Phenolic profile and bioactivity of the aerial part and roots of Mentha rotundifolia L. grown in two different localities in northeastern Algeria: A comparative study

Abstract

Mentha rotundifolia L is a valuable plant with an interesting chemical composition. However, the phenolic composition of the Algerian M. rotundifolia was poorly reported. Furthermore, the variation in the phenolic composition of this plant is influenced by many factors that consequently determine its bioactivity. Thus, the present work aimed to assess the effect of provenance and plant organ on the phenolic composition of M. rotundifolia and its bioactivity. Samples were collected in Mila and Jijel and the aerial part and the roots were thus separated. The phenolic contents were determined by colorimetric methods, individual phenolic compounds were identified and quantified by means of LC-ESI-MS, and in vitro assays were employed to assess the bioactivity of the different extracts. The roots of the Mila plant contained the highest total phenolics content with a value of 241.52 ± 2.83μg GAE/mg, while the aerial part of the plant recorded the highest flavonoids (77.026 ± 1.61 μg RE/mg extract) and flavonols (54.85 ± 0.35 μg EQ/mg extract). A total of sixteen phenolic compounds have been identified including phenolic acids and flavonoids. Rosmarinic acid, quinic acid, and salvianolic acid were the main phenolic compounds with the highest amounts (from 3.996 to 125.411 μg/g of extract depending on the plant organ and origin). Most of the compounds present higher levels in the plant from Mila than that of Jijel. Quinic acid was concentrated in the aerial part than in the roots and the inverse for rosmarinic and salvianolic acid. All extracts showed remarkable antioxidant activity, which varied according to the origin and the organ of the plant. The roots of the plant from the Mila region showed the strongest inhibition on ACHE (IC50 = 36.89 ± 0.25 μg/mL) and on α-glucosidase (IC50 = 17.29 ± 0, 09 μg/mL). High UV protection was achieved with SPF values between 35.70 ± 0.07 and 39.49 ± 1.42. These conclude that the soil environmental conditions of Mila are more adequate for polyphenols synthesis and better bioactivity.