In the present study, the antioxidant activity of Lycium extract in Chang liver cells was evaluated in two categories: direct action on hydroxyl radical and superoxide scavenging in a cell-free system, as shown by ESR spectrometry, and indirect action through induction of antioxidant enzymes. Lycium extract had direct scavenging activity on hydroxyl radical and superoxide. Antioxidant enzymes such as SOD, CAT, and GSH-Px are critical antioxidant defenses in cells. To protect against the damaging effect of oxygen radicals, most eukaryotes express cytoplasmic Cu/Zn SOD and mitochondrial Mn SOD that convert superoxide to hydrogen peroxide, which is subsequently converted to water by CAT and GSH-Px. CAT is located at the peroxisome and plays important roles in cellular protection by oxidative stress-induced cell damages (Pietarinen et al., 1995). And seleno-dependent GSH-Px catalyzes the degradation of H2O2 and hydroperoxide originating from unsaturated fatty acids at the expense of reduced glutathione (Laila et al., 1991). Lycium extract increased the activities and protein levels of these enzymes, which may mediate its inhibition of ROS production. Thus, Lycium extract not only directly quenches free radicals, but also indirectly induces antioxidant enzymes. As H2O2 treatment attacks vital cellular sites, such as DNA, cell membrane lipid, and protein (Ivancsits et al., 2002, Calabrese et al., 2008), the effect of Lycium extract on these sites in H2O2-treated cells was investigated. H2O2 treatment increased tail length in the comet assay, and Lycium extract protected against this increase, indicating that it protected cellular DNA. Lyciumextract also protected cell membrane lipids from peroxidation induced by H2O2, as shown by 8-isoprostane and DPPP results. ROS can promote the formation of protein-bound carbonyl groups and compromise cellular function (Hawkins and Davies, 2001). Lycium extract blocked the increase in protein carbonyl content after H2O2 treatment. These inhibitory effects of Lycium extract against DNA, lipid, and protein damage protected the cells against H2O2-induced cell death, resulting in increase of the cell viability against H2O2 treatment. The cells exposed to H2O2 exhibited distinct features of apoptosis such as apoptotic body and DNA fragmentation. However, cells pretreated with Lycium extract had significantly reduced the apoptotic phenomenon.

Lycium extract is consumed as a health food supplement and a medicinal herb in China, Korea, and other countries and contains a lot of flavonoids (Le et al., 2007). Flavonoids are known as phenolic antioxidants, which play an important role in the oxidation process by being preferentially oxidized by the attacking radical (Tsao and Deng, 2004). Phenolic compounds are the most abundant antioxidant in our food diet. Dietary intake of phenolic compounds for prevention of disease related with oxidative damage is very important for maintaining healthy life (Scalbert and Williamson, 2000). The antioxidant activity of Lyciumextract in our results might be related with phenolic compounds. In addition to phenolic compounds, there are some previous studies regarding hepatoprotective compounds such as glycolipid, pyrrole derivatives, cerebroside, zeaxanthine dipalmitate, and betaine (Chin et al., 2003, Jung et al., 2005, Kim et al., 1998, Kim et al., 2000, Kim et al., 2002). However, same herbs cultivated in different areas or harvested in different climate and seasons may vary in their chemical and biological properties. It is some difficult to make specific biomarkers in medicinal herbs, therefore further study is remained to isolate distinctive antioxidant components for standardization and quality control of Lycium extracts.

In conclusion, Lycium extract has a protective effect against hepatotoxicity induced by oxidative stress via scavenging ROS and enhancing antioxidant enzymes activities.

From: https://doi.org/10.1016/j.jep.2010.05.007