title: Isolation and characterisation of acaricidal and larvicidal novel compound (2S,5R,6R)-2-hydroxy-3,5,6-trimethyloctan-4-one from Streptomyces sp. against blood-sucking parasites.
abstract: The aim of the present study was to assess the acaricidal and larvicidal property of marine actinobacterial compound (2S,5R,6R)-2-hydroxy-3,5,6-trimethyloctan-4-one extracted and isolated from Streptomyces sp. VITDDK3 tested against the larvae of Rhipicephalus (Boophilus) microplus Canestrini (Acari: Ixodidae), Anopheles subpictus Grassi and Culex quinquefasciatus Say (Diptera: Culicidae). The isolate was taxonomically characterised, identified and designated as Streptomyces sp. VITDDK3. The crude compound was loaded on silica gel column and eluted with chloroform-methanol-water. The purity of the compound isolated was analysed by thin layer chromatography using chloroform and methanol as the solvent system and confirmed by high-performance liquid chromatography. The structure of the purified compound was established from infrared, ultraviolet, (1)H-nuclear magnetic resonance (NMR), (13)C-NMR and mass spectral data. The chemical shift assignments obtained for the aliphatic compound from (1)H-NMR corresponding to the molecular formula C(11)H(22)O(2). Bioassay-guided fractionation led to the isolation of compound, which was identified as (2S,5R,6R)-2-hydroxy-3,5,6-trimethyloctan-4-one. In the present study, Streptomyces sp. VITDDK3 crude extract and different fractions were tested against the larvae of parasites at a concentration of 1,000 ppm. Those fractions showing 100% mortality in 24 h alone was selected for further column chromatographic separation. The purified compound (2S,5R,6R)-2-hydroxy-3,5,6-trimethyloctan-4-one was tested in the concentrations of 250, 200, 150, 100 and 50 ppm and observed the per cent mortality of 100, 88, 62, 50 and 36 against R. microplus; 100, 100, 87, 62 and 39 against A. subpitcus; and 100, 94, 79, 51 and 33 against C. quinquefasciatus, respectively. The crude extract showed parasitic effects after 24 h of exposure at 1,000 ppm, and parasite mortality was observed against the larvae of R. microplus (LC(50) = 88.74 ppm; r (2) = 0.865) against the larvae of A. subpictus (LC(50) = 162.59 ppm; r (2) = 0.817) and against C. quinquefasciatus (LC(50) = 120.15 ppm; r (2) = 0.782), respectively. The maximum efficacy was observed in purified marine actinobacterial compound (2S,5R,6R)-2-hydroxy-3,5,6-trimethyloctan-4-one with LC(50) and r (2) values against the larvae of R. microplus (94.49 ppm; 0.982) and A. subpictus (69.65 ppm; 0.906) and against C. quinquefasciatus (82.82 ppm; 0.957), respectively. The control (distilled water) showed nil mortality in the concurrent assay.
authors.affiliation: Biomolecules and Genetics Division, School of Biosciences and Technology, VIT University, Vellore, 632 014, Tamil Nadu, India.
authors.forename: Thimiri Lakshmipathi
authors.initials: TL
authors.lastname: Deepika
authors.forename: Krishnan
authors.initials: K
authors.lastname: Kannabiran
authors.forename: Venkatesan Gopiesh
authors.initials: VG
authors.lastname: Khanna
authors.forename: Govindasamy
authors.initials: G
authors.lastname: Rajakumar
authors.forename: Chidambaram
authors.initials: C
authors.lastname: Jayaseelan
authors.forename: Thirunavukkarasu
authors.initials: T
authors.lastname: Santhoshkumar
authors.forename: Abdul Abdul
authors.initials: AA
authors.lastname: Rahuman
mesh_terms: D056810:Acaricides / Q000737:chemistry* / Q000494:pharmacology*; D000818:Animals; D009033:Culicidae / Q000187:drug effects; D007306:Insecticides / Q000737:chemistry* / Q000494:pharmacology*; D007659:Ketones / Q000737:chemistry* / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D008958:Models, Molecular; D015394:Molecular Structure; D000442:Octanols / Q000737:chemistry* / Q000494:pharmacology*; D010802:Phylogeny; D048494:Rhipicephalus / Q000187:drug effects*; D013302:Streptomyces / Q000737:chemistry* / Q000235:genetics
chemical_list: C577603:2-hydroxy-3,5,6-trimethyloctan-4-one; D056810:Acaricides; D007306:Insecticides; D007659:Ketones; D000442:Octanols