Phytochemistry, micromorphology and bioactivities of Ajuga chamaepitys (L.) Schreb. (Lamiaceae, Ajugoideae): Two new harpagide derivatives and an unusual iridoid glycosides pattern

Ajuga chamaepitys (L.) Schreb, well-known as Ground Pine, is an annual herb typical of the Mediterranean area accounting several uses in the traditional medicine. In this work we have, analyzed the plant iridoid fraction together with the essential oil composition and study of the plant indumentum. Finally, we assayed the polar extracts and essential oil obtained from the aerial parts for antioxidant activity and cytotoxicity on tumor cells. The analysis of the monoterpene glycosides allowed us to isolate from roots and aerial parts and to structurally elucidate by NMR and MS the following compounds: ajugoside (1), reptoside (2), 8-O-acetylharpagide (3), harpagide (4), 5-O-β-D-glucopyranosyl-harpagide (5), asperulosidic acid (6), deacetyl asperulosidic acid (7) and 5-O-β-D-glucopyranosyl-8-O-acetylharpagide (8), among which 5 and 8 were two new natural products. Chemotaxomic relevance of these constituents was discussed. The chemical analysis of A. chamaepitys essential oil by GC-FID and GC-MS showed ethyl linoleate (13.7%), germacrene D (13.4%), kaurene (8.4%), β-pinene (6.8%), and (E)-phytol (5.3%) as the major volatile components. The micro morphological and histochemical study showed that iridoids and essential oil are mainly produced in the type III capitates and peltate trichomes of leaves and flowers. Biological evaluations of A. chamaepitys polar extracts and essential oil showed that the former were more potent as radical scavengers than the latter. MTT assay revealed that essential oil and ethanol extracts were moderately cytotoxic on tumor cells with IC50 of 36.88 and 59.24 μg/mL on MDA-MB 231 cell line, respectively, and IC50 of 60.48 and 64.12 μg/mL on HCT116, respectively.