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The antimicrobial activity of the essential oils of Mentha spicata L. and Anethum sowa Roxb. (Indian dill) were studied. The major chemical constituents of the hydrodistilled essential oils and their major isolates from cultivated M. spicata and A. sowa were identified by IR, 1 H-and 13 C-NMR and GC: (S)-( )-limonene (27.3%) and (S)-( )-carvone (56.6%) (representing 83.9% of the spearmint oil) and (R)-(C)-limonene (21.4%), dihydrocarvone (5.0%), (R)-(C)-carvone (50.4%) and dillapiole (17.7%) (together 76.9% in Indian dill oil), respectively. In vitro bioactivity evaluation of the isolated oil components revealed that both the optical isomers of carvone were active against a wide spectrum of human pathogenic fungi and bacteria tested. (R)-(C)-limonene showed comparable bioactivity profile over the (S)-( )-isomer. The activity of these monoterpene enantiomers was found to be comparable to the bioactivity of the oils in which they occurred.

The essential oil of Artemisia annua L. was tested for its toxic repellent and development inhibitory activities against 2 economically important stored product insects: Tribolium castaneum (Herbst) and Callosobruchus maculatus (L.). Adult beetles of T. castaneum were repelled significantly by oil of A. annua at 1% concentration (vol:vol) and above in filter paper arena test. Dose-response relationship of A. annua oil revealed a significant negative correlation between larval survival; pupal survival and adult emergence of T. castaneum (i.e., increase in dose caused decrease in survival and adult emergence). Effective concentration (EC50) to reduce F1 progeny by 50% was calculated to be 2.6 and 4.1 microl/ml solvent against both the insect species, C. maculatus and T. castaneum, respectively. The relationship between bioactivity of oil from A. annua and responses of T. castaneum and C. maculatus is discussed. We found that oil from A. annua was largely responsible for both repellent (behavioral) and toxic (physiological) actions on 2 species of insect tested.

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Anopheles stephensi (Liston) is a well-known vector of malarial parasite in tropical countries. The developing trend of resistance in mosquitoes toward synthetic mosquitocidal agents makes their management extremely difficult. Effectiveness of essential oils with aroma therapeutic values seems to be an emerging tool to combat this vector. Piperitenone oxide isolated from essential oil of a new genotype, Mentha spicata L. variety viridis, has been evaluated for larvicidal, ovicidal, oviposition-deterrent, developmental toxicity, and repellent properties against various stages of A. stephensi. The results indicated the higher efficacy of piperitenone oxide than the crude essential oil of M. spicata variety viridis in all the bioassay experiments. The lethal response of piperitenone oxide and the oil toward fourth instar larvae showed LD50 values of 61.64 and 82.95 microg/ml, respectively. Female adults of A. stephensi exposed to the oil laid approximately 42 times less number of eggs at the dose of 60.0 microg/ml as compared with control, whereas exposure of piperitenone oxide at the same dose completely inhibited the oviposition. Furthermore, piperitenone oxide also completely inhibited egg hatching at the dose of 75.0 microg/ml in ovicidal assay. Developmental toxicity studies showed the significant developmental inhibition potential of the compound and oil. Additionally, piperitenone oxide was found to be highly toxic and repellent toward adults of A. stephensi as compared with oil.

The cloves are grown as plantation crops in the agroclimatic conditions of the Indian island of Little Andaman. The dried leaves, on hydrodistillation, gave 4.8% of the oil. GC and GC-MS analysis of the oil resulted in the identification of 16 compounds. The major compound was eugenol (94.4%) followed byˇ-caryophyllene (2.9%). The clove oil from Little Andaman was found to be comparable with the best oil produced in south India in terms of its eugenol content. It is suggested that clove can be grown as an economically viable crop in the Andaman, Nicobar and Lakshdeep islands.

1,8-cineole, one of the components of the essential oil of Artemisia annwa, was evaluated for repellency and toxicity against three stored product coleopterans-Callosobruchus maculatus F. (Coleoptera: Bruchidae), Rhyzopertha dominica F. (Coleoptera: Bostrychidae) and Sitophilns oryzae L. (Coleoptera: Curculionidae). It was found to be moderately repellent to all three species, with a mean repellency in the range of 65-74% at the highest dose tested (4.0 |al/ml) within lh. A contact toxicity assay revealed that direct topical application was more effective than using impregnated filter paper. The compound was more effective as a fumigant and gave 93-100% mortality against all the three pest species at the dose of 1.0 jil/1 air under empty jar conditions as compared to treatment of jars filled with grain (11-26% mortality). The lethal dose and lethal concentration required to kill 50% of the beetles (LD 5() and LC 50 respectively) varied.with the toxicity assay method. LD. () values of 0.03, 0.04 and 0.04 (il/insect against C. maculatus, R. dominica and S. oryzae respectively were found in the topical application assay while the LC 50 in the fumigant assay was 0.28, 0.33 and 0.46 (aI /1 against C. maculatus, R. dominica and S. oryzae respectively.

The leaf oil of Cinnamomum zeylanicum Blume grown in Little Andaman was analysed by GC and GC-MS. Forty-seven constituents, representing 99.96% of the oil, were identified. The main constituents of the oil were eugenol (76.60%), linalool (8.5%) and piperitone (3.31%). The composition of the oil is comparable to cinnamon leaf oil produced in Bangalore and Hyderabad (south India) in terms of eugenol and linalool contents.