Impact of Infusion Time on the Physical Characteristics, Antioxidant Properties, and in-vitro Antidiabetic Activity of Roselle Tisane Herbal Drink Blends

Abstract

Background: Tisane or herbal tea prepared from Hibiscus sabdariffa L. (roselle), either alone or blended with other herbs, is widely recognised for its health-promoting properties, including antidiabetic potential. Infusion time plays a crucial role in the extraction of colour pigments, bioactive compounds, and functional properties that determine both sensory quality and health benefits. Aim: This study investigated the influence of infusion time on the physicochemical characteristics, antioxidant capacity, and in-vitro antidiabetic potential of a tisane blend comprising roselle and Garcinia atroviridis (garcinia). Materials and Methods: Tisane samples were infused for 5–30 minutes in hot water and evaluated for colour parameters (L*, a*, b*, C, h°), pH, total anthocyanin content, total phenolic content (TPC), total flavonoid content (TFC), antioxidant activities (ferric reducing antioxidant power (FRAP), trolox equivalent antioxidant capacity (TEAC), free radical scavenging activity (DPPH)), and α-amylase and α-glucosidase inhibitory activities. Results: Infusion time did not significantly (P > 0.05) affect lightness (L*) or pH (2.21–2.23) but enhanced colour intensity and total anthocyanin content (15.33 to 18.69 mg/100 mL). Antioxidant activity increased with infusion time: TPC rose from 20.49 to 35.19 mg GAE/100 mL, FRAP from 109.18 to 136.55 mg Fe²⁺/100 mL, TEAC from 61.14 to 84.58 mg TE/100 mL, and DPPH inhibition from 56.39% to 65.22%. The 20-minute tisane exhibited stronger enzyme inhibition (IC₅₀ α-amylase: 7.431 mg/mL; α-glucosidase: 23.612 mg/mL) than the 5-minute infusion but was less potent than acarbose. Conclusion: A 20-minute infusion optimised colour, bioactive compound extraction, antioxidant capacity, and antidiabetic potential, suggesting it as the ideal infusion duration to maximise the functional and sensory qualities of roselle–garcinia tisane.