Experimental and theoretical evaluation of antioxidant capacity of flavone glycosides extracted from Cleome turkmena Bobrov.

Background and purpose: In traditional medicine, species of Cleome (known in Persian as alaf-e-mar) are used to treat wounds and earaches, as well as for their antihelmintic, carminative, and anti-arthritic properties. Flavonoids, among the most significant phytochemicals in this family, hold pharmacological importance, mainly due to their ability to scavenge free radicals. Experimental approach: Cleome turkmena Bobrov was collected and extracted in methanol. Compounds were isolated by open-column and size-exclusion chromatography. Free radical scavenging ability and reduction potential of isolated flavonols along with allantoin were determined according to the scavenging of the DPPH (diphenyl-picrylhydrazyl) radical and reducing power of Fe3+ assays. A theoretical study of their antioxidant capacity was done using density functional theory calculations. Findings/Results: Allantoin (compound 1), 2 known flavonol glycosides (compounds 2, 4), and 1 undescribed flavonol glycoside (compound 3) were isolated, and their structures were identified using different spectroscopic techniques for the first time in this plant. Among them, compound 4, quercitin-3-O-β-D-glucoside-7-O-α-L-rhamnoside, exhibited the best free radical scavenging and reducing power effects compared to the standards. Conclusion and implications: All flavone glycosides isolated from Cleome turkmena Bobrov showed favorable DPPH radical scavenging and Fe3+ reducing power.