Effects of SCOBY Fermentation on the Phytochemical Profile, Antioxidant and Antibacterial Activity of Sonneratia caseolaris (L.) Engl. Leaf Infusion
Abstract
Indonesia harbors extensive mangrove ecosystems with considerable untapped potential as sources of functional bioactive ingredients. Sonneratia caseolaris (L.) Engl., a mangrove species traditionally used in ethnomedicine, contains diverse polyphenolic compounds. However, its application as a functional beverage remains unexplored, particularly regarding how SCOBY fermentation may influence its phytochemical composition and biological activities. This study evaluated the effects of SCOBY fermentation on the physicochemical characteristics, phytochemical profile, antioxidant capacity, and antibacterial activity of S. caseolaris leaf infusion. Fermentation was conducted for 14 days, and a fermented product was compared with an unfermented sample. The fermentation process resulted in a reduction in pH. Phytochemical analysis showed an increase in total phenolic content (TPC) from 21.92±0.18 to 24.23±0.09 mg GAE/g (≈10.5%) and total flavonoid content (TFC) from 11.02±0.06 to 11.58±0.13 mg QE/g (≈5.1%). UPLC–MS profiling revealed fermentation-associated alterations in phytochemical composition, including changes in flavonoid glycosides and sterol derivatives. Antioxidant activity evaluated using the DPPH assay showed comparable IC50 values between the unfermented infusion (46.05±0.12 µg/mL) and its fermented counterpart (45.26±0.26 µg/mL). Notably, the unfermented infusion exhibited no antibacterial activity, whereas the fermented product demonstrated strong inhibition against Pseudomonas aeruginosa (16±2.00 mm at 5%) and weak inhibition against Staphylococcus aureus (7.33±1.15 mm at 5%). Overall, SCOBY fermentation modified the chemical profile and generated selective antibacterial activity. These findings support the potential of fermented S. caseolaris leaf infusion as a potential functional beverage and contribute to the valorization of mangrove plant resources.