Naucleactonin D, an Indole Alkaloid and other Chemical Constituents from Roots and Fruits of Mitragyna inermis

Phytochemical investigation of the roots and fruits of Mitragyna inermis (Rubiaceae) resulted in the isolation of a new indole alkaloid, named naucleactonin D (1), together with fourteen known compounds: nauclefiline (2), naucleficine (3), nauclefidine (4), angustoline (5), angustine (6), barbinervic acid (7), quinovic acid 3-O-alpha-L-rhamnopyranoside (8), betulinic acid (9), a mixture of ursolic (10) and oleanolic acid (11), a mixture of stigmasterol and beta-sitosterol, beta-sitosterol 3-O-beta-D-glucopyranoside, and strictosamide (12) as the major compound. The structures of the isolated compounds were elucidated by detailed spectroscopic analysis and by comparison with published data. No C-13 NMR data for 2 and 3 exist in the literature and compounds 2, 3, 5, 7, and 12 are reported for the first time from the genus Mitragyna. The crude extract and isolated compounds were tested in vitro for their preliminary cytotoxicity against brine shrimps (Artemia sauna).