Natural Anophelin mosquito repellents and phytochemical analysis of ethanol and hexane leaf extracts from four plant species

Abstract

Currently mosquitoes control is the cornerstone to minimize the rising number of mosquito borne diseases. There is an urgent need looking for alternatives to the current reliance on synthetic insecticides for the vectors control. Application of active toxic agents from plant extracts as an alternative control strategy was available from ancient times. These are non-toxic, easily available at affordable prices, biodegradable and show broad-spectrum target-specific activities against different species of vectors. Natural products with repellency properties are urgently needed. An insect repellent works by masking human scent, and a number of natural and synthetic mosquito repellents were studied. The main aim of this study was to identify the phytochemicals and compare their potentials as mosquito repellents from the ethanol (Et. OH) and hexane (hex) leaf extracts (LEs) of Ocimum basilicum, Coleus forskohlii, Eucalyptus camaldulensis and Cymbopogon flexuosus under laboratory conditions at 50 and 100% concentrations. Phytochemical analysis showed that alkaloids, saponins, flavonoids, terpenes, tannins and terpenoids were present/or absent in the 4 plant-LEs. At 50% concentration of Et. OH extracts, C. forskohlii exhibited higher repellency potential on Anopheles gambiae with protection time of 137.3 min, while O. basilicum, E. camaldulensis and Cy. flexuosus registered protection time of 30.6, 15.3 and 19 min, respectively. At 100% concentration of ethanol- extracts, C. forskohlii caused the highest protection time against the vector with protection time of 182 min. O. basilicum, E. camaldulensis and Cy. flexuosus were equally less potent against the insect, with protection time 42.6, 32.6 and 28 min, respectively. Regarding hex-extract, at 50% concentration of C. forskohlii, the highest repellency potential , with protection time of 174 was registered, while O. basilicum, E. camaldulensis and Cy. flexuosus registered protection times of 44, 18 and 28.6 min, respectively. However, the 100% concentration of Et. OH-extracts of, C. forskohlii and O. basilicum exhibited the highest protection time, with protection times of 228 and 116min, respectively. E. camaldulensis and Cy. flexuosus were less potent, with protection times 28.6 and 54.6 min, respectively. The EOs of C. forskohlii and O. basilicum L EOs proved to have potentials as repellency agents against Anopheles. GC-MS analysis of the extracts identified the compounds of both solvents extracts and the terpens were the major compounds. According to the results, further studies are required, especially on the extracts of basil and coleus since they proved to be effective.

Keywords

• mosquito repellent, anopheles, essential oils, sweet basil, wild thyme, kafure, lemon grass