Comparative biochemistry of the flavonoids-VI. : Flavonoid patterns in the bignoniaceae and the gesneriaceae

Abstract

3-Desoxyanthocyanins which characterize the sub-family Gesneriodeae of the Gesneriaceae have been reported once in the closely related Bignoniaceae, in Arrabidaea. A search of sixteen representative species has now failed to reveal any further occurrences of these rare plant pigments in the Bignoniaceae. The common anthocyanin, cyanidin 3-rutinoside was found, instead, in Campsis radicans, Catalpa bignonoides, Eccremocarpus scaber, Incarvillea mairei and Tecoma garrocha petals. Orange and yellow petal colours in Anemopaegma chamberlaynii and Pyrostegia venusta were found to be due to carotenoids, not to 3-desoxyanthocyanins. An examination of the other flavonoids in leaf and petal of bignoniads showed that most species contained flavones rather than flavonols. A new pigment, 5,6,7,3′,4′-pentahydroxyflavone (6-hydroxyluteolin) was identified in fresh leaves of Catalpa bignonioides and C. speciosa and in herbarium material of C. bungei and Tecoma australis. An earlier chemotaxonomic survey of flavonoids in leaf and flower of the closely allied Gesneriaceae has been extended to a further twenty-five species and the previously noted differences in flavonoid pattern at the sub-family level have been confirmed. 3-Desoxyanthocyanins were identified in a further eleven species of the Gesnerioideae and the yellow chalcone isosalipurposide or the yellow aurone cernuoside noted in a further six species of the Cyrtandroideae. Preliminary evidence was obtained that a C-glycosylcyanidin derivative occurs in sepals of Cyrtandra pendula.