Revision of the NMR Assignments of Pterostilbene and of Dihydrodehydrodiconieferyl alcohol: Cytotoxic Constituents fromAnogeissus acuminata

Abstract
Further phytochemical work on Anogeissus acuminata var. lanceolata (Combretaceae) led to the isolation of pterostilbene (1), dihydrodehydrodiconiferyl alcohol (2), and conocarpan (3). The structure of these compounds were determined by spectroscopic means, mainly through 1D and 2D NMR experiments. A revision of some of the 13C NMR chemical shifts of 1 and 2 were made possible by HETCOR, FLOCK, and selective INEPT experiments. Homonuclear spin-decoupling and 1H-1H COSY experiments also enabled the precise assignment of the 1H NMR chemical shifts of 2. Compounds 1–3 exhibited in vitro cytotoxicity in various cancer cell lines. This is the first isolation of 1–3 from Anogeissus.