Phenolic profile of Cynara scolymus L. and Silybum marianum (L.) Gaertn. aqueous and hydromethanolic extracts
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The flowers and leaves of Cynara scolymus L. (artichoke) and the leaves of Silybum marianum (L.) Gaertn. (milk thistle), medicinal plants native to the Mediterranean Basin, are used in the treatment of liver, spleen, and gallbladder disorders[1], and for their cholagogue, choleretic, and choliokinetic actions, as also for the treatment of dyspepsia and as anti-diabetics[2], respectively. The beneficial properties of medicinal plants are often ascribed to their phenolic composition, among a large diversity of phytochemicals. Thereby, the aim of
the present study was to obtain and compare the phenolic profiles of artichoke and milk thistle aqueous and hydromethanolic (80% ethanol, v/v) extracts, using HPLC-DAD-ESI/MS. The aqueous extract of artichoke presented a higher concentration of phenolic compounds than the hydromethanolic extract, with slight differences between the respective profiles; the major flavonoid found in the aqueous and hydromethanolic extract was luteolin-7-O-glucuronide, followed by luteolin-7-O-glucoside. Monocaffeoylquinic acid derivatives were only present in the hydromethanolic extract, being 5-O-caffeoylquinic acid the most abundant one, while dicaffeoylquinic acid derivatives were mostly identified in the aqueous extract; 1,3-O-dicaffeoylquinic acid was the most abundant one in both extracts.
Regarding milk thistle preparations, similar profiles were observed, with only quantitative differences between them. The aqueous extract revealed a higher phenolic compounds concentration than the hydromethanolic extract, with apigenin-7-O-glucuronide as the major compound quantified in both preparations. Total flavonoids were higher in the aqueous extract, with apigenin-7-O-glucuronide, luteolin-7-O-glucuronide, and apigenin-O-deoxyhexosyl-glucuronide as the main constituents. The phenolic acids found in the hydromethanolic extract included 5-O-caffeolyquinic and protocatechuic acids. Besides these phenolic acids, the hydromethanolic extract also revealed high levels of luteolin-7-O-glucuronide. Overall, the aqueous extracts presented higher phenolic contents than the hydromethanolic extracts in both plants, which could be related with the heat treatment to which infusions were subjected.
