Rubescins A, B and C: New Havanensin Type Limonoids from Root Bark of Trichilia rubescens (Meliaceae)

Abstract

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 H₂O₂. 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).