EVALUATION OF ANTIOXIDANT ACTIVITY AND PROTECTIVE EFFECT OF CASSIA AREREH (CAESALPINIACEAE) EXTRACTS AGAINST FREE RADICAL-INDUCED OXIDATIVE HAEMOLYSIS

Laure Brigitte KOUITCHEU MABEKU*, Thibau Flaurant TCHOUANGUEU, Emmanuel TALLA, Jacques KOUAM

In this study, the cellular and non cellular antioxidant and free radical scavenging properties of the methanol and ethyl acetate extract of Cassia arereh leaves were evaluated. The antioxidant and free radical scavenging activity of the plant extracts and the standard (ascorbic acid and gallic acid) were assessed through DPPH radical, hydroxyl radical, nitric oxide scavenging activity and reducing power at various concentrations ranging from 1.62 to 200 μg/ml. For cellular antioxidant assay, we evaluated the haemolysis and the haematoprotective effect of Cassia arereh against hydrogen peroxide-mediated cytotoxicity of red blood cells (RBCs) induced with CuSO₄/H₂O₂. Total polyphenol and flavonoid content of extracts were also determined using colorimetric methods. DPPH assay showed IC₅₀ values of 4.27 ± 0.9 and 3.21 ± 0.55 μg/ml respectively for methanol and ethyl acetate extract, instead of 12.5 ± 2.99 μg/ml for standard. Methanol extract (IC₅₀ = 41.597 ± 7.46 μg/ml) had a significantly higher reducing power than the ethyl acetate one (IC₅₀ = 238.89 ± 26.56 μg/ml). The reducing power of the methanol extract was found to be not significantly different from standards. Our results showed a non significant decrease in the nitric oxide radical production due to the extracts compared to ascorbic acid or gallic acid. It was also found that, the methanol extract (IC₅₀ = 17.06 ± 0.82 μg/ml) was significantly more effective than that of ethyl acetate (IC₅₀ = 76.34 ± 3.4 μg/ml) as hydroxyl radical scavenging activity. Both extracts induced haemolysis of sheep RBCs in a dose dependant-manner. Incubation of RBCs with extracts before exposing them to CuSO₄/H₂O₂ reduced the hydrogen peroxide-mediated cytotoxicity of RBCs respectively by 30.71 and 34.75 %, for methanol and ethyl acetate extracts after one hour. The antihaemolytic activity decreased with time for all the tested products. These results demonstrate the antioxidant properties of Cassia arereh and reveal that methanol is the best extractant for antioxidant agents of this plant.