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. D ON . (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 1 H‐ and 13 C‐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.