Microwave-assisted green synthesis of Cassia alata-mediated gold nanoparticles and evaluation of its antioxidant, anti-inflammatory, and antibacterial activities

The increasing prevalence of antibiotic resistance has directed scientific inquiry toward the development of substitute therapies. Gold nanoparticles (AuNPs) have a variety of biological uses, including antioxidant, antibacterial, anticancer, and anti-inflammatory activities. Green synthesis was applied to the production of AuNPs using Cassia alata leaves (CAL) extract as a reducing agent. AuNPs were then characterized. The AuNPs were successfully synthesized as confirmed by the UV–Vis data with a maximum absorption peak at 534 nm. An average particle size distribution of 63.647 ± 1.334 nm. These CAL-AuNPs were dominated by a spherical shape. X-ray diffraction studies indicated that the biosynthesized AuNP structures are crystallized. The intensity fluctuations of many peaks from Fourier-transform infrared spectroscopy analysis suggested the existence of bioconstituents responsible for capping and stability. Transmission electron microscopy (TEM) study revealed a spherical morphology for the AuNPs, agreeing with the findings obtained by dynamic light scattering (DLS). Following that, the biological performance of biomolecule-functionalized AuNPs was investigated. This study looked into the possible antioxidant, anti-inflammatory, and antibacterial benefits of produced AuNPs. CAL-AuNPs strongly inhibited the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals with IC₅₀ of 6.890 µg/mL. A low CAL-AuNPs concentration of 50 µg/mL highly suppressed protein denaturation (45.22%). CAL-AuNPs possessed antibacterial activity against Staphylococcus aureus, Streptococcus pyogenes, and Bacillus subtilis with MIC values in the range of 125 to 250 µg/mL. In conclusion, green-synthesized AuNPs using C. alata leaf extract have great potential as antioxidant, anti-inflammatory, and antibacterial agents.