A new diketopiperazine alkaloid from <i>Aspergillus oryzae</i>

<div><p>Investigation of bioactive secondary metabolites from terrestrial <i>Aspergillus oryzae</i> sp. MMAO1 using M<sub>2</sub> medium afforded a new diketopiperazine alkaloid, 7,9-dihydroxy-3-(1<i>H</i>-indol-3-ylmethyl)-8-methoxy-2,3,11,11a-tetrahydro-6<i>H</i>-pyrazino[1,2-b]isoquinoline-1,4-dione (<b>1a</b>), containing the unusual amino acid l-6,8-dihydroxy-7-methoxyphenylalanine. This was co-isolated with ditryptophenaline (<b>2</b>), cyclo-(Tryp,Tyr) (<b>4</b>), cyclo-(Pro,Val), α-cyclopiazonic acid (<b>3</b>), kojic acid and uridine. Re-cultivation of the fungal strain on Dox medium led to the production of bisdethio(bismethylthio)gliotoxin (<b>5</b>), pseurotin A (<b>6</b>) along with linoleic acid, α-cyclopiazonic acid (<b>3</b>) and kojic acid. The chemical structure of the new diketopiperazine alkaloid including the relative configuration was determined by 1D and 2D NMR spectroscopy and HR-ESI-MS spectrometry, and by comparison with the related literature. The new alkaloid (<b>1a</b>) showed no antimicrobial activity or cytotoxicity against brine shrimps.</p></div>



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