Seco-neferine A-F, three new pairs of benzyltetrahydroisoquinoline alkaloid epimers from Plumula Nelumbinis and their activity

Abstract

Three new pairs of benzyltetrahydroisoquinoline (BIQ) alkaloid epimers, Seco-neferine A-F (1-6), were isolated from an EtOH extract of Plumula Nelumbinis. The structures of these compounds were identified by a combination of NMR, HR-ESI-MS, circular dichroism, UV spectroscopic analyses and specific rotations. The structure of compounds 1-6 possesses high similarity with neferine, because these three pairs of epimers have the same skeleton as neferine. Compounds 1,2 and 5,6 are open-loop compounds of position 1' and 1 of neferine respectively. The H connects with position 2' N of compounds 1,2 is replaced by methyl, forming the structure of compounds 3,4. Moreover, six compounds were tested for cytotoxicity against MDA-MB-231 breast cancer cell. Compound 6 displayed moderate inhibitory effects on breast cancer with IC₅₀ of 38.96 μM, while compounds 2,3,4 show certain inhibitory effects.

Keywords: Benzyltetrahydroisoquinoline; Cytotoxicity; Plumula Nelumbinis; Seco-neferine.