Metabolite profiling of polyphenols in the Tunisian plant Tamarix aphylla (L.) Karst

In this study, a detailed investigation on the composition of polyphenols of Tamarix aphylla (L.) Karst., consisting of phenolic acids and flavonoids, was carried out. In order to optimize the yield of secondary metabolites, three extraction techniques were compared, including dynamic maceration, ultrasound-assisted extraction and Soxhlet extraction. The latter technique provided the best results in terms of both recovery and selectivity, using ethyl acetate as extraction solvent for 2h. The analysis of T. aphylla polyphenols was performed by means of HPLC-UV/DAD, HPLC-ESI-MS and MS(2), using an ion trap mass analyzer. Phenolic acids and flavonoids were separated on an Ascentis C18 column (250mm×4.6mm I.D., 5μm), with a mobile phase composed of 0.1M formic acid in water and acetonitrile, under gradient elution. The proposed method was fully validated in agreement with ICH guidelines and then applied to the analysis of T. aphylla leaves and stems. A total of 14 phenolic compounds were characterized for the first time in this plant extracts by using UV, MS and MS(2) data. The amount of total phenolics was found to be 993.1±22.5μg/g in the leaves and 113.1±25.8μg/g in the stems, respectively. The most abundant constituents found in the leaves include ellagic acid (211.4±10.8μg/g), quercetin (125.7±4.7μg/g) and gallic acid (120.6±1.2μg/g), whereas those in the stems were ellagic acid (44.4±3.9μg/g), gallic acid (24.3±3.3μg/g) and kaempferol (16.3±1.6μg/g). The developed method can be considered a useful tool for the metabolite profiling of T. aphylla, which represents a potential source of bioactive compounds to be used in phytotherapy.