Exploring Caralluma europaea (Guss.) NEBr. as a potential source of bioactive molecules: In vitro antioxidant and antidiabetic properties, and phenolic profile of crude extracts and fractions

Caralluma europaea (Guss.) N.E.Br is a succulent medicinal species used in the Moroccan traditional medicine for its anticancer and antidiabetic properties. In this work, this species was explored for the in vitro antidiabetic and antioxidant properties of crude methanol and dichloromethane extracts, and obtained fractions, from its aerial organs. In vitro antidiabetic properties were evaluated towards baker's yeast and rat's intestinal alpha-glucosidase, and alpha-amylase. Four in vitro methods were used to appraise the antioxidant potential, namely radical scavenging activity (RSA) on 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), and iron and copper chelating assays. Finally, the profile of the main phenolic compounds present in the samples was assessed by high-performance liquid chromatography equipped with diodearray detection (HPLC-DAD). The highest inhibition of baker's yeast alpha-glucosidase was obtained with the methanol extract (87%), and its fractions, with a maximum inhibition of 83% at the concentration of 10 mg/ml. The most significant inhibition of mammalian alpha-glucosidase was obtained with the dichloromethane crude extract (85%), and corresponding fractions at 10 mg/ml. Moderate activity was achieved with the two extracts against a-amylase (52-53%) at 10 mg/ml, but no relevant activity was detected for most fractions. Crude extracts had a significant RSA against DPPH and ABTS, with range values of 83-98% (methanol extracts) and 53-80% (dichloromethane extracts). Fractions from the methanol extract were more active against tested radicals. Crude extracts had chelating activity on both metals, and the highest copper chelation was achieved with the methanol extract, while the dichloromethane extract and the majority of fractions from both extracts presented the highest iron chelation at 10 mg/ml. A total of 21 phenolic compounds were identified and quantified by HPLC-DAD in the samples, and the main compounds detected were catechine hydrate and salicylic and caffeic acids. Our results suggest that C. europaea extracts contain compounds with in vitro antioxidant and antidiabetic properties with potential applications in the pharmaceutical and food industries.Foundation for Science and Technology (FCT)Portuguese Foundation for Science and TechnologyPortuguese National Budget [CCMAR/Multi/04326]FCT Scientific Employment Stimulus [CEECIND/00425/2017]FCTPortuguese Foundation for Science and Technology [SFRH/BD/116604/2016]FCT Investigator Programme [IF/00049/2012