title: Toxicity of herbal extracts used in ethno-veterinary medicine and green-encapsulated ZnO nanoparticles against Aedes aegypti and microbial pathogens.
abstract: Dengue and chikungunya are arboviral diseases mainly vectored by the mosquito Aedes aegypti. Presently, there is no treatment for these viral diseases and their prevention is still based on vector control measures. Nanopesticides fabricated using herbal extracts as reducing and capping agents currently represent an excellent platform for pest control. In this scenario, the present study assessed the acute toxicity of seven plants employed in ethno-veterinary medicine of southern India, as well as the green synthesis of zinc oxide nanoparticles, on third-instar larvae of A. aegypti. Larvae were exposed to extracts of the seven plants obtained with solvents of different polarity (acetone, ethanol, petroleum ether, and water) for 24 h. Maximum efficacy was observed for Lobelia leschenaultiana leaf extracts prepared using all the four solvent extracts (LC50= 22.83, 28.12, 32.61, and 36.85 mg/L, respectively). Therefore, this plant species was used for the synthesis and stabilization of ZnO nanoparticles based on its maximum efficacy against third-instar larvae of A. aegypti. L. leschenaultiana-encapsulated ZnO nanoparticles showed 100% mortality when tested at 10 mg/L, the LC50was extremely low,  1.57 mg/L. Zinc acetate achieved only 65.33% when tested at 60 mg/L, with a LC50of 51.62 mg/L. Additionally, ZnO nanoparticles inhibited growth of Pseudomonas aeruginosa, Proteus vulgaris, Shigella sonnei, and Vibrio parahaemolyticus and also inhibited biofilm formation on selected microbila pathogens, showing impact on EPS production and hydrophobicity. Overall, our results suggest that L. leschenaultiana-fabricated ZnO nanoparticles have a significant potential to control A. aegypti mosquitoes and Gram-negative bacterial pathogens.
authors.affiliation: Biomaterials and Biotechnology in Animal Health Lab, Department of Animal Health and Management, Alagappa University, Science Block, 6th Floor, Burma Colony, Karaikudi, Tamil Nadu, 630 003, India.
authors.forename: Balan
authors.initials: B
authors.lastname: Banumathi
authors.affiliation: Biomaterials and Biotechnology in Animal Health Lab, Department of Animal Health and Management, Alagappa University, Science Block, 6th Floor, Burma Colony, Karaikudi, Tamil Nadu, 630 003, India. vaseeharanb@gmail.com.
authors.forename: Baskaralingam
authors.initials: B
authors.lastname: Vaseeharan
authors.affiliation: Biomaterials and Biotechnology in Animal Health Lab, Department of Animal Health and Management, Alagappa University, Science Block, 6th Floor, Burma Colony, Karaikudi, Tamil Nadu, 630 003, India.
authors.forename: Ramachandran
authors.initials: R
authors.lastname: Ishwarya
authors.affiliation: Unit of Vector Control, Phytochemistry and Nanotechnology, Department of Zoology, Annamalai University, Annamalainagar, Tamil Nadu, 608 002, India.
authors.forename: Marimuthu
authors.initials: M
authors.lastname: Govindarajan
authors.affiliation: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Naiyf S
authors.initials: NS
authors.lastname: Alharbi
authors.affiliation: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Shine
authors.initials: S
authors.lastname: Kadaikunnan
authors.affiliation: Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Jamal M
authors.initials: JM
authors.lastname: Khaled
authors.affiliation: Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto 80, 56124, Pisa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Benelli
mesh_terms: D000330:Aedes / Q000187:drug effects*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003715:Dengue; D020834:Ethnopharmacology; D055772:Green Chemistry Technology; D007194:India; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects; D053758:Nanoparticles; D010936:Plant Extracts / Q000494:pharmacology; D018515:Plant Leaves; D012834:Silver / Q000494:pharmacology; D019155:Veterinary Drugs; D015034:Zinc Oxide / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D007306:Insecticides; D010936:Plant Extracts; D019155:Veterinary Drugs; D012834:Silver; D015034:Zinc Oxide
keywords: Acute toxicity; Biofilm; Dengue; Green synthesis; Zinc oxide nanoparticles