Surface flavonoids in Catalpa ovata, Greyia sutherlandii and Paulownia tomentosa

Abstract

Exudate flavonoids have been found on the green fruits of Catalpa ovata (Bignoniaceae) and Paulownia tomentosa (Scrophulariaceae) and on the leaf surfaces of Greyia sutherlandii (Melianthaceae) and Paulownia tomentosa, respectively. The flavonoid aglycones are mostly flavone and flavonol methyl ethers, including some rare natural products. Several flavanones and 2 dihydrochalcones have also been detected, the flavanones produced by Paulownia being geranylated products. The occurrence of exudate flavonoids on fruit tissue has been rarely noticed in the past.