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This study describes the biosynthesis of gold nanoparticles (AuNPs) using the extract of Ganoderma lucidum in the buffer zone of Bach Ma National Park, Vietnam, as a reducing and protecting agent using microwave-assisted synthesis. The as-synthesized AuNPs were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. Compared to the conventional method, the proposed microwave-assisted method produced AuNPs having a small size of 22.07 ± 8.11 nm in a short synthesis time period. In excess NaBH 4 , the as-prepared AuNPs demonstrated good catalytic activity for reducing 4-nitrophenol to 4aminophenol. Furthermore, AuNPs demonstrated improved reusability after four cycles. The pseudo-first-order apparent rate constant was estimated to be 0.086 min −1 at 303 K. Both the catalytic mechanism and reaction path of reduction were proposed. Moreover, activation energy and thermodynamic parameters, including activation enthalpy and entropy, were examined.

Chromatographic purification of the ethyl acetate extract of the entomopathogenic fungus Aspergillus tamarii NL3 culture broth led to the isolation of griseofulvin (1), isogriseofulvin (2), cytochalasin J (3), solamargine (4), and solasonine (5). The chemical structures of these compounds were identified by HRESIMS and NMR spectra, as well as by comparison with literature data. This is the first report on the isolation of 1-4 from the Aspergillus genus and compound 5 from A tamarii. Compounds 1 and 2 exhibited antifungal activity against the reference fungi with MICs of 16 to 128 µg/mL. Compound 3 displayed weak antimicrobial activity against most of the tested microorganisms with MICs ≥ 128 µg/mL, except for Bacillus subtilis and Aspergillus niger with MICs of 64 µg/mL. Compounds 4 and 5 showed activity against a wide spectrum of the reference microorganisms with MICs of 16 to 128 µg/mL but showed stronger antifungal than antibacterial activity. Furthermore, all isolates exhibited weak ABTS and DPPH scavenging activities with scavenging rates of 18.92% to 32.64% and 24.62% to 31.06%, respectively, at the concentration of 100 µg/mL.

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