Abstract
Present study aimed at evaluation of mosquito larvicidal and antibacterial activities of mixture of crude and solvent extracts of Curcuma amada rhizome and Tamarindus indica leaf against Culex vishnui larvae and eight pathogenic bacteria. Larvicidal bioassay was performed by graded concentrations of crude, methanol and aqueous extracts. Log-probit analysis for estimation of LC 50 and LC 90 values was performed. ANOVA analysis was also conducted. Effects of the extracts on non-target organisms were also examined. Antibacterial activity was examined through standard methods. Preliminary phytochemical analysis and Fourier Transform Infra Red (FT-IR) spectroscopic analysis of the most potent extract were also done. Highest mortality (100%) was recorded at 100 ppm concentration of methanol extract after 72 hours in 1 st , 2 nd and 3 rd instars larvae. LC 50 and LC 90 values were 72.32 and 131.14 ppm respectively after 24 h for the 3 rd instar larvae. No effects on non-target organisms found. Crude and methanol extracts showed antibacterial activity against all tested bacteria while aqueous extracts showed none. Highest inhibition zone (19.00±0.00 mm) was observed against Pseudomonas fluorescens MTCC 103 by methanolic extract. Preliminary phytochemical screening of most potent extract detected tannins, flavonoids, alkaloids and terpenoids. Presence of various functional groups was revealed by FT-IR analysis. Results confirm the potential mosquito larvicidal and antibacterial activities of mixture C. amada rhizome and T. indica leaf extracts. This approach of using mixture of extracts for getting better result against harmful biological agents is a promising finding which may further approve application of coactivity of bioactive compounds of plant origin. 
Highlights
Among the well-known disease vectors mosquitoes are important in terms of public health concerns as they transmit a variety of fatal diseases like malaria, filariasis, dengue, Japanese encephalitis, yellow fever and many other diseases (Ghosh et al, 2012).In India all the three members of Culex vishnui group viz., Cx. vishnui, Cx. pseudovishnui and Cx. tritaeniorhynchus, responsible for transmission of Japanese Encephalitis virus, are present in areas where paddy fields are abundant (Chandra, 2000; Rawani et al, 2017).Recent mosquito control programme mainly focuses on avoidance of transmission by mosquito vectors either by killing adult mosquitoes by using fumigants or by destroying larvae at their breeding sites (Alouani et al, 2017)
1.1 Collection and authentication of plants Rhizome of C. amada was collected from local market of Burdwan and T. indica leaves were collected from outskirts of Burdwan (23°16 ́N, 87°54 ́E) in March 2018 and identified by Dr Ambarish Mukherjee, former Professor, Department of Botany, The University of Burdwan, Burdwan, West Bengal, India
The highest mortality i.e., 100.00% mortality was recorded at 0.5% concentration of crude extract against 1st instar larvae and 2nd and 3rd instars larvae after 48 h and 72 h of exposure respectively (Table 1)
Summary
Among the well-known disease vectors mosquitoes are important in terms of public health concerns as they transmit a variety of fatal diseases like malaria, filariasis, dengue, Japanese encephalitis, yellow fever and many other diseases (Ghosh et al, 2012).In India all the three members of Culex vishnui group viz., Cx. vishnui, Cx. pseudovishnui and Cx. tritaeniorhynchus, responsible for transmission of Japanese Encephalitis virus, are present in areas where paddy fields are abundant (Chandra, 2000; Rawani et al, 2017).Recent mosquito control programme mainly focuses on avoidance of transmission by mosquito vectors either by killing adult mosquitoes by using fumigants or by destroying larvae at their breeding sites (Alouani et al, 2017). Among the well-known disease vectors mosquitoes are important in terms of public health concerns as they transmit a variety of fatal diseases like malaria, filariasis, dengue, Japanese encephalitis, yellow fever and many other diseases (Ghosh et al, 2012). As mosquitoes are continuously gaining resistant against chemical insecticides, alternative measures such as applying botanical based insecticides are practiced worldwide (Singh et al, 2016). Researchers are continuously searching new botanicals with more effectiveness as they could fulfill the criteria of being environment friendly, inexpensive, and available in nature (Sharma et al, 2006). Infectious diseases caused by bacteria are our concern. Increasing resistance to commercial antibacterials or antibiotics in disease causing bacteria of human and livestock turned the focus of the researchers
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