Identification of bioactivity markers of Sorbus domestica leaves in chromatographic, spectroscopic and biological capacity tests: Application for the quality control

Abstract

This work is aimed at establishing analytical and bioactivity markers for the quality control of polyphenol-rich extracts of Sorbus domestica leaves – an antioxidant and anti-inflammatory agent. The potential marker analytes, representative of the main groups of S. domestica polyphenols, were pre-selected by LC–MS/MS analysis of the methanol-water (7:3, v/v) leaf extract (MED). For structural identification, two of them (rare flavonoids) were isolated from MED by preparative HPLC and analysed by 1D and 2D NMR (COSY, HMBC, HMQC) spectroscopy. The in vitro tests revealed that all analytes increase the non-enzymatic antioxidant capacity of plasma, effectively protect human plasma components against oxidative/nitrative damage induced by peroxynitrite (reduce the levels of thiobarbituric acid-reactive substances and 3-nitrotyrosine), and inhibit lipoxygenase and hyaluronidase. Considering the activity parameters and concentration levels, the highest contribution (70–80%) to the activity of the total phenolic fraction of MED was attributed to flavanols represented by (–)-epicatechin, procyanidin B2 and procyanidin C1. However, taking into account the observed synergistic effects, flavonoid and phenolic acid fractions (represented by chlorogenic acid, quercitrin, rutin, quercetin and its 3-O-(2′'-O-β-d-glucopyranosyl)-α-l-rhamnopyranoside and 3-O-(2′'-O-β-d-xylopyranosyl)-α-l-rhamnopyranoside) had also a substantial impact. All nine markers were thus applied as calibration standards, and a simple, accurate, reproducible and fully validated RP-HPLC-PDA method for the standardisation of the target extracts was proposed.