State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, PR China; Yunnan Key Laboratory of Natural Medicinal Chemistry, Kunming 650201, PR China. Electronic address: [Email]
A new flavoalkaloid racemate, leucoflavonine (1), together with its flavonoid precursor pectolinarigenin (2), was isolated from the leaves of Leucosceptrum canum collected from Tibet. Its structure was established by comprehensive spectroscopic analysis. Chrial separation of the enantiomers of 1 was achieved, and their absolute configurations were determined as S-(+)- and R-(-)-leucoflavonines ((+)-1a and (-)-1b) by comparison of their computational and experimental optical rotations. Biological assays indicated that both (+)-1a and (-)-1b exhibited inhibitory activity against acetylchlorinesterase (AChE) in vitro (IC50 = 68.0 ± 8.6 and 18.3 ± 1.8 μM, respectively). Moreover, (-)-1b displayed cytotoxicity against human hepatoma cells HepG2 (IC50 = 52.9 ± 3.6 μM), and inhibited the production of interleukelin-2 (IL-2) in Jurkat cells (IC50 = 16.5 ± 0.9 μM), while (+)-1a showed no obvious activity in these assays.