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 (1H-1H COSY, HMQC, HMBC and NOESY) and NOEDS (NOE difference spectra) as 1beta-O-beta-D-glucopyranosyl-5alpha,6beta H-eudesma-3-en-12,6alpha-olide (1), 1beta-O-beta-D-glucopyranosyl-15-O-( p-hydroxyphenylacetyl)-5alpha,6beta H-eudesma-3,11(13)-dien-12,6alpha-olide (2), 1beta-O-beta-D-glucopyranosyl-(6'-O-p-hydroxyphenyl acetate)-15-O-(p-hydroxyphenylacetyl)-5alpha,6beta H-eudesma-3,11(13)-dien-12,6alpha-olide (3) and 1beta-hydroxy-15-O-(p-methoxyphenylacetyl)-5alpha,6beta H-eudesma-3,11(13)-dien-12,6alpha-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 microM and those for 3 were 74.1, 117.3 and 135.0 microM, respectively. The structure-activity relationship is discussed.