Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review

While use of synthetic antioxidants (such as butylated hydroxytoluene and butylated hydroxyanisole) to maintain the quality of ready-to-eat food products has become commonplace, consumer concern regarding their safety has motivated the food industry to seek natural alternatives. Phenolic antioxidants can inhibit free radical formation and/or interrupt propagation of autoxidation. Fat-soluble vitamin E (α-tocopherol) and water-soluble vitamin C (L-ascorbic acid) are both effective in the appropriate matrix. Plant extracts, generally used for their flavoring characteristics, often have strong H-donating activity thus making them extremely effective antioxidants. This antioxidant activity is most often due to phenolic acids (gallic, protocatechuic, caffeic, and rosmarinic acids), phenolic diterpenes (carnosol, carnosic acid, rosmanol, and rosmadial), flavonoids (quercetin, catechin, naringenin, and kaempferol), and volatile oils (eugenol, carvacrol, thymol, and menthol). Some plant pigments (anthocyanin and anthocyanidin) can chelate metals and donate H to oxygen radicals thus slowing oxidation via 2 mechanisms. Tea and extracts of grape seeds and skins contain catechins, epicatechins, phenolic acids, proanthocyanidins, and resveratrol, all of which contribute to their antioxidative activity. The objective of this article is to provide an overview of natural antioxidants, their mechanisms of action, and potential applications.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1541-4337.2011.00156.x

Natural antioxidants: sources, compounds, mechanisms of action, and potential applications

An Oxygen Scavenging System for Improvement of Dye Stability in Single-Molecule Fluorescence Experiments

Antioxidant, antimicrobial, antiulcer and analgesic activities of nettle (Urtica dioica L.).

Antioxidant and pro-oxidant properties of ascorbic acid and gallic acid

Antioxidant activity of sesame coat

The antioxidant activity of roasted coffee residues was evaluated. Extraction with four solvents (water, methanol, ethanol, and n-hexane) showed that water extracts of roasted coffee residues (WERCR) produced higher yields and gave better protection for lipid peroxidation. WERCR showed a remarkable protective effect on oxidative damage of protein. In addition, WERCR showed scavenging of free radicals as well as the reducing ability and to bind ferrous ions, indicating that WERCR acts as both primary and secondary antioxidants. The HPLC analyses showed that phenolic acids (chlorogenic acid and caffeic acid) and nonphenolic compounds [caffeine, trigonelline, nicotinic acid, and 5-(hydroxymethyl)furfuraldehyde] remained in roasted coffee residues. These compounds showed a protective effect on a liposome model system. The concentrations of flavonoids and polyphenolic compounds in roasted coffee residues were 8,400 and 20,400 ppm, respectively. In addition, the Maillard reaction products (MRPs) remaining in roasted coffee residues were believed to show antioxidant activity. These data indicate that roasted coffee residues have excellent potential for use as a natural antioxidant source because the antioxidant compounds remained in roasted coffee residues.

Antioxidant properties of roasted coffee residues.

The antioxidant effects of water extracts of roasted barley (WERB) were investigated under different roasting temperatures and compared with those of the water extracts of unroasted barley (WEUB). ...

Antioxidant effects of water extracts from barley (Hordeum vulgare L.) prepared under different roasting temperatures.

The biological action of water extract of pu-erh tea (WEPT) was evaluated by Salmonella mutagenesis assay and bacteria test. Like green tea, oolong tea and black tea, WEPT showed neither cytotoxicity and nor mutagenicity toward Salmonella typhimurium TA98 and TA100 with or without S9 mix (an external metabolic activation system). WEPT at 0.5–5 mg/plate expressed a dose-dependent inhibitory effect against both the mutagenicity of aflatoxin B1 (AFB1), an indirect mutagen which requires metabolic activation, and 4-nitroquinoline-N-oxide (NQNO), a direct mutagen, in Salmonella typhimurium TA98 and TA100. In general, the antimutagenic activity of WEPT against AFB1 and NQNO was weaker than other tea extract because of the least amount of total catechin in WEPT. For antimicrobial action, WEPT, green tea, oolong tea and black tea at 2.0 mg/ml showed inhibitory effect on growth of Staphylococcus aureus and Bacillus subtilis, but no effect on Escherchia coli. Obviously, WEPT has potential antimicrobial effect on gram-positive Staphylcoccus aureus and B. subtilis than that of gram-negative E. coli. In addition, caffeine and epicatechin (EC), main polyphenolic compounds in WEPT, showed both antimutagenic and antimicrobial effect against strains mentioned above, which may partially account for the antimutagenic and antimicrobial action of pu-erh tea.

Antimutagenic and antimicrobial activities of pu-erh tea

The effects of pu-erh tea, which is prepared by fermentation of tea, on oxidative damage and nitric oxide scavenging, compared with various other brands of tea were investigated. The total antioxidant activity was determined using the Trolox equivalent antioxidant capacity (TEAC) assay. The results showed that TEAC values of the 200 μg/mL water extracts of pu-erh tea (WEPT), green tea, oolong tea, and black tea were 86.3, 85.3, 87.4, and 80.3 (μg/mL), respectively, indicating that WEPT showed a significant antioxidant activity. WEPT, like green tea extract, oolong tea extract, and black tea extract, exhibited a remarkable protective effect in lipid (liposome) and nonlipid (protein and deoxyribose) model systems, implying that it is an inhibitor of lipid and nonlipid oxidative damage. It also exhibited metal-binding ability, reducing power, and scavenging effect for free radicals. Moreover, WEPT showed a decreasing effect on nitric oxide production of lipopolysaccharide-induced RAW 264.7 macrophages. In ad...

Wen-Jye Yen

Papers

Antioxidant activity of sesame coat

Antioxidant properties of roasted coffee residues.

Antioxidant effects of water extracts from barley (Hordeum vulgare L.) prepared under different roasting temperatures.

Antimutagenic and antimicrobial activities of pu-erh tea

Effects of pu-erh tea on oxidative damage and nitric oxide scavenging.