External flavonoids from Heliotropium megalanthum and H. huascoense (Boraginaceae). Chemotaxonomic considerations

From the CH,CI, washings of fresh Heliotropium spp. (Cochranea section), flavonoids and aromatic geranyl derivatives have been isolated. Among the flavonoids, flavanones and flavonols are the most common compounds, and only few flavones have been reported. In this communication we report the isolation of several flavonoids from the exudates of H, megalanthum, and H. huascoense. Two of the compounds isolated from H, huascoense are novel flavonoids, belonging to the uncommon groups of penta-O-substituted flavanones and hexa-O-substituted flavonols. Our results show a different external flavonoid composition of H. huascoense from the other Heliotropium spp. so far studied. They are supported by morphological considerations, in special, the presence or absence of glandular trichomes in Heliotropium spp.