Larvicidal efficacy of 4-Dodecene derived from marine Streptomyces sp. VITVSK1 on Blood-Sucking Parasites

The present study was aimed to assess the larvicidal activity of the lead compound 4-dodecene isolated from Streptomyces sp. VITVSK1 against cattle ticks, Haemaphysalis bispinosa and Rhipicephalus (Boophilus) microplus; Anopheles subpictus and Culex quinquefasciatus larvae. The compound was methanol extracted and purified by silica gel column chromatography and preparative thin layer chromatography using a solvent system of chloroform: methanol (9:1 v/v). The active fractions were concentrated and analyzed by mass spectroscopy (MS) and based on the similarity index with reference compounds available in the mass spectra library, National Institute of Standards and Technology (NIST) the structure of the pure compound was elucidated. The structure of the purified compound was further confirmed with the help of 1H-NMR and 13C-NMR spectra. In this study, the crude extract and the lead compound 4-dodecene extracted from Streptomyces sp. VITVSK1 were tested against the larvae of the selected parasites at varying concentrations. Based on the spectral studies the compound was identified as 4-dodecene and the molecular formula of the aliphatic compound was established as C14H20O2. The methanolic extract (1000 ppm) showed antiparasitic effects after 24 h of exposure and the mortality of the parasites was observed in the larvae of A. subpictus (LC50=116.1 ppm; r2=0.864); R. microplus (LC50=331.79 ppm; r2=0.948); C. quinquefasciatus (LC50=168.59 ppm; r2=0.425) and H. bispinosa (LC50=284.02 ppm; r2= 0.885). The maximum efficacy was observed with the extracted compound 4-dodecene and the LC50 and r2 values were calculated against the larvae of A. subpictus (82.65 ppm; 0.688), R. microplus (173.48 ppm; 0.857), C. quinquefasciatus (78.32 ppm; 0.769) and against H. bispinosa (126.59 ppm; 0.840) respectively. The active compound 4-dodecene from Streptomyces sp. VITVSK1 exhibited profound larvicidal activity against blood-sucking parasites, A. subpictus, R. microplus, C. quinquefasciatus and H. bispinosa. The results of this study suggest that the active compound 4-dodecene can be probed further to be developed as a larvicidal agent.