Characterization of cultivars within species of Ocimum by exudate flavonoid profiles

The surface flavonoid profiles of four plants each of 15 cultivars or varieties of basil species, Ocimum americanum, O. basilicum, O. x citriodorum and O. minimum, were studied by HPLC with diode array detection. Up to 14 different exudate flavones were detected in the different genotypes, the highest number and largest amounts in specimens of O. americanum var. americanum, and the lowest number and smallest amounts in specimens of O. minimum. The percentage of every flavone in each extract was calculated and principal component analysis was applied to the results. The flavonoid profiles of the two genotypes of O. americanum var. americanum investigated were very similar and typical of the main flavonoid chemotype of the species. The profiles of the three cultivars of O. minimum studied were also very similar to each other. However, only some of the cultivars of O. basilicum clustered together, whereas others showed considerable differences and sometimes grouped together with O. x citriodorum cultivars. The profiles found for O. x citriodorum cultivars were also not homogeneous. Therefore it may not be possible to identify a sample to species level by using surface flavone profiles. Within each cultivar of O. basilicum and O. x citriodorum, on the other hand, there was little chemical variation, as the profiles in the four samples of each accession studied were generally very similar. Therefore, surface flavone profiles could be used together with essential oil and morphological features for the delimitation and characterization of different cultivars of Ocimum species. (C) 2004 Elsevier Ltd. All rights reserved.