Antioxidant activity of a new multiflorane-type triterpene from seeds of Cucurbita Argyrosperma and their protective role on hydrogen peroxide induced oxidative stress

Abstract

Background: Cucurbita Argyrosperma seeds have acquired a reputation as an herbal remedy to treat various diseases because this plant is a predominant source of natural compounds with potent anti-inflammatory, antioxidant properties, and seed supplementation improves oxidative stress. Previous studies indicated that an imbalance between H₂O₂ production and elimination capacity is responsible for β-cell vulnerability, making β-cell a target susceptible to pathological disasters.

This investigation aimed to evaluate the protective effects of one new multiflorane-type triterpene  3β-trans-caffeoyloxymultiflor-8-ene- 7α,12β, 18 β-triol (1)  from MeOH extract from C. Argyrosperma, on rat pancreatic β cells (INS-1 cells) exposed to hydrogen peroxide (H₂O₂) induced oxidative stress conditions.

Methods: The chemical structure of the novel triterpene, which was identified as 3β-trans-caffeoyloxymultiflor-8-ene- 7α,12β, 18 β-triol (1), was established based on the interpretation of spectroscopic analyses. The antioxidant activities of 1 were leaded by detect radical scavenging potential of 2,2-dyphenyl-1-picrylhydrazyl (DPPH) and 3.1 2,2′-Azino-bis(3-Ethylbenzothiazoline-6-Sulfonic Acid) ABTS. The assays were conducted on INS-1 cells line exposed to increasing concentrations of 1 at 5,10 and 20 µg/mL and H₂O₂ at 250 µM. Then, the experiments, cell viability, cell integrity ((LDH; lactate dehydrogenase release), mitochondrial function (ATP analysis), ROS formation, lipid peroxidation (MDA) and caspase-3, 9 activities were measured in the cells. We also determined the effect of 1 on antioxidant enzyme levels and cytotoxicity in pancreatic β cells under oxidant conditions.

Results: The results showed that triterpene displayed high free-radical-scavenging activity, which is similar to that of standard antioxidants used. At concentrations of 5, 10, and 20 ?g/mL protect INS-1 cells against H₂O₂ induced cytotoxicity decrease in cell death, with a marked increase in cell viability, sustained cellular functionality (ATP). Antioxidant enzymes such as glutathione peroxidase (GPx), glutathione reduced (GSH), catalase (CAT), superoxide dismutase (SOD), and the non-antioxidant enzyme (GSH) increased in INS-1 cells with 1 pretreatment. MDA in pancreatic cells was ameliorated by 1 pretreatment reducing intracellular reactive oxygen species level. Findings also demonstrated that H₂O₂-induced apoptosis in INS-1 cells and produced modulation of the caspase-3, 9 expressions in INS-1 cells exposed to 1. Exposure to 1significantly inhibited ROS and apoptosis production, reducing β cell dysfunction under oxidant conditions.

Conclusions: Triterpene consequently could be a promising natural antioxidant for use in maintaining the integrity of pancreatic β-cells exposed to oxidative stress conditions being able to participate in the control type 2 diabetes.

Keywords: Cucurbita Argyrosperma; antioxidants; multiflorane; free radical scavenging: oxidative stress