Therefore, this technique is an effective method for improving the dissolution and oral bioavailability of poorly soluble drugs. Due to the high dispersion of the drug and the high hydrophilicity of the carrier, the wettability of the drug is improved. The solid dispersions (SDs) technique refers to the uniform dispersion system of drugs in the form of molecules, microcrystallines, amorphous, and other states in a solid carrier. Ĭhemical structure of glycyrrhetinic acid (a) and polyvinylpyrrolidone (b). In order to overcome poor solubility of GA, in recent years, some research on new drug delivery systems of GA have been done, including GA liposomes, GA nanoemulsions, GA microparticles, and GA solid dispersion. In general, the solubility of hydrophobic drug can be improved by adding a surfactant, but a large amount of solubilizer is prone to side effects such as hemolysis. This also limits the oral bioavailability of glycyrrhetic acid. However, due to the strong hydrophobicity of glycyrrhetic acid, its solubility and dissolution rate are poor. Currently, it is often used clinically to treat chronic hepatitis and liver cancer.
Studies have shown that glycyrrhetic acid has anti-inflammatory, antiviral, antitumor, and other pharmacological effects. The structural formula is shown in Figure 1. The molecular formula of GA is C 30H 46O 4, and the molecular weight is 470.69. It is also a degradation product of glycyrrhetic acid in the body, which is the main active component of licorice. Glycyrrhetinic acid (GA) is one of the main active ingredients extracted from the root or rhizome of licorice. The samples with PVP K30 as the carrier have the best dissolution performance. In conclusion, the findings of this study demonstrated that the dissolution performance of the PVP-GA-SDs prepared by the solvent method is related to the molecular weight of PVP, and the change in the molecular weight of PVP does not cause a monotonic change in dissolution of GA.
SEM results showed that there were no significant differences in the appearance of SDs prepared with four PVPs, and no crystalline morphology of GA was seen. Based on FTIR and Raman detection, a hydrogen-bond between PVP and drug molecules is formed. The DSC and XRD patterns showed that the crystallization of GA in SDs prepared by PVP K30 and PVP K60 was significantly inhibited, and both were transformed to amorphous. In addition, the dissolution rate and solubility of the SDs with a carrier-drug ratio of 8 : 1 were better than the samples of 4 : 1. The results showed that the enhancement effect of molecular weight on dissolution rate and equilibrium solubility follows. PVP-GA-SDs prepared with all four molecular weight PVPs displayed good enhancement of dissolution rate and equilibrium solubility compared with pure drug and corresponding physical mixtures. The effect of polyvinylpyrrolidone (PVP) as glycyrrhetic acid (GA) solid dispersions carrier at different molecular weights on the dissolution behavior and physicochemical properties was investigated.
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