Green-synthesized gold nanoparticles from Omani pomegranate peel: Phytochemical characterization and antileishmanial activity

Abstract

Omani pomegranate peel is a rich source of phenolic compounds with antioxidant and antimicrobial properties, making it a promising source of antiparasitic bioactive compounds. This study compared air-dried (PPE1) and oven-dried (PPE2) Omani pomegranate peel extracts, chemically synthesized gold nanoparticles (AuNPs), and their green-synthesized AuNP formulations (PPE1–AuNPs and PPE2–AuNPs). Methanolic extracts are prepared from air-dried and oven-dried peels and characterized using UPLC and GC–MS. AuNPs are synthesized using both extracts and characterized by UV–vis spectroscopy and ATR–FTIR. Antileishmanial activity is evaluated against Leishmania tropica promastigotes using dose-dependent viability assays. PPE1 exhibited a phytochemical profile characterized by higher total phenolic content and ellagic acid enrichment (~58% of total phenolics), whereas PPE2 is enriched in chlorogenic acid (~45% of total phenolics) and rutin hydrate, which accounted for approximately 99% of the quantified flavonoid content. UV–Vis and ATR–FTIR analyses confirmed successful AuNP formation and phytochemical-mediated surface functionalization. Both extracts inhibited promastigote viability in a dose-dependent manner, with PPE1 exhibiting greater potency (IC₅₀ = 15,200 µg/mL) than PPE2 (IC₅₀ = 36,710 µg/mL). Among all tested formulations, chemically synthesized uncoated AuNPs display the greatest antileishmanial activity (IC₅₀ = 12.0 µg Au/mL), whereas peel-capped AuNPs are less potent (PPE1–AuNPs: IC₅₀ = 71.9 µg Au/mL; PPE2–AuNPs: IC₅₀ = 118.2 µg Au/mL). These findings demonstrate the dual role of Omani pomegranate peel phytochemicals as antiparasitic bioactive compounds and as effective reducing and stabilizing agents for environmentally sustainable AuNP synthesis. The results further demonstrate that phytochemical-mediated surface functionalization influences the antileishmanial activity of gold nanoparticles and support the potential of pomegranate-derived nanomaterials for future antiparasitic applications. Further studies should evaluate activity against intracellular amastigotes and determine host-cell selectivity to further assess therapeutic potential.