In vivo and in vitro phototoxicity of different parts of Heracleum laciniatum.

Experimental phytophotodermatitis was produced using homogenates from different parts of Heracleum laciniatum and long-wave ultraviolet light. The homogenates of leaves and flowers produced strong phototoxic reactions, fruit slightly less. Stems were either non-phototoxic or only slightly phototoxic. The roots of young plants did not evoke photosensitivity reactions, whereas the roots of older plants were strongly phototoxic; even roots collected from the frozen ground in December elicited strong reactions. Abdominal and midback skin were more photosensitive than skin of the lateral aspects of the underarms and legs.