Antioxidant activity of 3,4-DHPEA-EA and protocatecuic acid: a comparative assessment with other olive oil biophenols

Abstract

Olive oil contains several phenolic compounds with antioxidant activity, whose levels depend strongly on the kind of cultivar grown, fruit ripening effects and the oil extraction process. Therefore, the beneficial effects exerted by olive oil consumption on the resistance of low density lipoproteins (LDLs) to oxidation depend not only on an increased intake of mono-unsaturated fatty acids (e.g. oleate) which are less prone to oxidation, but also phenolic antioxidants. The aim of this study was to analyze in vitro effects exerted on the oxidative modification of Cu-stimulated human LDL by two olive oil biophenols, i.e. 3,4-dihydroxyphenylethanol-elenolic acid (3,4-DHPEA-EA) and protocatecuic acid. These compounds have not been investigated in as much detail as the better-known olive oil biophenols - such as tyrosol (p-HPEA), o-coumaric acid, vanillic acid, caffeic acid, oleuropein and 3,4-dihydroxyphenylethanol (3,4-DHPEA). Modification of LDL was tested by measuring the formation of intermediate and end products of lipid peroxidation such as conjugated dienes, lipid hydroperoxides, cholesterol and cholesteryl ester oxides, as well as studying the decrease in oxidizable substrates like polyunsaturated fatty acids. In addition, the increase in LDL negative charges was evaluated. The results demonstrate the two-tested olive oil biophenols show high antioxidant activities. In particular, protocatecuic acid and 3,4-DHPEA-EA show an antioxidant activity comparable with that of caffeic acid, oleuropein and 3,4-DHPEA. They are not only able to retard lipid peroxidation, but also to reduce the extent of its activity.

Inhibitory effects of olive oil phenolics on invasion in human colon adenocarcinoma cells in vitro

“…33 Strong antioxidant activity of 3,4-dihydroxyphenylethanol-elenolic acid was also reported. 26 The higher concentration of the linked forms of hydroxytyrosol and tyrosol present in our OVP extract 7 may account for the effects shown by OVP as compared with the isolated compounds studied.…”

“…25,26 Quiles et al 27 reported that olive oil phenolics showed the most significant antioxidative effects in the order of hydroxytyrosol > caffeic acid > tyrosol at 10-250 lM in PC3 human prostate cancer cell line. However, in our study, only hydroxytyrosol and pinoresinol showed significant anti-invasive effects at 25 lM, while at the lowest concentration tested (1.56 lM), pinoresinol showed the highest anti-invasive effects (65% of control).…”

Effects of Alcoholic Solvents on Antiradical Abilities of Protocatechuic Acid and Its Alkyl Esters

“…Methyl protocatechuate (2) was prepared from protocatechuic acid by heating with methanol containing 10% hydrogen chloride. Butyl (4) and isopropyl (5) protocatechuates were prepared by heating of protocatechuic acid and corresponding alcohols with a catalytic amount of concentrated sulfuric acid. tert-Butyl protocatechuate (6) was prepared as follows.…”

“…[1][2][3][4][5][6][7][8][9][10][11] Among them, protocatechuic acid (3,4-dihydroxybenzoic acid) and gallic acid (3,4,5-trihydroxybenzoic acid) are typical molecules which show potent antiradical activity. 1,2,[5][6][7][8]11) We have examined the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging reaction 12,13) of those acids and methyl esters and found that methyl protocatechuate and gallate were converted to their oxidative dimers with different connectivities during reaction in an aprotic solvent.…”

Suppression of Chemical Mutagens-Induced SOS Response by Phenolic Acids from Black Rice Bran Using Salmonella typhimurium TA1535/pSK1002 umu Test

“…Various compounds, such as phenolic acids, ferulic acid, vanillic acid and protocatechuic acid, phenolic acid ester (g-Oryzanol, and phytic acid and inositol were found from rice bran (8)(9)(10)(11). Phenolic acids act as an antioxidant (12)(13)(14)(15)(16), as a radical scavenger (13), as an inhibitor of hepatic cytochrome P450 (17), as an antibacterial agent (18) and also as an antiinflammatory agent (19,20). In our search for new naturally occurring antimutagenic compounds in plants, with a history of safe use as Chinese crude drugs (21,22), we found that the methanol extract of black rice bran exhibited a suppression of the furylfuramideinduced SOS response.…”