Algerian mint species: high performance thin layer chromatography quantitative determination of rosmarinic acid and in vitro inhibitory effects on linoleic acid peroxidation

Objective: To determine the quantitative parameters of rosmarinic acid in Algerian mints, Mentha spicata L. (M. spicata), Mentha pulegium L. and Mentha rotundifolia (L.) Huds by high performance thin-layer chromatography (HPTLC)-densitometric method and screen the effects of these plant extracts on linoleic acid peroxidation. Methods: The analyses were performed on HPTLC silica gel 60 F254 plates with chloroform: acetone : formic acid (75:16.5:8.5, v/v) as the mobile phase. Rosmarinic acid was determined in UV at 365 nm and fluorescence at exc 325 nm with a 550 nm filter, respectively. The effects of plant extracts on linoleic acid peroxidation were measured by an indirect in vitro colorimetric method.
Results: Chromatographic resolution permitted reliable quantification in both measurement modes and calibration curves were linear in a range of 150 - 1000 ng/spot. Mentha spicata L was found to contain significantly higher concentrations of RA. The densitometric quantification allowed the analysis of many samples in a short time with reasonable precision (total precision for Mentha spp extracts, 5.1 and 5.8 % for UV and fluorescence detection, respectively). The HPTLC data, allied to assays of linoleic acid peroxidation prevention, suggested the potential of M. spicata (52% Trolox® equivalents) as a natural source for inhibitors of lipid peroxidation. Conclusions: Densitometry can be used for routine determination and quality control of rosmarinic acid in herbal and formulations containing Mentha species.