Twelve compounds (1-12), kaempferol (1), luteolin (2), luteolin 4'-O-β-xyloside (3), luteolin 4'-O-β-glucoside (4), quercetin 4'-O-β-xyloside (5), kaempferol-3-O-[6″-O-(E)-p-coumaroyl]-β-D-glucoside (trans-tiliroside) (6), protocatechuic acid (7), gallic acid (8), methyl gallate (9), ethyl gallate (10), shikimic acid-3-O-gallate (11), and 3,3',4'-tri-O-methyl-ellagic acid 4-sulfate (12), were isolated and identified from the aerial parts of Helianthemum cinereum (Cav.) Pers (synonym: Helianthemum rubellum C. Presl. All compounds were isolated by applying different chromatographic procedures, such as silica gel, RP-18 and Sephadex LH-20 columns. The structures were elucidated by extensive spectroscopic methods, mainly nuclear magnetic resonance NMR 1D and 2D, and mass spectrometry, as well as by comparison with the reported spectroscopic data. The two organic extracts, ethyl acetate (EtOAc) and butanol (BuOH), were evaluated for their potent phenolic and flavonoid contents using the Folin-Ciocalteu and aluminum chloride colorimetric methods. Furthermore, the antioxidant activity of the two extracts was determined using the DPPH, FRAP, and ABTS methods. Pure trans-tiliroside (6), the main isolated compound, and luteolin 4'-O-β-xyloside (3) were evaluated for their antitumor activity against the lung cancer (A549), melanoma (A375) and pancreatic cancer (Mia PaCa-2 and Panc-1) cell lines by MTT assay.
Keywords: Cistaceae; Helianthemum; NMR; antioxidant activity; antitumor activity; flavonoids.