Formulation of dried lignans nanosuspension with high redispersibility to enhance stability, dissolution, and oral bioavailability.

Herpetospermum caudigerum lignans (HTL), one of the potential drugs with anti-hepatitis B virus and hepatoprotective effects, has limited clinical applications because of poor aqueous solubility and low bioavailability. Both herpetrione (HPE) and herpetin (HPN) are the most abundant ingredients in HTL and exhibit weak acidity. The purpose of the present study was to produce dried preparations of HTL (composed of HPE and HPN) nanosuspensions (HTL-NS) with high redispersibility using lyophilization technology. The HTL-NS was prepared by utilizing precipitation-combined homogenization technology based on acid-base neutralization reactions, and critical formulation and process parameters affecting the characteristics of HTL-NS were optimized. The resultant products were characterized by particle size analysis, SEM, XRD, stability, solubility, dissolution and in vivo bioavailability. HTL-NS showed near-spherical-shaped morphology and the size was 243 nm with a narrow PDI value of 0.187. The dried preparations with a relatively large particle size of 286 nm and a PDI of 0.215 were achieved by using 4% (W/V) mannitol as cryoprotectants, and had a better stability at 4 or 25 °C for 2 months, compared to HTL-NS. In the in vitro test, the dried preparations showed markedly increased solubility and dissolution velocity. Besides, in the in vivo evaluation, it exhibited significant increases in AUC, CMRT and a decrease in T, compared to the raw drug. In conclusion, our results provide a basis for the development of a drug delivery system for poorly water-soluble ingredients with pH-dependent solubility.