Three New Flavonoids from the Root of Tephrosia emoroides and their Antifeedant Activity against the Larvae of the Spotted Stalk Borer Chilo partellus Swinhoe

Abstract

Three new and two previously known flavonoids were isolated and identified from the roots o/Tephrosia emoroides A. Rich. The new flavonoids included the flavanone 4″,5″-dihydro-5-methoxy-5″-isopropenylfurano-[2″,3″:7,8]-flavanone, the flavone 7-hydroxy-5-methoxy-8-(3″-hydroxy)-isopent-1-eneflavone and the pterocarpan 4′, S'-dihydro-5′-isopropenyl-8, 9-methylenedioxyfurano-[2′,3′:2,3]-pterocarpan. The three new compounds were named emoroidenone, emoroidone, and emoroidocarpan, respectively. The previously known flavonoids that were isolated were the flavanone, 5-methoxyisolonchocarpin and the flavene, hildegardtene. The flavonoids were tested for antifeedant activity against the larvae of Chilo partellus Swinhoe using the maize leaf disc bioassay. The flavanone emoroidenone showed strong feeding deterrent activity against C. partellus larvae with a mean percentage deterrence of 66.1% at a dose of 100 μg/disc. The other flavonoids showed little or no feeding deterrent activity against C. partellus larvae.