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Safety and Toxicity of Medicinal Plants
Published in Dilip Ghosh, Pulok K. Mukherjee, Natural Medicines, 2019
Neeraj Tandon, Satyapal Singh Yadav
Most of the plants which are toxic to humans, basically contain inherent toxic principle(s) like pyrrolizidine alkaloids, colchicine, alpha gliadin, cyanogenic glycosides, thiocyanates and lectins. There are handful of plants that contain toxic concentrations of poisonous constituent(s) and some of these have been well known for causing health hazards, like anticholinergic poisoning with Atropa belladonna due to the presence of atropine and other alkaloids (Ulbricht et al. 2004); severe gastroenteritis and internal bleeding with Arnica montana due to helenalin; cardiotoxicity and neurotoxicity with Aconitum species due to aconitine (Tak et al. 2016); cardiotoxicity with Digitalis species due to digoxin-like glycosides; hepatotoxicity with pyrrolizidine alkaloid–containing plants such as Senecio, Crotalaria, Cynoglossum, Amsinckia, Heliotropium and Echium species (Stegelmeier 2011); and teratogenicity and other toxicity of Solanaceous plants due to presence of toxic alkaloid chaconine, solasodine and solanine (Crawford and Kocan 1993). However, with the discovery of new phytochemicals may further enhance this list of toxic plants.
Catalog of Herbs
Published in James A. Duke, Handbook of Medicinal Herbs, 2018
Scolimoside, cynaroside, apigenin-3-O-beta-D-gluco-pyranoside, isoquercetrin, astra-galin, scopoletin, and umbelliferene are reported from the flowers. The flavone causes fall in blood pressure. Hager’s Handbook adds astragalin, caffeic acid, helenien, isoquercitrin, beta-lactucerol, beta-sitosterol, taraxasterol, thymol, thymolmethylether, xanthophyllepox-ide, and zeaxanthin.31 Dihydrohelenalin, helenalin, and their esters are said to be analgesic, antibiotic, and antiinflammatory.37 Helenalin is allergenic and may induce contact dermatitis.
Pyrrolizidine Alkaloids
Published in Amritpal Singh Saroya, Contemporary Phytomedicines, 2017
Phytochemistry: Pyrrolizidine alkaloids: viridiflorine, cynaustraline, amabiline, supinine, echinatine, and rinderine (Edgar et al. 1992) and sesquiterpene lactones: eupafolin, euperfolitin, eufoliatin, eufoliatorin, euperfolide, eucannabinolide, and helenalin (Woerdenbag 1986).
Bioactivation of herbal constituents: mechanisms and toxicological relevance
Published in Drug Metabolism Reviews, 2019
Helenalin (Figure 14(b)), a sesquiterpene lactone isolated from plants in the Arnica and Helenium genera, is a highly toxic compound particularly targeting hepatic and lymphatic tissues (Jodynis-Liebert et al. 2000). Despite its toxic effects, helenalin possesses anti-inflammatory and anti-tumor activities (Drogosz and Janecka 2019). Helenalin is a known covalent protein binder with two Michael acceptors, an α-methylene-γ-lactone and an α, β-unsaturated cyclopentenone ring (Figure 14(b)), both of which can engage biological thiols such as GSH and cysteine yielding covalent adducts (Schmidt 1997; Schmidt et al. 2009). The anti-inflammatory properties of helenalin can be attributed to covalent modification of Cysteine 38 of the NF-κB transcription factor p65, which prevents DNA binding of the p50/p65 heterodimer leading to suppression of NF-κB activation (Widen et al. 2018). Helenalin-based bis-electrophiles were recently developed as covalent binders to specifically target NF-κB p65 (Widen et al. 2017). Helenalin is also a potent, selective inhibitor of human telomerase via cysteine alkylation which may partially account for its antitumor effects (Zhang et al. 2014). Removal of one of the two Michael acceptors of helenalin, such as reduction of the cyclopentenone (yielding 2,3-dihydrohelenalin) or α-methylene-γ-lactone (yielding 11,13-dihydrohelenalin; plenolin), significantly diminishes cytotoxicity in human cancer cell lines as compared to the parent compound helenalin (Beekman et al. 1997). Reduction of both Michael acceptors abolishes the biological activities of helenalin. These data suggested that the electrophilic α, β-unsaturated carbonyl groups of helenalin are the pharmacophores contributing to its anti-inflammatory and anti-cancer effects.