Suppression of anthracnose disease by orsellinaldehyde isolated from the mushroom Coprinus comatus.

AIMS: Anthracnose caused by Colletotrichum species is one of the most devastating diseases of fruits and crops. We isolated and identified an antifungal compound from the mushroom Coprinus comatus and investigated its inhibitory potential against anthracnose disease-causing fungi with the goal of discovering natural products that can suppress anthracnose-caused plant disease. METHODS AND RESULTS: The culture filtrate of C. comatus was subjected to a bioassay-guided isolation of antifungal compounds. The active compound was identified as orsellinaldehyde (2,4-dihydroxy-6-methylbenzaldehyde) based on mass spectroscopy and nuclear magnetic resonance analyses. Orsellinaldehyde displayed broad-spectrum inhibitory activity against different plant pathogenic fungi. Among the tested Colletotrichum species, it exhibited the lowest IC50 values on conidial germination and germ tube elongation of Colletotrichum orbiculare. The compound also showed remarkable inhibitory activity against Colletotrichum gloeosporiodes. The staining of Colletotrichum conidia with fluorescein diacetate and propidium iodide demonstrated that the compound is fungicidal. The postharvest in-vivo detached fruit assay indicated that orsellinaldehyde suppressed anthracnose lesion symptoms on mango and cucumber fruits caused by C. gloeosporioides and C. orbiculare, respectively. CONCLUSIONS: Orsellinaldehyde was identified as a potent antifungal compound from the culture filtrate of C. comatus. The inhibitory and fungicidal activities of orsellinaldehyde against different Colletotrichum species indicate its potential as a fungicide for protecting various fruits against anthracnose disease-causing fungi.

Identification of two phthalide derivatives and an oxindole compound isolated from the edible mushroom Pleurotus ostreatus and their inhibitory activities against plant pathogenic microorganisms.

The excessive use of chemical pesticides in agricultural fields for controlling plant pathogenic microorganisms harms human health, the environment, and other beneficial microorganisms in the soil and plants. To address this challenge, it is essential to isolate and discover bioactive compounds from biological resources that could inhibit plant pathogenic microorganisms. In this study, the culture filtrate of the edible mushroom Pleurotus ostreatus was subjected to bioassay-guided isolation, and two phthalide derivatives-4,6-dimethoxyphthalide (1) and 5,7-dimethoxyphthalide (2)-were identified, along with an oxindole compound-3-hydroxy-3-methyloxindole (3). The inhibitory activities of the three compounds were evaluated against four fungal and five bacterial pathogens. Remarkably, 1 and 2 exhibited the lowest IC50 values against the conidial germination and germ tube elongation of the rice blast fungus Pyricularia oryzae. However, their effectiveness against bacterial pathogens was relatively low. The (S) and (R)-enantiomers of 3-hydroxy-3-methyloxindole showed different activities against plant fungal pathogens and bacterial plant pathogens.