Plant Disease Control Efficacy of and Its Antifungal Compounds.

Plants contain a number of bioactive compounds that exhibit antimicrobial activity, which can be recognized as an important source of agrochemicals for plant disease control. In searching for natural alternatives to synthetic fungicides, we found that a methanol extract of the plant species suppressed the disease development of rice blast caused by . Through a series of chromatography procedures in combination with activity-guided fractionation, we isolated and identified a total of eleven compounds including four labdane-type diterpenes (-), six isopimarane-type diterpenes (-), and one sesquiterpene (). Of the identified compounds, the MIC values of compounds , , & mixture, , and ranged from 100 to 200 μg/mL against , whereas the other compounds were over 200 μg/mL. When rice plants were treated with the antifungal compounds, compounds , , and effectively suppressed the development of rice blast at all concentrations tested by over 75% compared to the non-treatment control. In addition, a mixture of compounds & that constituted 66% of the ethyl acetate fraction also exhibited a moderate disease control efficacy. Together, our data suggest that the methanol extract of including terpenoid compounds has potential as a crop protection agent.