Green Synthesis of Silver Nanoparticles Using Extracts of Ehretia cymosa and Evaluation of Its Antibacterial Activity in Cream and Ointment Drug Delivery Systems

Objectives. The use of antibacterial drugs for the treatment of infections has been on for several decades but not without some challenges such as resistance. Research on natural products is on-going to mitigate this challenge. The aim of this study was to synthesize silver nanoparticles (SNPs) with aqueous and methanol extract of Ehretia cymosa leaf and to explore its antibacterial potentials in semisolid dosage delivery system as topical antibacterial cream and ointment. Methods. E. cymosa leaf was extracted by macerating in distilled water and methanol. The extracts were used to synthesize SNPs. SNPs were characterized and confirmed by visual observation, UV-visible spectroscopy, FTIR, atomic absorption spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. SNPs were used to formulate cream and ointment, and the antibacterial activity of the formulations was evaluated against Staphylococcus aureus and Escherichia coli. Results. Absorption band was observed at 450 nm for aqueous extract SNPs and 420 nm for methanol extract SNPs due to surface plasmon resonance. SNPs were agglomerated with the irregular size of 55 nm and 90 nm. The formulations had acceptable physicochemical properties with good drug-excipient compatibility. The antibacterial activity of cream formulations had a significantly ( $p<0.0001$ ) higher antibacterial activity compared to ointment formulations. Both formulations with SNPs had higher antibacterial activity than ciprofloxacin. Conclusion. Cream and ointment formulations loaded with green synthesized E. cymosa leaf extract SNPs present a potential for a more efficient and effective antibacterial drug delivery to ameliorate the impact of antibacterial drug resistance.