Separation, Characterization and Mammal Pancreatic Lipase Inhibitory Potential of Cucumber Flower Flavonoids

Edible flowers are a new “old” trend in modern gastronomy and healthy nutrition aimed at increasing food attractiveness and improving the consumption of beneficial phytocompounds that have valuable properties. Cucumber (Cucumis sativus L., Cucurbitaceae family) is a well-known agricultural product; it is an important crop that is commonly used across the globe. Despite sufficient knowledge of nutrients and secondary metabolites in cucumber fruits, the use of cucumber flowers for food purposes is still understudied. In this study, the total flavonoid fraction of cucumber flowers was isolated and purified after liquid–liquid and solid-phase extraction and polyamide and Amberlite XAD-2 separation followed by high-performance liquid chromatography with photodiode array detection and electrospray ionization triple quadrupole mass spectrometric detection (HPLC–PDA–ESI–tQ–MS/MS), resulting in the detection of 47 compounds. Identified flavonoids included luteolin, apigenin, and chrysoeriol-based flavones such as C-, O-, and C,O-glycosides, most of which were detected for the first time in C. sativus. Flower extracts from ten cucumber cultivars were quantified, and isoorientin, isoorientin-4′-O-glucoside, and cucumerins B and D were predominant. The use of in vitro assay potential to inhibit mammalian pancreatic lipases was demonstrated for the C. sativus extracts. The dominant compounds were studied separately, and luteolin derivatives were determined to be responsible for the bioactivity. To the best of our knowledge, this is the first study on cucumber flowers that has shown their wide potential for use as a beneficial dietary supplement.