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Evaluation of the toxicity of different phytoextracts of Ocimum basilicum against Anopheles stephensi and Culex quinquefasciatus
Journal of Asia-Pacific Entomology 12 (2009) 113–115
Contents lists available at ScienceDirect
Journal of Asia-Pacific Entomology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / j a p e
Short Communication
Evaluation of the toxicity of different phytoextracts of Ocimum basilicum against Anopheles stephensi and Culex quinquefasciatus Prejwltta Maurya, Preeti Sharma, Lalit Mohan, Lata Batabyal, C.N. Srivastava ⁎ Applied Entomology and Vector Control Laboratory, Department of Zoology, Faculty of Science, Dayalbagh Educational Institute (Deemed University), Dayalbagh, Agra-282005, India
a r t i c l e
i n f o
Article history: Received 29 December 2008 Revised 7 February 2009 Accepted 10 February 2009 Keywords: Anopheles stephensi Culex quinquefasciatus Larvicide Ocimum basilicum Phytoextract
a b s t r a c t The larvicidal effect of the crude carbon tetrachloride, methanol and petroleum ether leaf extracts of a widely grown medicinal plant, Ocimum basilicum, against Anopheles stephensi and Culex quinquefasciatus was evaluated. Petroleum ether extract was found to be the most effective against the larvae of both mosquitoes, with LC50 values of 8.29, 4.57; 87.68, 47.25 ppm and LC90 values of 10.06, 6.06; 129.32, 65.58 ppm against A. stephensi and C. quinquefasciatus being observed after 24 and 48 h of treatment, respectively. The efficacy of petroleum ether was followed by that of the carbon tetrachloride and methanol extracts, which had LC50 values of 268.61, 143.85; 446.61, 384.84 ppm and LC90 values of 641.23, 507.80; 923.60, 887.00 ppm against A. stephensi after 24 and 48 h, respectively, and LC50 values of 24.14, 17.02; 63.48, 53.77 ppm and LC90 values of 295.38, 204.23; 689.71, 388.87 ppm against C. quinquefasciatus after 24 and 48 h of treatment, respectively. These extracts are highly toxic against mosquito larvae from a range of species; therefore, they may be useful for the management of mosquito larvae to control vector borne diseases. © Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2009 Published by Elsevier B.V. All rights reserved.
Introduction Anopheles stephensi and Culex quinquefasciatus are the potential vectors of malaria and filariasis, respectively. Worldwide, these vectors are responsible for the transmission of 500 and 100 million clinical cases of malaria and filariasis diseases per annum, respectively; therefore, they can be referred to as global vectors (Das, 2007). In addition, the cost of mosquito borne diseases is not restricted to the loss of human, but also includes the lost of labour and productivity which impacts the overall social and economic progress of a country. Conventional synthetic pesticides such as, DDT, malathion and pyrethroides are used for mosquito management to protect humans from the adverse effects of mosquito borne diseases. However, unsystematic prolonged application of these pesticides can have adverse effects on the environment, as well as cause residual effects and induce the development of resistance to the pesticide by the vector (Mohan and Ramaswamy, 2007). Therefore, it is necessary to develop environmentally safe, biodegradable, economical and indigenous methods for the control of vectors that can be used with minimum care by individuals and communities (Mittal and Subbarao, 2003). A review indicated that assessment of the efficacy of different phytochemicals obtained from various plants is the best way to develop novel synthetic insecticides (Sukumar et al., 1991; Sharma et al., 2006; Mohan and Ramaswamy, 2007). ⁎ Corresponding author. Fax: +91 562 2801226. E-mail address: [email protected] (C.N. Srivastava).
Therefore, in this study, the larvicidal effects of different (petroleum ether, carbon tetrachloride and methanol) leaf extracts of a widespread aromatic medicinal plant, Ocimum basilicum (Linnaeus) on the malaria and filarial vectors, A. stephensi and C. quinquefasciatus, were evaluated. Materials and methods Collection of plant and preparation of extract Freshly harvested leaves of O. basilicum Linnaeus (Family: Lamiaceae) were collected from the botanical garden of Dayalbagh Educational Institute (Deemed University), Dayalbagh, Agra. The leaves were washed and dried in the shade at room temperature (37–39 °C) till they become brittle. The completely dried leaves (250 g) were then powdered manually and extracted using a soxhlet apparatus. Extraction was conducted using the three different solvents according to their polarity range (petroleum ether successively followed by carbon tetrachloride and then methanol) for 72 h. The extracts were then concentrated by evaporation of the solvents in a rotary vacuum evaporator (Biocraft Scientific Industries, India) to obtain 44.40 g/kg (petroleum ether), 20.0 g/kg (carbon tetrachloride) and 54.0 g/kg (methanol) of a semi solid crude extract, which was stored in the refrigerator for later use. Preparation of stock and test concentrations The residue (10 g) obtained from each fraction was dissolved in 100 ml of ethanol independently to obtain stock solutions of
1226-8615/$ – see front matter © Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2009 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.aspen.2009.02.004
114
P. Maurya et al. / Journal of Asia-Pacific Entomology 12 (2009) 113–115
Table 1 Efficacy of different leaf extracts of Ocimum basilicum against anopheline larvae Extraction solvent (stock concentration)
Exposure (h)
Regression equation
Carbon tetrachloride (100,000 ppm)
24
1.89X–1.47
3.77
48
2.34X–2.39
2.12
24
4.06X–9.82
26.34
48
3.53X–7.67
19.69
24
1.25X ± 2.60
3.70
48
1.26X ± 2.90
6.02
Methanol (100,000 ppm)
Petroleum ether (10,000 ppm)
Chi-square
LC50 ± SE (fiducial limits) ppm 268.61 ± 40.28 347.56–89.66 143.85 ± 26.54 195.87–91.84 446.61 ± 31.76 508.86–384.36 384.84 ± 30.70 445.01–324.66 8.29 ± 1.92 12.05–4.52 4.57 ± 1.24 6.99–2.15
100,000 ppm. The stocks solutions were then further diluted in ethanol to obtain concentrations of 10,000 ppm (petroleum ether), 50,000 ppm (carbon tetra chloride extract) and 100,000 ppm (methanol extract). These stock solutions were then used to prepare the desired test concentrations of the solvents. Treatment of larvae For bioassay, the required quantity of the above prepared stock solution (1 ml) was added to 500 ml beakers that contained 199 ml of tap water (Borosil, Mumbai, India) to obtain working test concentrations that ranged from 2.5 to 80 ppm for petroleum ether, 12.5 to 300 ppm for carbon tetrachloride and 50 to 700 ppm for methanol extracts. In addition, a control was run parallel to each experimental series using 200 ml of tap water that was amended with a quantity of ethanol (1 ml) equal to the maximum quantity of ethanol present in the beakers that contained the stock solutions of the extract (1 ml). Next 20 third instar larvae of A. stephensi and C. quinquefasciatus were exposed to different concentrations of extract solutions and the control. All experiments were conducted in triplicate, following the Standard WHO (1975) Procedure. The larval mortality in both the treatment and the control groups were then recorded after 24 and 48 h of treatment. All data were then subjected to probit analysis (Finney, 1971) to calculate the LC50 and LC90 values. In addition, the data were analyzed by a chi-square test, and the regression coefficients, fiducial limits and relative potency of the data were also evaluated. Results and discussion The data presented in Tables 1 and 2 reveal that the petroleum ether extract of the leaves of O. basilicum was the most effective against the Anopheline and Culicine larvae with LC50 values of 8.29 and
Relative toxicity irrespective of time period 1.66 3.10 1.00 1.16 53.87 97.73
LC90 ± SE (fiducial limits) ppm 641.23 ± 250.62 1132.53–299.83 507.80 ± 95.17 694.33–321.27 923.60 ± 140.33 1198–648.56 887.00 ± 139.01 1159.46–614.54 87.68 ± 34.35 154.99–20.36 47.25 ± 16.01 78.61–15.88
Relative toxicity irrespective of time period 1.44 1.82 1.00 1.04 10.53 19.55
4.57 ppm and 10.06 and 6.06 ppm being observed after 24 and 48 h of exposure, respectively. However, when petroleum ether was used, the LC90 values were 87.68 and 47.25 ppm and 129.32 and 65.68 ppm after 24 and 48 h of exposure, respectively. The LC90 values of the petroleum ether were lower than those of the carbon tetrachloride and methanol extracts, regardless of which organism was evaluated or the time of treatment. Moreover, the potentiality of each of the tested extracts increased as the time period for which the larvae were treated increased. The efficacy of the phytochemicals obtained from various plants has been evaluated in several studies. For example, Sukumar et al. (1991) conducted an extensive review of botanical derivatives used in mosquito control. In addition, Chavan and Nikam (1982) noted the larvicidal nature of the essential oil of O. basilicum, which induced 100% mortality against C. quinquefasciatus at concentration of 0.12%. Furthermore, Stephens et al. (1995) and White (1971), studied the use of freshly harvested Ocimum spp., referred to as kivumbasi, and freshly cut twigs of Ocimum suave and Ocimum canum, which are traditionally placed in the corners of rooms to prevent mosquitoes from entering homes in Tanzania. Furthermore, Palsson and Jaenson (1999) found that fresh O. canum (also known as Ocimum americanum) provided 63.6% protection from mosquito bites for 2 h. Additionally, Lukwa et al. (1999) evaluated the use of 250 mg/ml of dried O. canum leaves in ethanol and found that it provided 70% repellency against Aedes aegypti for 2 h. Finally, Tawatsin et al. (2001) reported that a 25% concentration of O. canum essential oil in ethanol was effective for preventing from A. aegypti, Anopheles dirus, and C. quinquefasciatus, for 3 h, 4 h, and 8 h, respectively. Plants have also been evaluated for their larvicidal activity against mosquitoes. For example, George and Vincent (2005) evaluated the larvicidal activity of Annona squamosa (LC50 — 674.41, 59.75 ppm), Pongamia glabra (LC50 — 282.57 ppm), Azadirachta indica (LC50 — 176.91, 75.65 ppm) against C. quinquefasciatus and A. stephensi,
Table 2 Efficacy of different leaf extracts of Ocimum basilicum against culicine larvae Extraction solvent (stock concentration)
Exposure (h)
Carbon tetrachloride (50,000 ppm)
24
1.18X ± 2.19
1.26
48
1.19 X ± 2.35
1.24
24
1.24X ± 1.53
1.11
48
1.19X ± 0.93
0.91
24
1.15X ± 2.69
5.31
48
1.24X ± 2.79
5.98
Methanol (50,000 ppm)
Petroleum ether (10,000 ppm)
Regression equation
Chi-square
LC50 ± SE (fiducial limits) ppm 24.14 ± 7.85 39.52–8.71 17.02 ± 6.38 29.53–4.52 63.48 ± 20.78 104.21–22.76 53.77 ± 16.30 85.72–21.82 10.06 ± 2.69 15.28–4.71 6.06 ± 1.80 9.60–2.53
Relative toxicity irrespective of time period 2.63 3.73 1.00 1.18 6.31 10.48
LC90 ± SE (fiducial limits) ppm 295.38 ± 108.40 507.84–82.92 204.23 ± 68.59 338.66–69.80 689.71 ± 315.96 1308.99–76.42 388.87 ± 116.19 616.61–161.13 129.32 ± 53.48 234.15–24.49 65.58 ± 21.37 107–23.78
Relative toxicity irrespective of time period 2.33 3.38 1.00 1.77 5.33 10.50
P. Maurya et al. / Journal of Asia-Pacific Entomology 12 (2009) 113–115
respectively. Further, Mohan et al. (2005) analyzed the larvicidal effect of Solanum xanthocarpum fruit extracts and found that they had an LC50 of 28.62 ppm and 26.09 ppm after 24 and 48 h, respectively, against Anopheles and an LC50 of 62.62 ppm and 59.45 ppm after 24 and 48 h, respectively, against Culex. Additionally, Sharma et al. (2006) screened several plants for their larvicidal activity, and found that Artimisia annua was the most toxic against Anopheles with an LC50 of 16.85 ppm and 11.45 ppm after 24 and 48 h of exposure, respectively. In addition, Singh et al. (2006) evaluated the larvicidal effects of Momordica charantia fruit against A. stephensi (LC50 66.05 ppm) and C. quinquefasciatus (LC50 96.11 ppm) and Batabyal et al. (2007) reported that the seed extracts of A. indica (LC50 131.32 ppm), Ricinus communis (LC50 194.98 ppm), and M. charantia (LC50 87.00 ppm) exerted larvicidal properties against A. stephensi larvae. Finally, Mohan and Ramaswamy (2007) evaluated the efficacy of Ageratina adenophora against Culex and found that it showed an LC50 of 227.19 ppm after 24 h of treatment. These results clearly indicate that the plant-based insecticides, which are less expensive than synthetic insecticides, exert high larvicidal effect. Therefore, the results of this and previous studies indicate that the extract of O. basilicum, may be effectively used for the control of mosquito larvae in public health operations. The use of indigenous plant based products by individual and communities can provide a prophylactic measure for protection against various mosquito borne diseases. However, there is a need to promote the use of herbal products through community based vector control programs. Acknowledgment The authors are thankful to the University Grant Commission, New Delhi for financial assistance.
115
References Batabyal, L., Sharma, P., Mohan, L., Maurya, P., Srivastava, C.N., 2007. Larvicidal efficiency of certain seed extracts against Anopheles stephensi, with reference to Azadirachta indica. J. Asia Pac. Entomol. 10, 241–255. Chavan, S.R., Nikam, S.T., 1982. Mosquito larvicidal activity of Ocimum basilicum Linn. Indian J. Med. Res. 75, 220–222. Das, A.P., 2007. Insecticide resistance in mosquitoes: possible approaches for its management, National Institute of Malaria Research, Delhi-54. Finney, D.J., 1971. Probit Analysis, 3rd Edn. Cambridge University Press, Cambridge. George, S., Vincent, S., 2005. Comparative efficacy of Annona squamosa Linn. and Pongamiaglabra Vent. to Azadirachta indica A. Juss against mosquitoes. J. Vector Borne Dis. 42, 159–163. Lukwa, N., Nyazema, N.Z., Curtis, C.F., Mwaiko, G.L., Chandiwana, S.K., 1999. People's perceptions about malaria transmission and control using repellent plants in a locality in Zimbabwe. Cent. Afr. J. Med. 45, 64. Mittal, P.K., Subbarao, S.K., 2003. Prospects of using herbal products in the control of mosquito vector. ICMR Bull. 33, 1–10. Mohan, D.R., Ramaswamy, M., 2007. Evaluation of the larvicidal activity of the leaf extract of a weed plant, Ageratina adenophora, against two important species of mosquitoes, Aedes aegypti and Culex quinquefasciatus. Afr. J. Biol. 6, 631–638. Mohan, L., Sharma, P., Srivastava, C.N., 2005. Evaluation of Solanum xanthocarpum extracts as mosquito larvicides. J. Environ. Biol. 26, 399–401. Palsson, K., Jaenson, T.G., 1999. Plant products used as mosquito repellents in Guinea Bissau, West Africa. Acta Trop. 72, 39. Sharma, P., Mohan, L., Srivastava, C.N., 2006. Phytoextract-induced developmental deformities in malaria vector. Bioresour. Technol. 97, 1599–1604. Singh, R.K., Dhiman, R.C., Mittal, P.K., 2006. Mosquito larvicidal properties of Momordica charantia Linn (Family: Cucurbitacae). J. Vector Borne Dis. 43, 88–91. Stephens, C., Masamu, E.T., Kiama, A.J., Kinenekejo, M., Ichimori, K., Lines, J., 1995. Knowledge of mosquitoes in relation to the public and domestic control activities in the cities of Dares Salaam and Tangavv. WHO Bull. 73, 97. Sukumar, K., Perich, M.J., Boobar, L.R., 1991. Botanical derivatives in mosquito control: a review. J. Am. Mosq. Control Assoc. 7, 210–237. Tawatsin, A., Wratten, S.D., Scott, R.R., Thavara, U., Techadamrongsin, Y., 2001. Repellency of volatile oils from plants against three mosquito vectors. J. Vector Ecol. 26, 76. White, G.B., 1971. The insect repellent value of Ocimum spp. (Labiatae): traditional antimosquito plants. East Afr. Med. J. 50, 248. W.H.O., 1975. Instructions for determining the susceptibility of resistance mosquito larvae to insecticides. Mimeographed document WHO/VBC/75 583.
Contents lists available at ScienceDirect
Journal of Asia-Pacific Entomology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / j a p e
Short Communication
Evaluation of the toxicity of different phytoextracts of Ocimum basilicum against Anopheles stephensi and Culex quinquefasciatus Prejwltta Maurya, Preeti Sharma, Lalit Mohan, Lata Batabyal, C.N. Srivastava ⁎ Applied Entomology and Vector Control Laboratory, Department of Zoology, Faculty of Science, Dayalbagh Educational Institute (Deemed University), Dayalbagh, Agra-282005, India
a r t i c l e
i n f o
Article history: Received 29 December 2008 Revised 7 February 2009 Accepted 10 February 2009 Keywords: Anopheles stephensi Culex quinquefasciatus Larvicide Ocimum basilicum Phytoextract
a b s t r a c t The larvicidal effect of the crude carbon tetrachloride, methanol and petroleum ether leaf extracts of a widely grown medicinal plant, Ocimum basilicum, against Anopheles stephensi and Culex quinquefasciatus was evaluated. Petroleum ether extract was found to be the most effective against the larvae of both mosquitoes, with LC50 values of 8.29, 4.57; 87.68, 47.25 ppm and LC90 values of 10.06, 6.06; 129.32, 65.58 ppm against A. stephensi and C. quinquefasciatus being observed after 24 and 48 h of treatment, respectively. The efficacy of petroleum ether was followed by that of the carbon tetrachloride and methanol extracts, which had LC50 values of 268.61, 143.85; 446.61, 384.84 ppm and LC90 values of 641.23, 507.80; 923.60, 887.00 ppm against A. stephensi after 24 and 48 h, respectively, and LC50 values of 24.14, 17.02; 63.48, 53.77 ppm and LC90 values of 295.38, 204.23; 689.71, 388.87 ppm against C. quinquefasciatus after 24 and 48 h of treatment, respectively. These extracts are highly toxic against mosquito larvae from a range of species; therefore, they may be useful for the management of mosquito larvae to control vector borne diseases. © Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2009 Published by Elsevier B.V. All rights reserved.
Introduction Anopheles stephensi and Culex quinquefasciatus are the potential vectors of malaria and filariasis, respectively. Worldwide, these vectors are responsible for the transmission of 500 and 100 million clinical cases of malaria and filariasis diseases per annum, respectively; therefore, they can be referred to as global vectors (Das, 2007). In addition, the cost of mosquito borne diseases is not restricted to the loss of human, but also includes the lost of labour and productivity which impacts the overall social and economic progress of a country. Conventional synthetic pesticides such as, DDT, malathion and pyrethroides are used for mosquito management to protect humans from the adverse effects of mosquito borne diseases. However, unsystematic prolonged application of these pesticides can have adverse effects on the environment, as well as cause residual effects and induce the development of resistance to the pesticide by the vector (Mohan and Ramaswamy, 2007). Therefore, it is necessary to develop environmentally safe, biodegradable, economical and indigenous methods for the control of vectors that can be used with minimum care by individuals and communities (Mittal and Subbarao, 2003). A review indicated that assessment of the efficacy of different phytochemicals obtained from various plants is the best way to develop novel synthetic insecticides (Sukumar et al., 1991; Sharma et al., 2006; Mohan and Ramaswamy, 2007). ⁎ Corresponding author. Fax: +91 562 2801226. E-mail address: [email protected] (C.N. Srivastava).
Therefore, in this study, the larvicidal effects of different (petroleum ether, carbon tetrachloride and methanol) leaf extracts of a widespread aromatic medicinal plant, Ocimum basilicum (Linnaeus) on the malaria and filarial vectors, A. stephensi and C. quinquefasciatus, were evaluated. Materials and methods Collection of plant and preparation of extract Freshly harvested leaves of O. basilicum Linnaeus (Family: Lamiaceae) were collected from the botanical garden of Dayalbagh Educational Institute (Deemed University), Dayalbagh, Agra. The leaves were washed and dried in the shade at room temperature (37–39 °C) till they become brittle. The completely dried leaves (250 g) were then powdered manually and extracted using a soxhlet apparatus. Extraction was conducted using the three different solvents according to their polarity range (petroleum ether successively followed by carbon tetrachloride and then methanol) for 72 h. The extracts were then concentrated by evaporation of the solvents in a rotary vacuum evaporator (Biocraft Scientific Industries, India) to obtain 44.40 g/kg (petroleum ether), 20.0 g/kg (carbon tetrachloride) and 54.0 g/kg (methanol) of a semi solid crude extract, which was stored in the refrigerator for later use. Preparation of stock and test concentrations The residue (10 g) obtained from each fraction was dissolved in 100 ml of ethanol independently to obtain stock solutions of
1226-8615/$ – see front matter © Korean Society of Applied Entomology, Taiwan Entomological Society and Malaysian Plant Protection Society, 2009 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.aspen.2009.02.004
114
P. Maurya et al. / Journal of Asia-Pacific Entomology 12 (2009) 113–115
Table 1 Efficacy of different leaf extracts of Ocimum basilicum against anopheline larvae Extraction solvent (stock concentration)
Exposure (h)
Regression equation
Carbon tetrachloride (100,000 ppm)
24
1.89X–1.47
3.77
48
2.34X–2.39
2.12
24
4.06X–9.82
26.34
48
3.53X–7.67
19.69
24
1.25X ± 2.60
3.70
48
1.26X ± 2.90
6.02
Methanol (100,000 ppm)
Petroleum ether (10,000 ppm)
Chi-square
LC50 ± SE (fiducial limits) ppm 268.61 ± 40.28 347.56–89.66 143.85 ± 26.54 195.87–91.84 446.61 ± 31.76 508.86–384.36 384.84 ± 30.70 445.01–324.66 8.29 ± 1.92 12.05–4.52 4.57 ± 1.24 6.99–2.15
100,000 ppm. The stocks solutions were then further diluted in ethanol to obtain concentrations of 10,000 ppm (petroleum ether), 50,000 ppm (carbon tetra chloride extract) and 100,000 ppm (methanol extract). These stock solutions were then used to prepare the desired test concentrations of the solvents. Treatment of larvae For bioassay, the required quantity of the above prepared stock solution (1 ml) was added to 500 ml beakers that contained 199 ml of tap water (Borosil, Mumbai, India) to obtain working test concentrations that ranged from 2.5 to 80 ppm for petroleum ether, 12.5 to 300 ppm for carbon tetrachloride and 50 to 700 ppm for methanol extracts. In addition, a control was run parallel to each experimental series using 200 ml of tap water that was amended with a quantity of ethanol (1 ml) equal to the maximum quantity of ethanol present in the beakers that contained the stock solutions of the extract (1 ml). Next 20 third instar larvae of A. stephensi and C. quinquefasciatus were exposed to different concentrations of extract solutions and the control. All experiments were conducted in triplicate, following the Standard WHO (1975) Procedure. The larval mortality in both the treatment and the control groups were then recorded after 24 and 48 h of treatment. All data were then subjected to probit analysis (Finney, 1971) to calculate the LC50 and LC90 values. In addition, the data were analyzed by a chi-square test, and the regression coefficients, fiducial limits and relative potency of the data were also evaluated. Results and discussion The data presented in Tables 1 and 2 reveal that the petroleum ether extract of the leaves of O. basilicum was the most effective against the Anopheline and Culicine larvae with LC50 values of 8.29 and
Relative toxicity irrespective of time period 1.66 3.10 1.00 1.16 53.87 97.73
LC90 ± SE (fiducial limits) ppm 641.23 ± 250.62 1132.53–299.83 507.80 ± 95.17 694.33–321.27 923.60 ± 140.33 1198–648.56 887.00 ± 139.01 1159.46–614.54 87.68 ± 34.35 154.99–20.36 47.25 ± 16.01 78.61–15.88
Relative toxicity irrespective of time period 1.44 1.82 1.00 1.04 10.53 19.55
4.57 ppm and 10.06 and 6.06 ppm being observed after 24 and 48 h of exposure, respectively. However, when petroleum ether was used, the LC90 values were 87.68 and 47.25 ppm and 129.32 and 65.68 ppm after 24 and 48 h of exposure, respectively. The LC90 values of the petroleum ether were lower than those of the carbon tetrachloride and methanol extracts, regardless of which organism was evaluated or the time of treatment. Moreover, the potentiality of each of the tested extracts increased as the time period for which the larvae were treated increased. The efficacy of the phytochemicals obtained from various plants has been evaluated in several studies. For example, Sukumar et al. (1991) conducted an extensive review of botanical derivatives used in mosquito control. In addition, Chavan and Nikam (1982) noted the larvicidal nature of the essential oil of O. basilicum, which induced 100% mortality against C. quinquefasciatus at concentration of 0.12%. Furthermore, Stephens et al. (1995) and White (1971), studied the use of freshly harvested Ocimum spp., referred to as kivumbasi, and freshly cut twigs of Ocimum suave and Ocimum canum, which are traditionally placed in the corners of rooms to prevent mosquitoes from entering homes in Tanzania. Furthermore, Palsson and Jaenson (1999) found that fresh O. canum (also known as Ocimum americanum) provided 63.6% protection from mosquito bites for 2 h. Additionally, Lukwa et al. (1999) evaluated the use of 250 mg/ml of dried O. canum leaves in ethanol and found that it provided 70% repellency against Aedes aegypti for 2 h. Finally, Tawatsin et al. (2001) reported that a 25% concentration of O. canum essential oil in ethanol was effective for preventing from A. aegypti, Anopheles dirus, and C. quinquefasciatus, for 3 h, 4 h, and 8 h, respectively. Plants have also been evaluated for their larvicidal activity against mosquitoes. For example, George and Vincent (2005) evaluated the larvicidal activity of Annona squamosa (LC50 — 674.41, 59.75 ppm), Pongamia glabra (LC50 — 282.57 ppm), Azadirachta indica (LC50 — 176.91, 75.65 ppm) against C. quinquefasciatus and A. stephensi,
Table 2 Efficacy of different leaf extracts of Ocimum basilicum against culicine larvae Extraction solvent (stock concentration)
Exposure (h)
Carbon tetrachloride (50,000 ppm)
24
1.18X ± 2.19
1.26
48
1.19 X ± 2.35
1.24
24
1.24X ± 1.53
1.11
48
1.19X ± 0.93
0.91
24
1.15X ± 2.69
5.31
48
1.24X ± 2.79
5.98
Methanol (50,000 ppm)
Petroleum ether (10,000 ppm)
Regression equation
Chi-square
LC50 ± SE (fiducial limits) ppm 24.14 ± 7.85 39.52–8.71 17.02 ± 6.38 29.53–4.52 63.48 ± 20.78 104.21–22.76 53.77 ± 16.30 85.72–21.82 10.06 ± 2.69 15.28–4.71 6.06 ± 1.80 9.60–2.53
Relative toxicity irrespective of time period 2.63 3.73 1.00 1.18 6.31 10.48
LC90 ± SE (fiducial limits) ppm 295.38 ± 108.40 507.84–82.92 204.23 ± 68.59 338.66–69.80 689.71 ± 315.96 1308.99–76.42 388.87 ± 116.19 616.61–161.13 129.32 ± 53.48 234.15–24.49 65.58 ± 21.37 107–23.78
Relative toxicity irrespective of time period 2.33 3.38 1.00 1.77 5.33 10.50
P. Maurya et al. / Journal of Asia-Pacific Entomology 12 (2009) 113–115
respectively. Further, Mohan et al. (2005) analyzed the larvicidal effect of Solanum xanthocarpum fruit extracts and found that they had an LC50 of 28.62 ppm and 26.09 ppm after 24 and 48 h, respectively, against Anopheles and an LC50 of 62.62 ppm and 59.45 ppm after 24 and 48 h, respectively, against Culex. Additionally, Sharma et al. (2006) screened several plants for their larvicidal activity, and found that Artimisia annua was the most toxic against Anopheles with an LC50 of 16.85 ppm and 11.45 ppm after 24 and 48 h of exposure, respectively. In addition, Singh et al. (2006) evaluated the larvicidal effects of Momordica charantia fruit against A. stephensi (LC50 66.05 ppm) and C. quinquefasciatus (LC50 96.11 ppm) and Batabyal et al. (2007) reported that the seed extracts of A. indica (LC50 131.32 ppm), Ricinus communis (LC50 194.98 ppm), and M. charantia (LC50 87.00 ppm) exerted larvicidal properties against A. stephensi larvae. Finally, Mohan and Ramaswamy (2007) evaluated the efficacy of Ageratina adenophora against Culex and found that it showed an LC50 of 227.19 ppm after 24 h of treatment. These results clearly indicate that the plant-based insecticides, which are less expensive than synthetic insecticides, exert high larvicidal effect. Therefore, the results of this and previous studies indicate that the extract of O. basilicum, may be effectively used for the control of mosquito larvae in public health operations. The use of indigenous plant based products by individual and communities can provide a prophylactic measure for protection against various mosquito borne diseases. However, there is a need to promote the use of herbal products through community based vector control programs. Acknowledgment The authors are thankful to the University Grant Commission, New Delhi for financial assistance.
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