The in vitro and in vivo safety of norartocarpetin. Cell viability of norartocarpetin in B16F10 (A) and human dermal fibroblast cells (B) and skin irritation of norartocarpetin in nude mice (C). Data are expressed as mean ± SD of 3 independent experiments. The different superscript letters indicate significant difference at p < 0.05 as analyzed by Student’s t test. *Significantly different from control. Scoring system of Draize test: (0): no erythema or no edema, (1): very slight erythema or edema, (2) well-defined erythema or edema, (3): moderate erythema or edema, (4): severe erythema or edema.