INTRODUCTION: α-Mangostin (α-M), one of the xanthon compound isolated from PURPOSE: The lack of solubility of α-mangostin in water limited its formulation and pharmacological application. This study was done to enhance the solubility of α-M by complexation with γ-cyclodextrin (γ-CD) and its application in Alginate/Chitosan Hydrogel Mucoadhesive Film (HMF) for RAS treatment. METHODS: This complex was made by dissolved α-M and γ-CD in separated solution. α-M solution gradualy added into γ-CD to formed α-M/γ-CD complex (α-M/γ-CD CX). This complex then evaporated to yield the dry complex powder. The complex was successfully formulated into hydrogel mucoadhesive film (HMF) preparations based on characterization using Scanning Electron Microscope (SEM), Fourier Transform Infra-Red (FTIR), and X-Ray Diffractometry (XRD). The complex was formulated in hydrogel mucoadhesive film, followed by in-vitro drug release and the study of recurrent aphthous stomatitis (RAS) activity in rats. RESULTS: The α-M/γ-CD CX HMF film has a higher mucoadhesive force and mucoadhesive time than other HMFs resulting in a prolonged retention time in the oral mucosa. The drug release of α-M/γ-CD CX HMF followed the Korsmeyer-Peppas Model with a total amount of drug released 80.34+0.32%. The inclusion complex of α-M/γ-CD CX HMF exhibited increased anti-RAS activity compared to HMF base, α-M HMF, and α-M/γ-CD PM HMF. This was evidenced by a significant decrease in wound area of approximately 79.05±3.30%, an increase in epithelial thickness of about 1.24±0.09 μm, and a decrease in neutrophil score 1.10±0.26. These findings highlight the potential use of α-M/γ-CD CX as an effective RAS agent in HMF. CONCLUSION: The complex of α-M/γ-CD CX has improved solubility of α-M, resulting in the transparent and homogenous film. The film containing this complex has the better physical characteristic, increasing the release and RAS activity.