P nitrophenyl palmitate

The lipase assay was carried out using the method described by Buchholz et al. [64 (link)] with minor modifications. Pancreatic lipase enzyme solution (10 mg/mL) from porcine pancreas (Sigma-Aldrich, Merck, St. Louis, MO, USA) was prepared in Tris buffer (pH = 8.0), centrifuged and stored at 2–8 °C until use. The substrate used in this study was 30 mg p-nitrophenyl palmitate (Sigma-Aldrich, Merck) dissolved in 10 mL isopropanol and made up to a volume of 100 mL with a warm mixture containing 100 mg sodium deoxycholate, 50 mg gum arabic and 2 mL Triton X. The reaction mixture (30 μL of pancreatic lipase, 100 μL of buffer (pH = 8.0), 20 μL of extracts (50 mg/mL)) was incubated at 37 °C for 20 min. Then, 130 μL of p-nitrophene palmitate solution was added and incubated again at 37 °C for 30 min and the absorbance (A) was measured at 405 nm (Multiskan GO 1510, Thermo Fisher Scientific, Vantaa, Finland). A control sample containing only the solvent used instead of the extract was performed, and the results were reduced by the value of the blank representing the enzyme-free sample. The positive control was a sample containing a solution of orlistat instead of the extract tested (Formula (2)).

Palm racemes were utilized as a starting raw material to produce the activated carbon. Palm raceme samples were collected from a variety found in the west of the Baghdad area of Iraq. To remove dust and impurities, the raceme was washed several times in purified water before drying at 100 °C and 24 h, being crushed with a knife’s Mill, and being sieved. For the preparation, a portion with an average particle size of 5 mm was chosen. Palm raceme was chemically activated with sodium hydroxide and hydrochloric acid (Poch SA Company, Poland). In addition to sodium deoxycholate (purity 97%), isopropanol, and Arabic gum, Sigma-Aldrich provided the standards and substrate for the lipase assay: p-nitrophenol (pNP) and p-nitrophenyl palmitate (pNPP). Lipases from the porcine pancreas (PPL) (100 to 500 units, mg⁻¹ protein) and Amano lipase PS originated from Burkholderia cepacia (AML) (30 units, mg⁻¹ protein) and were acquired from Sigma-Aldrich. HmbG Chemicals and MERCK (Hamburg, Germany) provided additional analytical-grade chemicals.