Abstract
Four new bibenzyl derivatives were isolated, together with other known bibenzyls, by bioassay-guided fractionation of a CHCl3-MeOH extract of Notholaena nivea Desv. (Pteridaceae) aerial parts. The structures were elucidated by NMR, ESIMS and other spectral analyses. Their antioxidative effects towards superoxide, lipidic peroxidation and the 2,2’-azino-bis-3-ethilbenzothiazoline-6-sulfonic acid (ABTS) radical were assayed. Results showed that the compound 3,12-dihydroxy-5-methoxybibenzyl (6) is the most active compound in the ABTS free-radical scavenging test, while in the coupled oxidation of β-carotene and linoleic acid assay the compound 5,12-dihydroxy-3-methoxydibenzyl-6-carboxylic acid (1) exerted the highest activity after 1h. A superoxide anion enzymatic test was also carried out and the results were confirmed by an inhibition of xanthine oxidase activity assay. The putative protective role played by compounds 1 and 6 on the injurious effects of reactive oxygen metabolites on the intestinal epithelium, using a Caco-2 human cell line, was investigated. H2O2-induced alterations were prevented by preincubating the cells with compounds 1 and 6.
Highlights
Developments in biomedical science have shown that free radicals are involved in many diseases.They interact chemically with the unsaturated fatty acids in the biomembrane resulting in membrane lipid peroxidation, which is strongly connected to aging, carcinogenesis and atherosclerosis
The antioxidant activity recorded in this preliminary test were confirmed by the Trolox equivalent antioxidant capacity (TEAC) assay, in order to have a value indicating the free radical activity of each pure compound; the activity of compounds 1-6 against the inhibition of lipid peroxidation according to autoxidation of linoleic acid and in the interaction with the xanthine-oxidase enzymatic system and superoxide anion product was assayed
The chemical shift of the -CH2 groups suggest their position as a linkage between the two benzene rings, leading to a dihydrostilbene skeleton, which is in accordance with the UV spectrum and literature data for bibenzyls [3,12]
Summary
Developments in biomedical science have shown that free radicals are involved in many diseases They interact chemically with the unsaturated fatty acids in the biomembrane resulting in membrane lipid peroxidation, which is strongly connected to aging, carcinogenesis and atherosclerosis. During our continuing search for plant-derived bioactive compounds, a CHCl3-MeOH extract of Notholaena nivea leaves was found to exhibit significant antioxidant effects in a bioautographic TLC assay [2]. The antioxidant activity recorded in this preliminary test were confirmed by the TEAC assay, in order to have a value indicating the free radical activity of each pure compound; the activity of compounds 1-6 against the inhibition of lipid peroxidation according to autoxidation of linoleic acid and in the interaction with the xanthine-oxidase enzymatic system and superoxide anion product was assayed. This paper deals with the structure elucidation of new compounds 1-4, as well as the antioxidant evaluation of all isolated compounds measured by their radical scavenging activity in the radical cation 2,2'-azino-bis-(3-ethilbenzothiazoline-6-sulfonate) (ABTS) test [5,6], the coupled oxidation of β-carotene and linoleic acid assay [7,8], superoxide anion enzymatic generation assay [9,10] and xanthine oxidase (XOD) activity assay [9], and cytotoxicity assay in Caco-2 cells [11]
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