Inhibitory action of ginkgolic acid against pathogenic fungi and characterisation of its inhibitory activities on Nigrospora oryzae

ABSTRACT Ginkgolic acid is a natural plant antifungal substance with important biological activities, present in the testa of Ginkgo biloba. This research aims to analyse the antifungal action of ginkgolic acid against pathogenic fungi. Ginkgolic acid was analyzed by HPLC and FTIR, and the in vitro inhibitory activities of ginkgolic acid against pathogenic fungi has been investigated. Results showed that ginkgolic acid was a small hydrophobic molecule composed of five ginkgolic acids and their derivatives, with the alkyl and phenolic hydroxyl groups being located on the skeleton of the aromatic ring. Among Nigrospora oryzae (N. oryzae), Alternaria alternata (A. alternata) and Penicillium expansum (P. expansum), ginkgolic acid showed the strongest inhibition against N. oryzae, and the inhibition rate of ginkgolic acid at 5 mg · mL-1 reached 65.82%. Ginkgolic acid lysed the cell membrane of N. oryzae, causing the leaking of the mycelial protein and enhancement of the permeability of the cell membrane, which caused the electrical conductivity of the liquid medium to increase. In addition, it also decreased the activities of superoxide dismutase and catalase in the mycelium of N. oryzae, thereby weakening the cell’s protective function by damaging the integrity of the biomembrane. Furthermore, ginkgolic acid can effectively protect the leaves of Epipremnum aureum from infection by N. oryzae. It was concluded that ginkgolic acid effectively inhibited the activity of N. oryzae.