Co-Processed Starch–Beeswax Composites as Natural Tablet Lubricants: Preparation, Characterization, and Performance Evaluation
Background: The development of naturally derived pharmaceutical excipients has attracted increasing interest as alternatives to conventional synthetic materials. Methods: In this study, starch–beeswax composites were prepared using native rice starch (RS) and spray-dried rice starch (SDRS) through melt levigation (ML) and emulsification (EM) techniques at starch-to-beeswax ratios of 9:1, 8:2, and 7:3. The physicochemical properties, surface hydrophobicity, morphology, tabletability, and lubrication performance of the resulting composites were evaluated and compared with magnesium stearate (MGS) and hydrogenated vegetable oil (HVO). Results: Co-processing with beeswax markedly increased the water contact angle from 35.4° and 59.7° for RS and SDRS, respectively, to values ranging from 94.5° to 125.1°, indicating successful modification of surface hydrophobicity. SEM analysis demonstrated changes in particle morphology and surface appearance following co-processing, while FT-IR confirmed the coexistence of characteristic starch- and beeswax-associated spectral features without evidence of detectable covalent modification. Co-processed formulations generally maintained or improved tabletability relative to their corresponding starch bases, with SDRS-based composites producing substantially harder tablets than RS-based formulations. The composites also reduced tablet ejection force and improved tablet mechanical properties compared with lubricant-free formulations. Among all samples, SDRS-EM-73 exhibited the best overall performance, reducing ejection force from 386.5 N for the lubricant-free control to 89.2 N, a value comparable to HVO (93.0 N), while producing tablets with high hardness (60.9 N), low friability (0.16%), and acceptable disintegration time (44.8 s). Conclusions: These findings demonstrate that co-processed starch–beeswax composites, particularly SDRS-EM-73, show considerable potential as naturally derived excipients for tablet manufacturing and may serve as sustainable alternatives to conventional tablet lubricants.