In vitro antioxidant activity of olive leaf extract (Olea europaea L.) and its protective effect on oxidative damage in human erythrocytes.

AIMS: This study aimed to evaluate in vitro antioxidant capacity of olive leaf extract (OLE), Olea europaea L., and its protective effect on peroxyl radical-induced oxidative damage in human erythrocytes. MAIN METHODS: The OLE was evaluated by the following assays: i) total phenolic and flavonoid content; ii) oleuropein content; iii) Ferric reducing antioxidant power (FRAP); iv) antioxidant activity against ABTS•+, DPPH• and reactive oxygen and nitrogen species: superoxide anion ( O2·- ), hypochlorous acid (HOCl) and nitric oxide (NO•) and v) protective effect on peroxyl radical-induced oxidative damages in human erythrocytes as hemolysis, thiobarbituric acid reactive substances (TBARS) formation and oxyhemoglobin oxidation. KEY FINDINGS: Total phenolic and flavonoid contents were 131.7 ± 9.4 mg gallic acid equivalents/g dry weight (dw) and 19.4 ± 1.3 mg quercetin equivalents/g dw, respectively. Oleuropein content was 25.5 ± 5.2 mg/g dw. FRAP analysis was 281.8 ± 22.8 mg trolox equivalent/g dw and OLE inhibited ABTS•+ (50% effective concentration (EC50) = 16.1 ± 1.2 µg/mL) and DPPH• (EC50 = 13.8 ± 0.8 µg/mL). The extract demonstrated effective ability to scavenge O2·-  (EC50 = 52.6 ± 2.1 µg/mL), NO• (EC50 = 48.4 ± 6.8 µg/mL) and HOCl (EC50 = 714.1 ± 31.4 µg/mL). The extract inhibited peroxyl radical-induced hemolysis (EC50 = 11.5 ± 1.5 µg/mL), TBARS formation (EC50 = 38.0 ± 11.7 µg/mL) and hemoglobin oxidation (EC50 = 186.3 ± 29.7 µg/mL) in erythrocytes. SIGNIFICANCE: OLE is an important source of natural antioxidants; it has effective antioxidant activity against different reactive species and protects human erythrocytes against oxidative damage.

Evaluation of the antimicrobial activity and cytotoxic effect of hydroxyapatite containing Brazilian propolis.

The aim of this work was to produce hydroxyapatite powder (HA) containing the dry extract of green and red propolis, and to evaluate the possible bactericidal activity of these materials over a short period of time through a fast release system. The ethanolic extracts of green and red propolis (EEP) were incorporated into the material by spray drying. After release tests, powders containing dry EEP were characterized regarding the content of total phenolics and flavonoids. Material characterization was undertaken by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The antimicrobial activity was evaluated by plate colony counting, minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) against Staphylococcus aureus (S. aureus). The cytotoxicity of the materials was determined by the neutral red incorporation method. The materials showed apparently spherical morphology, indicating a decrease in the degree of agglomeration with the addition of propolis. Characteristic HA and propolis functional groups were observed in the FTIR. The materials showed a higher release of phenolics and lower amounts of flavonoids when compared to the EEP, with the higher amounts of flavonoids observed for HA with red propolis. A bactericidal effect was observed for all materials within the interval of 0.5 and 1 h, showing lower inhibitory activity (MIC) and higher bactericidal activity (MBC) when compared to the EEP, with the best results attributed to HA with red propolis. The IC50 values (which is the concentration needed to inhibit cell growth by 50%) obtained from the cytotoxicity assay for HA with the green and red propolis lay between MIC and MCB. Considering these results, it is suggested that HA and propolis may be used as a possible antimicrobial agent, inhibiting the growth of S. aureus, although further in vivo biocompatibility should be investigated before using this material as a medical device with bactericidal potential.