Encapsulation of oregano (Origanum vulgare) leaf polyphenols: Development, characterization and in-vitro release study

Abstract

Oregano (Origanum vulgare) leaf polyphenols show high antioxidative properties. However, their low stability to external conditions like temperature, light, pH and moisture require an efficient encapsulation for bioactive preservation, shelf-life extension and sustained release. This work aimed at encapsulating the sensitive polyphenols obtained from oregano leaves by freeze drying technique, using a combination of reconstituted aloe vera hydrogel as the base material, with maltodextrin and gum Arabic as coating materials. The encapsulation efficiency (85.11 ± 1.15 to 95.60 ± 0.17%) showed good retention of polyphenols by freeze drying method. The microparticles were further characterized on color, moisture content, water activity, solubility, flowability, cohesiveness, morphological analysis and in-vitro release. The powder gave good flowability, less cohesiveness and good reconstitution properties, making it suitable for food applications. Sustained release was obtained at low temperature (15 °C) and low pH (2 and 5) conditions (upto 50% release for a time of 120 min). among the various mathematical models used, Korsmeyer-Peppas model (R2 = 0.96–0.99) was the best fit one, followed by Higuchi model (R2 = 0.94–0.99), which were suitable for simulating intestinal phase release. The polyphenol release occurred through diffusion, obeying Fick's law of molecular diffusion.