Phytochemical study of Rourea minor stems and the analysis of therein contained Bergenin and Catechin derivatives by capillary electrophoresis

Abstract

A detailed phytochemical investigation of Rourea minor, a climbing shrub with medicinal relevance in South-Eastern Asia, resulted in the isolation of 23 compounds from the methanolic stem extract. All of them were found for the first time in this species, however two constituents (lethedocin 3′-O-β-D-glucopyranoside and 3-O-(6′-O-vanilloyl)-β-D-glucopyranosyl 4-hydroxyphenethyl alcohol) represented overall new natural products. The majority of the known constituents were phenolic compounds (derivatives of bergenin, catechin, and lignans) and fatty acids; extensive NMR and MS studies permitted their structural elucidation. In order to characterize the extract analytically, a CE method was developed using seven standards (three bergenin and four catechin derivatives). The optimum buffer showed to be a 30 mM borax solution with pH 10.5, and together with an applied voltage and temperature of 25 KV and 30 °C all compounds could be baseline resolved within 11 min. Method validation confirmed that the assay is linear (R2 = 0.999), accurate (recovery rates from 97.1 to 103.1%), precise (inter-day variation ≤2.8%), and repeatable (σrel ≤ 3.8%); LOD values varied from 2.0 to 6.2 μg/mL. The analysis of plant material showed that bergenin (0.12%) was the most abundant of the quantified compounds.