Abstract
Kudingcha is a traditional Chinese tea, and insect tea is a special drink produced by the metabolism of insect larvae using the raw Kuding tea. Insect tea polyphenols (ITP) and its raw tea (Kuding tea) polyphenols (KTP) are high-purity polyphenols extracted by centrifuge precipitation. The present study was designed to compare the antioxidative effects of insect tea polyphenols (ITP) and its raw tea (Kuding tea) polyphenols (KTP) on d-galactose-induced oxidation in Kunming (KM) mice. KM mice were treated with ITP (200 mg/kg) and KTP (200 mg/kg) by gavage, and vitamin C (VC, 200 mg/kg) was also used as a positive control by gavage. After determination in serum, liver and spleen, ITP-treated mice showed higher superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione (GSH) activities and lower nitric oxide (NO), malonaldehyde (MDA) activities than VC-treated mice, KTP-treated mice and untreated oxidation mice (control group). By H&E section observation, the mice induced by d-galactose-induced oxidation showed more changes than normal mice, and oxidative damage appeared in liver and spleen tissues; ITP, VC and KTP improved oxidative damage of liver and spleen tissues, and the effects of ITP were better than VC and KTP. Using quantitative polymerase chain reaction (qPCR) and western blot experiments, it was observed that ITP could increase the mRNA and protein expression of neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), manganese superoxide dismutase (Mn-SOD), cupro/zinc superoxide dismutase (Cu/Zn-SOD), catalase (CAT), heme oxygenase-1 (HO-1), nuclear factor erythroid 2 related factor 2 (Nrf2), gamma glutamylcysteine synthetase (γ-GCS), and NAD(P)H:quinone oxidoreductase 1 (NQO1) and reduce inducible nitric oxide synthase (iNOS) expression in liver and spleen tissues compared to the control group. These effects were stronger than for VC and KTP. Both ITP and KTP had good antioxidative effects, and after the transformation of insects, the effects of ITP were better than that of KTP and even better than VC. Thus, ITP can be used as an antioxidant and anti-ageing functional food.
Highlights
Ageing is a spontaneous biological process wherein the biological body gradually shows a decline in function, adaptability and immunity
A small amount of normal body D-galactose can be transformed into glucose and involved in metabolism, but a large amount of D-galactose will lead to cellular metabolic disorders and alter activity of tissue cell oxidase to produce a large number of superoxide anion and oxidation products; the latter process will lead to biological macromolecular structure and functional damage, eventually leading to cell ageing [3]
Various extraction methods have been compared by other scholars, but the purity of polyphenols extracted by this method is the highest, and precipitants and hydrochloric acid have no effect on the composition
Summary
Ageing is a spontaneous biological process wherein the biological body gradually shows a decline in function, adaptability and immunity. Ageing is closely associated with many diseases, including hypertension, type 2 diabetes, atherosclerosis and Alzheimer’s disease. The onset of these diseases can be slowed by delaying ageing [1]. A small amount of normal body D-galactose can be transformed into glucose and involved in metabolism, but a large amount of D-galactose will lead to cellular metabolic disorders and alter activity of tissue cell oxidase to produce a large number of superoxide anion and oxidation products; the latter process will lead to biological macromolecular structure and functional damage, eventually leading to cell ageing [3]. Antioxidant components in natural plants have been gradually applied to the development of antioxidant and health care products after the antioxidant effect was verified by the D-galactose model test [4]
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