Extracts of M. pulegium (L.) and M. spicata(L.): Effect of Extraction Conditions on Phenolics and Flavonoïds Contents and Their Antioxidant Power

The correlation between the contents of polyphenols and flavonoïds and the degree of antioxidant activity of various extracts from M. pulegium (L.) and M. spicata (L.), obtained by different solvents and methods, was investigated. The crude extracts were prepared by mixing areal parts in powder with methanol/water solution. They were subjected later to liquid-liquid extraction via solvents with progressive polarity (chloroform, ethyl acetate and n-butanol) by maceration and soxhlet techniques. The total phenol and flavonoïds contents from crude extracts and their fractions were determined by using Folin-Ciocalteu and AlCl3 assays respectively. The antioxidant activity of extracts was evaluated by DPPH• (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging test. This activity was measured by inhibition concentration 50% (IC50) values. Generally, higher extract yields were obtained by the soxhlet extraction technique; the crude extracts recorded the best yields for M. pulegium by soxhlet (26.37%) and maceration (13%) while for M. spicata, the aqueous extract by soxhlet (34.9%) and crude one by maceration (9.4%) showed the higher yields. The higher phenolic and flavonoïds contents were found in crude extracts by maceration for both mints whereas by soxhlet, the ethyl acetate and/or n-butanol extracts demonstrated the strongest contents. These extracts, rich in flavonoïds, showed a positive correlation since they have exhibited better antioxidant activity compared to ascorbic acid as the antioxidant reference (IC50= 0.051 mg/ml).