In vitro effect of antifungal fractions from the plants Baccharis glutinosa and Jacquinia macrocarpa on chitin and beta-1,3-glucan hydrolysis of maize phytopathogenic fungi and on the fungal beta-1,3-glucanase and chitinase activities.

摘要

B accharis glutinosa and J acquinia macrocarpa are medicinal plants whose antifungal activity has been observed on maize phytopathogenic fungi. However, the specific site where those compounds act has not been studied. The objective of this work was to evaluate the hydrolytic effect of antifungal fractions from B. glutinosa (BgF) and J. macrocarpa (JmF) on beta-glucan and chitin isolated from A spergillus flavus and F usarium verticillioides, as well as their inhibition activity on the fungal hydrolases beta-glucanase and chitinase. The antifungal fractions did not show beta-1,3-glucanase activity, instead, they showed chitinase activity against polymeric extracts from fungi. None of the antifungal fractions inhibited the chitinase activity of the fungi. However, both BgF and JmF antifungal fractions inhibited fungal beta-1,3-glucanase activity acting as competitive inhibitors. It is possible that the antifungal fractions inhibit the beta-1,3-glucanase activity affecting beta-1,3-glucan synthesis, causing the production of a defective cell wall. These defects in the cell wall may allow the antifungal fractions to hydrolyze chitin causing delay in fungal growth. Practical Applications. Studies have proved that plants are one of the major sources for drug discovery and development, because plant-derived drugs have been reported to be safe and with no side effects. B. glutinosa and J. macrocarpa are plants used in traditional medicine by native people of Mexico, and their antifungal activity has been observed against mycotoxigenic fungi commonly associated with maize and other cereal grains. Although the effect on hyphae and spores suggests the interaction between the antifungal fractions and the fungal cell walls, as far as we know, there are no studies designed to elucidate the mode of action and the specific site of the cell wall where those compounds act. The results obtained in the present study suggest the presence of chitinase activity and a beta-1,3-glucanase inhibitor found together in the antifungal fractions, which makes them a potential valuable alternative to synthetic fungicides for protecting maize and other cereal grains from fungal contamination