Antioxidant and Cytotoxic Effects and Identification of Ophiocordyceps sinensis Bioactive Proteins Using Shotgun Proteomic Analysis

Abstract

Research background. Ophiocordyceps sinensis, a highly valued medicinal fungus, is close to extinction due to overexploitation. Successful cultivation of O. sinensis fruiting body (OCS02®) shows that the cultivar has a promising nutritional value and numerous bioactive compounds. Antioxidant and antiproliferative properties and biologically active proteins of the OCS02® are investigated for possible development into nutraceuticals. Experimental approach. The chemical composition of the OCS02® cold water extract was determined, and the antioxidant activities were examined using ferric reducing, DPPH• and O2•- scavenging assays. Tetrazolium dye (MTT) cytotoxic assay was performed to assess the antiproliferative activity of the extract. Bioactive proteins in the active fraction of the extract were identified using liquid chromatography (LC) and tandem-mass spectrometry (MS/MS). Results and conclusions. The OCS02® extract exhibited strong O2•- scavenging (expressed as Trolox equivalents (18.4±1.1) mol/g) and potent cytotoxic activities against adenocarcinomic human alveolar basal epithelial (A549) cells (IC50=(58.2±6.8) µg/mL). High molecular mass polysaccharides, proteins and protein-polysaccharide complexes could have contributed to the antioxidant and cytotoxic selectivity of the OCS02®. LC-MS/MS analysis identified several potential cytotoxic proteases and an oxalate decarboxylase protein which may exhibit protection effects on kidneys. Novelty and scientific contribution. The findings demonstrate the potential of OCS02® to be developed into functional food due to its promising superoxide anion radical scavenging capacity, cytotoxic effect and presence of biopharmaceutically active proteins.

Keywords

• Ophiocordyceps sinensis
• antioxidant activity
• cytotoxic effect
• bioactive proteins
• protein-polysaccharide complexes