Baicalin is one of the main bioactive
flavone glucuronides derived as a medicinal herb from the dried roots of Scutellaria baicalensis Georgi, and it is widely used for the treatment of
fever,
inflammation, and other conditions. Due to
baicalin's poor solubility in water, its absolute bioavailability after
oral administration is only 2.2%. The objective of this study was to develop a novel
baicalin-loaded nanoemulsion to improve the oral bioavailability of
baicalin. Based on the result of pseudoternary phase diagram, the nanoemulsion formulation consisting of soy-
lecithin, tween-80,
polyethylene glycol 400,
isopropyl myristate, and water (1:2:1.5:3.75:8.25, w/w) was selected for further study.
Baicalin-loaded nanoemulsions (BAN-1 and BAN-2) were prepared by internal or external
drug addition and in vivo and in vitro evaluations were performed. The results showed that the mean droplet size, polydispersity index, and
drug content of BAN-1 and BAN-2 were 91.2 ± 2.36 nm and 89.7 ± 3.05 nm, 0.313 ± 0.002 and 0.265 ± 0.001, and 98.56% ± 0.79% and 99.40% ± 0.51%, respectively. Transmission electron microscopy revealed spherical globules and confirmed droplet size analysis. After dilution 30-fold with water, the solubilization capacity of BAN-1 and BAN-2 did not change. In vitro release results showed sustained-release characteristics. BAN-1 formulation was stable for at least 6 months and was more stable than BAN-2. In rats, the area under the plasma
drug concentration-time curve value of BAN-1 was 1.8-fold and 7-fold greater than those of BAN-2 and free
baicalin suspension after
oral administration at a dose of 100 mg/kg. In conclusion, these results demonstrated that the
baicalin-loaded nanoemulsion formulation, in particular BAN-1, was very effective for improving the oral bioavailability of
baicalin and exhibited great potential for future clinical application.