Antioxidant evaluation and formulation development of Zingiber officinale extract loaded in solid lipid nanoparticles for skin delivery

Abstract

The objective of this study was to evaluate antioxidative activity of ginger extracts, to formulate and characterize solid lipid nanoparticles (SLN) containing ginger extract. Ginger extracts which were reported to contain the main principle namely, [6]-gingerol were evaluated using the DPPH method and the hydroxyl radicals scavenging assay. The DPPHscavenging activity of acetone and isolated [6]-gingerol extracts were lower than vitamin E and vitamin C, while the standard [6]-gingerol had the greatest activity. In the hydroxyl radical scavenging test, acetone and isolated [6]-gingerol extract exhibited higher activity than quercetin. Consequently, acetone extract which was prepared by simple extraction method was selected to load in SLN. SLN were produced by high pressure homogenization technique using two lipids, glyceryl palmitostearate (GP) and glyceryl behenate (GB). Either Poloxamer 188 (P188) or Tween 80 (Tw80) of 1-5% was used as stabilizer. The sizes measured by photon correlation spectroscopy of GP-SLN were smaller than those of GB-SLN with acceptable size distribution. SLN displayed better stability profiles at 4 °C than at room temperature. Six stable SLN formulations were obtained from the GP-SLN with 3 and 5% of P188 or Tw80 and GB-SLN with 3 and 5% Tw80. The particle sizes from transmission electron electroscopy of SLN were predominantly 200-300 nm. The entrapment efficiency of [6]-gingerol of six formulations were ranged from 84.36-96.24% and changed to 78.91- 93.26% at 2 months storage. Differential scanning calorimetry and powder x-ray diffraction studies revealed that lipid transformation to stable polymorph was occurred during storage and affected the expulsion of ginger extract from lipid core. The release profiles showed that [6]-gingerol released approximately 25-30% from all SLN formulations was achieved at 24 hours. The sustained release profiles were performed according to high entrapment efficiency of SLN. The release mechanism of [6]-gingerol was analyzed to be proportional to the square root of time, indicating that [6]-gingerol might be released from the nanoparticles by diffusion. The skin permeation study using porcine skin as model membrane showed that [6]-gingerol permeated into skin approximately 2.54±0.43%.