Biotransformation of Turmerones by <i>Aspergillus niger</i>

Abstract

Biotransformation studies conducted on (+)-(<i>S</i>)-<i>ar</i>-turmerone (<b>1</b>) and (+)-(<i>S</i>)-dihydro-<i>ar</i>-turmerone (<b>2</b>) by the fungus <i>Aspergillus niger</i> have revealed that <b>1</b> was metabolized to give four oxidized metabolites, (+)-(7<i>S</i>)-hydroxydehydro-<i>ar</i>-todomatuic acid (<b>3</b>), (+)-(7<i>S</i>,10<i>E</i>)-12-hydroxydehydro-<i>ar</i>-todomatuic acid (<b>4</b>), (+)-(7<i>S</i>,10<i>E</i>)-7,12-dihydroxydehydro-<i>ar</i>-todomatuic acid (<b>5</b>), and (+)-(7<i>S</i>)-15-carboxy-9,13-epoxy-7-hydroxy-9,13-dehydro-<i>ar</i>-curcumene (<b>6</b>), and (+)-(<i>S</i>)-dihydro-<i>ar</i>-turmerone (<b>2</b>) was metabolized to (+)-7,11-dihydroxy-<i>ar</i>-todomatuic acid (<b>7</b>). Metabolites <b>3</b>−<b>7</b> were characterized using spectroscopic techniques. Metabolites <b>3</b>−<b>7</b> inhibited acetylcholinesterase (AChE) although less so than the parent substrates.