Studies on effects of indigenous plant extracts on filarial vector Culex tritaeniorhynchus Giles

Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The purpose of the present study was to assess the effect of leaf ethyl acetate, acetone and methanol extracts of Aegle marmelos (L.) Correa ex Roxb (Rutaceae), Andrographis lineata Wallich ex Nees. (Acanthaceae), Andrographis paniculata (Burm.f.) Wall. ex Nees. (Acanthaceae), Cocculus hirsutus (L.) Diels (Menispermaceae), Eclipta prostrata L. (Asteraceae) and Tagetes erecta L. (Compositae) on ovicidal and oviposition-deterrent activities against Culex tritaeniorhynchus Giles (Diptera: Culicidae). The percentage of egg hatching in methanol extracts of Andrographis lineata, Cocculus hirsutus and T. erecta were 16, 12 and 16 exerted at 500 ppm, respectively. The percentage of effective oviposition repellency was 97.77 at 500 ppm and the lowest repellency was 42.06 at 31.25 ppm in methanol and acetone extracts of Andrographis lineata and Andrographis paniculata, respectively. The oviposition activity index values revealed that the solvent plant extracts have deterrent effect, and they caused a remarkable negative response resulting in oviposition of very few eggs. These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal ecofriendly approach for the control of the Culex tritaeniorhynchus.     

Efficacy of medicinal plant extracts against malarial vector, <Emphasis Type="Italic">Anopheles subpictus</Emphasis> Grassi

Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The aim of this study was to evaluate the adulticidal activity and adult emergence inhibition (EI) of leaf hexane, chloroform, ethyl acetate, acetone, and methanol extracts of Aegle marmelos (Linn.) Correa ex Roxb, Andrographis lineata Wallich ex Nees., Andrographis paniculata (Burm.f.) Wall. ex Nees., Cocculus hirsutus L. Diels, Eclipta prostrata L., and Tagetes erecta L. tested against malarial vector, Anopheles subpictus Grassi (Diptera: Culicidae). All plant extracts showed moderate adulticidal activity and EI effects after 24 h of exposure at 1,000 ppm; however, the highest adulticidal activity was observed in ethyl acetate extract of A.lineata, chloroform extract of A.paniculata, acetone extract of C.hirsutus, and methanol extract of T.erecta (LD₅₀ = 126.92, 95.82, 109.40, and 89.83 ppm; LD₉₀ = 542.95, 720.82, 459.03, and 607.85 ppm); and effective EI was found in leaf acetone extract of the A. marmelos, ethyl acetate extract of A.lineata, methanol extracts of C. hirsutus, and T.erecta, (EI₅₀ = 128.14, 79.39, 143.97, and 92.82 ppm; EI₉₀ = 713.53, 293.70, 682.72, and 582.59 ppm), respectively, against A. subpictus. These results suggest that the leaf methanol extract of C. hirsutus and T.erecta have the potential to be used as an ideal eco-friendly approach for the control of A. subpictus. Therefore, this study provides first report on the mosquito adulticidal activity and EI of plant extracts against malaria vector.     

Oviposition-deterrent,ovicidal, and repellent activities of indigenous plant extracts against <Emphasis Type="Italic">Anopheles subpictus</Emphasis> Grassi (Diptera: Culicidae)

Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The leaf acetone, ethyl acetate, and methanol extracts of Aegle marmelos (Linn.) Correa ex Roxb, Andrographis lineata Wallich ex Nees, and Cocculus hirsutus (L.) Diels were tested for oviposition-deterrent, ovicidal, and repellent activities against Anopheles subpictus Grassi (Diptera: Culicidae). The percentage of effective oviposition repellency of 92.60 , 93.04, 95.20, 88.26, 92.80, 94.01, 95.77, 96.93, and 92.54 at 500 ppm and the lowest repellency of 47.14, 58.00, 56.52, 64.93, 71.09, 66.42, 50.62, 57.62, and 65.73 at 31.25 ppm in acetone, ethyl acetate, and methanol extracts of Aegle marmelos, Andrographis lineata, and Cocculus hirsutus, respectively. The oviposition activity index (OAI) value of acetone, ethyl acetate, and methanol extracts of Aegle marmelos, Andrographis lineata, and Cocculus hirsutus at 500 ppm were −0.86, −0.87, −0.90, −0.78, −0.87, −0.86, −0.91, −0.94, and −0.86 respectively. The OAI values revealed that the solvent plant extracts have deterrent effect, and they caused a remarkable negative response resulting in oviposition of very few eggs. Mean percent hatchability of the ovicidal activity was observed 24 h after treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Mortality of 100% with ethyl acetate extract of Aegle marmelos, methanol extracts Aegle marmelos, Andrographis lineata, and Cocculus hirsutus were exerted at 1,000 ppm. The maximum repellent activity was observed at 500 ppm in methanol extracts of Aegle marmelos, Andrographis lineata, and ethyl acetate extract of Cocculus hirsutus, and the mean complete protection time ranged from 90 to 120 min with the different extracts tested. These results suggest that the leaf extracts of Aegle marmelos, Andrographis lineata, and Cocculus hirsutus have the potential to be used as an ideal ecofriendly approach for the control of the Anopheles subpictus. Therefore, this study provides first report on the oviposition, ovicidal, and repellent activities against malaria vector, Anopheles subpictus of plant extracts from Southern India.     

Evaluation of medicinal plant extracts against ticks and fluke

The present study was based on assessments of the antiparasitic activities to determine the efficacies of leaf hexane, chloroform, ethyl acetate, acetone and methanol extracts of Aegle marmelos (Linn.) Correa ex Roxb, Andrographis lineata Wallich ex Nees., Andrographis paniculata (Burm.f.) Wallich ex Nees., Cocculus hirsutus (L.) Diels, Eclipta prostrata L., and Tagetes erecta L. against the adult cattle tick Haemaphysalis bispinosa Neumann 1897 (Acarina: Ixodidae), the larvae of Rhipicephalus (Boophilus) microplus Canestrini 1887 (Acari: Ixodidae) and sheep fluke Paramphistomum cervi Zeder 1790 (Digenea: Paramphistomatidae). All plant extracts showed moderate toxic effect on parasites after 24 h of exposure; however, the highest parasitic activity was found in leaf ethyl acetate extract of A. lineata, methanol extract of A. marmelos, A. paniculata, and C. hirsutus against H. bispinosa (LC₅₀ = 395.27, 358.45, 327.21 and 420.50 ppm); ethyl acetate extract of A. paniculata, C. hirsutus, methanol extracts of A. marmelos, A. lineata, and E. prostrata against the larvae of R. microplus (LC₅₀ = 207.70, 258.61, 134.09, 206.00, and 274.33 ppm); hexane extract of A. lineata, ethyl acetate extract of A. paniculata, E. prostrata, acetone extracts of T. erecta, methanol extracts of A. marmelos and C. hirsutus against P. cervi (LC₅₀ = 254.23, 451.17, 425.73, 253.60, 542.71, and 360.17 ppm), respectively. The present study is the first report on the veterinary parasitic activity of plant extracts from Southern India.     

Laboratory study on larvicidal activity of indigenous plant extracts against <Emphasis Type="Italic">Anopheles subpictus</Emphasis> and <Emphasis Type="Italic">Culex tritaeniorhynchus</Emphasis>

Anopheles subpictus and Culex tritaeniorhynchus have developed resistance to various synthetic insecticides, making its control increasingly difficult. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The leaf acetone, chloroform, ethyl acetate, hexane, and methanol extracts of Aegle marmelos (Linn.) Correa ex Roxb, Andrographis lineata Wallich ex Nees., Andrographis paniculata (Burm.f.) Wall. ex Nees., Cocculus hirsutus (L.) Diels, Eclipta prostrata L., and Tagetes erecta L. were tested against fourth-instar larvae of malaria vector, A. subpictus Grassi and Japanese encephalitis vector, C. tritaeniorhynchus Giles (Diptera: Culicidae). All plant extracts showed moderate larvicidal effects after 24 h of exposure at 1,000 ppm; however, the highest larval mortality was found in leaf ethyl acetate of A. marmelos, E. prostrata, hexane, methanol of A. paniculata and C. hirsutus against the larvae of A. subpictus (LC₅₀ = 167.00, 78.28, 67.24, 142.83 ppm; LC₉₀ = 588.31, 360.75, 371.91, and 830.01 ppm) and against the larvae of C. tritaeniorhynchus (LC₅₀ = 99.03, 119.89, 88.50, 105.19 ppm; LC₉₀ = 479.23, 564.85, 416.39, and 507.86 ppm), respectively. These results suggest that the leaf hexane extract of A. paniculata and ethyl acetate extract of E. prostrata have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus and C. tritaeniorhynchus. Therefore, this study provides first report on the mosquito larvicidal activity of plant extracts against vectors from Southern India.     

Efficacy of botanical extracts against Japanese encephalitis vector, Culex tritaeniorhynchus

The purpose of the present study was to assess the effect of leaf hexane and chloroform extracts of Aegle marmelos, Andrographis lineata, Andrographis paniculata, Cocculus hirsutus, Eclipta prostrata, and Tagetes erecta on repellent, ovicidal, and oviposition-deterrent activities against Culex tritaeniorhynchus Giles (Diptera: Culicidae). The repellent action of the plant extracts tested varied depending on the plant species, part, solvent used in extraction, and the extract dose. The hexane extract of A. paniculata was more effective in exhibiting the repellent action against the mosquito as compared with A. lineata extract. Complete protections for 150 min were found in hexane extract of A. paniculata at 500 ppm against mosquito bites. Mean percent hatchability of the ovicidal activity was observed 24 h after treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. No hatchability was observed with hexane, and chloroform extracts of A. lineata, A. paniculata, and hexane extract of T. erecta were exerted at 1,000 ppm. The percentage of effective oviposition repellency were 95.90, 94.75, 95.04, 90.58, 87.93, 87.14, 94.82, 95.71, 92.26, 90.58, 83.35, and 78.16 at 500 ppm, and the lowest repellency was 69.93, 53.06, 64.81, 70.06, 51.82, 54.54, 48.31, 66.71, 68.82, 61.85, 34.84, and 39.53 at 31.25 ppm in hexane and chloroform extracts of A. marmelos, A. lineata, A. paniculata, C. hirsutus, E. prostrata, and T. erecta, respectively. The oviposition activity index values revealed that the solvent plant extracts have deterrent effect, and they caused a remarkable negative response resulting in oviposition of very few eggs. These results clearly reveal that the hexane extracts of A. marmelos and A. paniculata served as a potential repellent, ovicidal, and oviposition deterrent against Japanese encephalitis vector, C. tritaeniorhynchus.     

Screening for feeding deterrent activity of herbal extracts against the larvae of malaria vector Anopheles subpictus Grassi

This no-choice, laboratory study focuses on the feeding of homogeneous powdered, dried, yeast with different plant extracts on mosquito fourth-instar larvae to determine the effects on their mortality. Screening for antifeedant activity of plant extracts with some known medicinal attributes could lead to the discovery of new agents for vector control. The aim of this study was to investigate the antifeedant activity of crude leaf hexane, ethyl acetate, acetone, and methanol extracts of Andrographis lineata Wallich ex Nees. (Acanthaceae), Anisomeles malabarica (L.) Sims. (Lamiaceae), Argemone mexicana L. (Papaveraceae), Aristolochia bracteolata Lam. (Aristolochiaceae), Chrysanthemum indium L. (Asteraceae), Datura metal L. (Solanaceae), Eclipta prostrata L. (Asteraceae), and Sesbania grandiflora (L.) Pers. (Fibaceae) against the fourth-instar larvae of Anopheles subpictus Grassi (Diptera:Culicidae). All the crude extracts showed antifeedant activity in a dose-dependent manner. The plant extracts exhibited a significant antifeedant activity after 24 and 48 h of exposure; however, the highest larval mortality was found in leaf ethyl acetate extract of A. malabarica, acetone extract E. prostrata, methanol extract of A. lineata, C. indium, and S. grandiflora after 24 h (LC₅₀ = 2.53, 2.82, 2.31, 2.56, and 2.08 mg/mL; LC₉₀ = 6.40, 8.06, 7.45, 6.98, and 6.20 mg/mL), respectively. The hexane extract of A. lineata, D. metal, methanol extract of A. bracteolata and E. prostrata showed larval mortality after 48 h (LC₅₀ = 3.05, 2.11, 3.00, and 2.18 mg/mL; LC₉₀ = 9.06, 6.22, 8.23, and 5.77 mg/mL), respectively. One hundred percent larval mortality was observed in methanol extract of A. lineata, and C. indium after 24 h and the hexane extract of A. lineata and D. metal after 48 h at 10 mg/100 mL. The methanol extracts of A. lineata and C. indium significantly increased larval mortality in comparison to larvae fed with untreated diet. Bacillus thuringiensis subsp. israelensis is widely accepted as a biological pesticide because of its highly specific activity against dipteran insects without adverse effects on other organisms. The feeding deterrent activity of different herbal extracts against the larvae of malaria vector A. subpictus exhibited significantly lower toxicity compare with the bio larvicides, B. thuringiensis. These results suggest that the methanol extract of A. lineata, C. indium, the hexane extract of A. lineata and D. metal have the potential to be used as an ideal eco-friendly approach for the control of the medically important vector A. subpictus. These findings corroborate traditional insecticidal application of selected plants and the results can be extended for the control of mosquitoes.     

Evaluation of larvicidal and nymphicidal potential of plant extracts against <Emphasis Type="Italic">Anopheles subpictus</Emphasis> Grassi, <Emphasis Type="Italic">Culex tritaeniorhynchus</Emphasis> Giles and <Emphasis Type="Italic">Aphis gossypii</Emphasis> Glover

The acetone, chloroform, ethyl acetate, hexane and methanol extracts of peel and leaf extracts of Citrus sinensis, Ocimum canum, Ocimum sanctum and Rhinacanthus nasutus were tested against fourth instar larvae of malaria vector, Anopheles subpictus Grassi, Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae) and feeding deterrence to nymphs of cotton pest, Aphis gossypii Glover (Homoptera: Aphididae). The larval and nymph mortality were observed after 24 h of exposure. All extracts showed moderate larvicidal and nymphicidal effects; however, the highest mortality was found in peel chloroform extract of C. sinensis, leaf ethyl acetate extracts of O. canum and O. sanctum and leaf chloroform extract of R. nasutus against the larvae of A. subpictus (LC₅₀ = 58.25, 88.15, 21.67 and 40.46 ppm; LC₉₀ = 298.31, 528.70, 98.34 and 267.20 ppm), peel methanol extract of C. sinensis, leaf methanol extract of O. canum, ethyl acetate extracts of O. sanctum and R. nasutus against the larvae of C. tritaeniorhynchus (LC₅₀ = 38.15, 72.40, 109.12 and 39.32 ppm; LC₉₀ = 184.67, 268.93, 646.62 and 176.39 ppm), peel hexane extract of C. sinensis, leaf methanol extracts of O. canum and R. nasutus and leaf ethyl acetate extract of O. sanctum against the nymph of A. gossypii (LC₅₀ = 162.89, 80.99, 73.27 and 130.19 ppm; LC₉₀ = 595.40, 293.33, 338.74 and 450.90 ppm), respectively. These results suggest that the peel methanol extracts of C. sinensis and O. canum, ethyl acetate leaf extract of O. sanctum and leaf chloroform and ethyl acetate extract of R. nasutus have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus, C. tritaeniorhynchus and A. gossypii.     

Laboratory determination of efficacy of indigenous plant extracts for parasites control

The present study was based on assessments of the antiparasitic activities to determine the efficacies of acetone, chloroform, ethyl acetate, hexane, and methanol dried leaf, flower, and seed extracts of Achyranthes aspera L., Anisomeles malabarica (L.) R. Br., Gloriosa superba L., Psidium guajava L., Ricinus communis L., and Solanum trilobatum L. tested against the larvae of cattle tick Rhipicephalus (Boophilus) microplus (Canestrini 1887) (Acari: Ixodidae), sheep internal parasite Paramphistomum cervi (Zeder 1790) (Digenea: Paramphistomatidae) at 2,000 ppm and fourth instar larvae of Anopheles subpictus Grassi and Culex tritaeniorhynchus Giles (Diptera: Culicidae) at 1,000 ppm. All plant extracts showed moderate effects after 24 h of exposure; however, the highest parasite mortality was found in the leaf ethyl acetate extract of A. aspera, leaf methanol extract of A. malabarica, flower methanol extract of G. superba, and leaf methanol extract of R. communis against the larvae of R. microplus (LC₅₀ = 265.33, 95.97, 153.73, and 181.49 ppm; LC₉₀ = 1,130.18, 393.88, 1,794.25, and 1,829.94 ppm); leaf acetone and chloroform of A. malabarica, flower acetone extract of G. superba, and leaf chloroform and methanol of R. communis against the adult of P. cervi (LC₅₀ = 108.07, 106.69, 157.61, 69.44, and 168.24 ppm; LC₉₀ = 521.77, 463.94, 747.02, 256.52, and 809.45 ppm); leaf ethyl acetate extract of A. aspera, leaf chloroform extract of A. malabarica, flower methanol of G. superba, and leaf methanol extract of R. communis against the larvae of A. subpictus (LC₅₀ = 48.83, 135.36, 106.77, and 102.71 ppm; LC₉₀ = 225.36, 527.24, 471.90, and 483.04 ppm); and leaf ethyl acetate extract of A. aspera, leaf chloroform extract of A. malabarica, flower methanol extract of G. superba, and leaf methanol extract of R. communis against the larvae of C. tritaeniorhynchus (LC₅₀ = 68.27, 95.98, 59.51, and 93.94 ppm; LC₉₀ = 306.88, 393.83, 278.99, and 413.27 ppm), respectively. These results suggest that the leaf ethyl acetate extract of A. aspera, leaf acetone and chloroform extract of A. malabarica, flower methanol extract of G. superba, and leaf methanol extract of R. communis have the potential to be used as an ideal eco-friendly approach for the control of the R. microplus, P. cervi, A. subpictus, and C. tritaeniorhynchus. Therefore, this study provides the first report on the larvae and adult parasitic activity of crude solvent extracts, indigenous plants consumed by the natives in southern India.     

Larvicidal, repellent, and ovicidal activity of marine actinobacteria extracts against Culex tritaeniorhynchus and Culex gelidus

The purpose of the present study was to assess the effect of crude extracts of marine actinobacteria on larvicidal, repellent, and ovicidal activities against Culex tritaeniorhynchus and Culex gelidus (Diptera: Culicidae). The early fourth instar larvae of C. tritaeniorhynchus and C. gelidus, reared in the laboratory, were used for larvicidal, ovicidal, and repellent assay with crude extracts of actinobacteria. Saccharomonospora spp. (LK-1), Streptomyces roseiscleroticus (LK-2), and Streptomyces gedanensis (LK-3) were identified as potential biocide producers. Based on the antimicrobial activity, three strains were chosen for larvicidal activity. The marine actinobacterial extracts showed moderate to high larvicidal effects after 24 h of exposure at 1,000 ppm and the highest larval mortality was found in extract of LK-3 (LC₅₀ = 108.08 ppm and LC₉₀ = 609.15 ppm) against the larvae of C. gelidus and (LC₅₀ = 146.24 ppm and LC₉₀ = 762.69 ppm) against the larvae of C. tritaeniorhynchus. Complete protections for 240 min were found in crude extract of LK-2 and LK-3 at 1,000 ppm, against mosquito bites of C. tritaeniorhynchus and C. gelidus, respectively. After 24-h treatment, mean percent hatchability of the ovicidal activity was observed. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Crude extracts of LK-1 and LK-3 showed no hatchability at 1,000 ppm against C. tritaeniorhynchus and C. gelidus, respectively. This is an ideal ecofriendly approach for the control of Japanese encephalitis vectors, C. tritaeniorhynchus and C. gelidus.     

Anthelmintic activity of botanical extracts against sheep gastrointestinal nematodes, <Emphasis Type="Italic">Haemonchus contortus</Emphasis>

The source of chemical anthelmintics (levamisole, flubendazole, and thiabendazole) had limited the success of gastrointestinal nematodiasis control in sheep and goats and thus awakened interest in the study of medicinal plant extracts as alternative sources of anthelmintics. The egg hatching and larvicidal effect of indigenous plant extracts were investigated against the sheep parasite, Haemonchus contortus. The purpose of the present study was to assess the efficacy of leaf, bark, and seed ethyl acetate, acetone and methanol extracts of Andrographis paniculata (Burm.f.) Wall. ex Nees., Anisomeles malabarica (L.) R. Br., Annona squamosa L., Datura metel L., and Solanum torvum Swartz were tested against the parasitic nematode of small ruminants H. contortus using egg hatch assay (EHA) and larval development assay (LDA). The assays were run in 24-well cell culture plates at room temperature with five replicates. All plant extracts showed moderate parasitic effects after 48 and exposure for egg hatching and LDA, respectively; however, 100% egg hatching and larvicidal inhibition were found in the methanol extracts of A. paniculata, A. squamosa, D. metel, and S. torvum at 25 mg/ml and the effect was similar to positive control of Albendazole (0.075 mg/ml) and Ivermectin (0.025mg/ml) against H. contortus, respectively. The EHA result showed the ED₅₀ of methanol extracts of A. paniculata and D. metel, which were 2.90 and 3.08 mg/ml, and in larval development assay, the ED₅₀ was 4.26and 3.86 mg/ml, respectively. These effects remain to be confirmed through in vivo studies.     

Insecticidal and larvicidal activities of medicinal plant extracts against mosquitoes

In recent years, use of environment friendly and biodegradable natural insecticides of plant origin have received renewed attention as agents for vector control because they are rich in bioactive chemicals, active against a limited number of species including specific target insects, and biodegradable. The present study was carried out to evaluate the adulticidal, repellent, and larvicidal activity of crude hexane, ethyl acetate, and methanol extracts of eight plants, viz. Aristolochia indica L., Cassia angustifolia Vahl, Diospyros melanoxylon Roxb., Dolichos biflorus L., Gymnema sylvestre (Retz) Schult, Justicia procumbens L., Mimosa pudica L., and Zingiber zerumbet L., were tested against adult and early fourth instar larvae of Culex gelidus Theobald and Culex quinquefasciatus Say (Diptera: Culicidae). The effective adult mortality was observed in methanol extract of A. indica, ethyl acetate extract of D. biflorus, and ethyl acetate and hexane extract of Z. zerumbet against C. gelidus and C. quinquefasciatus (LD₅₀ = 37.75, 78.56, 129.44, 86.13, 80.06, 112.42, 53.83, and 46.61; LD₉₀ = 166.83, 379.14, 521.50, 289.83, 328.18, 455.72, 181.15, and 354.50 ppm, respectively). Complete protections for 150 min were found in hexane and methanol extract of A. indica and Z. zerumbet at 1,000 ppm against mosquito bites. The highest larval mortality was found in the hexane extract of Z. zerumbet, ethyl acetate extract of D. biflorus, and methanol extracts of A. indica against C. gelidus (LC₅₀ = 26.48, 33.02, and 12.47 ppm; LC₉₀ = 127.73, 128.79, and 62.33 ppm) and against C. quinquefasciatus (LC₅₀ = 69.18, 34.76, and 25.60 ppm; LC₉₀ = 324.40, 172.78, and 105.52 ppm), respectively, after 24 h. The plant extracts are potential to be used as an ideal eco-friendly approach for the control of the Japanese encephalitis vector, C. gelidus, and lymphatic filariasis vector, C. quinquefasciatus.     

Adulticidal and repellent properties of indigenous plant extracts against <Emphasis Type="Italic">Culex quinquefasciatus</Emphasis> and <Emphasis Type="Italic">Aedes aegypti</Emphasis> (Diptera: Culicidae)

Several diseases are associated to the mosquito–human interaction. Mosquitoes are the carriers of severe and well-known illnesses such as malaria, arboviral encephalitis, dengue fever, chikunguniya fever, West Nile virus, and yellow fever. These diseases produce significant morbidity and mortality in humans and livestock around the world. The adulticidal and repellent activities of crude hexane, ethyl acetate, benzene, chloroform, and methanol extracts of leaf of Eclipta alba and Andrographis paniculata were assayed for their toxicity against two important vector mosquitoes, viz., Culex quinquefasciatus and Aedes aegypti (Diptera: Culicidae). The adult mortality was observed after 24 h of exposure. All extracts showed moderate adulticide effects; however, the highest adult mortality was found in methanol extract of A. paniculata against the adults of C. quinquefasciatus and A. aegypti with the LC₅₀ and LC₉₀ values were 149.81, 172.37 ppm and 288.12, 321.01 ppm, respectively. The results of the repellent activity of hexane, ethyl acetate, benzene, chloroform, and methanol extract of E. alba and A. paniculata plants at three different concentrations of 1.0, 2.5, and 5.0 mg/cm² were applied on skin of forearm in man and exposed against adult female mosquitoes. In this observation, these two plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. These results suggest that the leaf solvent plant extracts have the potential to be used as an ideal ecofriendly approach for the control of mosquitoes. This is the first report on the mosquito adulticidal and repellent activities of the reported E. alba and A. paniculata plants.     

Evaluation of indigenous plant extracts against the malarial vector, Anopheles stephensi (Liston) (Diptera: Culicidae)

Since ancient times, plant and microbial products were used in various aspects. However, their use against insects decreased when chemical products became developed. Recently, concerns increased with respect to public health and environmental security requiring detection of natural products that may be used against insects. In this study, mosquito Larvicidal and ovicidal activity of crude hexane, ethyl acetate, benzene, chloroform, and methanol extracts of the leaf of three plants, Eclipta alba, Cardiospermum halicacabum, and Andrographis paniculata, were tested against the early third-instar larvae of Anopheles stephensi (Liston) (Diptera: Culicidae). The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in methanol extract of A. paniculata, E. alba, and C. halicacabum against the larvae of A. stephensi (LC₅₀ = 79.68, 112.56, and 133.01 ppm; LC₉₀ = 154.66, 220.68, and 270.72 ppm), respectively. Mean percent hatchability of the ovicidal activity was observed 48 h post-treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Mortality of 100% with methanol and ethyl acetate extract of A. paniculata and methanol extract of E. alba were exerted at 200 ppm and methanol and benzene extract of C. halicacabum exerted at 150 ppm. This is an ideal eco-friendly approach for the control of the malaria vector, A. stephensi. Therefore, this study provides first report on the larvicidal and ovicidal activities against malaria vector, A. stephensi of E. alba plant extracts.     

Larvicidal potential of medicinal plant extracts against Anopheles subpictus Grassi and Culex tritaeniorhynchus Giles (Diptera: Culicidae)

Mosquito control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. The acetone, chloroform, ethyl acetate, hexane, methanol and petroleum ether extracts of leaf, flower and seed of Cassia auriculata L., Leucas aspera (Willd.), Rhinacanthus nasutus KURZ., Solanum torvum Swartz and Vitex negundo Linn. were tested against fourth instar larvae of malaria vector, Anopheles subpictus Grassi and Japanese encephalitis vector, Culex tritaeniorhynchus Giles (Diptera: Culicidae). The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest mortality was found in leaf petroleum ether, flower methanol extracts of C. auriculata, flower methanol extracts of L. aspera and R. nasutus, leaf and seed methanol extracts of S. torvum and leaf hexane extract of V. negundo against the larvae of A. subpictus (LC₅₀ = 44.21, 44.69, 53.16, 41.07, 35.32, 28.90 and 44.40 ppm; LC₉₀ = 187.31, 188.29, 233.18, 142.66, 151.60, 121.05 and 192.11 ppm, respectively) and against the larvae of C. tritaeniorhynchus (LC₅₀ = 69.83, 51.29, 81.24, 71.79, 44.42, 84.47 and 65.35 ppm; LC₉₀ = 335.26, 245.63, 300.45, 361.83, 185.09, 351.41 and 302.42 ppm, respectively). These results suggest that the leaf petroleum ether, flower methanol extracts of C. auriculata, leaf and seed methanol extracts of S. torvum and leaf hexane extract of V. negundo have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus and C. tritaeniorhynchus. This is the first report on the mosquito larvicidal activity of the medicinal plant extracts.     

Evaluation of botanical extracts against Haemaphysalis bispinosa Neumann and Hippobosca maculata Leach

In the current study, in vitro evaluation of crude hexane, chloroform, ethyl acetate, acetone, and methanol extracts of Anisomeles malabarica (L.) R. Br., Gloriosa superba L., Psidium guajava L., Ricinus communis L., and Solanum trilobatum L. exhibited acaricidal and insecticidal activities against the adult of Haemaphysalis bispinosa Neumann (Acarina: Ixodidae) and hematophagous fly Hippobosca maculata Leach (Diptera: Hippoboscidae). All plant extracts showed moderate toxic effect on parasites after 24 h of exposure; the complete inhibition (100%) at the maximum concentration tested (3,000 ppm) was obtained in acetone, methanol, hexane, and chloroform extracts of A. malabarica; methanol, chloroform, and ethyl acetate extracts of G. superba; acetone extract of P. guajava; methanol extract of R. communis; and leaf hexane extract of S. trilobatum; and the lowest inhibition (38%) was recorded for the seed hexane extract of S. trilobatum. The highest parasite dead was found in leaf acetone and methanol extracts of A. malabarica, seed methanol of G. superba, leaf methanol of R. communis against H. bispinosa (LC₅₀ = 466.15, 719.78, 476.06, and 243.87 ppm; LC₉₀ = 1,837.96, 2,014.47, 1,904.36, and 2,692.15 ppm), leaf hexane and chloroform extracts of A. malabarica, seed chloroform and ethyl acetate of G. superba, leaf acetone of P. guajava, leaf methanol of R. communis, and leaf hexane extract of S. trilobatum against H. maculata (LC₅₀ = 495.61, 414.81, 360.02, 479.37, 646.30, 506.13, and 432.77 ppm; LC₉₀ = 1,914.84, 1,956.59, 1,598.54, 1,636.41, 2,192.73, 1,982.66, and 1,872.33 ppm), respectively. These results suggest that the leaf methanol of R. communis, chloroform extracts of A. malabarica, and chloroform extract of G. superba have the potential to be used as an ideal eco-friendly approach for the control of the H. bispinosa and H. maculata. Therefore, this study provides first report on the parasitic activities of plant extracts from Southern India.     

Adulticidal, repellent, and ovicidal properties of indigenous plant extracts against the malarial vector, Anopheles stephensi (Diptera: Culicidae)

Mosquito-borne diseases with an economic impact create loss in commercial and labor outputs, particularly in countries with tropical and subtropical climates. Mosquito control is facing a threat because of the emergence of resistance to synthetic insecticides. Extracts from plants may be alternative sources of mosquito control agents because they constitute a rich source of bioactive compounds that are biodegradable into nontoxic products and potentially suitable for use to control mosquitoes. Insecticides of botanical origin may serve as suitable alternative biocontrol techniques in the future. In view of the recently increased interest in developing plant origin insecticides as an alternative to chemical insecticide, this study was undertaken to assess the adulticidal, repellent, and ovicidal potential of the crude hexane, ethyl acetate, benzene, aqueous, and methanol solvent extracts from the medicinal plants Andrographis paniculata, Cassia occidentalis, and Euphorbia hirta against the medically important mosquito vector, Anopheles stephensi (Diptera: Culicidae).The adult mortality was observed after 24 h of exposure. All extracts showed moderate adulticide effects; however, the highest adult mortality was found in methanol extract of A. paniculata followed by C. occidentalis and E. hirta against the adults of A. stephensi with LC₅₀ and LC₉₀ values of 210.30, 225.91, and 263.91 ppm and 527.31, 586.36, and 621.91 ppm, respectively. The results of the repellent activity of hexane, ethyl acetate, benzene, aqueous, and methanol extract of A. paniculata, C. occidentalis, and E. hirta plants at three different concentrations of 1.0, 3.0, and 6.0 mg/cm² were applied on skin of forearm in man and exposed against adult female mosquitoes. In this observation, these three plant crude extracts gave protection against mosquito bites without any allergic reaction to the test person, and also, the repellent activity is dependent on the strength of the plant extracts. Mean percent hatchability of the ovicidal activity was observed 48 h post-treatment. The percent hatchability was inversely proportional to the concentration of extract and directly proportional to the eggs. Mortality of 100 % with methanol extract of A. paniculata exerted at 150 ppm and aqueous, methanol extract of C. occidentalis and E. hirta were exerted at 300 ppm. These results suggest that the leaf extracts of A. paniculata, C. occidentalis, and E. hirta have the potential to be used as an ideal eco-friendly approach for the control of the A. stephensi. Further detailed research is needed to identify the active ingredient in the extracts and implement the effective mosquito management program.     

Screening for antifeedant and larvicidal activity of plant extracts against <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hübner), <Emphasis Type="Italic">Sylepta derogata</Emphasis> (F.) and <Emphasis Type="Italic">Anopheles stephensi</Emphasis> (Liston)

Plant extracts, especially botanical insecticides, are currently studied more and more because of the possibility of their use in plant protection. Biological activity of five solvent plant extracts were studied using fourth instar larvae of gram pod borer Helicoverpa armigera (Lepidoptera: Noctuidae), cotton leaf roller Sylepta derogata (Lepidoptera: Pyralidae) and malaria vector Anopheles stephensi (Diptera: Culicidae). Antifeedant and larvicidal activity of acetone, chloroform, ethyl acetate, hexane and methanol peel, leaf and flower extracts of Citrus sinensis, Ocimum canum, Ocimum sanctum and Rhinacanthus nasutus were used in this study. During preliminary screening, the extracts were tested at 1,000 ppm concentration. The larval mortality was observed after 24 h of exposure. All extracts showed moderate larvicidal effects; however, the highest larval mortality was found in peel chloroform extract of C. sinensis, flower methanol extract of O. canum against the larvae of H. armigera (LC₅₀ = 65.10,51.78, LC₉₀ = 277.39 and 218.18 ppm), peel methanol extract of C. sinensis, flower ethyl acetate extract of O. canum and leaf acetone extract of O. sanctum against the larvae of S. derogata (LC₅₀ = 20.27,58.21,36.66, LC₉₀ =113.15,285.70 and 668.02 ppm), peel methanol extract of C. sinensis, leaf and flower ethyl acetate extracts of O. canum against the larvae of A. stephensi (LC₅₀ = 95.74,101.53,28.96, LC₉₀ = 303.20,492.43 and 168.05 ppm), respectively. These results suggest that the chloroform and methanol extract of C. sinensis, ethyl acetate flower extracts of O. canum and acetone extract of O. sanctum have the potential to be used as an ideal eco-friendly approach for the control of the agricultural pests H. armigera, S. derogata and medically important vector A. stephensi.     

Larvicidal activity of lignans from Phryma leptostachya L. against Culex pipiens pallens

The larvicidal activity of crude petroleum ether, ethyl acetate, and methanol extracts of the whole plants of Phryma leptostachya L. was assayed for its toxicity against the early fourth instar larvae of Culex pipiens pallens. The larval mortality was observed after 24 h of exposure. Among three solvent extracts from Phyrma leptostachya L., the petroleum ether extract exhibited the best larvicidal activity. The corresponding LC₅₀ values of petroleum ether, ethyl acetate, and methanol extracts were 3.23, 5.23, and 61.86 ppm against the early fourth instar larvae of Culex pipiens pallens. The petroleum ether extract was successively subjected to column chromatography and preparative high performance liquid chromatography, and yielded the three lignans, phrymarolin-I, haedoxane A, and haedoxane E, which were isolated and identified as new mosquito larvicidal compounds. Phrymarolin-I, haedoxane A, and haedoxane E showed high larvicidal activity, for which the lethal doses LC₅₀ were estimated at 1.21, 0.025, and 0.15 ppm against the early fourth instar larvae of Culex pipiens pallens, respectively. The structures were elucidated by analyses of IR, UV, MS, and NMR spectral data. This is the first report on the mosquito larvicidal activity of the three compounds, phrymarolin-I, haedoxane A, and haedoxane E from Phyrma leptostachya L.     

Evaluation of medicinal plant extracts against blood-sucking parasites

The present study was based on assessments of the antiparasitic activities to determine the efficacies of acetone, chloroform, ethyl acetate, hexane, and methanol dried leaf, flower, and seed extracts of Cassia auriculata L., Rhinacanthus nasutus KURZ., Solanum torvum Swartz, Terminalia chebula Retz., and Vitex negundo Linn. were tested against larvae of cattle tick Rhipicephalus (Boophilus) microplus Canestrini, 1887 (Acari: Ixodidae), adult of Haemaphysalis bispinosa Neumann, 1897 (Acarina: Ixodidae), hematophagous fly Hippobosca maculata Leach (Diptera: Hippoboscidae), nymph of goat-lice Damalinia caprae Gurlt (Trichodectidae), and adult sheep parasite Paramphistomum cervi Zeder, 1790 (Digenea: Paramphistomatidae). All plant extracts showed moderate parasitic effects after 24 h of exposure at 3,000 ppm; however, the highest parasite mortality was found in leaf ethyl acetate, flower methanol of C. auriculata, leaf and seed methanol of S. torvum, seed acetone of T. chebula, and leaf hexane extracts of V. negundo against the larvae of R. microplus (LC₅₀ = 335.48, 309.21, 297.43, 414.99, 167.20, and 611.67 ppm; LC₉₀ = 1571.58, 1111.82, 950.98, 1243.64, 595.31, and 1875.50 ppm), the leaf and flower methanol of R. nasutus, leaf and seed methanol of S. torvum, and seed methanol extracts of T. chebula against the nymph of D. caprae (LC₅₀ = 119.26,143.10,164.93,140.47, and 155.98 ppm; LC₉₀ = 356.77, 224.08, 546.20, 479.72, and 496.06 ppm), the leaf methanol of R. nasutus, leaf and seed methanol of S.torvum, and seed acetone of T. chebula against the adult of H. bispinosa (LC₅₀ = 333.15, 328.98, 312.28, and 186.46 ppm; LC₉₀ = 1056.07, 955.39, 946.63, and 590.76 ppm), the leaf methanol of C. auriculata, the leaf and flower methanol of R. nasutus, the leaf ethyl acetate of S. torvum against the H. maculata (LC₅₀ = 303.36, 177.21, 204.58, and 211.41 ppm; LC₉₀ = 939.90, 539.39, 599.43, and 651.90 ppm), and the leaf acetone of C. auriculata, the flower methanol of R. nasutus, the seed methanol of S. torvum, and the seed acetone of T. chebula were tested against the adult of P. cervi (LC₅₀ = 180.54, 168.59, 200.89, and 87.08 ppm; LC₉₀ = 597.51, 558.65, 690.37, and 433.85 ppm), respectively. Therefore, this study provides first report on the veterinary parasitic activity of plant extracts from Southern India.