Iridoid Glucosides with Free Radical Scavenging Properties from Fagraea blumei

Four new iridoid glucosides 1 – 4 , named blumeosides A–D, were isolated from the methanolic stem-bark extract of Fagraea blumei G. DON . (Loganiaceae). They were accompanied by the benzyl-alcohol derivative di-O-methylcrenatin ( 5 ) and the flavone C-glucoside swertisin ( 6 ). The structures of 1 – 4 were established by spectroscopic methods, including FAB-MS, and ¹H- and ¹³C-NMR, and by alkaline hydrolysis. Blumeosides A ( 1 ) and C ( 3 ) are 10-O-(2,5-dihydroxytercphthalo) adoxosidic acid and 10-O-(2-hydroxyterephthalo)adoxosidic acid, respectively. In blumeosides B ( 4 ) and D ( 2 ), both carboxylic groups of the terephthalic-acid moiety are esterified by adoxosidic-acid units, Blumeosides A–D ( 1 – 4 ) inhibited bleaching of crocin induced by alkoxyl radicals. Blumeosides A ( 1 ) and D ( 2 ) also demonstrated scavenging properties towards the 2,2-diphenyl-1-picryl-hvdrazvl (CDPPH) radical in TLC autographic and spectrophotometric assays.