Hen-Sik Koh

C-glycosylflavones from Oryza sativa

Abstract Eight flavone C-glycosides isolated from rice plant were found to act as probing stimulants for planthoppers. They have been identified as the known compounds schaftoside, neoschaftoside, carlinoside, isoorientin 2″-glucoside and the new constituents neocarlinoside (6-C-β- D -glucopyranosyl-8-C-β- L -arabinopyranosylluteolin), isoscoparin 2″-glucoside (chrysoeriol 6-C-β- D -(2-O-β- D -glucopyranosyl)glucopyranoside) and its 6‴-p-coumaric and ferulic acid esters.

Isolation ofC-glycosylflavones as probing stimulant of planthoppers in rice plant

Three species of planthopper,Nilaparvata lugens,Sogatella furcifera, andLaodelphax striatellus, showed characteristic behavior of stylet probing in parenchymal tissues of plants. Feeding experiments of planthoppers on aqueous sucrose solution containing the extract of rice plants or barnyard grass revealed the presence of the stimulant for the probing behavior in the plant tissues. EightC-glycosylflavones which stimulated stylet probing were isolated from rice plants. Four of them were identified to be schaftoside, neoschaftoside, carlinoside, and neocarlinoside, the last one being a new compound isolated from the plant. The isolatedC-glycosylflavones showed the same level of the activity for the probing ofN. lugens as the rice plant extract only when all of them were combined.

Antifeedants of Indian Barnyard Millet, Echinochloa frumentacea Link, against Brown Planthopper, Nilaparvata lugens (Stål)

Eight compounds isolated from Indian barnyard millet have been identified as l-malic acid, trans-aconitic acid, (+)-isocitric acid, 5-O-caffeoylquinic acid, 4-O-caffeoylquinic acid, isocarlinoside, 2″-O-rhamnosylisoorientin, and 7-O-(2″-O-glucuronosyl)glucuronosyltricin, respectively. These compounds showed high antifeeding activity against brown planthopper only when they were combined.