4-Hydroxycinnamic acid derivatives,including ferulic acid (FA) (1),sinapic acid (SA) (2) and caffeic acid (CA) (3),are widely distributed in the plant kingdom,and undergo oxidative cross-coupling leading to the corresponding dehydrodimers,trimers and even higher oligomers in plants. In order to evaluate the antioxidative ability of these 4-hydroxycinnamic acid derivatives and their oligomers,we synthesized 8-8'-bis-lactone-dimers (8-8'-DiFA (4),8-8'-DiSA (5) and 8-8'-DiCA (6)),as well as a new trimer (7),by the reaction of the corresponding monomers (1-3) with Ag2O in methanol,and assayed their free radical-scavenging activity by the reaction with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·). It was found that CA (3) and 8-8'-DiCA (6) bearing o-dihydroxyl groups exhibited significantly higher radical-scavenging activity than those bearing no such groups,and oxidative coupling of CA (3) resulted in remarkable enhancement in the activity.
JIN XiaoLing YANG RuTing SHANG YaJing DAI Fang QIAN YiPing CHENG LiXia ZHOU Bo LIU ZhongLi
