Saba banana, a popular fruit crop grown in Southeast Asia, is an economical source of a variety of beneficial agents. This study examined the variations in total phenolic, flavonoid, and antioxidant activities of five maturity stages of Saba banana, and their changes during simulated in vitro gastrointestinal digestion as affected by varying structural compositions. Antioxidant activities were evaluated using ferric reducing antioxidant power (FRAP), metal ion chelating (MIC) activity, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. Results of DPPH and ABTS were compared in terms of TEAC (Trolox Equivalent Antioxidant Capacity) and VCEAC (Vitamin C Equivalent Antioxidant Capacity) values. Bio-properties were found to be highest in mature green stage with values slightly decreased as ripening proceeded. Simulated digestion showed a continuous increase in total phenolic with comparatively faster release in structure-less state (slurry) than samples with intact structure (cut). The trend of antioxidant activities was increased in the gastric phase and then decreased at the onset of intestinal phase, except for MIC which showed a reverse effect. Our study indicated that the bio-properties of Saba banana were affected by maturity and modifications in its physical structure and composition could influence the release behaviors of food components during simulated digestion. Owing to its increasing demand and whole-year availability, banana is considered as one of the world's most important fruit crops in terms of commercial production and one of the most consumed staple food commodities after major cereals 1,2. An estimated of 19.2 million tons of banana had been exported globally in 2018 which accounted to the strong supply growth from the two leading exporters, Ecuador and the Philippines 3. Among the economically important banana cultivars in the Philippines, foremost of which is Saba (Musa 'saba'[Musa acuminata × Musa balbisiana]), an ABB genome group, which accounts to more than 25% of the country's banana production. This banana variety can be utilized at all stages of maturity either raw or cooked and is used primarily for manufacturing various food products such as condiments (banana ketchup), snacks (banana chips), viands, and desserts 4. Saba banana is also relished in other Southeast Asian countries 5 but is gaining popularity in Latin America 2 and Southern Nigeria 6. Banana is not only an important source of starchy staple food but could also exert a beneficial effect on human health. It contains phytonutrients, including vitamins and different classes of phenolic compounds 2,7. In plants, phenolic compounds may exist in free, soluble conjugated (esterified), and insoluble-bound forms 8,9. Research studies have shown that bound phenolics have demonstrated a significantly higher antioxidant capacity compared to free phenolics in numerous in vitro antioxidant assays carried out 10. Insoluble bound phenolics are localized in the cell wall matri...