Effect of column chromatography studies on quality of lemongrass (Cymbopogon flexuosus stapf) essential oil and its nematicidal activity
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Date
2010
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CCSHAU
Abstract
Lemongrass belongs to genus Cymbopogon (Family Gramineae Syn. Poaceae). In good quality
lemongrass oil, the content of aldehyde i.e. citral-a (geranial) and citral-b (neral) should be maximum
and citronellal and geraniol should be minimum. Laboratory studies were conducted to study the effct
of silica gel and aluminium oxide (neutral) column chromatography on the quality of essential oil of
lemongrasss (Cymbopogon flexuosus). Nematicidal activity of aqueous extracts of essential oil of
lemongrass (C. flexuosus) was also studied against the root-knot nematode Meloidogyne incognita. For
column chromatographic studies, silica gel (3g), aluminium oxide (neutral, 3g) and mixture of silica gel
and aluminium oxide (1:1, w/w) were taken as adsorbents. Three eluants viz., hexane, carbon
tetrachloride and ethanol were taken for each adsorbent. Elution was done with 60 ml of eluant and six
eluant fractions (each 10 ml) were collected for each Set. Essential oils were recovered from different
eluant fractions of each Set. The essential oil sample thus collected were analyzed by Gas Liquid
Chromatography for quantitative estimation of citral-a (geranial), citral-b (neral), total citral, citronellal
and geraniol content. The oil recovered from hexane, carbon tetrachloride and ethanol fractions was in
the range from 10.0 to 28.2%. Moreover, sum of oil recovered from all fractions was 100 percent which
showed that oil sample passed through glass column was recovered completely. In column
chromatography experiment, citral-a (geranial), citral-b (neral) and total citral content increased when
hexane and carbon tetrachloride were used as eluants. The range of citral-a, citral-b and total citral
content was 44.5-48.5%, 25.2-30.5% and 70.0-76.8%, respectively when carbon tetrachloride was
taken as eluant which was higher in comparison to the corresponding values (41.5%, 28.6% and 70.1%,
respectively) in pure oil sample. In case of hexane as eluant, the range of citral-a, citral-b and total citral
content was 42.4-45.3%, 28.1-30.5% and 71.2-75.2%, respectively. However, these constituents
decreased significantly when ethanol was taken as eluant and the range of these constituents was
12.1-39.6%, 11.6-26.1% and 23.7-65.7%, respectively. Aqueous extracts of oils recovered from various
hexane, carbon tetrachloride and ethanol fractions were found to be effective in controlling root-knot
nematodes M. incognita. However, the magnitude of mortality was different for different fractions and
some fractions were 100 percent effective even at 1:5 concentration in comparison to 91.5% mortality
data of aqueous extract of pure oil sample at same concentration. The variation in magnitude of
mortality may be due to different amounts of chemical constituents present in the oils recovered in
different fractions. Keeping in view of these studies, it can be inferred that silica gel and aluminium
oxide (neutral) as adsorbents and carbon tetrachloride and hexane as eluants play a vital role in
improving the quality of lemongrass essential oil.