title: Suppressive Effects of Edible Thai Plants on Superoxide and Nitric Oxide Generation.
abstract: We screened ethanol extracts from a total of 134 species of edible Thai plants for their suppressive effects on superoxide (O2(-)) generation using a xanthine (XA)-xanthine oxidase (XOD) assay system. When the extracts were tested at a concentration of 500 &mgr;/g/ml, 28.4% significantly suppressed O2(-) generation. Of these active extracts, it was found that in 17.9% of cases the action was due to XOD inhibition, in 1.5% due to O2(-) scavenging activity, and in 9% due to both XOD inhibition and O2(-) scavenging. In addition, some plant extracts (25 species) which had been known to possibly possess anti-tumor promoting activity were tested for O2(-) and NO generation in cellular systems. In this test, 13 species exhibited strong inhibitory activity toward both O2(-) and NO generation. From the fruit pods of Oroxylum indicum (Bignoniaceae), a traditional vegetable in Thailand, two flavones, oroxylin A and chrysin, and a triterpene carboxylic acid, ursolic acid (UA), were identified as inhibitors of O2(-) generation in XA/XOD system. These compounds also showed marked inhibitory effects on the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced O2(-) generation in dimethylsulfoxide (DMSO)-differentiated HL-60 cells. Our results suggest that, as we have reported earlier, edible Thai plants are promising sources of antioxidants with chemopreventive potential.
authors.affiliation: Central Laboratory and Greenhouse Complex, Kasetsart University, Kamphaeng Saen, Nakhon Pathom 73140, Thailand. rdiswj@nontri.ku.ac.th
authors.forename: Suratwadee
authors.initials: S
authors.lastname: Jiwajinda
authors.forename: Vilai
authors.initials: V
authors.lastname: Santisopasri
authors.forename: Akira
authors.initials: A
authors.lastname: Murakami
authors.forename: Oe-Kyung
authors.initials: OK
authors.lastname: Kim
authors.forename: Ha Won
authors.initials: HW
authors.lastname: Kim
authors.forename: Hajime
authors.initials: H
authors.lastname: Ohigashi