Enzyme-ultrasound-assisted valorization of tomato pomace into glutamic acid- and phenolic-rich extracts: Characterization and bioactivity assessment in RAW264.7 macrophages

This study optimized enzyme-ultrasonic-assisted extraction (Enz-UAE) conditions for the recovery of multifunctional bioactive compounds from tomato pomace and evaluated their antioxidant and anti-inflammatory properties. Response surface methodology identified the optimum extraction condition as 15% (w/w) bromelain with 30 min of ultrasonic treatment (UE-12). Under this condition, the extract exhibited a high glutamic acid content (37,656.63 mg/100 g), which was approximately five-fold higher than of untreated tomato pomace. The extract contained appreciable levels of total phenolic compounds (6,223 mg GAE/100 g) and total flavonoids (5,996.12 mg QE/100 g). The extract demonstrated strong antioxidant activities against DPPH (70.18%), ABTS (84.82%), hydroxyl radical (97.38%), and ferric reducing antioxidant power (0.154 mmol Fe2+/mg). High-performance liquid chromatography identified gallic acid and naringin as dominant phenolic compounds, followed by chlorogenic acid, caffeic acid, p-coumaric acid, ferulic acid, 2-hydroxycinnamic acid and rutin. Enz-UAE also reduced volatile compounds associated with undesirable tomato-like, green, and fruity aromas, such as cis-3-hexenal, 1-nitro-peptene, 2-nonadecanol, 6-methyl-5-hepten-2-one, and geranyl acetone. Furthermore, the extract exhibited low cytotoxicity toward RAW264.7 macrophage cells (viability > 80% at 100 µg/mL) and significant anti-inflammatory activity by suppressing nitric oxide production and selectively reducing IL-6 levels without affecting TNF-α levels. Overall, Enz-UAE represents an effective and environmentally-friendly strategy for valorizing tomato pomace into bifunctional ingredients with enhanced umami taste and health-promoting potential, suitable for incorporation into functional and sensory-enhanced food products.