Environmental Friendly Vector Control Potentials of Plant Secondary Metabolites

Abstract

Whole plants (wp) of Evolvulus nummularius, Mentha piperita, Mimosa pudica, Parthenium hysterophorus, Phyllanthus niruri, Polygonum hydropiper, Pouzolzia zeylanica, Synedrella nodiflora, aerial part (ap) and roots (r) of Lantana camara, and aerial part and rhizome (rh) of Zingiber zerumbet were extracted in petroleum ether (PetE), chloroform (CHCl3) and methanol (CH3OH), and were screened against four vectors i.e. eggplant aphid, Aphis gossypii; larvae of the mosquito, Culex quinquefasciatus; red flour beetle, Tribolium castaneum and brine shrimp, Artemia salina nauplii under laboratory conditions to yield their efficacy through dose-mortality assay and repellent activity against A. gossypii and T. castaneum; lethality against A. salina; larvicidal activity against C. quinquefasciatus larvae with much success. Antimicrobial activity tests were carried out in this connection for further justification of efficacy of the extractives. Isolation, purification and characterization of plant component(s) were also done to establish step-forward positive control measure(s) against four selected vectors from the pest control and pharmaceutical points of view. The mortality of A. gossypii were found in the descending order started with the E. nummularius (wp/PetE) giving LD50 0.034 mg/cm2 and ended with L. camara (ap/PetE) giving LD50 0.080mg/cm2. The larvicidal activity against C. quinquefasciatus larvae the descending order of intensity was started with Ph. niruri (wp/CHCl3) provided with the LC50 3.220ppm and ended with Mi. pudica (wp/PetE) giving LC50 88.187ppm). Methanol extract of Mi. pudica (wp), Pz. zeylanica (wp) and Z. zerumbet (ap) did not show any larvicidal effect. Brine shrimp lethality against A. salina nauplii the efficacy was in the descending order of Po. hydropiper (wp/CHCl3) provided with the LC50 1.590ppm and ended with Ph. niruri (wp/CHCl3) giving LC50 24.331ppm. The mortality of T. castaneum adults through dose-mortality assay were found in the descending order of M. piperita (wp/CH3OH) provided with the LD50 0.238mg/cm2 and ended with L. camara (r/PetE) giving LD50 2.672mg/cm2. While, no activity was traced for whole plant of Mi. pudica; and the methanol extract of Pz. zeylanica (wp); methanol and CHCl3 extracts of L. camara (r) and CHCl3 extract of S. nodiflora (wp) didn’t show any mortality against the adult beetles of T. castaneum. Against the eggplant aphids CH3OH extracts of E. nummularius (wp), L. camara (ap), Mi. pudica (wp) and Pz. zeylanica (wp) offered repellent activity, while the PetE and CHCl3 extracts of the same didn’t show repellency; however PetE, CHCl3 and CH3OH the extracts of Ph. niruri (wp), S. nodiflora (wp) and Z. zerumbet (ap); PetE extracts of M. piperita (wp), P. hysterophorus (wp) and Z. zerumbet (rh); CHCl3 extracts of L. camara (r) and Po. hydropiper (wp) and CH3OH extracts of P. hysterophorus (wp) and Po. hydropiper (wp) offered no repellent activity at all. For the repellency against T. castaneum adults CH3OH extracts of Po. hydropiper (wp) offered the most promising activity, however except L. camara (ap/CHCl3 and CH3OH); L. camara (r/PetE); M. piperita (wp/PetE); Mi. pudica (wp/PetE and CH3OH); P. hysterophorus (wp/CH3OH); Ph. niruri (wp/CHCl3 and CH3OH); Pz. zeylanica (wp/CHCl3) showed repellent activity of different degree; and aerial and rhizome part of Z. zerumbet extracts of all the three solvents showed no repellent activity. Activity tests of the extracts against eight selected pathogenic bacteria at concentrations of 200μg disc-1 and 400μg disc-1 compared with the standard antibiotic, Ampicilin 10μg disc-1 provided a promising outcome. The chloroform extract was found most effective in comparison to PetE and CH3OH extracts. Finding potential activity the PetE extract of E. nummularius (wp) and CH3OH extract of Po. hydropiper (wp) were attempted for chromatographic fractionation to isolate bioactive compound(s) and as a result two compounds named ENP and POM were isolated, and only the ENP was determined as palmitic acid. All the selected arthropod test agents are vectors [Aphid (Ng and Perry, 2004), Mosquito larvae (Michigan Mosquito Control Organization, 2013; Wilcox and Ellis, 2006: Janet, 2010), Red flour beetle (Channaiah et al., 2009); Brine shrimp (Sudhakaran et al., 2006: Hameed et al., 2002)] and the data achieved from the bioassays clearly showed the presence of insecticidal properties and vector control potentials in the test plants. Thus, comprehensive phytochemical analyses of the test plants for their insecticidal, insect repellent, cytotoxic and larvicidal leads, as well as the pharmacological studies of the active ingredients are very much to be solicited for their possible use in the future vector control and pharmaceutical endeavors.