Concurrent measurement of cellular turbidity and hemoglobin to evaluate the antioxidant activity of plants

Oxidative stress as an underlying mechanism of anticancer drugs cytotoxicity on human red blood cells' membrane

The aim of this study is to investigate the direct in vitro effects of anticancer drugs on red blood cells (RBCs) and to explore the underlying mechanism, mainly by measuring RBCs oxidative stress (OS) status. After RBCs direct contact with fourteen (14) anticancer drugs, several parameters were assessed including: cellular turbidity, methemoglobin (metHb) generation, released Hb and Hb stability. Moreover, intracellular Hb, considered as new molecular target of anticancer drugs, was quantified inside RBCs. MDA level, the main biomarker of OS, was simultaneously measured. The cellular turbidity reveled severe (docetaxel "TXT", 0.03 ± 0.002), moderate (methotrexate "MTX", 0.49 ± 0.009), or none (5-fluorouracil "5-FU", 0.76 ± 0.029) membrane cytotoxicity (MC). An inverse relationship between cell concentration, released Hb and metHb content was obtained. High metHb generation, revealing intense OS, was also mostly expressed in paclitaxel "TXL" and etoposide "VP16". Further, epirubicin "EPI" and "TXT" induced important oxidation of membrane lipids with 0.32 ± 0.014 and 0.26 ± 0.004, respectively. Also, MTX (0.17 ± 0.006) and doxorubicin "DOX" (0.32 ± 0.034) affected significantly Hb stability by a direct contact with molecule. These findings demonstrated that anticancer drugs have the ability to induce membrane damages by the exacerbation of OS through membrane lipid peroxidation and Hb oxidation even inside RBCs.

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 ( O 2 · - ), 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 O 2 · -  (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.