Abstract:
A population of lemongrass (Cymbopogon citratus) was investigated in this research for
changes in metabolite profiles in the leaves of different ages i.e. penultimate (second fully
expanded leaf from the top), middle (a leaf from the central position of a tiller) and bottom (a
lowermost green leaf on a tiller) with changing seasons round the year for two consecutive years
(2010-2011). Measurements were made for some primary and secondary metabolites while the
essential oils profile of leaves was analyzed using GC-MS. The photosynthetic pigments
displayed sharp variations in the leaves of different ages with changes in the environmental
conditions. Higher chlorophyll a, b and carotenoid were recorded during summer months. The
accumulation trends of osmolytes in lemongrass showed notable seasonal variation. The
accumulation of total free amino acids, free proline and GB were higher during summer months.
The antioxidant enzymes minimized the effect of oxidative damage by scavenging H 2 O 2 and
reuced MDA contents in extreme environmental conditions especially during summer. The
younger leaves of lemongrass exhibited much higher concentrations of vitamins as compared to
bottom leaves. The secondary metabolites i.e. alkaloid, phenolic and flavonoid contents in
lemongrass leaves were markedly increased with increased temperature. Seasonal variation
affected the nutritional profile of lemongrass substantially. The production of NDF ADF, ADL,
cellulose and starch was greater during summer. Cellulose and silica contents were higher in
bottom leaf possibly due to plant aging. Starch content was higher in penultimate leaf, which
declined with leaf age. Mineral concentration of lemongrass appears to be largely dependent on
temperature and evapotranspiration. The GC-MS analysis of lemongrass oil carried out in the
leaf samples collected during January, April, July and October revealed that out of 54
compounds analyzed, neral, citral, geranial, allerthin, caryophyllene oxide were major ones
synthesized in various sesasons.
