The In vitro Biological Activity of Biosynthesized Silver Nanoparticles Produced Using Mangifera indica Stem Bark Extract and Properties of Its Pharmaceutical Gel Formulation

This study reports the production of silver nanoparticles using Mangifera indica stem bark (aqueous and methanol) extracts as capping agents and formulation of pharmaceutical gel loaded with the nanoparticles. The extracts were prepared using standard procedures and utilized in biosynthesizing silver nanoparticles. Biosynthesis was ascertained through colour changes, UV-Visible and FTIR spectroscopy. Antioxidant activity of the extracts and biosynthesized nanoparticles were examined by DPPH method. The antimicrobial evaluation was carried out on Pseudomonas aeruginosa and Staphylococcus aureus. Pharmaceutical gels were produced (F1-F5), and loaded with the nanoparticles. Nanoparticles exhibited maximum absorption under UV-visible spectroscopy between 315 and 320 nm. FTIR spectrum showed that alkene and ester functional groups were conferred on the silver nanoparticles by the extracts used. The nanoparticles demonstrated antimicrobial activity against the organisms, which was significantly higher (p < 0.05) than for extracts and reference drug. The antioxidant capacity was in a concentration-dependent manner but significantly lower (p < 0.05) than that of the reference drug. Formulated gels had acceptable organoleptic profiles, pH range of 6.8-7.1, high viscosity, and pseudoplastic flow patterns. The in vitro release profiles of the gels showed was gradual, with t(90) higher than 2 h. The release seemed to be influenced by the viscosity of the gel systems. In addition, the release kinetics of the nanoparticle-loaded gel systems followed Higuchi model with r(2) ranging from 0.9958 to 0.9980. Mangifera indica extracts were successfully used as bio-reducing agents in the synthesis of silver nanoparticles. The gel formulations had acceptable physical properties and release profiles.