Evaluating the Content of Some Metal Elements in Soil and Their Effects on the Total Phenolic and Flavonoid Contents of Some Medicinal Plants Using X-Ray Fluorescence (XRF) Method

Abstract Soil factors, especially metal elements in the soil, play a significant role in forming and accumulating secondary metabolites, which determine the medicinal properties of medicinal herbs. In this study, the concentrations of some metal elements (K, Mn, Fe, Cu, Zn, and Cr) in Cam Mountain and Tinh Bien Town, An Giang Province, Vietnam, were determined using the XRF method. We simultaneously determined the total phenolic and flavonoid content of some medicinal herbs collected from the collected soil sample areas, thereby assessing the influence of these elements on the formation of secondary metabolites in medicinal plants. The results showed that K, Mn, and Cr were mainly concentrated in the topsoil and transition layers; Fe and Cu elements tended to concentrate in the transition layer and the subsoil when surveying the soil profile. K, Mn, Cu, and Cr concentrations were more focused in Tinh Bien area, while Fe and Zn had higher concentrations at Cam Mountain. Additionally, results from evaluating the relationship between the content of the elements in the soil and the content of two active compounds also showed the corresponding relationship between Cr/Phenolic, Cu/Phenolic, and Zn/Flavonoid (R2 = 0.74; R2 = 0.75; R2 = 0.90, respectively) with the corresponding correlation equations at level six.