Leaf flavonoids as chemotaxonomic markers for two Erythroxylum taxa

Abstract

Leaf extracts of Erythroxylum coca var. coca Lam. (E. c. var. coca) yielded six O-conjugates of Eriodictyol flavonoids, while the equivalent extracts from Erythroxylum novogranatense var. novogranatense (Morris) Hieron (E. n. var. novogranatense) contained five flavonoids, two of which were O-conjugates of Luteolin and three were O-conjugates of Kaempferol. All six of E. c. var. coca methanolic extracted peaks (resolved by HPLC) were found to have a 2, 3 single bond, which in E. n. var. novogranatense is replaced by a 2-hydroxy allene. The other primary difference in the predominant flavonoids between these taxa is the chemical composition of the sugar and/or acyl O-conjugation and site(s) at which this conjugation occurred. The results suggest that the most abundant O-conjugated flavonoids of E. c. var. coca and E. n. var. novogranatense may be used as chemotaxonomic markers for the two taxa. Therefore, the O-conjugated peaks of Eriodictyol, are distinct chemotaxonomic markers for E. c. var. coca and the O-conjugated peaks Luteolin and Kaempferol for E. n. var. novogranatense. These taxa are two of the four cultivated Erythroxylum taxa that contain commercial quantities of the cocaine alkaloid in their leaves, this entity also sets apart the taxa from other members of Erythroxylum. We suggest that the biochemistry of flavonoids of other Erythroxylum taxa may also be species selective.