Himalayan Asphaltum-Driven Synthesis of Gold and Selenium Nanoparticles: Investigation of Antimicrobial Activity and Urolithin Levels.

This work examines the utilization of the natural product shilajit resin, sourced from the Himalayas, for the extraction of diverse components suitable to the synthesis of gold nanoparticles (AuNPs) and selenium nanoparticles (SeNPs). The study evaluated the extraction efficiency of Uro-A, a polar phenolic component, from shilajit samples utilizing various solvent systems, followed by the eco-friendly synthesis and characterization of AuNPs and SeNPs. The LC-MS/MS analysis demonstrated that the methanol/ethyl acetate (MeOH/EA) extract was particularly effective and contained the highest concentration of Uro-A. A robust positive association was discovered between Uro-A content in shilajit and the efficiency of nanoparticle production. Sample 2, with 0.002 ppm Uro-A, produced suboptimal yields (15% for AuNPs; 34% for SeNPs), while sample 1, with 2.504 ppm Uro-A, noticeably enhanced the yields to 90% (AuNPs) and 96% (SeNPs). The synthesized AuNPs and SeNPs were characterized using SEM, EDS, PSD, ZP, XRD, FTIR, and XPS techniques, demonstrating spherical particles with an average diameter of around 100 nm. XPS spectra confirmed the elemental form of the obtained AuNPs and SeNPs. Antimicrobial studies revealed that SeNPs exhibit moderate efficacy (MIC = 0.125-1 mg/mL) against bacteria (e.g., Bacillus subtilis, Staphylococcus aureus) and fungi (e.g., Penicillium italicum, Mucor mucedo), but higher in comparison to AuNPs (MIC 0.25-5 mg/mL).