In vitro antifungal activity of a 29-kDa glycoprotein purified from the galls of Quercus infectoria

The antifungal activity of 30 medicinal plants belonging to different families was tested in vitro on the phytopathogenic fungus Rhizoctonia solani. The results revealed that protein extract from the galls of Quercus infectoria belonging to Fagaceae family was highly effective in inhibiting the mycelial growth of R. solani. The gall extract of Q. infectoria also inhibited the growth of other agronomically important fungal pathogens viz. Fusarium oxysporum, Cochliobolus miyabeanus, Macrophomina phaseolina, Colletotrichum gloeosporioides, Magnaporthe salvinii, Cochliobolus lunatus, Alternaria solani, Pythium aphanidermatum and Colletotrichum falcatum. A 29-kDa glycoprotein was purified from the galls of Q. infectoria by ammonium sulphate fractionation followed by gel filtration on Sephadex G-50 column. The purified protein showed the absorption maxima at 640 nm and 308 nm. The purified protein was stable even after heating at 100 °C for 10 min or autoclaving at 121 °C for 20 min. When the 29-kDa protein was treated with NaIO₄ and pronase the antifungal activity was drastically reduced. The 29-kDa protein inhibited the mycelial growth of R. solani and C. miyabeanus at 2 μg level.