Isolation And Characterization Of Essential Oils From Ocimum Americanum, Lantana Camara, Lantana Trifolia And Tephrosia Vogelii

ABSTRACT

The botanical insecticides are generally pest-specific, relatively harmless to non-target

organisms and biodegradable. Unlike conventional insecticides which are based on a single

active ingredient, plant-derived insecticides comprise of an array of chemical compounds which

act concertedly on both behavioural and physiological processes. Thus the chances of pest

developing resistance to such substances are less likely. Essential oils are good example of plant

compounds with such properties. Toxicity of a large number of essential oils and their

constituents has been evaluated against several stored-product pests. Consequently,

determination of the extraction yield of the essential oils and comparison of the chemical

composition of essential oil of different plant species and chemotypes is an important step in

promoting and understanding their use as insecticides. This study involved characterisation of

essential oils of Lantana camara, Lantana trifolia, Ocimum americanum and Tephrosia vogelii,

which have known repellent, insecticidal and antifeedant activities against various insect pests.

The fresh leaves of L. camara, L. trifolia and T. vogelii were collected and hydro-distilled for 3h

in a modified Clevenger apparatus. The essential oil from the leaves of L. lantana and T. vogelii

was obtained in a yield of 0.63% w/w and 0.056%, respectively, after drying over anhydrous

Na2SO4. The leaves and flowers of L. trifolia gave 0.060% and 0.064% of essential oil

respectively. The leaves of O. americanum were collected, air-dried under shade to constant

weight and ground to a fine powder. The essential oil obtained by steam distillation using a

modified clevenger apparatus gave 4% based on dry weight. The main components of the

essential oil from L. camara were β-caryophyllene (21.35%), α-humulene (8.73%), sabinene

(9.15%), 1, 8-cineole (5.54%). L. trifolia essential oil had germacrene D as the main component

in leaves (23.14%) and flowers (24.88%). Other components in essential oil from the leaves'

were cis-ocimene (7.27%), ß-caryophyllene (6.32%); and ß-caryophyllene (11.93%) and α-

humulene (4.65%) in flowers. In O. americanum essential oil the major components were

terpinen-4-ol (43.21%) and 1, 8-cineole (16.13%) while in T. vogelii essential oil nerolidol

(7.73%), β-caryophylene (6.89%), caryophyllene oxide (6.22%) and germacrene D (6.20%) were

the main components. A number of compounds in the oils are known to exhibit insecticidal and pharmacological properties, and are used in the cosmetic, flavour and fragrance industries