A preliminary investigation of furanocoumarin metabolism by Aspergillus niger

Kyung Myung, John A. Manthey, Jan A. Narciso

Abstract


Fungi metabolize polycyclic aromatic hydrocarbons by a number of detoxification processes. Prevalent fungal detoxification pathways for aromatic compounds include the formation of sulfated and glycosylated conjugates. Furanocoumarins, a class of aromatic compounds, are important for their diverse biological activities and clinical applications. The 6,7dihydroxybergamottin (DHB), 6,7-epoxybergamottin (EB), and bergamottin (BM) are three major furanocoumarins in grapefruit, and their metabolism in humans is involved in the "grapefruit/drug interactions." The metabolism by fungi of these furanocoumarins has received little research attention. In our study, the metabolism by Aspergillus niger of DHB, EB, and BM has been investigated. Aspergillus niger metabolized EB, DHB, and BM into a water-soluble sulfate conjugate possibly using etherase- and sulfotransferase-like enzyme activities. In addition, A. niger showed a specificity in metabolizing furanocoumarins, in which the fungus metabolized bergaptol and xanthotoxol into sulfate conjugates but did not metabolize 5-methoxypsoralen and 8-methoxypsoralen. These sulfate conjugates, i.e., bergaptoyl sulfate and xanthotoxoyl sulfate, were characterized by ultraviolet spectroscopy, mass spectrometry, and acid hydrolysis.

Keywords


bergamottin; bergaptol; bergaptoyl sulfate; 6; 7-dihydroxybergamottin; 6; 7-epoxybergamottin; grapefruit; psoralens; xanthotoxol; xanthotoxoyl sulfate

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283