Antielastase Activity of Macassar Kernels (Rhus javanica) Stem Extract and Skin Elasticity Evaluation of Its Topical Gel Formulation

BACKGROUND: Macassar kernels (Rhus javanica L.) has potential as an antiaging agent as it has antielastase activity, especially its stem extract which has best percent inhibition compared to its leaves and fruit extract. Moreover, the antiaging agent can be commonly used in the form of gel for topical applications. Hence, formulation of HEC-based topical gel from the stem extract of Macassar kernels was conducted. This study aims to determine the antielastase activity of the stem extract of Macassar kernels and evaluate the skin elasticity of its topical gel formulation by conducting dermatological safety and skin antiaging efficacy test. METHODS: The stem extract was in vitro tested for antielastase activity using a microplate reader. Then, a formulation of a topical gel containing Rhus javanica stem extract was made. Five stages of quality control, which consisted of an organoleptic test, homogeneity test, pH measurement, viscosity measurement, and physicochemical stability test, were conducted to ensure the quality of topical gel formulation. Last, clinical studies were conducted to evaluate the dermatological safety and antiaging efficacy of gel preparation containing stem extract of Rhus javanica. Results. The stem extract provided antielastase activity (IC50 = 245.68 μg/mL), and its polyphenol was valued at 23.28 ± 1.52 mg GAE/g). The gel containing 10% stem extract had better stability than the gel containing 5% stem extract. The dermatology safety test and efficacy test results indicated that the topical gel containing 10% Rhus javanica stem extract did not cause any skin irritation and significantly improved skin elasticity (p < 0.05). In the treatment group, the moisture parameter was significantly changed on day 14 (p < 0.0001), day 21 (p < 0.0001), and day 29 (p < 0.0001). The elasticity parameter was also changed significantly on day 14 (p=0.0485), day 21 (p=0.0537), and day 29 (p=0.0002). CONCLUSION: The stem extract of Rhus javanica has potential antielastase activity. The topical gel containing Rhus javanica stem extract also has potential antielastase activity by increasing the skin moisture and enhancing skin elasticity.