Phenolic acid derivatives from Bauhinia glauca subsp. pernervosa

To study the chemical constituents of Bauhinia glauca subsp. pernervosa, eleven phenolic acids were isolated from a 95% ethanol extract by using a combination of various chromatographic techniques including column chromatography over silica gel, ODS, MCI, Sephadex LH-20, and semi-preparative HPLC.  By spectroscopic techniques including ¹H NMR, ¹³C NMR, 2D NMR, and HR-ESI-MS, these compounds were identified as isopropyl O-β-(6'-O-galloyl)-glucopyranoside (1), ethyl O-β-(6'-O-galloyl)-glucopyranoside (2), 3, 4, 5-trimethoxyphenyl-(6'-O-galloyl)-O-β-D-glucopyranoside (3), 3, 4, 5-trimethoxyphenyl-β-D-glucopyranoside (4), gallic acid (5), methyl gallate (6), ethyl gallate (7), protocatechuic acid (8), 3, 5-dimethoxy-4-hydroxybenzoic acid (9), erigeside C (10) and glucosyringic acid (11).  Among them, compound 1 is a new polyhydroxyl compound; compounds 2, 10, and 11 were isolated from the genus Bauhinia for the first time, and the other compounds were isolated from the plant for the first time.  Compounds 6 and 8 showed signi?cant protein tyrosine phosphatase1B (PTP1B) inhibitory activity in vitro with the IC₅₀ values of 72.3 and 54.1 mmol·L⁻¹, respectively.