Phytochemical study of Tamarix africana Poir. (Tamaricaceae)

Tamarix genus is a tree or shrub halophytes from coastal regions and desert, relatively long-living plants that can tolerate a wide range of environmental conditions and resist to abiotic stresses such as salt, high temperature, and drought stresses (1). Tamarix spp. are employed in traditional medicine as astringent, appetizer, stimulant of perspiration, diuretic, and spleen trouble and eye remedies (2). Younos et al. (2005) indicated the importance of this genus in some old civilizations and the actual uses of Tamarix species different organs (leaves, flowers, and galls) in the traditional Asian therapy as anti-inflammatory, anti-diarrhoic, healing and antiseptic agents (3). T. africana Poir. is an ornamental and folkloric medicinal halophyte particularly abundant in Mediterranean salt marshes (2); it’s a perennial shrub with brownish branches, punctuated, opaque, oval and acuminate leaves; its bunches reaching 6 cm long, 5-6 mm wide and contained flowers with four to five petals and four stamens. The ability of halophytes to tolerate salt and to overcome oxidative stress is determined by multiple biochemical pathways that facilitate water retention and/or acquirement, protect chloroplast functions, and maintain ion homeostasis. Essential pathways include the synthesis of compatibles solutes, specific proteins and radical scavenging molecules, such as phenolic acids and flavonoids (4). In recent years, the interesting feature of halophytes as a potential source of natural antioxidants, has aroused the interest of many researchers. In fact, it’s reported a beneficial preventive and therapeutic effects of phenolic compounds against diseases associated with oxidative stress. These constituents, and more particularly the flavonoids, are endowed with important biological activities including antioxidant, anti-inflammatory, anti-ulcer and anti-tumor. Previous studies on Tamarix species reported the isolation of hydrolyzable tannins (5), flavonoids (6) and phenolic compounds (7), while in a phytochemical work on T. africana trans-coniferyl alcohol 4-sulphate was purified and other cinnamyl alcohol sulphates were detected (8). Furthermore, several researches proved antioxidant, antimicrobial and anticancer activities of some Tamarix species such as T. ramosissima (9), T. hispida (10), and T. gallica (11). In this context, the aim of the present work was to carry out a phytochemical study of the polar extract of T. africana aerial parts to isolate and identify bioactive compounds, including some sulphated derivatives, which could be responsible of its biological activities. The plant material was collected in Gabès (Tunisia) and dried at room temperature, then extracted with Soxhlet apparatus with n-hexane, dichloromethane and then at room temperature with methanol. The MeOH extract was partitioned between n-BuOH and H2O and the n-BuOH soluble fraction was separated by Sephadex LH-20 followed by RP-HPLC. Sulphated flavonoids, including some new compounds, were purified and fully characterized by spectroscopic techniques such as 1D and 2D-NMR, and mass spectrometry.