Abstract:
A study was done to establish the phytochemical profile of Synadenium grantii (Hook. F.) extracts and determine their larvicidal activity on mosquito larvae. Three parts of Synadenium grantii (leaves, stem and roots) were extacted using ethanol and diethyl ether by soaking for 7 days. The phytochemical profiles of the different concentrations of the extracts were determined after filtration. Synadenium grantii was found to contain tannins, reducing sugars, alkaloid salts, anthracenosides, coumarins, flavonosides, steroid glycosides and anthocyanosides. However, the leaf extracts lacked steroid glycosides, while the stem and the root lacked both steroid glycosides and flavonosides. A larvicidal assay of each extract in varying concentrations was evaluated against 10 mosquito larvae in vitro. The larvae were then observed after an exposure period of 24 hours at an interval of 2 hours. The results of the larvicidal assay demonstrated that the ethanol extract from the stem had the strongest larvicidal activity at all the concentrations used of 20%, 8%, 2%, 1% and 0.5% causing a mean death of 86.7%, 90.8%, 85.8%, 85.8% and 84.1%, respectively. The diethyl ether extract from the stem showed the least larvicidal activity with a mean death of 35.8%, 29.2%, 30.0%, 21.7% and 33.3%, respectively. Generally, all the extracts from the different parts of the plant had larvicidal activity to a varying degree. It was further observed, that even for the larvae which did not die, had evidence of larval development inhibition. This study showed that extracts from this plant had phytochemicals which had larvicidal activity on mosquito larvae. The stem ethanol extracts had the most pronounced larvicidal effect on mosquito larvae with nearly 100% mortality at concentrations as low as 0.5% in 6 hrs. This study has showed that this plant has biopesticide effects and its application should be integrated with other mosquito control programmes. However, more work should be carried out on larvicidal efficacy of the active ingredients in the extracts of Synadenium grantii.
