Heat capacity for the binary system of silybin and poly(vinylpyrrolidone) K30

The heat capacity Cp of solid mixtures of silybin and poly(vinylpyrrolidone) (PVP) K30 was measured by differential scanning calorimetry (DSC). The IUPAC name for PVP is 1-ethenylpyrrolidin-2-one, and that for silybin is 3,5,7-trihydroxy-2-[3-(4-hydroxy-3-methoxyphenyl)-2-hydroxymethyl-2,3-dihydrobenzo-[1,4]dioxin-6-yl]-chroman-4-one. By analyzing the curves of (dCp/dT) against temperature T, some apparent points, a maxima point and a minima point, to characterize the Cp curve were obtained. The maxima point in the region of w1 < 0.4 is a character of amorphous solid state of PVP, where w1 is the mass fraction of silybin. In this region, silybin is dispersed into the amorphous solid of PVP. The minima point in the region of w1 > 0.4 is a character of crystalline silybin. In this region, a mixture of crystalline silybin and an amorphous solid dispersion is observed.

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► Solid dispersion of silybin in PVP can be found from the curves of dCp/dT ∼ T.
► Extreme points of dCp/dT ∼ T curve characterize the mixing behavior of solids.
► Solid dispersion of silybin is formed as the mass fraction of silybin <0.4.