Abstract
The solubility of reserpine in eight different green solvents, namely, water, ethanol, ethylene glycol (EG), ethyl acetate (EA), isopropanol (IPA), propylene glycol (PG), poly(ethylene glycol)-400 (PEG-400), and transcutol, was measured and correlated from (298.15 to 338.15) K using the shake flask method. The experimental solubilities were correlated with temperature-dependent Apelblat and ideal equations. For the Apelblat equation, the root-mean-square deviations (RMSD) and correlation coefficients (R2) were obtained as 0.005 to 0.053 and 0.9978 to 0.9999, respectively. For an ideal Apelblat equation, the RMSD and R-2 were obtained as 0.005 to 0.018 and 0.9950 to 0.9990, respectively. The mole fraction solubility of reserpine was observed highest in PEG-400 (1.44.10(-3) at 298.15 K) followed by transcutol, EG, PG, IPA, ethanol, and water from (298.15 to 338.15) K. However, the mass fraction solubility of reserpine was observed highest in EA (3.60.10-3 at 298.15 K). The dissolution enthalpy, Gibbs energy, and dissolution entropy were determined by vant Hoff and Krug analysis, and results showed endothermic and spontaneous dissolution of reserpine in all green solvents investigated.