Antioxidant efficacy of Kalanchoe daigremontiana bufadienolide-rich fraction in blood plasma in vitro.

Context:The main source of bufadienolides is toad venom; however, plants such as members ofKalanchoeAdans. (Crassulaceae) genus may also synthesize these bioactive substances. Objective:This is the first study on antioxidant effects and cytotoxicity of bufadienolide-rich fraction isolated fromKalanchoe daigremontianaRaym.-Hamet & H. Perrier. Materials and methods:The methanolic fraction was extracted from the plant roots and contained 0.48 mg bufadienolides/mg of dry mass (11α,19-dihydroksytelocinobufagin, bersaldegenin-1-acetate, bersaldegenin-1,3,5-orthoacetate, 19-(acetyloxy)-3β,5β,11α,14-tetrahydroxyl-12-oxo-bufa-20,22-dienolide and 19-(acetyloxy)-1β,3β,5β,14-tetrahydroxyl-bufa-20,22-dienolide, mainly). The cytotoxicity ofK. daigremontianafraction was evaluated in anin vitroexperimental model of blood platelets. The viability of blood platelets was determined on the basis of a release of lactate dehydrogenase. Results:The fraction scavenged DPPH•radicals, with EC50of 21.80 μg/mL. Studies on an experimental model of blood plasma under peroxynitrite-induced oxidative stress revealed that the plant preparation had moderate antioxidant properties. Levels of 3-nitrotyrosine and thiol groups indicated that the protective effect ofK. daigremontianawas significant mainly for its concentration of 50 μg/mL. No effect was found in prevention of oxidation of low-molecular plasma thiols (glutathione, cysteine and cysteinylglycine). Simultaneously, measurements of lipid hydroperoxides and thiobarbituric acid-reactive substances (TBARS) indicated that the examined fraction might be effective antioxidant at broader concentration range, that is 1–5 and 25–50 μg/mL for hydroperoxides and TBARS generation, respectively. No cytotoxicity was observed at the concentration range of 1–50 μg/mL. Conclusions:Based on the obtained results, we suggest that antioxidant activity may additionally contribute to beneficial properties ofK. daigremontiana-derived extracts. [ABSTRACT FROM AUTHOR]