Evaluation of antioxidant, antidiabetic and cytotoxic effects of silver nanoparticles biosynthesized by aspalathus linearis

Rooibos (Aspalathus linearis), a South African plant, has traditional medicinal uses in various fields due to its flavonoids and phenolic compounds. In recent years, silver nanoparticles (AgNP) have gained attention for their physical and chemical properties, making them versatile in healthcare and many other fields. This study aims to determine the in vitro antioxidant, antidiabetic, and cytotoxic potential of silver nanoparticles prepared using Rooibos (Aspalathus linearis) plant. For this purpose, green synthesis of silver nanoparticles was performed using Rooibos (Aspalathus linearis), which is reported to be rich in flavonoids and phenolic acids with properties for use as a popular dietary supplement and in the treatment of various diseases. The synthesized silver nanoparticles were characterized using techniques such as UV, SEM, and EDX. The color change from yellow to brown observed in the silver nitrate solution with Rooibos (Aspalathus linearis) aqueous extract indicated the formation of silver nanoparticles. UV-vis spectroscopy confirmed a strong absorption peak at λ=432 nm for Rooibos AgNPs (R-AgNPs). R-AgNPs exhibited mostly spherical morphology and were smaller than 100 nm in size. They showed a dose-dependent decrease in cell viability and approximately 90% cytotoxicity at higher concentrations in SK-MEL 30 cells (with an IC50 value of 17.32 μg/mL). The DPPH radical scavenging activity ranged from 25.87% to 65.91%. α-glucosidase activity inhibition ranged from 31.86% to 100%. This study demonstrates that Aspalathus linearis extract can be used for the synthesis of silver nanoparticles and biologically synthesized silver nanoparticles can be potentially used as an agent in treatment approaches due to their antioxidant, antidiabetic, and cytotoxic effects.