Paviosides A-H, eight new oleane type saponins from Aesculus pavia with cytotoxic activity

A phytochemical analysis of Aesculus pavia has led to the isolation of eight novel triterpenoid saponins, based on oleane type skeleton and named paviosides A-H (1a, 1b-4a, 4b). On the basis of chemical, and 2D NMR and mass spectrometry data, the structures of the new compounds were elucidated as 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-d-glucopyranosyl (1 -> 4)]-?-D-glucopyranosiduronic acid 21-tigloyl-22-acetyl barringtogenol C (1a), 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-D-glucopyranosyl (1 -> 4)]-?-D-glucopyranosiduronic acid 21-angeloyl-22-acetyl barringtogenol C (1b), 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-D-galactopyranosyl (1 -> 4)]-?-D-glucopyranosiduronic acid 21-tigloyl-22-acetyl barringtogenol C (2a), 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-D-galactopyranosyl (1 -> 4)]-?-D-glucopyranosiduronic acid 21-angeloyl-22-acetyl barringtogenol C (2b), 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-D-xylopyranosyl (1 -> 4)]-?-D-glucopyranosiduronic acid 21-tigloyl-22-acetyl barringtogenol C (3a), 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-D-xylopyranosyl (1 -> 4)]-?-d-glucopyranosiduronic acid 21-angeloyl-22-acetyl barringtogenol C (3b), 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-D-xylopyranosyl (1 -> 4)]-?-D-glucopyranosiduronic acid 21-tigloyl-22-acetyl protoaescigenin (4a), and 3-O-[?-D-xylopyranosyl (1 -> 2)] [-?-D-xylopyranosyl (1 -> 4)]-?-D-glucopyranosiduronic acid 21-angeloyl-22-acetyl protoaescigenin (4b). The compounds showed cytotoxic activity on J-774, murine monocyte/macrophage, and WEHI-164, murine fibrosarcoma, cell lines. Among them, paviosides E-H (3a, 3b and 4a, 4b) showed higher activity with values ranging from 2.1 to 3.6 ?g/mL. Structure-activity relationship studies indicated the positive effect on the activity of xylose unit in the place of glucose, while a little detrimental effect is observed when glucose is substituted by galactose. The aglycone structure and the presence of a tigloyl or an angeloyl group at C-21 do not affect significantly the inhibitory activity on both tested cell lines.