Changes in aroma profiles of 11 Indian Ocimum taxa during plant ontogeny

The genus Ocimum is an important source of many essential oils and aromatic chemicals used principally in the food and cosmetic industries. The aromas (compositions) of essential oils of genus Ocimum are characterized by a great chemical variability affecting the commercial value of this genus. This study was conducted to evaluate the ontogenic variations in aroma profiles of 11 Indian Ocimum taxa belonging to 5 Ocimum species, viz. O. basilicum L., O. americanum L., O. gratissimum L., O. tenuiflorum L., and O. kilimandscharicum Guerke, grown in foot hills of Uttarakhand, India during rain-autumn cropping season. Essential oil yield was found to vary significantly during different phenophases: from 0.34 to 0.87 % in four landraces of O. basilicum, 0.16 to 0.38 % in ‘Green and Purple’ of O. tenuiflorum, 0.23 to 0.43 % in O. americanum, 0.34 to 0.78 % in O. kilimandscharicum and 0.48 to 0.68 % in O. gratissimum. The variation in composition of the essential oils was analyzed by gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. Analyses of the essential oils led to the identification of 95 constituents forming 93.8–99.7 % of the total essential oil compositions, with phenyl propanoids (≤0.1–90.0 %) and monoterpenoids (2.8–95.5 %) as the prevalent components. Substantial variations in essential oil yield, and qualitative and quantitative compositions due to different stages of plants growth were noticed. These results indicated that the knowledge of appropriate growth stage is very important to obtain higher essential oil yield and desired active constituents of Ocimum, which were used extensively in food, cosmetics and allied industries.