*4.6. Phenylalanine Ammonialyase (PAL) Activity*

PAL activity was determined according to the method described by Liu et al. [57] with slight modifications. Enzyme extract was prepared at 4 ◦C, with 250 mg of crushed date palm roots in 3 mL of borate buffer (100 mM, pH 8.8, 4 ◦C) with EDTA (1 mM) and 5% (*w*/*v*) of insoluble polyvinyl polypyrrolidone (PVPP). The enzyme extract was recovered after centrifugation for 30 min and at 10,000× *g*. The reaction mixture of PAL activity assay composed of enzymatic extract (600 μL), l-phenylalanine at 20 mM (250 μL) and borate buffer (1 mL). An amount of 100 μL HCl was added after incubation (1 h, 30 ◦C). The results were obtained at 920 nm. The Bradford method [58] was then used to quantify the total protein in the enzyme extract.
