Ophiocordyceps sinensis: Antioxidant, Proteolytic Activities and Synthesis of Silver Nanoparticles

Natural Ophiocordyceps sinensis is a highly valued medicinal fungus known for its antitumor, immunomodulatory, and antiviral properties. Due to extensive overharvesting in Asia, cultivated alternatives have become increasingly important. This study aimed to evaluate the biological activity and chemical composition of extracts obtained from cultivated Ophiocordyceps sinensis grown using different rice substrates. Methanolic extracts were prepared from solid-state cultivated Ophiocordyceps sinensis grown on Oryza sativa var. indica and Oryza sativa var. japonica. Antioxidant activity was determined using the DPPH assay, while proteolytic activity was evaluated with the azocasein substrate. Chemical characterization of major compounds was performed using ¹D and ²D NMR spectroscopy, together with IR spectroscopy. UV/Vis spectrophotometry was employed to confirm the formation of silver nanoparticles in AgNO₃ solution. Antimicrobial activity was tested against bacterial strains, including Escherichia coli and Staphylococcus aureus. All prepared methanolic extracts exhibited measurable antioxidant and proteolytic activities. The dominant identified compounds were Z-oleic acid, linoleic acid, and D-mannitol. Selected extracts successfully induced the formation of silver nanoparticles. The highest antimicrobial activity against Escherichia coli was observed for sample 1OS, reaching a mean % RIZD value of 129.32 ± 0.58%.