The purpose of this study was to assess the relative antioxidant activities of a range of carotenes and xanthophylls through the extent of their abilities to scavenge the ABTS "+ radical cation. The results show that the relative abilities of the carotenoids to scavenge the ABTS "÷ radical cation are influenced by the presence of functional groups with increasing polarities, such as carbonyl and hydroxyl groups, in the terminal rings, as well as by the number of conjugated double bonds.

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The comparative mechanisms and relative rates of nitrogen dioxide (N0 2 "), thiyl (RS') and sulphonyl (RS0 2 ') radical scavenging by the carotenoid antioxidants lycopene, lutein, zeaxanthin, astaxanthin and canthaxanthin have been determined by pulse radiolysis. All the carotenoids under study react with the N0 2 " radical via electron transfer to generate the carotenoid radical cation (Car' + ). In marked contrast the glutathione and 2-mercaptoethanol thiyl radicals react via a radical addition process to generate carotenoid-thiyl radical adducts |RS-Car]'. The RS0 2 ' radical undergoes both radical addition, [RS0 2 -Car|' and electron abstraction, Car" and follow the sequence HO(CH 2 ) 2 S' > RS0 2 ' > GS' > N0 2 \ Although there were some discernible trends in carotenoid reactivity for individual radicals, rate constants varied by no greater than a factor of 2.5. The mechanism and rate of scavenging is strongly dependent on the nature of the oxidising radical species but much less dependent on the carotenoid structure. © 1997 Federation of European Biochemical Societies.

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The biological activities [15] of the phenylpropanoids and their role as antimicrobial agents [16,17] is well recognised, as well as their properties as antiallergic and anti-inflammatory agents through lipoxygenase inhibition [18] and their antimutagenic actions [19,20].In this study we have examined the antioxidant properties of the hydroxycinnamic acids in terms of their abilities to increase the resistance of low density lipoproteins (LDL) to cholesterol oxidation, lipid peroxidation and oxidative modification of the apoprotein B,j 0. The results show that the sequence of the effectiveness against lipid peroxyl radicals generated in the lipophilic phase of LDL and in protecting LDL cholesterol from oxidation is: chlorogenic = caffeic > ferulic > p-coumaric acid.

Salvia lavandulaefolia Vahl. (Spanish sage) essential oil and individual monoterpenoid constituents have been shown to inhibit the enzyme acetylcholinesterase in-vitro and in-vivo. This activity is relevant to the treatment of Alzheimer's disease, since anticholinesterase drugs are currently the only drugs available to treat Alzheimer's disease. Other activities relevant to Alzheimer's disease include antioxidant, anti-inflammatory and estrogenic effects. Results of in-vitro tests for these activities are reported here for S. lavandulaefolia extracts, the essential oil and its major constituents. Antioxidant activity (inhibition of bovine brain liposome peroxidation) was found in the EtOH extract of the dried herb (5 mg mL(-1)) and the monoterpenoids (0.1 M) alpha- and beta-pinene and 1,8-cineole. Thujone and geraniol had lower antioxidant effects, while camphor had no antioxidant effects. Possible anti-inflammatory activity (eicosanoid inhibition in rat leucocytes) was found in the EtOH extract (50 microg mL(-1)) and was shown by the monoterpenoids alpha-pinene and geraniol (0.2 mM), but not 1,8-cineole, thujone or camphor. Possible estrogenic activity (via induction of beta-galactosidase activity in yeast cells) was found in the essential oil (0.01 mg mL(-1)) and the monoterpenoid geraniol (0.1-2 mM). 1,8-Cineole, alpha- and beta-pinene and thujone did not exhibit estrogenic activity in this analysis. These results demonstrate that S. lavandulaefolia, its essential oil and some chemical constituents have properties relevant to the treatment of Alzheimer's disease and provide further data supporting the value of carrying out clinical studies in patients with Alzheimer's disease using this plant species.

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