Biochemical Variation and Chemotaxonomic Classification of Alhagi maurorum Medik. (Fabaceae) Populations Across Contrasting Habitats in Anbar Governorate, Iraq

Abstract

The halophytic medicinal shrub Alhagi maurorum Medik. (Fabaceae) occurs in diverse habitats in Anbar Governorate of Iraq; however, no studies have compared the variation in its secondary metabolites in different habitats. The objectives of this study were to characterize the biochemical diversity among populations in four different habitats (riverbank, farm, saline soil, and desert fringe) and to assess the usefulness of the variation or chemotaxonomy. Samples of aerial parts were collected during flowering from ten plants in each habitat, and the pH, electrical conductivity (EC) and organic matter content of soil were determined. Methanolic extracts of samples were analyzed for total levels of phenolics, flavonoids, condensed tannins, alkaloids, saponins, and proline as well as for individual phenolic compounds by HPLC. Analyses were done using ANOVA, correlation, PCA, and UPGMA cluster analyses. Soil EC varied from 1.8 to 14.2 dS m⁻¹. All populations showed the same main classes of metabolites, yet phenolic compounds, flavonoids, tannins, and proline were significantly higher under conditions of salinity (p < 0.05), where flavonoids increased from 14.3 to 27.5 mg QE g⁻¹ and proline from 8.5 to 41.3 µmol g⁻¹, while the amount of alkaloids showed no significant differences. The presence of catechin was found only in low-salinity environments, and isorhamnetin content was maximal in the desert population. According to principal component and cluster analysis, the samples were separated into low-stress (river bank, agricultural land) and high-stress (salt, desert) groups. The results of the chemical classification coincide with the environmental gradient, which indicates that the majority of the variation is due to plasticity of the plant, while catechin and isorhamnetin can be considered the candidates for further research.