Metabolic transformation and attenuation characteristics of endogenous alkaloid toxic components of Tibetan medicinal herbs:a review / 中国药理学与毒理学杂志

ABSTRACT

The active ingredients in some Tibetan medicinal herbs are toxic components as well,and we need to have a clear understanding of their mechanism and metabolic pathways in use. The endogenous toxic components of highly toxic Tibetan herbal medicines are mainly alkaloids, such as aconitum alkaloids, methyllycaconitine, tropane alkaloids, brucine, strychnine, papaverine and swainso-nine. The majority of endogenous toxic alkaloids in Tibetan medicine herbs exist in roots, fruits and seeds of plants, exerting neurotoxicity or cardiotoxicity as highly toxic inherent chemicals. Most alka-loids are metabolized in phaseⅠvia de-alkylation, hydroxylation, hydrolysis and other reactions, as well as in phaseⅡvia glucuronic acid and sulfonic acid conjugation. They form various metabolites with high polarities and reduced toxicities so as to be easily excreted. The closeness between the therapeutic dose and toxic dose of alkaloids components in Tibetan medicinal herbs leads to their attenuated prep-aration via frying, dairy, highland barley wine soaking, or in combination with Terminalia Chebula to decrease toxicity, as is cited classic books on in Tebitan medicine. Focused on twelve alkaloids of five classes including aconitine, tropane and brucine, we have reviewed the characteristics of their metabo-lism and transformation, as well as their toxicity attenuation and safety evaluation.