Rubescins A, B and C: New havanensin type limonoids from root bark of trichilia rubescens (meliaceae)

Three new limonoids, rubescins A-C (1-3), and three known compounds including, havanensin type limonoid TS3 (4), β-sitosterol, and stigmasterol were isolated from the root bark of Trichilia rubescens. Their structures were elucidated by means of extensive spectroscopic analyses, particularly one dimensional (1D)- and 2D-NMR techniques in conjunction with mass spectrometry. Rubescins A-C (1-3) and limonoid TS3 (4) were evaluated for their protective effects against oxidative stress induced in HC-04 cells by H2O 2. Compound (1) showed strong inhibitory effects on lactase dehydrogenase (LDH) leakage, being as active (IC50 value of 0.0026 μM) as the positive control quercetin (IC50 value of 0.0030 μM). © 2013 The Pharmaceutical Society of Japan.