Chemical compositions, biological and antioxidant activities of plants are widely affected by several parameters and conditions, such as geographical and climatic conditions, type of extract (aqueous or organic), as well as the polarity of the extracting solvent. Therefore the present study was the first one designed to study the phytochemical composition, the content of polyphenols, tannins and flavonoids, the antioxidant activities and the chemical composition analysis by FTIR spectroscopic of organic (ethanol, methanol, ethyl Acetate, petroleum ether) and aqueous extracts of Marrubium vulgare L. leaves, collected from two different sampling localities in the North-East of Morocco: Oulad Daoud Zkhanine and the Cape Three Forks. A phytochemical screening was carried out by specific coloring and precipitation reactions. The colorimetric method Folin- Ciocalteu was used for the quantification of total phenolic content. The method of aluminum chloride was employed for the quantification of total flavonoid content and the method of vanillin for the determination of tannins. The antioxidant power was evaluated by the DPPH and ABTS methods. The chemical composition of the organic extracts was analyzed by the FTIR spectroscopy method. Depending on the sampling location of M.vulgare L., the type of extract (aqueous or organic), the polarity of the extracting solvent, and the phytochemical screening revealed the presence of the following secondary metabolites: catechic tannins, terpenoids, polyphenols and flavonoids. The total concentrations of total polyphenols, flavonoids and tannins varied respectively between 0.27 ± 0.1 and 86.91 ± 1.22 μg gallic acid equivalents/mg,6.08 ± 0.17 and 33.82 ± 0.90 μg quercetin equivalents/mg and 2.73 ± 1.15 and 252.68 ± 4.50 μg catechin equivalents/mg. The antioxidant activity that was evaluated by DPPH and ABTS method showed that ethanol extract, methanol and ethyl acetate extract had the highest percentages of inhibition, unlike petroleum ether extract. The inhibitory concentrations (IC50) ranged from 324.55 ± 0.66 to 980 ± 0.62 μg/ml for DPPH and from 107.85 ± 0.19 to 890.74 ± 0.17 μg/ml for ABTS. FTIR spectroscopic analysis has revealed different characteristic peak values with various functional groups in the extracts such as amide, alcohol, phenol compounds. In general, the organic and aqueous extracts of M.vulgare L. that were harvested from Oulad Daoud Zkhanin were richer in secondary metabolites, and showed higher concentrations of polyphenol, flavonoids and tannins. In addition, they revealed a higher antioxidant capacity than the extracts of M. vulgare L.from the Cape Three Forks. Overall this study highlighted the potential benefits and richness of M.vulgare L. harvested from the two study areas and suggested it as a potential source of natural antioxidants that could be used in the food and pharmaceutical fields.
Keywords: Agricultural science; Antioxidant activity; Biological sciences; Chemistry; Environmental science; Flavonoids; Food science; Marrubium; Morocco; Polyphenols; Tannin.
© 2020 The Authors.