Novel tetranortriterpenoid derivatives from Munronia henryi

Six novel tetranortriterpenoid derivatives were isolated from the methanolic extract of the whole bodies of Munronia henryi, namely, munronins A–F (). In compounds (), the side chains are rare in tetranortriterpenoids. Their structures were established by extensive NMR experiments. Based on the diversity of the side chains, possible biodegradations for the side chains of compounds from euphane or tirucallane skeleton are proposed. Munronins A–E exhibited moderate antifeeding activity against Pieris brassicae L, while munronin F showed negative activity.