Antioxidative flavanone glycosides from the branches and leaves of Viscum coloratum

Two new flavanone glucosides, (2S)-homoeriodictyol 7,4'-di-O-beta-D-glucopyranoside (4) and (2R)-eriodictyol 7,4'-di-O-beta-D-glucopyranoside (5) were isolated from the branches and leaves of Viscum coloratum (KOMAR) NAKAI (Loranthaceae), along with three known flavanone glucosides: (2S)-homoeriodictyol 7-O-beta-D-glucopyranoside (1), (2S)-eriodictyol 7-O-beta-D-glucopyranoside (2), and (2S)-naringenin 7-O-beta-D-glucopyranoside (3). The structures of these compounds were elucidated using spectroscopic methods. The antioxidant activities of these isolated compounds were evaluated by colorimetric methods based on their scavenging effects on hydroxyl radicals and superoxide anion radicals, respectively. All the compounds showed potent albeit varied degrees of antioxidative activities and the structure-activity relationship is discussed.