Citriquinolinones A and B: Rare Isoquinolinone-Embedded Citrinin Analogues and Related Metabolites from the Deep-Sea-Derived Aspergillus versicolor 170217

Abstract

A systematic chemical investigation of the deep-sea-derived fungus <i>Aspergillus versicolor</i> 170217 resulted in the isolation of six new (<b>1</b>-<b>6</b>) and 45 known (<b>7</b>-<b>51</b>) compounds. The structures of the new compounds were established on the basis of exhaustive analysis of their spectroscopic data and theoretical-statistical approaches including GIAO-NMR, TDDFT-ECD/ORD calculations, DP4+ probability analysis, and biogenetic consideration. Citriquinolinones A (<b>1</b>) and B (<b>2</b>) feature a unique isoquinolinone-embedded citrinin scaffold, representing the first exemplars of a citrinin-isoquinolinone hybrid. Dicitrinones K-L (<b>3</b>-<b>4</b>) are two new dimeric citrinin analogues with a rare CH-CH₃ bridge. Biologically, frangula-emodin (<b>32</b>) and diorcinol (<b>17</b>) displayed remarkable anti-food allergic activity with IC₅₀ values of 7.9 ± 3.0 μM and 13.4 ± 1.2 μM, respectively, while diorcinol (<b>17</b>) and penicitrinol A (<b>20</b>) exhibited weak inhibitory activity against <i>Vibrio parahemolyticus</i>, with MIC values ranging from 128 to 256 μM.