Development and Characterization of a Natural Polymer from Manilkara Zapota Seed Gum with Phytochemical Evaluation of Leaf Extract for Sustained-Release Drug Delivery

Background: Natural plant-derived polymers have gained increasing attention as alternatives to synthetic excipients in sustained-release (SR) drug delivery systems owing to their biocompatibility, safety, and renewability. Manilkara zapota (L.) P. Royen, recognized for its gastroprotective and antioxidant potential, is rich in bioactive flavonoids and phenolic compounds, while its seed gum exhibits desirable swelling and gel-forming properties suitable for controlled drug delivery. Objective: The present study aimed to extract and perform phytochemical and physicochemical evaluation of Manilkara zapota leaf extract and to assess Manilkara zapota gum as a natural polymeric excipient. Methods: Leaves and seed gum of Manilkara zapota were isolated and characterized. Physicochemical evaluations, including pH, viscosity, and swelling index, were conducted. Structural and thermal characterization was performed using Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Results: The Manilkara zapota gum exhibited a high swelling capacity (324 ± 8%) and viscosity (428 ± 12 cps), confirming its suitability as a hydrophilic matrix-forming polymer. The total phenolic content was found to be 87.6 ± 2.3 mg GAE/g, while the total flavonoid content was 52.1 ± 1.8 mg QE/g, indicating the presence of significant bioactive phytoconstituents. Overall, the gum isolated from M. zapota demonstrated excellent swelling behavior, high viscosity, and good thermal stability, which are essential attributes for its application in sustained-release matrix drug delivery systems