Structure elucidation and hepatotoxicity evaluation against HepG2 human cells of neo-clerodane diterpenes from Teucrium polium L

Seven neo-clerodanes (teupolins VI–XII) and eleven known compounds were isolated and characterized from leaf extracts of Teucrium polium L., a medicinal plant used in traditional and herbal medicine for its hypolipidemic, hypoglycemic, antioxidant and antiproliferative properties. The structures of these compounds were elucidated by 1D (¹H, ¹³C and DEPT) and 2D (COSY, TOCSY, HSQC, HMBC) NMR experiments and by mass spectrometry analysis. The complete stereostructure of each compound was defined with a NOESY experiment. Because the overexploitation of herbal remedies containing T. polium extracts has resulted in several cases of hepatitis, the hepatotoxic activity of pure metabolites against the human hepatoblastoma cancer cell line HepG2 was assessed by the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) test. All of the compounds showed low toxicity values at the highest concentration tested (200 μM).