Changes in the essential oil content and its composition during palmarosa (Cymbopogon martinii (Roxb.) Wats. var. motia) inflorescence development



The flowering tops of palmarosa (Cymbopogon martinii) consist of spikelets and each spikelet is further composed of racemes and a leaf-like structure called a spathe. Both racemes and spathe contain essential oil. Changes in fresh weight, dry weight, chlorophyll and essential oil content and its major constituents, viz. geraniol and geranyl acetate, were examined for both racemes and spathe at various stages of spikelet development. The essential oil content was maximal at the unopened spikelets stage and decreased significantly thereafter. At unopened spikelets stage, the proportion of geranyl acetate (58.6%) in the raceme oil was relatively greater compared with geraniol (37.2%), whereas the spathe oil contained more geraniol (61.9%) compared with geranyl acetate (33.4%). The relative percentage of geranyl acetate in both the oils, however, decreased significantly with development and this is accompanied by a corresponding increase in the percentage of geraniol. Analysis of the volatile constituents from racemes and spathes (from mature spikelets) and seeds by capillary GC indicated 28 minor constituents besides the major constituent geraniol. (E)-Nerolidol was detected for the first time in an essential oil from this species. The geraniol content predominated in the seed oil, whereas the geranyl acetate content was higher in the raceme oil. Copyright © 2000 John Wiley & Sons, Ltd.