beta-carotene and kojic-acid

Two bischromones, 3,3'-dimethoxy-2'-oxychromone (1), 3,3'-dihydroxy-2,2'-oxychromone (2) and a biflavone, 5,7,4',5″,3'",4″″-hexahydroxy-3″-O-β-glucosyl-3',7″-O-biflavone (3) have been isolated from whole plant of Trifolium echinatum Bieb. together with five known flavonoids. The structures of the compounds were elucidated by 1D and 2D NMR analysis as well as HRESIMS. The isolated compounds were investigated for their antioxidant activity and tyrosinase inhibitory activity. Highly potent inhibition was found for compounds 1 (IC50=0.41 mM), 5 (IC50=0.47 mM) and 8 (IC50=0.45 mM) compared to those of standard tyrosinase inhibitors kojic acid (IC50=0.67 mM) and l-mimosine (IC50=0.64 mM). The antioxidative effect of the extracts was determined by using β-carotene-linoleic acid, DPPH scavenging, ABTS(+) scavenging, and CUPRAC assays. The experimental findings indicated that the compounds 2 and 8 were found to be active in radical scavenging and CUPRAC assays.

Topics: Antioxidants; beta Carotene; Biflavonoids; Chromones; Molecular Structure; Monophenol Monooxygenase; Nuclear Magnetic Resonance, Biomolecular; Phenols; Pyrones; Trifolium; Turkey