Sulfur-Containing Phenolic Compounds from the Cave Soil-Derived <i>Aspergillus fumigatus</i> GZWMJZ-152

Abstract

Six new sulfur-containing phenolic compounds (<b>1</b>-<b>6</b>) and their putative metabolic precursors (<b>7</b>-<b>9</b>) were isolated from the cave soil-derived fungus <i>Aspergillus fumigatus</i> GZWMJZ-152. Compound <b>1</b> represents an unusual benzophenone-diketopiperazine hybrid via a thioether linker, while compound <b>2</b> contains a naturally rare sulfoxide group. Both compounds <b>2</b> and <b>3</b> were initially isolated as racemic mixtures and then purified as the enantiomerically pure (+)-<b>2</b>, (-)-<b>2</b>, (+)-<b>3</b>, and (-)-<b>3</b>, respectively. Their structures, including absolute configurations, were elucidated by spectroscopic analysis, X-ray diffraction, and the calculations of electronic circular dichroism. The antioxidant activity of compounds <b>1</b>-<b>9</b> was evaluated based on oxygen radical absorbance capacity, 2,2-diphenyl-1-picrylhydrazyl radical scavenging, and the protective effect on the PC12 cell line against H₂O₂-induced damage. Compounds <b>5</b>-<b>7</b> and <b>9</b> showed radical-scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radicals with the IC₅₀ values of 3.45 ± 0.02, 23.73 ± 0.08, 18.90 ± 0.16, and 17.27 ± 0.15 μM, respectively. Compounds (±)-<b>2</b>, <b>4</b>, <b>7</b>, and <b>8</b> exhibited potent antioxidant capacity with oxygen radical absorbance capacity values of 1.73 ± 0.13, 1.65 ± 0.03, 6.14 ± 0.35, and 1.55 ± 0.04 μmol TE/μmol, respectively. Compounds (±)-<b>2</b> and (±)-<b>3</b> also exhibited protective effects on oxidative injury of PC12 cells induced by H₂O₂.