Active ingredient of marking nut is ?

Ans. is 'a' i.e., Semecarpol Semicarpus anacardium or marking nut or bhilawan Its seed are hea shaped, conical and black with acrid oily juice which is brownish but turns black on exposure to air. Active principles are semecarpol and bhilawanol. Juice applied to skin produces irritation, painful blisters followed by itching and eczema. Therefore it is used to produce aificial bruises. It is also used by washerman to mark clothes.