title: Antioxidant and tyrosinase inhibitory activities of flavonoids from Trifolium nigrescens Subsp. petrisavi.
abstract: Trifolium nigrescens was researched for its chemical constituents for the first time. Bioassay-guided isolation of the EtOAc extract from the leaves of T. nigrescens resulted in the purification of a new biflavone, 4''',5,5″,7,7″-pentahydroxy-3',3'''-dimethoxy-3-O-β-d-glucosyl-3″,4'-O-biflavone (1) along with eleven known compounds consisting of three phenolics (2-4), and eight flavonoid glycosides (5-12). Their structures were determined by extensive 1D and 2D NMR, and MS data analyses. The isolated compounds were evaluated for their antioxidant activity and inhibitory activity on mushroom tyrosinase. Highly potent inhibitions were found by compounds 7 (IC50 = 0.38 mM), 8 (IC50 = 0.19 mM), and 12 (IC50 = 0.26 mM) when compared with standard tyrosinase inhibitors kojic acid (IC50 = 0.67 mM) and l-mimosine (IC50 = 0.64 mM). The antioxidative effect of the isolated compounds and the extracts were determined by using β-carotene-linoleic acid, DPPH(•) scavenging, ABTS(+•) scavenging, superoxide scavenging, and CUPRAC assays. The experimental findings indicated that all the compounds demonstrated activity in all antioxidant activity tests employed except for the compounds 2-6. Compounds 2-6 showed moderate activity only in ABTS(+•) scavenging assay. The new compound 1 exhibited better activity than standard α-tocopherol in DPPH(•) scavenging, and ABTS(+•) scavenging assays. The results show that T. nigrescens can be regarded as a potential source of antioxidant compounds and tyrosinase inhibitors of significance in both the pharmaceutical and food industries.
authors: Department of Pharmacognosy, Faculty of Pharmacy, Trakya University , 22030, Edirne, Turkey.
authors: Ozlem
authors: O
authors: Demirkiran
authors: Temine
authors: T
authors: Sabudak
authors: Mehmet
authors: M
authors: Ozturk
authors: Gulacti
authors: G
authors: Topcu
mesh_terms: D000363:Agaricales / Q000737:chemistry / Q000201:enzymology*; D000975:Antioxidants / Q000737:chemistry*; D004791:Enzyme Inhibitors / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry*; D005656:Fungal Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006027:Glycosides / Q000737:chemistry; D015394:Molecular Structure; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D010936:Plant Extracts / Q000737:chemistry*; D018515:Plant Leaves / Q000737:chemistry; D029921:Trifolium / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D005419:Flavonoids; D005656:Fungal Proteins; D006027:Glycosides; D010936:Plant Extracts; D014442:Monophenol Monooxygenase