Herbicidal and Antifungal Xanthone Derivatives from the Alga-Derived Fungus <i>Aspergillus versicolor</i> D5

Abstract

Fungi have been proved as promising and prolific sources of functional secondary metabolites with potent agricultural applications. In this study, 14 xanthone derivatives (<b>1</b>-<b>14</b>), including six new ones, versicones I-N (<b>1-4</b>, <b>7</b>, <b>11</b>), and a biogenetically related derivative (<b>15</b>), were isolated from the alga-derived fungus <i>Aspergillus versicolor</i> D5. Their structures were elucidated by comprehensive spectroscopic methods. Versicone L (<b>4</b>) exhibited a broad antifungal spectrum and prominent inhibitory effects on <i>Botrytis cinerea</i> at a minimum inhibitory concentration (MIC) of 152 μM, 7-fold stronger than that of the positive control, carbendazim (MIC = 1.05 × 10³ μM). Dihydrosterigmatocystin (<b>13</b>) showed strong antifungal activity toward <i>B. cinerea</i> at MIC = 38.3 μM, almost 30-fold stronger than that of carbendazim. Meanwhile, <b>13</b> exhibited potent herbicidal activity toward <i>Amaranthus retroflexus</i> L. with an MIC of 24.5 μM, approximately 4-fold stronger than that of the positive control, glyphosate (MIC = 94.7 μM). Additionally, <b>13</b> also displayed remarkable activity against other weeds belonging to <i>Amaranth</i> sp. Analysis of the structure-herbicidal activity relationship indicated that the bifuranic ring played an important role in xanthone phytotoxicity and the presence of a double bond in the furan ring could decrease phytotoxicity. This study indicated that xanthones can be served as promising candidates for lead compounds of agrochemicals.