Exploring the halophyte Cistanche phelypaea (L.) Cout as a source of health promoting products: In vitro antioxidant and enzyme inhibitory properties, metabolomic profile and computational studies

In this study, ethyl acetate, acetone, ethanol and water extracts from flowers, stems and roots of Cistanche phelypaea (L.) Cout were appraised for radical scavenging activity (RSA) towards 1,1-diphenyl-2-picrylhydrazyl,2,2-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) and superoxide free radicals, and for metal chelating activities on iron and copper ions. The water extracts had the highest antioxidant activity, especially those from roots and flowers, and were further appraised for in vitro inhibition of enzymes implicated on the onset of human ailments, namely acetyl- (AChE) and butyrylcholinesterase (BuChE) for Alzheimer’s disease, α-glucosidase and α-amylase for diabetes, and tyrosinase for skin hyperpigmentation disorders. The extracts had a higher activity towards BuChE, and the roots extract had the highest capacity to inhibit tyrosinase. Samples showed a low capacity to inhibit carbohydrate hydrolysing enzymes, except for the root extract with a good inhibition on glucosidase. Samples were then characterized by NMR (1D and 2D): the main metabolites identified in the flowers extract were iridoid glycosides, in particular gluroside and bartsioside. In stems, phenylehanoid glycosides (PhGs) and iridoids were detected, especially acteoside. In roots were detected essentially PhGs, mainly echinacoside and tubuloside A. Docking studies were performed on the identified compounds. A favorable binding energy of tubuloside A to tyrosinase was calculated, and indicated this compound as a possible competitive inhibitor of α-glucosidase and tyrosinase. Our results suggest that C. phelypeae is a promising source of biologically-active compounds with health promoting properties for pharmaceutical and biomedical applications.