM technique and Scanning Electron Microscope-based imaging to determine the activity of the compounds. Of the six compounds tested, isomyristicin and bergapten showed significant anthelmintic activity against Schistosoma mansoni and Trichuris muris with bergapten being the most efficacious compound one against both parasites (S. mansoni IC₅₀ = 8.6 μg/mL and T. muris IC₅₀ = 10.6 μg/mL) and also against the schistosomulum stage of S. mansoni. These two compounds induced tegumental damage to S. mansoni and affected the cuticle, bacillary bands and bacillary glands of T. muris. The efficacy against multiple phylogenetically distinct parasites and different life stages, especially the schistosomulum where praziquantel is ineffective, makes isomyristicin and bergapten novel scaffolds for broad-spectrum anthelmintic drug development that could be used for the control of helminths infecting humans and animals.

Light-activated plant defence

Sunlight provides the energy required for all biochemical, physiological and developmental processes necessary for plant growth, reproduction and survival. The role of light in photosynthesis and photomorphogenesis has been appreciated for some time; however, the role of light in plant defence is a comparatively recent realization. Between 75-100 photosensitizers or phototoxins, molecules that become toxic in the presence of light, have been extracted from higher plant tissues. These biologically-active compounds have diverse biosynthetic origins and belong to at least 15 different phytochemical classes (i.e. acetophenones, acetylenes, benzophenanthrenes, β-carbolines, coumarins, extended quinones, furanochromones, furanocoumarins, furanoquinolines, isoquinolines, lignans, pterocarpans, quinolines, sesquiterpenes and thiophenes). Of more than 100 angiosperm families assayed, phototoxins and/or phototoxic activity have been reported in c. 40 families representing 32 orders and 8 subclasses of the Magnoliophyta. Most of these allelochemicals are acute toxins with little organism-specificity. As such, they are effective biocides capable of killing a wide-range of potentially harmful organisms including: viruses, pathogenic bacteria and fungi, nematodes and herbivorous insects, as well as competing plant species. This review focuses on the phytochemistry, taxonomic occurrence and toxicological consequences of phototoxic metabolites in flowering plants. The available information suggests that phototoxic phytochemicals: (i) are broad-spectrum allelochemicals capable of protecting plants against a variety of detrimental organisms in nature, (ii) represent a successful defensive strategy in both primitive and advanced plant taxa, and (iii) may be an effective defence under a variety of photoenvironmental conditions. CONTENTS Summary 401 I. Introduction 401 II. Chemistry/biochemistry of plant photosensitizers 402 III. Botanical distribution of photosensitizers 403 IV. Toxicology 405 V. Biological activity/defensive role of photosensitizers 408 VI. Concluding remarks 413 References 415.

Subacute toxicological evaluation of sclerotia of Sclerotinia sclerotiorum in rats

Weanling Wistar rats of both sexes were fed diets containing 0 (control), 1% and 5% ground sclerotia of Sclerotinia sclerotiorum derived from infected rapeseed (Brassica napus). Body weight, feed consumption and clinical appearance were monitored over an 84-day period. Blood samples were collected on days 41 and 84 and necropsies performed on day 84. Weight gain and feed consumption were similar in the control and 1% groups. In the 5% group, weight gain was depressed, feed wastage was greater and at termination more than half the rats were in poor body condition with alopecia and hyperkeratosis of the tail. These effects were probably nutritional and due to unpalatability of the diet. Blood urea nitrogen and blood glucose concentrations did not vary consistently among the groups. Serum glutamic-pyruvic transaminase activity was significantly depressed (p less than 0.001) by consumption of sclerotia. This depression was dose-related and consistent on days 41 and 84. There were no significant differences (p greater than 0.05) between groups in the ratios of liver weight and kidney weight to body weight.

Evaluation of Sclerotinia sclerotiorum as a potential mycotoxin producer on soybeans

Solvent extracts of Sclerotinia sclerotiorum sclerotia were nontoxic to mice and chicken embryos; psoralens were not detected. Solvent extracts of soybeans inoculated with 10 strains of S. sclerotiorum were toxic on injection but nontoxic on per os administration to mice. The presence of chlorinated hydrocarbons in the soybeans may partially help explain toxicity by intraperitineal injection.