Antifungal effects of amaryllidaceous alkaloids from bulbs of Lycoris spp. against Magnaporthe oryzae.

BACKGROUND: Rice blast caused by Magnaporthe oryzae is one of the most devastating diseases of rice, and novel fungicides for controlling rice blast are needed owing to the problem of resistance to commonly used control agents. We previously found that methanol extract of Lycoris radiata (L'Her.) Herb. showed an excellent inhibitory effect on mycelial growth of M. oryzae, indicating its potential for developing control agents against M. oryzae. In this study, we aim to investigate the antifungal effects of different Lycoris spp. against M. oryzae, and clarify the main active components. RESULTS: Extracts from bulbs of seven Lycoris spp. showed excellent inhibitory effects on mycelial growth and spore germination of M. oryzae at 400 mg L−1. Liquid chromatography–tandem mass spectrometry was employed to analyze the components of the extracts, and heatmap clustering analysis with Mass Profiler Professional software revealed that lycorine and narciclasine may be the main active components. Lycorine and narciclasine, together with three other amaryllidaceous alkaloids (AAs), were then isolated from bulbs of Lycoris spp. Antifungal assays showed that lycorine and narciclasine had good inhibitory activities against M. oryzaein vitro, but the other three AAs showed no antifungal activities under test concentrations. In addition, lycorine and the ethyl acetate part of L. radiata showed good antifungal effects against M. oryzaein vivo, but narciclasine showed phototoxicity on rice when used alone. CONCLUSION: Extracts of test Lycoris spp. and the main active component lycorine have excellent antifungal activities against M. oryzae, and are good candidates for developing control agents against M. oryzae. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]