An Assessment of the In Vitro Antioxidant Activity of Cobalt Nanoparticles Synthesized From Millettia pinnata, Butea monosperma, and Madhuca indica Extracts: A Comparative Study.

Objective This study aimed to synthesize cobalt nanoparticles (CoNPs) via the green synthesis method using , leaf (MPL), flower (BMF), and flower (MIF) as eco-friendly reducing agents. It further aimed to compare the effectiveness of these plant extracts in CoNPs production and evaluate the antioxidant activities of the synthesized nanoparticles (NPs), establishing a link between the phytochemical constituents of the extracts and the antioxidant capacity of CoNPs for potential applications in drug development and environmental sustainability. Materials and methods CoNPs were synthesized using aqueous extracts of MPL, BMF, and MIF. These extracts act as stabilizing and self-reducing agents. Initially, the presence of CoNPs was detected visually by observing a color change. To confirm this observation, UV-visible spectroscopy and Fourier transform infrared (FTIR) spectroscopy were employed. UV-visible spectroscopy helps in analyzing the absorption of light by the CoNPs, while FTIR spectroscopy is used to identify the functional groups present in the NPs. Subsequently, the antioxidant activity of the synthesized CoNPs was assessed using the 1,1-diphenyl-2-picryl hydroxyl (DPPH) radical-scavenging assay. This assay measures the ability of antioxidants to neutralize free radicals by determining the reduction in the DPPH radical's absorption. To ensure the reliability of the results, the experiments were conducted in triplicate. Statistical analysis was then performed to compare the antioxidant effectiveness of the different plant extracts used in synthesizing the CoNPs. This analysis helps in determining any significant differences in antioxidant activity among the extracts. Results UV-visible spectral analysis confirmed the successful synthesis of CoNPs, revealing characteristic absorption peaks. For leaf extract (MPLE), the maximum peak was observed at ~272 nm, while flower extract (BMFE) exhibited a peak at ~276 nm, and flower extract (MIFE) revealed a maximum peak at ~320 nm. FTIR analysis further validated the presence of organic molecules from plant components on the outer layer of CoNPs, indicating successful capping and stabilization by phytochemicals from the extracts. The spectra displayed various peaks at different wavenumbers: MPLE showed prominent peaks at 3335 cm, BMFE showed distinct peaks at 3314 cm, and MIFE exhibited significant peaks at 3261 cm. Among the three types of CoNPs tested, those synthesized using MIFE exhibited the highest inhibition of 87.67% at a concentration of 60 µL. This higher inhibition was compared to those synthesized using BMFE and MPLE. This study suggests that the CoNPs synthesized on MIFE can serve as an antioxidant agent because of their remarkable free radical-scavenging activity. Conclusions The study highlights the potential of CoNPs synthesized using MIFE as they exhibited superior antioxidant activity compared to those synthesized with BMFE and MPLE. Therefore, the study underscores the promise of MIFE as a valuable natural resource for producing CoNPs abundant in antioxidants. Furthermore, it emphasizes the importance of implementing environmentally friendly synthesis techniques to produce nanomaterials that are both safe for the environment and biologically effective.