Anti-inflammatory activity of a new triterpenoidal saponin from Crotalaria madurensis

The genus Crotalaria belonging to the family Leguminnosae. Several Crotalaria species have already been chemically studied and found to contain mainly flavonoids, chalcones and triterpenes. A new triterpene saponin, namely sophradiol 3-O-α-L-rhamnopyranosyl-(1'''→4'')-O-β-D-galactopyranosyl- (1''→6')-O-β-D-glucopyranoside (1) together with ten known constituents, have been isolated from the leaves of Crotalaria madurensis L. The structure of a new compound was established by chemical and physochemical analysis (UV, ESI-MS, ¹H-, ¹³C-NMR, ¹H-¹H COSY, HSQC and HMBC). The known compounds were identified as quercetin (2), isoquercetin (3), quercitrin (4), 8-hydroxy quercetin 3-O-β-D-arabinopyranoside (5), quercetin 3-O-neohespridoside (6), myo-inostol (7), sophradiol 3-O--β-D-glucuronopyranoside (8), 23-hydroxy-3α-[(O-α-L-rhamnopyranosyl-(1"→4')-O-α-L-arabinopyranosyl)-oxy]olean12-en-28-oic acid 3-O-α-L-rhamnopyranosyl-(1'''''→4'''')-O-β-D-glucopyranosyl-(1''''→6''')-O-β-D-glucopyranosyl ester (9), sophradiol 3-O-β-D-glucopyranosyl-(1''→4')-O-β-D-glucopyranoside (10), 23-hydroxy olean 12-en-28-oic acid 3-O-α-L-rhamnopyranosyl-(1''→6')-glucopyranoside (11). Moreover, as a conclusion for the biological study on male Swiss Albino mice (18 – 20 g), it was found that the new saponin (1) is non-toxic (LD₅₀ 1000 mg/kg b. wt.) and has a significant anti-inflammatory activity in comparison to indomethacine. A significant anti-inflammatory effect was concluded from the reduction recorded in granuloma diameter on treatment with (1) (18.2% & 19.9%) in comparison to indomethacine (32.1 & 35.5%) at 32 and 48 days after ova injection, respectively relative to control group. PGE₂ level in granuloma was also reduced after treatment with (1) (36.3 & 21.9%) with respect to that of indomethacine (44.6 & 32.6%) at 32 and 48 days after ova injection, respectively.