Phytochemical characterization of the date palm (Phoenix dactylifera L.) linked to chemical characteristics of the soil of backyard orchards

The fruits of Phoenix dactylifera L. contain bioactive compounds such as phenols, flavonoids, carotenoids, vitamins and minerals. However, its composition and content exhibit great variability depending on genetic and environmental factors, especially the physico-chemical properties of the soils where date palms develop. To elucidate the above, samples of dates from three backyard orchards and soil samples from each orchard were collected to determine the content of bioactive compounds and chemical characteristics of the substrate and to determine the correlations between these. For total contents of polyphenols and flavonoids, antioxidant activity and soluble solids, the following methods were used - Folin-Ciocalteu reagent based total polyphenol estimation; aluminium chloride based total flavonoid estimation; 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) free radical inhibition and a hand-held refractometer for soluble solid content determination. Each orchard was considered as a separate treatment and a completely randomized design was used, with the Tuckey’s test (alpha=0.05) applied to compare means. Pearson's linear correlation analysis was applied to establish the link between bioactive compounds of dates and chemical characteristics of the soils. The hypotheses were that the bioactive compounds present in dates obtained in different backyard orchards could vary depending on the chemical characteristics of their soils. The results reflected significant differences only for the soluble solids content of the dates. Statistically significant correlations were observed between two soil characteristics; organic matter (OM) and electrical conductivity (EC); and the soluble solids content of dates. It was concluded that higher organic matter in the soils is associated with higher soluble solids content in the fruit, while higher electric conductivity in the soils is linked to lower soluble solids content in the dates.