Phytochemical investigations of Polygoni avicularis herba. Quantification of phenolic compounds with UHPLC-CAD method

Polygonum aviculare L. also known as common knotgrass is an annual weed spread all over the world in the temperate regions. Recent studies showed that flavonol glucuronides are major constituents of this medicinal plant material. There is no comprehensive analytical procedure for the standardization of Polygoni avicularis herba available on the European market.

The aim of study was to develop a method for the proper standardization of Polygoni avicularis herba and to evaluate variability in chemical composition among commercial samples and samples from wild harvesting defined as Polygonum aviculare s.l.

A UHPLC-ESI(+)-MS method using Kinetex XB-C18 column was developed for the qualitative screening of nine independent samples of Polygonum aviculare herb. The UHPLC-CAD method was developed and validated for the quantification of the major compounds in water extract using quercetin-3-O-glucuronide as a standard.

Twenty-five major constituents, mostly flavonoids, were detected and characterized. Among them three new natural products were tentatively identified as myricetin-3-O-(2''- or 3''-O-acetyl-glucuronide), mearsetin-3-O-(2''- or 3''-O-acetyl-glucuronide) and kaempferide-3-O-(2'' or 3''-O-acetyl-glucuronide). Twelve compounds were quantified using a developed UHPLC-CAD method. In all nine samples flavonol glucuronides were confirmed as major constituents. The total flavonoid content was estimated for all samples and varied from 0.70 to 2.20%.

The developed procedure may be used for the standardization of common knotgrass. The results indicate that the method described in the pharmacopoeial monograph used for the authentication and standardization of Polygonum aviculare herb should be improved.

Acknowledgements: The project was financially supported by Polish Ministry of Science and Higher Education by the research grant Iuventus Plus – 9006/IP1/2014/72.