Antioxidant and antidiabetic properties of olive pomace's hydro-ethanolic extract and aqueous fraction using an animal model of diabetes produced by streptozotocin (STZ)

Abstract Purpose Numerous studies have emphasized the role of olive pomace in the prevention of various health problems due to its antioxidant properties. In line with this, our study aimed to explore the phytochemistry, antioxidant, and antidiabetic activities of the extracts. Methods The phytochemical study investigates the total phenolic content, tannin, and flavonoid levels, as well as the antioxidant and antidiabetic activities of the extracts from olive pomace. Results The hydro-ethanolic extract exhibited levels of phenolic compounds, tannins, and flavonoids, with antioxidant potentials of 90.14 ± 15.55 mg GAE/g DW, 7.31 ± 0.96 mg CE/g DW, and 73.97 ± 1.08 mg QE/g DW, respectively. The antioxidant capacity determined by the DPPH test showed an EC50 of 1.705 ± 0.023 mg/mL and a TAC of 45.41 ± 4.81 mg GAE/g DW. While the aqueous fraction showed 81 ± 13.99 mg GAE/g DW of phenolic compounds, 52.01 ± 3.41 mg QE/g DW of flavonoids, and 10.960 ± 0.966 mg CE/g DW of tannin, with an antioxidant activity tested by DPPH revealing an EC50 of 2.5 ± 0.04 mg GAE/mL and a TAC of 51.191 ± 3.72 mg GAE/g DW. The olive pomace has promoted insulin secretion and reduced glycemia levels. The polyphenols have thus demonstrated their antioxidant and cytoprotective potential by restoring the redox balance of organs and tissues and reducing oxidative damage caused by diabetes such as levels of malondialdehyde and carbonylated proteins. The histology of the liver, kidneys, and pancreas from treated rats showed a structure similar to that of the control group rats. However, the histology of these organs from the untreated rats presented alterations and inflammation due to streptozotocin's effect, such as infiltration of inflammatory cells, disruption of tissue architecture, and cellular necrosis. Conclusion The olive pomace extracts represent a potential source of pharmacological molecules for preserving cellular function, with a broad safety margin for therapeutic use.