Development and assessment of tyrosinase inhibitory activity of liposomes of Asparagus racemosus extracts

The purpose of this study was to develop liposomal formulations of Asparagus racemosus root extract (AR1-6) as well as evaluate the physicochemical properties and in vitro tyrosinase inhibitory activity. Liposomes composed of AR1-6 to lipid weight ratio of 1:10 and lecithin (LEC) or Phospholipon® 90G (PC90G) as structural phospholipid at 7:3 molar ratio to CHOL were prepared by various methods, i.e. chloroform-film (CF), reverse-phase evaporation (REV), polyol dilution (PD), and freeze-drying of monophase solution (MFD) methods. The results revealed that vesicles prepared by CF and MFD were multilamellar whereas those prepared by REV and PD were oligolamellar in nature with particle sizes ranging from 0.26 to 13.83 μm. The zeta potentials were in the range of −1.5 to −39.3 mV. AR1-6 liposomes with LEC possessed significantly higher entrapment than those with PC90G. The highest entrapment efficiency and in vitro tyrosinase inhibitory activity of 69.08% and 25%, respectively, were obtained from liposomes having LEC and prepared by PD method. The tyrosinase inhibitory activity were in the rank order of LEC > PC90G, and PD > CF > REV > MFD. It could be concluded that the mechanism of vesicle forming in each method of preparation was the key factor influencing physicochemical properties, particularly vesicle type, size, surface charge, and entrapment, which were well correlated with the biological activity.