Antifungal Activity of β-Asarone from Rhizomes of Acorus gramineus

An antifungal substance was isolated from the extract of Acorus gramineus using various chromatographic procedures. The antibiotic was identified as β-asarone, cis-2,4,5-trimethoxy-1-propenylbenzene, on the basis of the high-resolution El-mass, NMR, and UV spectral data. β-Asarone completely inhibited mycelial growth of some plant pathogenic fungi, Cladosporium cucumerinum, Colletotrichum orbiculare, Magnaporthe grisea, and Pythium ultimum, in a range of 0.5-30 μg/mL. The growth of Bacillus subtilis, Erwinia carotovora subsp. carotovora, Ralstonia solanacearum, and Xanthomonas campestris pv. vesicatoria was slightly suppressed by β-asarone. As the concentration of β-asarone increased, M. grisea infection was drastically inhibited on rice leaves. Treatment with 500 μg/mL of β-asarone also greatly suppressed lesion formation of Co. orbiculare on cucumber leaves. This is the first study to demonstrate in vitro and in vivo antifungal activity of β-asarone against plant fungal pathogens M. grisea and C. orbiculare.