LC-MS analysis of phenolic compounds and oleraceins in aerial parts of Portulaca oleracea L.

Abstract

Portulaca oleracea L. (purslane) is a well-known edible and ethnomedicinal plant and it has been called “vegetable for long life” in the Chinese herbal medicine. The plant is recognized for the high content of polyphenols, including flavonoids and phenolic acids.
In this study, hydromethanolic purslane extracts from Bulgarian and Greek locations were screened for polyphenolic content. Based on polyphenols, saponins and DPPH antioxidant activity, an orthogonal
design L9(3⁴) was performed in order to improve the ultrasound assisted extraction procedure of dry and fresh plant material. An UHPLC-Orbitrap-MS method in parallel-reaction monitoring mode was developed for the simultaneous identification and quantification of 14 compounds comprising hydroxybenzoic, hydroxycinnamic and caffeoylquinic acids, as well as 2 flavonol glycosides. The quantitative analysis was validated for curve fit, range, instrumental detection limit (IDL), instrumental quantification limit (IQL), LOD, LOQ, precision, recovery and accuracy. The UHPLC-MS quantification method revealed good linearity (r² > 0.9950), LOD < 925.85 ng/g dw and LOQ < 3055.31 ng/g dw. Moreover, 11 cylco-dopa amides (Oleraceins A-D, N-Q, S, U and W) were tentatively identified through UHPLC-MS and their MS² mass fragmentation was described.