Sequential ultrasound-hot water extraction of Tradescantia zebrina leaves: optimized bioactivities with limited gastrointestinal stability

Tradescantia zebrina is a leafy vegetable with potential as a functional food ingredient, but its optimal extraction and gastrointestinal (GI) stability require investigation. This study aimed to optimize phytochemical extraction from T. zebrina leaves using hot water extraction (HWE), ultrasound-assisted extraction (UAE), and sequential hybrid methods (UAE + HWE, HWE + UAE), and then evaluated the GI stability of the optimized extract using the INFOGEST model. Among nine extraction treatments, the sequential UAE-20 min followed by HWE-15 min (UAE-20 + HWE-15) yielded the highest total phenolic content (TPC, 8.11 mg GAE/g) and flavonoid content (TFC, 63 mg QE/g), along with the strongest antioxidant activities: 2,2-diphenyl-1-picrylhydrazyl (DPPH•) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS•+) scavenging, and Ferric reducing antioxidant power (FRAP). TPC and TFC correlated strongly with antioxidant parameters, while anthocyanin contents did not. Post-digestion analysis of the optimized extract, following solid-phase extraction cleanup, revealed marked reductions in the phenolic and flavonoid content (to 3.28 mg GAE/g and 6.44 mg QE/g, respectively) and a corresponding decline in DPPH•, ABTS•+, and H2O2 scavenging activities, FRAP, and anti-inflammatory (albumin denaturation inhibition) activities. Nitric oxide scavenging activity was nearly lost. These findings indicate that while the UAE-20 + HWE-15 method is optimal for extraction, the resulting bioactive compounds showed limited stability under simulated GI conditions, highlighting the need for strategies to preserve their activity for functional food applications. This highlights the need for protective strategies, like encapsulation, to preserve its efficacy for functional food applications.