JOHNSON, EMANUEL L.*, WALTER F. SCHMIDT, AND DONALD COOPER. USDA ARS , Bldg 001 Rm 329, 10300 Baltimore Ave, Beltsville, MD 20705-2350. - Flavonoids as chemotaxonomic markers for cultivated Amazonian Erythroxylum .
Purported Erythroxylum coca var. ipadu Plowman (E. c. var. ipadu;
Amazonian coca) leaves were harvested from fields in Colombia, South
America (S. A.) during the months of October, November and December,
1997 to: (i) determine if their flavonoid profiles were complementary
to those of our collection and (ii) determine if the leaf flavonoids
could be indicative of kinship to a specific taxon(s) of cultivated
Erythroxylum. Polar methanolic extracts from leaf tissue of Amazonian
coca harvested from fields in Colombia S. A., were assayed by HPLC,
GC-MS, LC-MS and 1H NMR to determine the flavonoid profile and
O-conjugation of aglycones. These leaf extracts afforded eight
O-conjugated flavonoids: two O-conjugates of taxifolin, one
O-conjugate of quercetin, two, O-conjugates of eriodictyol three,
O-conjugates of kaempferol. Present also in leaf tissue of Amazonian
field grown E. c. var. ipadu, but lacking in leaf tissue from our
collection was an O-ethyl ester typically found in E. c. var. coca,
kaempferols and a O-7-rutinoside commonly encountered in the E.
novogranatense taxons. Flavonoids in our collection of Amazonian
coca, previously obtained from Colombia, S. A., contained five
O-conjugated derivatives of taxifolin and an O-conjugated quercetin.
Thus, the leaf flavonoids of the taxon differ not only between species
but also within taxons. The flavonoids of E. c. var. ipadu (Amazonian
coca) currently under cultivation in fields in Colombian are a mixture
of those present in E. c. var. coca, E. c. var. ipadu and E. n. var.
truxillense, whereas the flavonoids present in our living collection
of E. c. var. ipadu are derivates of E. c. var. coca. Our data
strongly suggest that Amazonian coca (E. c. var. ipadu) currently
under cultivation in Colombian fields is a genetic hybrid between E.
c. var. coca and E. n. var. truxillense. We propose that this
hybridization occurred after the late 1970ís.
Key words: chemotaxonomic, Erythroxylum, flavonoids, hybridization