Gallic Thermosensitive Gel
Gallic acid (G) is a natural phenolic compound that has potent antioxidant and antityrosinase activities. The solubility of gallic acid in aqueous system is rather poor. The purpose of this research is to develop the thermosensitive gel containing G based on Lutrol® F127 (L) and the antioxidant of prepared gels was determined using modified ABTS.+ method expressed as Vitamin C Equivalent Antioxidant Capacity (VCEAC) method. N-methyl pyrrolidone (N) could be used to effectively solubilize G into L aqueous systems. This developed thermosensitive system could convert from solution in the cool place to the firm gel under physiological condition on the skin to delivery an anti-aging agent such as gallic acid. Gallic acid gel prepared from hydroxypropyl methyl cellulose (HPMC, H) was employed to compare with the developed system. The developed gel containing 25% L, 25% N and 5% G (L25N25G5) showed the good physical appearances. In vitro release study was performed using the membrane-less method. The release of G from L25N25G5 into citrate-phosphate buffer pH 5.5 was faster than that of the gel containing 3% H, 25% N and 5% G (H3N25G5). From rheology study, L25N25G5 exhibited as a Newtonian flow at 4 °C and plastic flow at 28°C and 35 °C whereas H3N25G5 demonstrated as a pseudoplastic flow at all the three temperatures. Additionally, from VCEAC method, L25N25G5 exhibited a good antioxidant activity.
S. Suttiruengwong and W. Sricharussin
K. Yodkhum et al., "Gallic Thermosensitive Gel", Advanced Materials Research, Vols. 93-94, pp. 433-438, 2010