Formulation and Antibacterial Activity of Gold (Au) Nanoparticles Serum from Green Coffee (Coffea canephora var. Robusta) Bean Extract

Serums are skincare products containing concentrated active substances, often used to enhance skin health and manage specific skin conditions. Green coffee (Coffea canephora var. Robusta) beans are rich in flavonoids and possess antibacterial activity. Gold nanoparticles are popular in cosmetics due to their ability to enhance skin elasticity and their anti-aging properties. The present study aims to formulate, characterize, and assess the antibacterial activity of green coffee bean extract gold nanoparticle serum. Green coffee beans were extracted by maceration in 96% ethanol. Gold nanoparticles of green coffee bean extract (GCBE) were prepared by mixing green coffee bean ethanol extract (70%), 1400 µL chloroauric acid (HAuCl4), and 50 µL polyvinyl alcohol following standard procedure. Different formulations of the serum (F1, F2, and F3) were prepared by combining different concentrations of GCBE; 5% (F1), 10% (F2), and 15% (F3) with serum base comprising carbopol, triethyl amine, propylene glycol, propylparaben, methylparaben, and sodium metabisulfite. The formulations were analyzed for their organoleptic properties, pH, viscosity, stability, spreadability, and adhesion. The antibacterial activity was evaluated against Staphylococcus epidermidis ATCC 12228 using the disc diffusion method. The resulting formulations F1 (light yellow), F2 (pink), and F3 (light purple) were slightly viscous, homogenous, and had pH values from 5.84 to 5.87. They were stable on storage at room and cold temperatures, evidenced by unchanged organoleptic properties, pH, and viscosity over a 28-day period. All three formulations exhibited antibacterial activity against Staphylococcus epidermidis, with F3 exhibiting the highest antibacterial activity with an inhibition zone diameter of 12.6 mm.