Phytochemical Profile and Evaluation of Antioxidant Activity, Enzyme Inhibition and Cell Viability of Leaves Extracts of Three Tunisian Varieties of Diospyros kaki L.

Because of their biological qualities, the leaves of Diospyros kaki L., also known as persimmon, have long been used in traditional Chinese medicine for the treatment of ischemic stroke, angina, internal hemorrhage, hypertension, atherosclerosis, and some infectious diseases. It has also been used in cosmetics, as well as in refreshing drink preparations. In the present study, we have compared the aqueous extract effects of the leaves of the three Tunisian varieties of D. kaki, namely Triumph, Jiro, and Rojo Brillante, prepared by decoction and then filtered. The obtained filtrates were lyophilized and kept cold until analysis. Phytochemical profile and biological activities were performed on the freeze-dried fractions of the different varieties of D. kaki. Analysis of the results shows that the leaf extracts of the three varieties are rich in total phenols and flavonoids (ranking: Rojo Brillante > Triumph > Jiro) and have a high antioxidant activity (EC₅₀ values of 3.8, 8.0 and 12.1 μg/mL respectively for Rojo Brillante, Triumph and Jiro). Using a quadrupole time-of-flight interface and high-resolution tandem liquid chromatography, 29 secondary metabolites of D. kaki leaf decoctions were identified in the three varieties, including several polyphenols such as flavonoids, tannins, organic acids, and others. In addition, these extracts were found to inhibit the function of two key enzymes, acetylcholinesterase (IC₅₀ values of 58, 96 and 210 μg/mL respectively for Rojo Brillante, Triumph and Jiro) and inhibition percentages of 3-hydroxy-3-methylglutaryl-CoA reductase were 61.44%, 57.35%, and 46.28% for Jiro, Triumph, and Rojo Brillante, respectively. However, we noted that these different extracts had no cytotoxic effect on human liver or breast cancer cells in culture until 10 μg/mL. The results reveal that the D. kaki leaves are a potential matrix for the launch of future nutraceuticals, cosmetics, and pharmaceutical specialties such as drugs to combat Alzheimer's disease or to reduce cholesterol levels, as well as an attractive source of ingredients beneficial to health. Comparative analysis of D. kaki leaves showed that the Rojo Brillante variety has a higher content of secondary metabolites than the other two varieties, thus increasing its antioxidant activity and enzyme inhibitory effect, although it is not as cytotoxic as the other two varieties.