New sesquiterpenes from Sonchus transcaspicus

Four new eudesmanolides were isolated from the whole plant of Sonchus transcaspicus and their structures were elucidated by means of spectroscopic methods, including 2D-NMR (H-1-H-1 COSY, HMQC, HM13C and NOESY) and NOEDS (NOE difference spectra) as 1 beta-O-beta-D-glucopyranosyl-5 alpha,6 beta H-eudesma-3-en-12,6 alpha-olide (1), 1 beta-0-beta-D-glucopyranosyl-15-O-(p-hydroxyphenylacetyl)-5 alpha,6 beta H-eudesma-3,11(13)-dien-12,6 alpha-olide (2), 1 beta-O-beta-D-glucopyranosyl-(6'-O-p-hydroxyphenyl acetate)-15-O-(phydroxyphenylacetyl)-5 alpha,6 beta H-eudesma-3,11(13)-dien-12,6 alpha-olide (3) and 1 beta-hydroxy-15-O-(p-methoxyphenylacetyl)-5 alpha,6 beta H-eudesma-3,11(13)-dien-12,6 alpha-olide (4). Compounds 1, 2 and 3 showed antibacterial activity against Escherichia coli and Staphylococcus aureus cells. Compounds 2 and 3 were evaluated for their in vitro cytotoxic activity against cultured SMMC-7721 (human hepatoma), HELA (human cervical carcinoma) and B-16 (murine melanoma) cells. The IC50 values for 2 were 108.0,161.1 and 203.0 mu M and those for 3 were 74.1, 117.3 and 135.0 mu M, respectively. The structure-activity relationship is discussed.