In Vitro and In Vivo Anti-Phytopathogenic Fungal Activity of a Culture Extract of the Marine-Derived Fungus, Aspergillus unguis KUFA 0098, and Its Major Depsidone Constituents

The crude ethyl acetate extract of the culture of a marine sponge-associated fungus, <i>Aspergillus unguis</i> KUFA 0098, was tested for its capacity to inhibit the growth of ten phytopathogenic fungi, <i>viz</i>. <i>Alternaria brassicicola</i>, <i>Bipolaris oryzae</i>, <i>Colletotrichum capsici</i>, <i>Curvularia oryzae</i>, <i>Fusarium semitectum</i>, <i>Lasiodiplodia theobromae</i>, <i>Phytophthora palmivora</i>, <i>Pyricularia oryzae</i>, <i>Rhizoctonia oryzae</i>, and <i>Sclerotium roflsii.</i> At a concentration of 1 g/L, the crude extract was most active against <i>P. palmivora</i>, causing the highest growth inhibition (55.32%) of this fungus but inactive against <i>R. oryzae</i> and <i>S. roflsii</i>. At a concentration of 10 g/L, the crude extract completely inhibited the growth of most of the fungi, except for <i>L. theobromae</i>, <i>R. oryzae</i>, and <i>S. roflsii</i>, with 94.50%, 74.12%, and 67.80% of inhibition, respectively. The crude extract of <i>A. unguis</i> KUFA 0098 exhibited growth-inhibitory effects against <i>B. oryzae</i> and <i>P. oryzae</i>, causative agents of brown leaf spot disease and leaf blast disease, respectively, on rice plant var. KDML105, under greenhouse conditions. Chromatographic fractionation and purification of the extract led to the isolation of four previously described depsidones, <i>viz.</i> unguinol (<b>1</b>), 2-chlorounguinol (<b>2</b>), 2,4-dichlorounguinol (<b>3</b>), and folipastatin (<b>4</b>), as well as one polyphenol, aspergillusphenol A (<b>5</b>). The major compounds, i.e., <b>1</b>, <b>2</b>, and <b>4</b>, were tested against the ten phytopathogenic fungi. Compounds <b>1</b> and <b>4</b> were able to inhibit growth of most of the fungi, except <i>L. theobromae, R. oryzae</i>, and <i>S. roflsii</i>. Compound <b>1</b> showed the same minimum inhibitory concentration (MIC) values as that of carbendazim against <i>A. brassicicola</i>, <i>C. capsici</i>, <i>C. oryzae</i>, and <i>P. oryzae</i>, while compound <b>4</b> showed the same MIC values as that of carbendazim against only <i>C. capsici</i> and <i>P. oryzae</i>. Compound <b>2</b> was not active against all of the ten phytopathogenic fungi tested.