Cucumis metuliferus L. Fruits Extract with Antioxidant, Anti-Inflammatory, and Antidiabetic Properties as Source of Ursolic Acid

Abstract

To identify healthy, nutritious, and sustainable plant-based products rich in biologically active compounds, this present study was conducted, and the phytochemical composition and biological properties of the hydroethanolic ultrasound-assisted extract of the fruits of Cucumis metuliferus were investigated. Cucumis metuliferus is an unexplored fruit of a climbing plant in the Cucurbitaceae family, widely distributed in the tropical and subtropical regions of sub-Saharan Africa and whose nutritional and medicinal benefits are well known in African countries, especially. Therefore, its cultivation in other regions could influence chemical composition. The structural identification of the compounds from the hydroethanolic extract from Cucumis metuliferus fruits grown in Romania was carried out by chromatographic techniques (HPLC). The main compounds identified were catechin, oleanolic acid, ursolic acid, p-coumaric acid, and epicatechin. Subsequently, a method was proposed to isolate and characterize ursolic acid, one of the major compounds. The obtained results show that the hydroethanolic extract is rich in antioxidant compounds evaluated using the DPPH radical inhibition method (IC50 = 32.74 ± 0.02 µg/mL) and ABTS cation radical inhibition method (IC50 = 11.37 ± 0.07 µg/mL). It also demonstrate in vitro anti-inflammatory activities, such as anti-lipoxygenase (IC50 = 32.90 ± 0.05 µg/mL) and anti-proteinase (IC50 = 16.34 ± 0.07 µg/mL), and antidiabetic properties by inhibiting α-amylase (IC50 = 429.541 ± 0.25 µg/mL) and β-glucosidase activity (IC50 = 385.685 ± 0.76 µg/mL). Therefore, C. metuliferus fruits could be effectively used in the development of various health-promoting products, being not only appetizing, with spectacular appearance and with extended storage life, but also curative and healthy.