Antioxidant activity of Robusta coffee peel extract (Coffea canephora Pierre ex A. Froehner) and its formulation as a face serum gel

Abstract

The utilization of coffee peel becomes crucial in the coffee manufacturing process since the amount of coffee peel waste produced is proportional to the amount of coffee harvested. The ethanolic extract of Robusta coffee peel contains polyphenolic, which known as natural antioxidants. Phytochemical screening, antioxidant activity of Robusta coffee peels by the DPPH radical scavenging assay, and their formulation into a face serum gel were carried out. Phytochemical screening showed that Robusta coffee peel extract contains alkaloids, flavonoids, tannins, saponins and triterpenoids. The antioxidant activity of Robusta coffee peel extract gave an IC₅₀ value 27.9657 µg/mL, which is considered to have very significant antioxidant activity. Formulas I and II of the serum gel formulation contain 0.006% and 0.009% of the Robusta coffee peel extract, respectively. The organoleptic, viscosity, pH, spreadability, adhesion, and stability tests have met all of the parameters. The serum gel passed the preparation’s irritation test without showing any signs of irritation. The antioxidant activity of face serum gel gave an IC₅₀ value of 56.2754 µg/mL in formula I, which was categorized as having strong antioxidant activity, and 30.3451 µg/mL in formula II, which was categorized as having very strong antioxidant activity. In summary, Robusta coffee peel extract has the potential to be a natural antioxidant and might be made into a face serum gel preparation.