Biosynthesis of gold nanoparticles using Kapok (Ceiba pentandra) leaf aqueous extract and investigating their antioxidant activity

Ceiba pentandra leaf extracts can be used as a reducing agent and capping agent in the green synthesis of gold nanoparticles (AuNPs) because it contains phenolic compounds including flavonoids, alkaloids, saponins, tannins, oxalate, phytate, and anthocyanins. This study aimed to obtain the optimum conditions for biosynthesis of AuNPs using Ceiba pentandra leaf extract (AuNPs-Cp) and investigated the antioxidant activities of the AuNPs-Cp. The effect of several parameters on the synthesis of AuNPs was studied and optimized, including the concentration of HAuCl4 as precursor AuNPs, volume ratio between HAuCl4 and Ceiba pentandra leaf extract, temperature, and reaction time. AuNPs-Cp were characterized using UV-Vis spectroscopy, XRD, TEM, and DLS techniques. The results showed that the synthesis method using 4 mL HAuCl4 2 mM and 8 mL Ceiba pentandra leaf extract at 75°C for 90 min was the optimum condition to synthesize AuNPs-Cp. Based on TEM and DLS data, it is known that AuNPs-Cp are spherical with a size of 21.92 ± 8.88 nm. In vitro antioxidant activity studies using DPPH revealed that the AuNPs-Cp have excellent free radical scavenging activity, with IC50 = 57.82 µg/mL. AuNPs were successfully synthesized using Ceiba pentandra aqueous leaf extract as an environmentally friendly bio-reducing agent and capping agent. DPPH scavenging activity indicated effective free radicals inhibition by AuNPs-Cp than Ceiba pentandra leaf extract.