Utilizing Ayurvedic literature for the identification of novel phytochemical inhibitors of botulinum neurotoxin A.

ETHNOPHARMACOLOGICAL RELEVANCE: Ayurveda, an ancient holistic system of health care practiced on the Indian subcontinent, utilizes a number of multi-plant formulations and is considered by many as a potential source for novel treatments, as well as the identification of new drugs. Our aim is to identify novel phytochemicals for the inhibition of bacterial exotoxin, botulinum neurotoxin A (BoNT/A) based on Ayurvedic literature. BoNT/A is released by Clostridium species, which when ingested, inhibits the release of acetylcholine by concentrating at the neuromuscular junction and causes flaccid paralysis, resulting in a condition termed as botulism, and may also lead to death due to respiratory arrest. METHODS: Fifteen plants were selected from the book 'Diagnosis and treatment of diseases in Ayurveda' by Vaidya Bhagwan Dash and Lalitesh Kashyap, based on their frequency of use in the formulations used for the treatment of six diseases with neuromuscular symptoms similar to botulism. Phytochemicals from these plants were screened using in silico, and in vitro methods. Structures of 570 reported phytochemicals from 14 plants were docked inside six reported BoNT/A light chain crystal structures using ensemble docking module in Maestro (Schrödinger, LLE). RESULTS: From the docking scores and structural diversity, nine compounds including acoric acid 1, three flavonoids, three coumarins derivatives, one kava lactone were selected and screened using an in vitro HPLC-based protease assay. The bioassay results showed that several compounds possess BoNT/A LC inhibition of 50-60% when compared to positive controls NSC 84094 and CB7967495 (80-95%). CONCLUSION: Further testing of the active compounds identified from Ayurvedic literature and structure-activity studies of acoric acid 1 using more sensitive bioassays is under way. The identification of acoric acid 1, a novel scaffold against BoNT/A, exemplifies the utility of Ayurvedic literature for the discovery of novel drug leads.

Progress in biological threat agent vaccine development: a repeat-dose toxicity study of a recombinant ricin toxin A-chain (rRTA) 1-33/44-198 vaccine (RVEc) in male and female New Zealand white rabbits.

A recombinant ricin toxin A-chain 1-33/44-198 vaccine (RVEc) was administered to male and female New Zealand white (NZW) rabbits (10/sex/group) in a repeat-dose toxicity study. The RVEc vaccine was administered on study days 1, 29, 57, and 85 via intramuscular (IM) injection (0, 100, or 200 µg/dose). All study animals were observed throughout treatment until euthanized and submitted for necropsy on study day 88 or 99 (recovery period). There were no treatment-related or toxicologically significant effects observed. There were no statistically significant differences noted in the antibody titers and/or concentrations in 100 µg RVEc-treated animals when compared to 200 µg RVEc-treated animals, suggesting that both doses produced comparable antibody titers/concentrations during the study. The highest immune response was observed on study day 99 (ie, 2 weeks after the last dose). The immune response observed demonstrated that RVEc is biologically active in the rabbit model, with no apparent marked sex differences.

Inhibition of the protease activity of the light chain of type A botulinum neurotoxin by aqueous extract from stinging nettle (Urtica dioica) leaf.

We investigated the inhibitory effect of stinging nettle leaf extract on the protease activity of botulinum neurotoxin type A and B light chains. The nettle leaf infusion was fractionated and HPLC-based enzymatic assays were performed to determine the capacity of each fraction to inhibit the protease activity of botulinum neurotoxin type A and B light chains. Assay results demonstrated that a water-soluble fraction obtained from the nettle leaf infusion inhibited type A, but did not inhibit type B light chain protease activity. The inhibition mode of water soluble fraction against protease activity of type A light chain was analyzed and found to be a non-competitive.