Unprecedented triterpenes with anti-inflammatory activity from Limax maximus

Four triterpenes with the unprecedented pentacyclic skeletons were isolated from Limax maximus, the traditional medicine of the Zhuang ethnic group in Guangxi. Notably, compounds 1-4 were characterized by rare 7/6/5 tricyclic ring moiety linked to 6/5 bicyclic moiety via three carbon chain. The structures of compounds 1-4 were elucidated by comprehensive spectroscopic analysis. The absolute configurations of compounds 1-2 were determined by single-crystal X-ray diffraction analysis using Cu Kα radiation. Biogenetically, compound 1 could be derived from the tetraepoxysqualenes, via cyclisation and hydroxylation reactions. Bioactivity assay results showed that compound 4 significantly inhibited LPS-induced NO production in RAW 264.7 cells at 25 µM with inhibition of NO production by 47%.