Self-nanoemulsifying drug delivery system of sinapic acid: In vitro and in vivo evaluation

Sinapic acid (SA) has been reported as a poorly soluble bioactive compound due to its dissolution rate and oral bioavailability, which are very poor. Therefore, in the current research work, different self-nanoemulsifying drug delivery systems (SNEDDS) of SA were developed for enhancement of its in vitro dissolution (drug release) and bioactivity. Different SA-loaded SNEDDS were prepared by low-energy emulsification methods, characterized and evaluated for various physicochemical and in vitro parameters such as thermodynamic stability, self-nanoemulsification efficiency, droplet size, polydispersity index (PDI), zeta potential (ZP), refractive index (RI), the % of transmittance (% T) and drug release profile. In vitro dissolution rate of SA was significantly enhanced from SNEDDS in comparison with SA suspension. The optimized SNEDDS of SA with droplet size of 12.4 nm, PDI value of 0.158, ZP value of − 32.8 mV, RI value of 1.335, % T value of 98.7% and drug release profile of 96.8% was selected for in vitro antioxidant and in vivo anti-inflammatory studies. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay indicated significant antioxidant activity of optimized SA SNEDDS (IC50 = 4.52 μg/ml) in comparison with free SA (IC50 = 7.62 μg/ml) and standard ascorbic acid (IC50 = 40.78 μg/ml). In vivo anti-inflammatory studies in rats also indicated that SA in optimized SNEDDS was significantly efficacious than SA suspension. Free SA as well as SA in SNEDDS was proved to be an excellent antioxidant in comparison with standard ascorbic acid. The results obtained in the current research work indicated the great potential of SNEDDS in the enhancement of in vitro dissolution rate and therapeutic efficacy of poorly soluble bioactive compounds such as SA.