Multifunctional Bioactivity and Other Properties of Silver Nanoparticles Synthesized in an Eco-Friendly Manner From Padina pavonica

Background: This study focuses on the bioactivity and other properties of silver nanoparticles (AgNPs) synthesized using the ethanolic and methanolic extracts of Padina pavonica—a brown alga rich in phytochemicals capable of reducing metal ions and boosting the biological activity of biogenic AgNPs. Methods: AgNPs were characterized using ultraviolet–visible spectroscopy, dynamic light scattering (DLS), zeta potential measurements, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Phytochemicals in ethanolic and methanolic extracts were identified using gas chromatography-mass spectrometry. Antibacterial, antifungal, antioxidant (free radical scavenging, superoxide anion scavenging, and total antioxidant), and in vitro α-glucosidase inhibition (antidiabetic) activities were evaluated using the corresponding assays. Cytotoxicity was tested using the TM3 cell line. Molecular docking studies were conducted to investigate the interactions of major phytochemicals with bacterial and fungal targets. Results: Ultraviolet–visible spectra showed a characteristic surface plasmon resonance peak at 350–500 nm, confirming AgNP formation. DLS and zeta potential analyses indicated a nanoscale size distribution and good colloidal stability, SEM revealed a predominantly spherical particle morphology, FTIR spectroscopy identified functional groups involved in nanoparticle synthesis, and XRD revealed a crystalline structure. The identified bioactive phytochemicals included 2,4-Di-tert-butylphenol, ethyl oleate, hexadecanoic acid ethyl ester, octadecanoic acid, ergosterol and n-hexadecanoic acid (palmitic acid). Both ethanolic and methanolic extract–derived AgNPs exhibited high activity against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhi (S. typhi), whereas activity against Candida albicans and Aspergillus niger was observed only for methanolic extract–derived AgNPs. Strong antioxidant and α-glucosidase inhibitory activities comparable with those of ascorbic acid and acarbose, respectively, were observed for biogenic AgNPs. TM3 cell line studies demonstrated high viability at a low concentration (3.125 mg/mL) of ethanolic AgNPs, indicating good biocompatibility. Molecular docking revealed that 2,4-Di-tert-butylphenol and chalcone engaged in stable interactions with microbial targets through hydrogen bonding, van der Waals, and π–π interactions. Conclusion: P. pavonica extract–derived AgNPs represent a promising eco-friendly nanoplatform with potential applications as antibacterials, antidiabetics, and antioxidants. The results of in silico studies corroborate the potential bioactivity of the selected bioactive phytochemicals, warranting further in vivo and clinical investigations.