Effects of lipids and surfactants on the characteristics of asiatic acid-loaded solid lipid microparticles

Abstract

The objective of this study was to evaluate the effects of solid lipids: beeswax and cetyl alcohol, and surfactants: Tween 80®, soybean lecithin and poloxamer 188 on the characteristics of solid lipid microparticles containing asiatic acid (AASLM). The AASLM were prepared from 10% or 15% of beeswax or cetyl alcohol together with 3% of surfactant F1-F12) by melt dispersion cum freeze-drying technique to obtain a solid dosage form. The physicochemical characteristics of the AASLM powders, including appearance, surface morphology, particle size, %labeled amount of asiatic acid (AA) and %entrapment efficiency (EE) were evaluated. The results revealed that AASLM prepared from 10% or 15% beeswax with 3% soybean lecithin (F2 and F8) could not yield a dry powder form, whereas those with Tween 80® (Tw80) or poloxamer 188 (F1, F3, F7 and F9) appeared as white to slightly yellowish coarse powders. AASLM were prepared from 10% or 15% cetyl alcohol with Tw80 or soybean lecithin or poloxamer 188 and appeared as white fine powders (F4, F5, F6, F10, F11, F12). The mean particle sizes of obtaining AASLM powders ranged from 7.46±0.08 to 38.86±0.34 microns. The surface morphology of AASLM powders, was examined by scanning electron microscope, showed a non-spherical shape. The morphology of AASLM dispersions before freeze-drying and after redispersion of the freeze-dried powder were also investigated using the optical microscope. In all the dispersions, the AASLM prepared from beeswax or cetyl alcohol with poloxamer 188 (F3, F6, F9, F12) had spherical shape, whereas those prepared from beeswax with Tw80 or soybean lecithin (F1, F7, F5, F11) and cetyl alcohol with Tw80 (F4, F10) seemed to have irregular shape. The %labeled amount of AASLMs ranged from 90.43±0.02% to 95.38±0.02% which were considered acceptable. The %EE of resultant AASLMs ranged from 53.75±0.01% to 100.00±0.00%. It was found that F3, F6, F9, F12 could entrap Asiatic acid of 100%. Therefore, it could be concluded that AASLM prepared with beeswax or cetyl alcohol with poloxamer 188 has the greatest potential among the test formulations as a topical carrier for AA. Further studies should be conducted to explore its utilization in cosmetics.