Abstract

Dennis Kipngeno Chirchir, Russell Ben Omondi Ouma, Peter Kiplagat Cheplogoi and Josiah Ouma Omolo*

The main objective of this investigation was to find mosquito larvicidal secondary metabolites from a basidiomycete – Stereum species (JO5289) – against Aedes aegypti. The Stereum species (JO5289) was collected in July 2005 from undisturbed habitat in Londiani forest in Rift Valley province, Kenya. Extracellular crude extracts from Stereum species (JO5289) produced strong activity against A. aegypti larvae. Purification of the crude extracts targeting larvicidal activity using chromatography gave three active compounds namely; tyrosol, 3-methoxy-5-methyl-1,2-benzenediol and 2-hydroxy-4-(4-hydroxychroman-7yl) but-3-enal. The chemical structures of the compounds were determined using the nuclear magnetic resonance (NMR) spectral data and comparison with literature values. When tested for larvicidal activity, the LC50 for the three compounds were 26.7, 17.3 and 14.5 ppm, respectively, while LC90 were 85.3, 83.5 and 82.9 ppm, respectively, after 24 h of exposure. These compounds have been produced from cultures of a Stereum species and reported to have mosquito larvicidal activity for the first time.