Lignans from Larrea tridentate (creosote bush) as fungal β-1,3-glucanase inhibitors

The enzyme β-1,3-glucanase has a physiological role in morphogenetic-morpholytic processes during fungal development and differentiation. This fungal enzyme has been demonstrated to be involved in fungal pathogen-plant interactions during pathogen attack; therefore fungal β-1,3-glucanase is a biological target for the development of new target-oriented fungicides. In this study, two naturally occurring lignans, nordihydroguaiaretic acid (NDGA) and methyl-nordihydroguaiaretic acid (methyl-NDGA) were isolated on the basis of the biological activity from Larrea tridentate, and the effects of the isolated compounds on fungal endo-β-(1,3)-glucanase were evaluated. The enzyme activity was completely inhibited by nordihydroguaiaretic acid at 10 and 25 μM under our experimental conditions. Methyl-NDGA displayed modest bioactivity; it was less potent than the parent compound. Our results suggest that nordihydroguaiaretic acid is a fungal endo-β-(1,3)-glucanase inhibitor, and therefore, could be a useful antifungal agent in crop protection.