Physicochemical Characterization of Spray-Dried Morinda citrifolia Extract Microcapsules Using an Alginate-Chitosan-STPP System
Abstract
Scopoletin, the primary bioactive marker of Morinda citrifolia L. with antihyperlipidemic activity, is susceptible to thermal and oxidative degradation during processing and storage. Despite the established role of microencapsulation in protecting herbal bioactives, studies on spray-dried polyelectrolyte wall systems for Morinda citrifolia extract remain limited, particularly regarding the influence of chitosan concentration on microcapsule formation and encapsulation performance. This study investigated the effect of chitosan concentration on the physicochemical properties and scopoletin encapsulation efficiency of spray-dried alginate-chitosan-sodium tripolyphosphate (STPP) microcapsules. Morinda citrifolia fruit extract was prepared by maceration in 70% ethanol and characterized prior to microencapsulation. Two formulations differing in chitosan concentration were spray-dried: F1 (1% w/v) and F2 (2% w/v), with sodium alginate (1% w/v), STPP (0.1% w/v), and extract concentration held constant. Microcapsules were characterized by FTIR spectroscopy, particle size analysis (PSA), differential scanning calorimetry (DSC), moisture content determination, scanning electron microscopy (SEM), and scopoletin quantification via validated TLC–densitometry. FTIR confirmed extract integration into the polymer matrix through hydrogen bonding, electrostatic interactions, and ionic crosslinking, with more pronounced polyelectrolyte interactions in F1. F1 also exhibited a narrower particle size distribution, greater thermal stability, lower moisture content (3.38 ± 0.20%), and higher encapsulation efficiency (88.37%) than F2 (moisture: 4.89 ± 0.16%; EE: 72.09%; p = 0.043). SEM revealed greater particle discreteness in F1, whereas F2 exhibited denser aggregation. These results demonstrate that chitosan concentration critically governs polyelectrolyte complex formation and encapsulation performance, with F1 showing optimal physicochemical characteristics as a stable, standardized Morinda citrifolia-based oral herbal formulation.