Inhibition of growth of some phytopathogenic and mycotoxigenic fungi by aqueous extracts of Combretum imberbe (Wawra) wood

Fungal attack of crop plants and the associated production of mycotoxins on edible produce from plants is a global concern. This is so because mycotoxins are carcinogenic. This study reports on an investigation of the effects of aqueous extracts of Combretum imberbe wood ash on the growth of some phytopathogenic and mycotoxigenic fungi including Aspergillus flavus, Fusarium oxysporum, Penicillium italicum, Penicillium notatum as well as Alternaria alternata. The aqueous extract of C. imberbe wood ash exhibited significant capacity to inhibit growth of all the test fungi, with the exception of A. alternata. Arrest of fungal growth by the extract involved inhibition of glucomamylase. Investigation of the chemistry of the ash using Fourier-Transform Infrared (FT-IR) spectroscopy and X-ray powder diffraction (XRPD) analysis revealed the presence of aluminium oxide (Al₂O₃), calcium carbonate (CaCO₃), calcium hydroxide (Ca(OH)₂), potassium chloride (KCI), potassium sulphate (K₂SO₄) and cobalt carbonate (C0CO3). We propose that the inhibition of fungal growth may be related to limited carbon supply as a result of inhibited activity of glucoamylase in the presence of C. imberbe wood ash extract.