This study aimed to provide new insight into the influence of nutritional properties and in-vitro gastrointestinal digestion on the antioxidant activities of roselle leaves (RL) by applying drying techniques, specifically freeze-drying, oven-drying, sun-drying, and hot air-drying. The results observed that freeze-dried RL had higher nutritional and physical properties compared to other drying techniques. It had the maximum values of protein (6.61 g/100 g), fat (7.74 g/100 g), ash (18.53 g/100 g), crude fiber (9.46 g/100 g), water activity (0.32), pH (2.54), and titratable acidity (0.027%). In addition, all treatments on RL samples were evaluated for their functional characteristics. Furthermore, after in-vitro digestion, the antioxidant potential of total phenolic contents and flavonoid levels exhibited a percentage rise of 2.1% and 12.03% across all treated samples (54.98 ± 0.02 to 57.08 ± 0.05 mg/g and 28.66 ± 0.02 to 40.69 ± 0.03 mg/g), respectively. Interestingly, the total anthocyanin, 2,2-diphenyl-1-picrylhydrazyl, ferric-reducing antioxidant power, and vitamin C in all dried samples levels decreased and ranged from 49.17 ± 02 to 4.91 ± 0.42 mg/g, 84.92 ± 0.21 to 80.81 ± 0.21%, 14.65 ± 0.48 to 1.12 ± 0.21 mg/g, and 8.8 ± 0.06 to 2.24 ± 0.04 mg/L, respectively, after digestion. Consequently, freeze-drying techniques demonstrate advantageous effects on RL antioxidant potential. RL may serve as a valuable component for incorporating into other products to enhance innovative and functional food products.
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