Antioxidant Capacity of Free and Bound Phenolics from Olive Leaves: In Vitro and In Vivo Responses

Abstract

Olive leaves are rich in phenolic compounds. This study explored the chemical profiles and contents of free phenolics (FPs) and bound phenolics (BPs) in olive leaves, and further investigated and compared the antioxidant properties of FPs and BPs using chemical assays, cellular antioxidant evaluation systems, and in vivo mouse models. The results showed that FPs and BPs have different phenolic profiles; 24 free and 14 bound phenolics were identified in FPs and BPs, respectively. Higher levels of phenolic acid (i.e., sinapinic acid, 4-coumaric acid, ferulic acid, and caffeic acid) and hydroxytyrosol were detected in the BPs, while flavonoids, triterpenoid acids, and iridoids were more concentrated in the free form. FPs showed a significantly higher total flavonoid content (TFC), total phenolic content (TPC), and chemical antioxidant properties than those of BPs (p < 0.05). Within the range of doses (20–250 μg/mL), both FPs and BPs protected HepG2 cells from H2O2-induced oxidative stress injury, and there was no significant difference in cellular antioxidant activity between FPs and BPs. The in vivo experiments suggested that FP and BP treatment inhibited malondialdehyde (MDA) levels in a D-galactose-induced oxidation model in mice, and significantly increased antioxidant enzyme activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), and the total antioxidant capacity (T-AOC). Mechanistically, FPs and BPs exert their antioxidant activity in distinct ways; FPs ameliorated D-galactose-induced oxidative stress injury partly via the activation of nuclear factor erythroid-2-related factor 2 (Nrf2) signaling pathway, while the BP mechanisms need further study.

Evaluation of Antioxidant Activity and Treatment of Eczema by Berberine Hydrochloride-Loaded Liposomes-in-Gel

“…The results of the MDA determination of mice in each group were shown in Figure 10. According to the absorbance results of MDA, the oxidation degrees of the skin and liver of mice were evaluated, respectively [47]. Compared with the blank group, the MDA values of the skin and liver were significantly increased, indicating that eczema caused oxidative damage in mice.…”

Two Olea europea extracts reduce deleterious effects induced by lead exposure in a model of neurotoxicity: involvement of the endoplasmic reticulum

“…The Fe 2+ ions have pro-oxidant properties capable of determining lipid oxidation resulting in cellular alterations and chelating agents can reduce these damages. The chelating activity can be studied by spectrophotometric evaluation of the inhibition of the Fe 2+ -ferrozine complex in which the agents reduce the formation of this complex: the reduction of the color is proportional to the chelating activity produced [27]. Experimentally different concentrations of each sample in 1 ml solvent were mixed with 0.5 ml methanol and 0.05 ml of 2 mM FeCl 2 .…”