Norfriedelins A–C with Acetylcholinesterase Inhibitory Activity from Acerola Tree (Malpighia emarginata).

Three novel norfriedelanes, A–C (1–3), were isolated from the branches and roots of Malpighia emarginata. Their structures and absolute configurations were determined by 1D and 2D NMR techniques and X-ray crystallographic analysis. Norfriedelin A (possessing an α-oxo-β-lactone group) and norfriedelin B (with a keto-lactone group) showed acetylcholinesterase inhibitory effects with the IC50values of 10.3 and 28.7 μM, respectively. [ABSTRACT FROM AUTHOR]