Physicochemical and Emulsifying Properties of Melia azedarach Gum

Abstract

Naturally occurring hydrophilic colloids are versatile excipients in drug delivery systems. They are often used as coating materials, disintegrating agents, binders, emulsion stabilizers, and other applications. This study sought to investigate the physicochemical and emulsifying properties of gum extracted from Melia azedarach (MA). The gum was harvested, authenticated, and purified using ethanol precipitation. Physicochemical, microbial, and proximate analyses were performed on the purified gum. Oil of olive emulsions containing different amounts (5–15%w/v) of the gum as emulsifiers were prepared by homogenization. The zeta potential, creaming index, and average droplet size of products were assessed. The effects of pH changes, temperature, and monovalent and divalent electrolytes on the stability of the emulsions were also investigated. The yield of the gum after purification was 68.3%w/w. The gum has low moisture content and good swelling properties. Lead, copper, cadmium, and mercury were not detected. Emulsions containing 15%w/v of acacia or MA gum had the smallest average (Z-average) droplet size (acacia: 1.837 ± 0.420 μm; MA gum: 2.791 ± 0.694 μm) and the highest zeta potential (acacia: −30.45 mV; MA gum: −32.867 mV). Increasing the concentration of the gums increased the emulsion viscosity with MA gum emulsions being more viscous than corresponding acacia emulsions. MA gum emulsions had higher emulsion capacity and stability but lower creaming index relative to acacia gum emulsions of similar concentrations. Potassium chloride (KCl) reduced zeta potential but increased Z-average for emulsions prepared with either gum. Calcium chloride (CaCl2) produced a similar but more pronounced effect. When the pH was decreased from 10 to 2, the zeta potential of the droplets was reduced, but the droplet size of emulsions prepared from either gum was increased. Increasing temperature from 25 to 90°C produced no significant (p value >0.9999) change in droplet size. These findings suggest that MA gum is a capable emulsifying agent at 15%w/v.