A new dimeric naphtho-γ-pyrone from an endophytic fungus Aspergillus Niger AKRN associated with the roots of Entandrophragma congoense collected in Cameroon

Abstract

A new dimeric naphtho-γ-pyrone, 2-hydroxydihydroNigerone (1), along with five compounds, Nigerone (2), pyrophen (3), kojic acid (4), 4-(hydroxymethyl)-5-hydroxy-2H-pyran-2-one (5), and p-hydroxyphenylacetic acid (6), was isolated from an endophytic fungus Aspergillus Niger AKRN associated with the roots of Entandrophragma congoense. The structure of the new compound has been elucidated using spectroscopic data including 1D and 2D NMR as well as the high-resolution mass spectrometry. Compounds 1.5 showed weak antimicrobial activity on five selected Gram-negative bacteria, namely Enterobacter aerogenes (CM64), Enterobacter cloacae (BM67), Klebsiella pneumonia (K2), and Escherichia coli (ATCC8739 and ATCC10536).