Effect of Thermal Extraction Conditions on Antioxidant Capacity, Phenolic Composition and Pancreatic Lipase Inhibitory Activity of Hibiscus Sabdariffa Water Extract

Thermal processing plays a critical role in modulating the phytochemical composition and biological activity of plant extracts. This study investigated the effects of extraction temperature (40–100 °C) and duration (15–180 min) on total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity, and pancreatic lipase inhibitory activity of Hibiscus sabdariffa water extract. TPC was maximized at 40 °C for 30 min (48 mg GAE/g), whereas TFC peaked at 60 °C for 30 min (650 mg CE/g). DPPH radical scavenging activity remained relatively stable across extraction conditions (75–90%), with optimal activity observed at 80 °C for 120 min. In contrast, ferric reducing antioxidant power (FRAP) increased with temperature, reaching a maximum at 100 °C for 120 min (2100 µM Fe²⠺/g). Notably, pancreatic lipase inhibition was highest at 100 °C for 30 min (92%), approaching the activity of the reference inhibitor orlistat. Antioxidant activity did not directly correlate with total phenolic or flavonoid content, indicating that qualitative changes in phytochemical composition contribute significantly to bioactivity. These findings demonstrate that extraction parameters should be optimized based on the targeted functional endpoint, with high-temperature short-time conditions favoring enzyme inhibition, while moderate conditions preserve antioxidant-associated phytochemicals. This study provides a bioactivity-driven framework for optimizing aqueous extraction of H. sabdariffa for functional food and nutraceutical applications.