Protective Effects of Shoumei (Camellia sinensis) Polyphenols against Hepatic Injury via Antioxidant Mechanisms

Tea is globally the second most consumed beverage after water, and its pharmacological properties are extensively documented. It has potent neuroprotective, free radical scavenging, antioxidative, antioncogenic, hepatoprotective, anti-diabetic, antiviral, and chemopreventive properties. This study investigated the hepatoprotective effects of polyphenols extracted from Shoumei, a slightly fermented white tea (Camellia sinensis). HPLC analysis identified gallic acid, catechin, hyperoside, and sulfuretin as the main phenolic constituents. In an in vitro model, Shoumei polyphenols (SPs) attenuated H₂O₂-induced oxidative damage in human normal hepatic L-02 cells. In an in vivo model of CCl₄-induced liver injury in mice, SPs effectively reduced the liver index and ameliorated histopathological damage. Biochemical analyses demonstrated that SPs significantly decreased serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), triglyceride (TG), total cholesterol (TC), blood urea nitrogen (BUN), nitric oxide (NO), malondialdehyde (MDA), interleukin-6 (IL-6), interleukin-12 (IL-12), tumour necrosis factor-alpha (TNF-α), and interferon-gamma (IFN-γ). Conversely, SPs increased serum levels of albumin (ALB), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). At the molecular level, qRT-PCR and Western blot analyses revealed that SPs up-regulated the mRNA and protein expression of neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), manganese-SOD (Mn-SOD), copper/zinc-SOD (Cu/Zn-SOD), CAT, and inhibitor of nuclear factor kappa B alpha (IκB-α), while down-regulating the expression of inducible nitric oxide synthase (iNOS) and NF-κB p65. The preventive effect of SPs against CCl₄-induced liver injury was comparable to that of silymarin. These results indicate that the identified polyphenols, primarily through their antioxidant capacity, mediate significant hepatoprotection, suggesting Shoumei polyphenols are high-quality natural agents for liver protection.