Inhibitory Effects of Bitter Kola (Garcinia kola) Seed Extract on Aspergillus Species Isolated from Maize

Abstract

Maize is an important crop worldwide, serving as good source of food and income. Contamination by Aspergillus makes it less suitable  for human intake as a result of discoloration and decrease in nutritional composition. This research sought to examine the inhibitory  effect of different concentrations of bitter kola seed extract on Aspergillus species isolated from maize grains. The invitro experiment was  carried out at the department of plant science laboratory, Modibbo Adama University, Yola in triplicate, using a Complete  Randomized Design with a total of thirty plates. The test plant active components used were extracted using ethanol. 10, 30, 60 and 100%  of bitter kola seed extract was added to Potato Dextrose Agar before inoculation. The effect of the extract on isolated Aspergillus species  increased with increase in concentration. Inhibition percentage at the highest concentration (100%) of the extract was more effective in  the control of Aspergillus niger (65.90%), an increased level of inhibition was also recorded against Aspergillus flavus (57.03%) at the  highest concentration. There was notable variation in the suppression of fungal growth across the different concentrations of the extract.  Phytochemical analysis showed the presence of alkaloids, flavonoids, tannins, saponins, phenol, terpenoids and glycosides. The  findings of this study are very important in the control of maize rot as they are biologically based, affordable and ecofriendly; hence  higher concentrations of bitter kola seed extract are recommended for use in the control of Aspergillus species causing maize rot.