title: Insecticidal compounds from Rhizophoraceae mangrove plants for the management of dengue vector Aedes aegypti.
abstract: OBJECTIVE
  Mosquito control is facing a threat due to the emergence of resistance to synthetic insecticides. Insecticides of botanical origin could serve as potential alternatives in future. Larvicidal efficacies of different parts of mangrove plants belonging to Rhizophoraceae family were tested against the late IV instar larvae of dengue vector, Aedes aegypti.
  
  
  METHODS
  Different plant parts (leaf, bark, root, stilt root, hypocotyl and flower) of Rhizophoraceae family mangrove plants (Bruguiera cylindrica, Ceriops decandra, Rhizophora mucronata and R. apiculata) were collected from Karangadu southeast coast of India. The larval mortality was observed after 24 h exposure. Repellency bioassays were carried out in a 10 Χ 10 Χ 3 m room at 27- 35°C and 60- 80% RH. The bark (A3 and E1) and stilt root (A3 and E4) fractions of R. mucronata with different concentrations (0.25, 0.50, 0.75, 1, 2 and 4 mg/cm) were applied on one arm.
  
  
  RESULTS
  The stilt root crude extract of R. mucronata showed maximum larvicidal activity (LC50 value 0.0275 ± 0.0066 μg/ml and LC90 = 0.0695 ± 0.156 μg/ml) followed by the bark extract (LC50 value of 0.03 ± 0.0076 μg/ml and LC90 = 0.0915 ± 0.156 μg/ml). Column chromatographic fractions of R. mucronata bark extracts (E1) showed maximum larvicidal activity (LC50 = 0.0496 ± 0.0085 μg/ml and LC90 = 0.1264 ± 0.052 μg/ml) followed by the acetone extract (LC50 = 0.0564 ± 0.0069 μg/ml and LC90 = 0.1187 ± 0.05 μg/ml). Ethanolic fraction (E4) of R. mucronata stilt root extracts showed maximum larvicidal activity (LC50 = 0.0484 ± 0.0078 μg/ml and LC90 = 0.1191 ± 0.025 μg/ml) followed by acetone fraction (A3) (LC50 = 0.0419 ± 0.0059 μg/ml and LC90 = 0.0955 ± 0.069 μg/ml). Repellent activity of R. mucronata stilt root and bark extracts (A3) showed maximum percentage of protection (97.5%) with 9.1 h protection time at 4 mg concentration of the stilt root extract. Moreover, ethanolic fraction of the stilt root (E4) extract showed maximum percentage of protection (100%) with 10 h protection time at 4 mg concentration. GC-MS analysis revealed that R. mucronata possesses variety of biopesticidal compounds.
  
  
  CONCLUSIONS
  The results as well as the significance of this preliminary investigation highlight the importance of R. mucronata as a novel source for natural insecticidal products.
authors.forename: M Syed
authors.initials: MS
authors.lastname: Ali
authors.affiliation: School of Marine Sciences, Department of Oceanography and CAS, Alagappa University, Thondi, India.
authors.forename: S
authors.initials: S
authors.lastname: Ravikumar
authors.forename: J Margaret
authors.initials: JM
authors.lastname: Beula
authors.forename: V
authors.initials: V
authors.lastname: Anuradha
authors.forename: N
authors.initials: N
authors.lastname: Yogananth
mesh_terms: D000330:Aedes / Q000187:drug effects* / Q000821:virology; D000818:Animals; D001681:Biological Assay / Q000379:methods; D003715:Dengue / Q000517:prevention & control*; D003716:Dengue Virus; D007194:India; D007303:Insect Vectors / Q000187:drug effects* / Q000821:virology; D007306:Insecticides / Q000032:analysis / Q000302:isolation & purification / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000821:virology; D007928:Lethal Dose 50; D009032:Mosquito Control / Q000379:methods*; D024301:Plant Bark / Q000737:chemistry; D010936:Plant Extracts / Q000032:analysis / Q000302:isolation & purification / Q000494:pharmacology*; D018517:Plant Roots / Q000737:chemistry; D043982:Rhizophoraceae / Q000737:chemistry*
chemical_list: D007306:Insecticides; D010936:Plant Extracts