Neem leaves (Azadirachta indica A. Juss) contain secondary metabolites with potential health benefits. Fermentation using a SCOBY may modify the phytochemical profile and enhance their potential as functional beverages; however, the strong bitterness of neem leaves remains a challenge for nutraceutical development. This study aimed to characterize the physical quality and initial total flavonoid content (TFC) of neem leaf kombucha at various concentrations and fermentation times. Four formulas (0.3%, 1%, 3%, and 1% with clay pretreatment) were evaluated on days 8, 12, and 14. Physical quality was assessed by measuring pH and alcohol content (refractometry), while TFC was determined using UV-Vis spectrophotometry. On day 14, pH ranged from 2.54 to 3.21 in undiluted samples and from 2.97 to 3.44 after 21-fold dilution, with alcohol contents of 4.3–6.3% and 0.3–0.5%, respectively. TFC values in undiluted samples were 0.02862, 0.03388, 0.03695, and 0.03016 mg QE/mL for the 0.3%, 1%, 3%, and clay-pretreated 1% formulas, respectively, while diluted samples contained 0.01416, 0.02094, 0.02440, and 0.01990 mg QE/mL. Fermentation for 14 days produced the highest flavonoid response, with the 3% concentration showing the highest TFC. The clay-pretreated 1% kombucha retained a substantial flavonoid content and may improve palatability.
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