Determination of antioxidant activity, phenolic contents and antiviral potential of methanol extract of Euphorbia spinidens Bornm (Euphorbiaceae)

Purpose: This study was aimed to evaluate the antioxidant activity of the methanol extract of Euphorbia spinidens Bornm (Euphorbiaceae) and its effect on Herpes simplex virus type-1 (HSV-1) replication. Methods: The methanol extract of aerial parts of E. spinidens collected from Khorasan State in North-Eastern part of Iran was used in this study. Total phenolic, flavonoid contents and the antioxidant activity were evaluated using Folin-Ciocalteu method, aluminum chloride colorimetric method and beta-carotene-linoleate model system, respectively. Both the cytotoxic and antiviral effects of the crude extract on Vero cell line were determined by quantifying the viability of Vero cells using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)2H-tetrazolium (MTS) assay. Results: Total phenolic and flavonoid contents of E. spinidens were 70 +/- 1 mg of gallic acid equivalent/g of dry extract (mg GAE/g extract) and 49.66 +/- 1.00 mg rutin equivalent/g of dry extract (mg RTN/g extract), respectively. Antioxidant activity was 44 +/- 1 % compared with the standard, buthylated hydroxytuloene (BHT). The 50 % cytotoxic concentration (CC50) of the extract on Vero cells was 5.072 +/- 0.063 mg/ml and its antiviral concentration of 50 % effectiveness (EC50) value was 0.34 +/- 0.003 mg/ml. Conclusion: The findings of this study show that the methanol extract of E. spinidens has high content of phenolic and flavonoid compounds with good antioxidant activity. Furthermore, this extract has significant antiviral effect on HSV-1 probably due to the inhibition of viral replication.