No animal studies have been designed to assess toxicity or LD50 (median lethal dose) values for corosolic acid or banaba extracts. No adverse effects have been observed or reported in animal studies or controlled human clinical trials , however information about toxicity in human subjects is lacking.
Various commercially available formulations are available including softgels, tablets, capsules, powders and cosmetics. Banaba (Lagerstroemia speciosa) leaf extracts usually contain from 1 to 18% of corosolic acid. It appears that corosolic acid is better absorbed in oil-based soft gelatin formulation compared to dry powder . Typical recommended dose (by manufacturers) is 1 capsule 20 to 30 minutes with or before morning and evening meals (some times even 3 times daily). Effects of corosolic acid are dose-dependent [2,3], however more human studies assessing proper dose are warranted.