Krishnan Kannathasan

Bio: Krishnan Kannathasan is an academic researcher from Annamalai University. The author has contributed to research in topic(s): Vitex trifolia & Antibacterial activity. The author has an hindex of 8, co-authored 12 publication(s) receiving 492 citation(s).

Differential larvicidal efficacy of four species of Vitex against Culex quinquefasciatus larvae.

Abstract: The early fourth instar larvae of Culex quinquefasciatus, reared in the laboratory were used for larvicidal assay with leaf extracts of Vitex negundo, Vitex trifolia, Vitex peduncularis and Vitex altissima. The methanol extracts of the four species possessed varying levels of larvicidal nature. The highest larvicidal activity was found with the extract of V. trifolia (LC50 = 41.41 ppm) followed by V. peduncularis (LC50 = 76.28 ppm), V. altissima (LC50 = 128.04 ppm) and V. negundo (LC50 = 212.57 ppm).

Chemical constituents and larvicidal property of the essential oil of Blumea mollis (D. Don) Merr. against Culex quinquefasciatus.

Abstract: The essential oil from the leaves of Blumea mollis was extracted and the chemical constituents and the larvicidal against Culex quinquefasciatus effects studied. The analyses of gas chromatography (GC) and GC–mass spectroscopy (GC–MS) revealed that the leaf essential oil of B. mollis contained 39 compounds, and the major chemical compounds identified were linalool (19.43%), γ-elemene (12.19%), copaene (10.93%), estragole (10.81%), Allo-ocimene (10.03%), γ-terpinene (8.28%) and Allo-aromadendrene (7.44%). The essential oil had significant toxic effect against early fourth-instar larvae of C. quinquefasciatus with LC50 = 71.71 and LC90 = 143.41 ppm. The results could be useful in search of newer, safer and more effective natural larvicidal agent against C. quinquefasciatus.

Antimicrobial activity of fatty acid methyl esters of some members of Chenopodiaceae.

Abstract: Fatty acid methyl ester (FAME) extracts of four halophytic plants, viz. Arthrocnemum indicum, Salicornia brachiata, Suaeda maritima and Suaeda monoica belonging to the family Chenopodiaceae, were prepared and their composition was analyzed by GC-MS. The FAME extracts were also screened for antibacterial and antifungal activities. The GC-MS analysis revealed the presence of more saturated fatty acids than unsaturated fatty acids. Among the fatty acids analyzed, the relative percentage of lauric acid was high in S. brachiata (61.85%). The FAME extract of S. brachiata showed the highest antibacterial and antifungal activities among the extracts tested. The other three extracts showed potent antibacterial and moderate anticandidal activities.

Antibacterial activity of some salt marsh halophytes and mangrove plants against methicillin resistant Staphylococcus aureus

Abstract: The antibacterial activity of aqueous and methanol extracts of leaves/shoots of five salt marsh halophytes and six mangroves was studied against methicillin resistant, clinical isolates of Staphylococcus aureus. There was a clear comparability between the salt marsh halophytes and mangroves in their antibacterial action. The mangrove plants possessed higher antibacterial potency than the salt marsh halophytes. The highest activity was recorded with the methanol extract of Excoecaria agallocha followed by the methanol extracts of Aegiceras corniculatum, Lumnitzera racemosa and Ceriops decandra. The minimum inhibitory concentration (MIC) values ranged from 0.125 to 4 mg/mL and 1 to 16 mg/mL for methanol and aqueous extracts, respectively. Further separation of active principle from the potent mangrove plant will be useful for the control of drug resistant strains of S. aureus.

Mosquito larvicidal activity of methyl-p-hydroxybenzoate isolated from the leaves of Vitex trifolia Linn.

Abstract: The vector-borne diseases caused by mosquitoes are one of the major health problems in many countries especially in tropical and sub-tropical countries. The resistance of mosquitoes to synthetic chemicals and environmental toxicity created by the chemicals raised the demand for finding of alternate natural molecules that control mosquito. In the present study, a crystalline compound methyl-p-hydroxybenzoate was isolated from the methanol extract of Vitex trifolia leaves and it was identified by (1)H and (13)C NMR and single crystal X-ray diffractometer. The larvicidal potential of the isolated compound was evaluated against early 4th instar larvae of Culex quinquefasciatus and Aedes aegypti. The compound exhibited 100% larval mortality of both the mosquitoes at 20 ppm with LC(50) values of 5.77 and 4.74 ppm against C. quinquefasciatus and A. aegypti, respectively. The methyl-p-hydroxybenzoate, which is reported for the first time to our best of knowledge from V. trifolia can be better explored for the control of mosquito population.

Plant extracts as potential mosquito larvicides

Abstract: Mosquitoes act as a vector for most of the life threatening diseases like malaria, yellow fever, dengue fever, chikungunya ferver, filariasis, encephalitis, West Nile Virus infection, etc. Under the Integrated Mosquito Management (IMM), emphasis was given on the application of alternative strategies in mosquito control. The continuous application of synthetic insecticides causes development of resistance in vector species, biological magnification of toxic substances through the food chain and adverse effects on environmental quality and non target organisms including human health. Application of active toxic agents from plant extracts as an alternative mosquito control strategy was available from ancient times. These are non-toxic, easily available at affordable prices, biodegradable and show broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on phytochemical sources and mosquitocidal activity, their mechanism of action on target population, variation of their larvicidal activity according to mosquito species, instar specificity, polarity of solvents used during extraction, nature of active ingredient and promising advances made in biological control of mosquitoes by plant derived secondary metabolites have been reviewed.

Essential oils for the development of eco-friendly mosquito larvicides: A review

Abstract: Mosquitoes serve as vectors for a wide variety of human and veterinary pathogens and parasites and cause extensive morbidity and mortality, and are a major economic burden within disease-endemic countries. Protection against mosquitoes is based on insecticides. However, the negative effects of synthetic insecticides have become the main impetus for an expeditious search for new alternatives, which would be acceptable for both the environment and public health. The use of insecticides based on plant extracts is currently highly promising from the alternatives of protection against insects. Many plant extracts that contain substances with insecticidal effects also include a large group of the so-called essential oils (EOs). The intensity of research focused on new EOs that could become suitable active substances for new botanical larvicides has been growing over the past few decades. The purpose of this review was to evaluate the current research on using EOs as potential larvicides based on their chemical composition and biological efficacy. The selected plants (their EOs), as the case may be, were therefore required to meet two essential conditions: (i) LC50 ≤ 100 ppm; and (ii) their chemical composition had to be known. In total, 122 plant species from 26 families were selected from the available literature. However, more than 2/3 of the plants (68.8%) were from only 5 families: Lamiaceae, Cupressaceae, Rutaceae, Apiaceae, and Myrtaceae. Considering the above-estimated LC50 value as the main criterion of efficacy, 77 showed LC50

Synthesis of silver nanoparticles using Nelumbo nucifera leaf extract and its larvicidal activity against malaria and filariasis vectors.

Abstract: The aim of this study was to investigate the larvicidal potential of the hexane, chloroform, ethyl acetate, acetone, methanol, and aqueous leaf extracts of Nelumbo nucifera Gaertn. (Nymphaeaceae) and synthesized silver nanoparticles using aqueous leaf extract against fourth instar larvae of Anopheles subpictus Grassi and Culex quinquefasciatus Say (Diptera: Culicidae). Nanoparticles are being used in many commercial applications. It was found that aqueous silver ions can be reduced by aqueous extract of plant parts to generate extremely stable silver nanoparticles in water. The results recorded from UV–vis spectrum, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared support the biosynthesis and characterization of silver nanoparticles. Larvae were exposed to varying concentrations of plant extracts and synthesized silver nanoparticles for 24 h. All extracts showed moderate larvicidal effects; however, the maximum efficacy was observed in crude methanol, aqueous, and synthesized silver nanoparticles against the larvae of A. subpictus (LC50 = 8.89, 11.82, and 0.69 ppm; LC90 = 28.65, 36.06, and 2.15 ppm) and against the larvae of C. quinquefasciatus (LC50 = 9.51, 13.65, and 1.10 ppm; LC90 = 28.13, 35.83, and 3.59 ppm), respectively. These results suggest that the leaf methanol, aqueous extracts of N. nucifera, and green synthesis of silver nanoparticles have the potential to be used as an ideal eco-friendly approach for the control of the A. subpictus and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.

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

Abstract: 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.

Larvicidal activity of Saraca indica, Nyctanthes arbor-tristis, and Clitoria ternatea extracts against three mosquito vector species

Abstract: Screening of natural products for mosquito larvicidal activity against three major mosquito vectors Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi resulted in the identification of three potential plant extracts viz., Saraca indica/asoca, Nyctanthes arbor-tristis, and Clitoria ternatea for mosquito larval control. In the case of S. indica/asoca, the petroleum ether extract of the leaves and the chloroform extract of the bark were effective against the larvae of C. quinquefasciatus with respective LC50 values 228.9 and 291.5 ppm. The LC50 values of chloroform extract of N. arbor-tristis leaves were 303.2, 518.2, and 420.2 ppm against A. aegypti, A. stephensi, and C. quinquefasciatus, respectively. The methanol and chloroform extracts of flowers of N. arbor-tristis showed larvicidal activity against larvae of A. stephensi with the respective LC50 values of 244.4 and 747.7 ppm. Among the methanol extracts of C. ternatea leaves, roots, flowers, and seeds, the seed extract was effective against the larvae of all the three species with LC50 values 65.2, 154.5, and 54.4 ppm, respectively, for A. stephensi, A. aegypti, and C. quinquefasciatus. Among the three plant species studied for mosquito larvicidal activity, C. ternatea was showing the most promising mosquito larvicidal activity. The phytochemical analysis of the promising methanolic extract of the seed extract was positive for carbohydrates, saponins, terpenoids, tannins, and proteins. In conclusion, bioassay-guided fractionation of effective extracts may result in identification of a useful molecule for the control of mosquito vectors.