Plectranthus amboinicus leaves in Kombucha fermentation: from traditional herb to functional beverage

This study developed a Kombucha enriched with Plectranthus amboinicus leaves (Malvarisco), evaluating its physicochemical properties, phytochemical composition, antioxidant and anti-inflammatory activities, acute toxicity, and sensory acceptance. The fermentation process was optimized using a factorial design, yielding an optimized Kombucha (OK) with a pH 3.35, total acidity 0.19%, and soluble solids of 8.77°Brix. Enrichment significantly increased total phenolics (532.09 mg GAE L^-1) and flavonoids (214.55 mg QE L^-1), accompanied by enhanced antioxidant activity, with 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity reaching 83.46% and ferric reducing antioxidant power (FRAP) values more than doubling relative to the control. Notably, ferulic acid was detected at high levels (10.44 ± 0.33 mg g^-1). In vivo zebrafish assays confirmed the absence of acute toxicity under the tested conditions. In the carrageenan-induced edema model, the optimized kombucha did not aggravate edema compared with the control beverage, although the observed differences were not statistically significant, indicating preliminary evidence of a potential biological effect. Sensory analysis showed that the addition of 15% P. amboinicus preserved the beverage's clarity and tea flavor, although the acceptability index of 61% indicated moderate consumer acceptance. These findings indicate that P. amboinicus enrichment modifies the phytochemical and antioxidant characteristics of kombucha and support further investigation of its potential as a botanical ingredient for fermented beverage development.