Preparation of Rubra (Paeonia lactiflora Pall.) extract and studies in activity and skin penetration

The inhibition rate of tyrosinase activity was used to determine extraction solvent of Paeoniae Radix Rubra extract (PRRE), which was established quality control standards by HPLC and verified the antioxidant activity. Ternary phase diagram was used to screen the best formulation of PRRE nanoemulsion, the skin permeability of PRRE and nanoemulsion were compared. The results show that 70% ethanol as the extraction solvent were highest (88.89%) and the contents of catechin (CC) and paeoniflorin (PF) in PRRE were 0.145 ± 0.0006 μg/mg and 21.783 ± 0.0247 μg/mg, respectively. The inhibition rate of PRRE on pyrogallol autoxidation was 6.94% ± 0.53%. The optimal formulation is Isopropyl myristate (IPM) as oil phase, Ethoxylated hydrogenated castor oil (RH40) as emulsifier, glycerine as coemulsifier, Km 3:1. The skin penetration of CC in PRRE nanoemulsion (0.79 ± 0.04 μg·cm−2) was significantly higher than that PRRE (0.17 ± 0.09 μg·cm−2) after 12 h.