Elucidation of phytochemical composition, anti-inflammatory mechanism mediated by the PI3K/Akt-NO-cytokine axis, and antibacterial/antioxidant properties of purple tea extract

This study aims to analyse the phytochemical composition of Kenyan purple tea extract(PPTE) and evaluate its anti-inflammatory, antibacterial, and antioxidant activities in vitro. The total polyphenols (414.30 ± 9.80 mg/g), polysaccharides (220.73 ± 14.10 mg/g) and 8 main components were quantified by colorimetry and HPLC, and 63 compounds were identified through UPLC-MS/MS. In LPS-induced THP-1 monocytes, CCK-8 confirmed PPTE was non-toxic at ≤25 µg/mL, and ELISA, Griess method, qPCR, and Western blot showed it dose-dependently reduced pro-inflammatory IL-6, TNF-α, and NO levels, upregulated anti-inflammatory IL-10, and inhibited inflammation by suppressing PI3K/Akt phosphorylation and downstream mTOR/NF-κB activation. Oxford cup and broth dilution showed PPTE had greater antibacterial activity against S.aureus (MIC = 1.56 mg/mL) than P.aeruginosa (MIC = 12.50 mg/mL). PPTE showed high antioxidant activity using DPPH/ABTS assays with IC50 of 23.22 μg/mL and 2.13 μg/mL, respectively. These findings support PPTE as a promising candidate for treating inflammatory diseases with infection.