Antioxidant and Cytotoxic Activities of Lipophilic and Hydrophilic Fractions of Mentha Spicata L. (Lamiaceae)

Total antioxidant activity (TAA) and cytotoxic effect of four solvent fractions of ethanol extract of Mentha spicata L. were estimated. Relative antioxidant activity (RAA) was also determined relative to quercetin and L-ascorbic acid. Polyphenolics (phenolics and flavonoids) and pigments (chlorophylls and carotenoids) were quantitated and expressed as mg/g of the ethanol fraction. The ABTS/HRP/H₂O₂ decoloration method was used to estimate the total antioxidant activity. Cytotoxic effect on human prostate cancer cell line (PC-3) was assessed by MTT assay. The TAA was highest for ethyl acetate fraction (83%) followed by aqueous (75%), chloroform (51%) and hexane (47%) fractions. RAAs of ethyl acetate and aqueous fractions were equal to quercetin and ascorbic acid but less in hexane and chloroform fractions. Phenolics and flavonoids were higher in ethyl acetate (54 and 22 mg/g), aqueous (32 and 24 mg/g) and chloroform (30 and 16 mg/g) fractions compared to the hexane (14 and 15 mg/g) fraction. Chlorophyll and carotenoids were higher in chloroform fraction (29 and 7 mg/g) than in ethyl acetate (13 and 5 mg/g), hexane (14 and 3 mg/g) and aqueous (5 and 0.9 mg/g) fractions. Cytotoxic effect against PC-3 cell line was found to be highest for the chloroform fraction and lower for the aqueous fraction. Polyphenolic content and TAAs of the ethanol fractions were positively correlated. Similarly pigment content and cytotoxic effect of PC-3 cells were positively correlated.