Arabica coffee (Coffea arabica L.) kintamani is a superior agricultural product from Bali. Arabica coffee (Coffea arabica L.) contains many compounds, one of which is caffeine which is beneficial for health and beauty. This study aims to formulate kintamani arabica coffee beans into a gel dosage form. The optimization formula of kintamani arabica coffee bean gel was made using the D-Optimal method using a combination of HPMC and propylene glycol as observation variables and spreadability, pH, and viscosity of the gel preparation as experimental responses. The study of caffeine from the gel preparation was carried out using a Franz diffusion cell. Caffeine content in the gel preparation and its release are determined by spectrophotometric method. The results showed that the amount of HPMC used would increase the viscosity value (+14113.92) and decrease the spreadability (-0.29) and pH (-6.59167E-003) of the gel. The greater the amount of propylene glycol used will decrease the viscosity value (-2484.54) and increase the spreadability value (+0.30) and pH (+0.31802) of the gel. The conclusion of this study is the use of a combination of HPMC and propylene glycol (6%:17%) resulted in the optimum formula with a viscosity value of 44,070 cps, a spreadability value of 3.6 cm, and a pH value of 5.32. The caffeine content obtained in the gel preparation was 188.47 g and the amount of caffeine released from the gel preparation for 6 hours of testing was 4.95%.

Green tea leaves contain lots of polyphenols and antioxidants that can reduce cell damage and prevent premature aging. Green tea extract is made in gel preparation to make it easier to use and increase convenience. HPMC base with propylene glycol additives can increase drug release and increase drug penetration into the skin. This study aims to optimize the levels of HPMC and propylene glycol in green tea extract gel formulations using the D-optimal method and calculate the total release of polyphenols using the Franz diffusion cell method. The extract is produced by infundation. The gel preparation was formulated by varying HPMC and propylene glycol levels in the manufacturing process. Each gel was evaluated for its physical properties, namely viscosity test, pH test, and dispersion test. The physical properties data obtained were then analyzed using Design-Expert software in the mixture design program to obtain the optimum formula. The optimum formula obtained was HPMC with a concentration of 6% and propylene glycol with a concentration of 17% resulting in the best correlation between viscosity, dispersion, and pH, with a desirability value of 0.921. In the green tea gel preparation, the resulting concentration was 8.00 GAE/g sample, and the gel content released at 360 min. was 3.30 GAE/g sample.