Undescribed 2-quinolines, onanaenine A and B, from Cameroonian Vepris onanae (Rutaceae)

Abstract

Leaves of herbarium specimen material of Vepris onanae, collected in Cameroon, have yielded two undescribed 2-quinolines, onanaenine A (1) and onanaenine B (2), alongside the known 6,7-dimethoxy-N-methylflindersine (3), evoxanthine (4), 6-methoxy-tecleanthine (5) and polybotrin. Compounds 1 and 2 were not cytotoxic against FM55 melanoma cells at a concentration up to 200 µM, and they did not show signs of stimulating fibroblast skin cells at concentrations, up to 20 µM. Vepris onanae, the source of the two new 2-quinoline alkaloids, is at high risk of extinction, being near-endemic to the threatened Bali-Ngemba forest of NW Region Cameroon. Bali Ngemba has already seen the global extinction of Vepris bali, before it could be researched for new compounds.