Comparative Evaluation of the Multifunctional Biological Activities of Palmyra Extract-Mediated Ag/Ag₂O, ZnO, and Ag/Ag₂O/ZnO Nanomaterials

This study presents a green approach for synthesizing silver and zinc-based nanoparticles (NPs)/nanocomposites (NCs) utilizing aqueous extracts of palmyra palm (Borassus flabellifer) sprouts and mature fruit pulp.

The formation of nanomaterial (NM) was confirmed with several characterization techniques. Plant extracts and plant-derived Ag/Ag₂O NPs, ZnO NPs, and Ag/Ag₂O/ZnO NCs were analyzed to determine their efficacies as antioxidant, anti-inflammatory, and antibacterial agents with standard biological assays.

Under optimized conditions, pulp and sprout-mediated Ag/Ag₂O NPs, ZnO NPs, and Ag/Ag₂O/ZnO NCs exhibited surface plasmon resonance peaks at 436–438 nm, 350–354 nm, and 350–450 nm, respectively. SEM imaging revealed of quasi-spherical Ag/Ag₂O NPs, hexagonal rod-shaped ZnO NPs, and both morphologies arranged into the formation of Ag/Ag₂O/ZnO NCs. The average sizes of all biogenic NMs were between 11 and 120 nm. Ag and Ag₂O were of face-centered cubic symmetries alongside hexagonal wurtzite ZnO crystallinities. Sprout-mediated Ag/Ag₂O/ZnO NCs revealed superior antioxidant potential, (IC₅₀ of 48 ppm for DPPH and 87 ppm for ABTS assays, 74 mg AAE/1 g for FRAP assay). Sprout-mediated Ag/Ag₂O NPs demonstrated significantly high (p ≤ 0.05) anti-inflammatory properties, (IC₅₀; 414 ppm for protein denaturation inhibition and 438 ppm for HRBC membrane stabilization assay). The sprout-mediated Ag/Ag₂O NPs exhibited the maximum growth inhibition zones (19 mm against E. coli and 17 mm against S. aureus).

To the best of our knowledge, this study remains the first comparative report on the anti-inflammatory and antibacterial activities of Ag/Ag₂O/ZnO NCs and their NP counterparts. The biological activities were size, morphology, and dose-dependent, and the synergistic combination of plant polyphenolics and NMs enhanced bioactivities.