Microalgae as natural sources for antioxidative compounds

Antioxidants are substances that have the ability to reduce free, energized radicals. Thus, they prevent the oxidation of sensitive metabolites like lipids or amino acids and shield them from being destroyed by interrupting auto- or photooxidative chain reactions inside the cell. Antioxidants are also of industrial importance because they can be used as food, drug, or plastics additives. Ubiquinol, the reduced form of coenzyme Q₁₀, is one of the most effective antioxidants in human cells. This paper explores optimization strategies to increase Q₁₀ concentration in the biomass of Porphyridium purpureum, based on the variation of photosynthetic photon flux density. In addition, a cultivation process was performed in the 120-L scale followed by an automized extraction procedure (Accelerated Solvent Extraction?) resulting in an increase of the product recovery by a factor of 14 compared to the standard extraction method, hence reaching a specific coenzyme Q₁₀ concentration of 141?μg?g _{dry weight} ^?1 and a volumetric coenzyme Q₁₀ concentration of 1.96?mg?L^?1, respectively.     

VA菌根化杉树苗抗酚能力的研究

利用 Ｖ Ａ 菌根化杉树苗进行了加酚水培和土培,试验结果表明, Ｖ Ａ 菌根化杉树苗对邻香草醛,对羟基苯甲酸、阿魏酸等酚类物质有明显的耐受性     

Antimutagenic effects of natural phenolic compounds in beans

Polyphenols in fruits, vegetables (e.g., flavonols like quercetin) and tea (e.g., catechins such as epigallocatechin gallate) are good antioxidants with antimutagenic and anticarcinogenic properties. In the present study, the Salmonella typhimurium tester strain YG1024 was used in the plate-incorporation test to examine the antimutagenic effect of phenolic compounds, extracted from common beans (Phaseolus vulgaris), on 1-NP and B[a]P mutagenicity. Dose-response curves for 1-NP and B[a]P were obtained; the number of net revertants/plate at the peak mutagenic dosage were 880 for 1-NP and 490 for B[a]P. For the antimutagenicity studies doses of 0.1 microg/plate and 2 microg/plate for 1-NP and B[a]P, respectively, were chosen. We obtained a dose-response curve of ellagic acid (EA) against B[a]P and 1-NP mutagenicity. To test the bean extract, a dose of 300 microg/plate of EA was chosen as the antimutagenic control. The EA and bean extracts were not toxic to the bacteria at the concentrations tested. The inhibitory effects of the bean extracts and EA against B[a]P mutagenicity were dose-dependent. The percentages of inhibition produced against B[a]P (2 microg/plate) using 300 microg/plate of EA and for the extracts 500 microg equivalent catechin/plate were 82%, 83%, 81% and 83% for EA, water extract, water/methanol extract and methanol extract, respectively. However, for 1-NP mutagenicity, only the methanolic extract from beans showed an inhibitory effect. These results suggest that common beans, as other legumes, can function as health-promoting foods.     

Effects of phenol and natural phenolic compounds on biofilm formation by Pseudomonas aeruginosa

A biofilm is formed as a result of adhesion of microorganisms to various surfaces with the production of extracellular polymers (polysaccharides and proteins). Biofilms cause serious problems in the chemical, medical and pharmaceutical industries. Recent findings indicate that some natural phenolic compounds found in plants have an anti-biofouling effect on biofilm formation by Gram-negative bacteria. The anti-biofouling activities of 14 selected phenol and natural phenolic compounds were tested against Pseudomonas aeruginosa, using a microtiter-plate. A modified microtiter-plate assay was used because it enabled indirect measurement of bacterial cells attached to the surface of the wells. This assay involved fixing the bacterial film with methanol, staining with crystal violet dye and then releasing the bound dye with 33% glacial acetic acid. The optical density (OD) of the solution was measured at 570 nm by using an automated ICN Flow Titertek Multiscan Plus reader. Phenol and natural phenolic compounds except ethyl linoleate and tocopherol showed a significant reduction in biofilm formation by P. aeruginosa.     

Antioxidant activities of natural phenolic compounds from Acacia confusa bark

The present study showed that the ethanolic extracts from the bark of Acacia confusa exhibited a strong antioxidant activity. Among all the fractions from ethanolic extracts of bark, the EtOAc soluble fraction exhibited the best antioxidant performance. Furthermore, following by CC and HPLC, 11 pure phenolic compounds were isolated and identified from the ethanolic extracts.     

Enhanced activity of strobilurin and fludioxonil by using berberine and phenolic compounds to target fungal antioxidative stress response

AIMS: Identify natural products that effectively target antioxidative signal transduction/stress response systems [i.e., mitogen-activated protein kinase (MAPK) pathway, mitochondrial superoxide dismutase (Mn-SOD)] of fungi. Enhance activity of strobilurin or fludioxonil with discovered compounds. METHODS AND RESULTS: Enhancement of antifungal activity of strobilurins, inhibitors of complex III of the mitochondrial respiratory chain, was tested using berberine hemisulfate and different phenolic compounds. The Saccharomyces cerevisiae sod2Delta, a deletion mutant lacking Mn-SOD gene, was highly sensitive to berberine and veratraldehyde. Functional complementation analysis verified these compounds target Mn-SOD. Activity of strobilurin (25-50 micromol l(-1)) was elevated on most aspergilli and Penicillium expansum by co-application with berberine or veratraldehyde (2-4 mmol l(-1)). These compounds also prevented Aspergillus fumigatus MAPK mutants (sakADelta and mpkCDelta) from escaping toxicity of fludioxonil (a phenylpyrrole fungicide potentiated by the MAPK pathway), a typical phenotype of fungal MAPK mutants. CONCLUSIONS: Strobilurin activity or prevention of fungal escape from fludioxonil toxicity can be enhanced by co-application of certain alkaloids or phenolics. SIGNIFICANCE AND IMPACT OF THE STUDY: Natural products can be used to target cellular stress response systems in fungal pathogens and serve as alternatives/additives to commercial antifungal agents.     

Polyphenolic compounds in clove and pimento and their antioxidative activities

Two new polyphenolic glucosides, 6'-O-acetylisobiflorin (1) and (2S)-3-(4-hydroxy-3-methoxyphenyl)-propane-1,2-diol 1-O-(6'-O-galloyl)-β-D-glucoside (2), were respectively isolated from the flower buds of Syzygium aromaticum and berries of Pimenta dioica. Each structure was elucidated on the basis of spectral analyses (NMR, MS and [α](D)) and chemical conversion. A total of twenty-seven known compounds from the plants were also characterized. The antioxidative activity of their extracts and the twenty-nine isolates including gallo- and ellagitannins was estimated by oxygen radical absorbance capacity (ORAC) assay, and eugenol (3), which was the most abundant ingredient in each plant extract, showed the most potent antioxidative activity [ORAC value of 39,270 μmol TE (trolox equivalent)/g].     

Inhibition of aflatoxin biosynthesis by phenolic compounds

The phenolic compounds acetosyringone, syringaldehyde and sinapinic acid inhibited the biosynthesis of aflatoxin B1 (AFB1) by A. flavus. Acetosyringone was the most active among the three compounds, inhibiting aflatoxin level by 82% at 2 m moll-1. The synthesis and accumulation of norsolorinic acid, an aflatoxin biosynthetic intermediate, was also inhibited. These results suggest that at least one step early in the AFB1 biosynthetic pathway is inhibited by the phenolics.     

Inhibition of enzymatic cellulolysis by phenolic compounds

Phenolics derived from lignin and other plant components can pose significant inhibition on enzymatic conversion of cellulosic biomass materials to useful chemicals. Understanding the mechanism of such inhibition is of importance for the development of viable biomass conversion technologies. In native plant cell wall, most of the phenolics and derivatives are found in polymeric lignin. When biomass feedstocks are pretreated (prior to enzymatic hydrolysis), simple or oligomeric phenolics and derivatives are often generated from lignin modification/degradation, which can inhibit biomass-converting enzymes. To further understand how such phenolic substances may affect cellulase reaction, we carried out a comparative study on a series of simple and oligomeric phenolics representing or mimicking the composition of lignin or its degradation products. Consistent to previous studies, we observed that oligomeric phenolics could exert more inhibition on enzymatic cellulolysis than simple phenolics. Oligomeric phenolics could inactivate cellulases by reversibly complexing them. Simple and oligomeric phenolics could also inhibit enzymatic cellulolysis by adsorbing onto cellulose. Individual cellulases showed different susceptibility toward these inhibitions. Polyethylene glycol and tannase could respectively bind and degrade the studied oligomeric phenolics, and by doing so mitigate the oligomeric phenolic's inhibition on cellulolysis.     

Biotransformation of phenolic compounds by Bacillus aryabhattai

Bioprocess and Biosystems Engineering - Phenolic compounds could pose environmental problems if they are in excess, although they could be a renewable resource of substances with industrial...     

Interaction of tocopherols and phenolic compounds with membrane lipid components: evaluation of their antioxidant activity in a liposomal model system

This paper describes the use of complex liposomes as real membrane models to evaluate the potential benefits of several antioxidants in relation to lipid peroxidation. The xanthine oxidase/Fe(3+)-ADP-EDTA and the Fe(2+)/H2O2 systems have been used to generate hydroxyl radicals and the water soluble azo-compound 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) to generate carbon centered radicals (A*) by thermal decomposition. The antioxidant behavior of the rosemary and citrus plant extracts and vitamin-E and vitamin-E acetate alpha-tocopherols have been analyzed. The order of effectiveness in avoiding radical chain reactions has been established by using the colorimetric thiobarbituric acid reaction and the fluorescent probe DPH-PA. ESR spectroscopy has been used to carry out the pursuit of the oxidation processes on the basis of the identification of the radical species resulting from the oxidant system and the ability of the antioxidants to act as scavengers for hydroxyl and AAPH-derived radicals. The modification of the main transition temperature for the lipid mixture and the splitting of the calorimetric peak in the presence of the antioxidants were demonstrated by differential scanning calorimetry. The results obtained showed that the phenols-containing plant extracts and alpha-tocopherols perturb the phase behavior of the BBE lipid bilayer and have a fluidifying effect that could favor the known antioxidant capability and scavenging characteristics of these compounds. 31P-NMR results could be interpreted as, after the incorporation of these antioxidants, those lipid molecules interacting with antioxidants give rise to lamellar phase spectral components with resonance position at lower fields or to isotropic signals in accordance with a higher motion of their phosphate groups.     

Characterization of plant phenolic compounds by cyclic voltammetry

Phenolic acids and flavonoids were characterized by cyclic voltammetry and total antioxidant activity in the reaction with the ABTS cation radical. Anode peak voltages (E_ap) and their pH dependences were determined for the studied phenolic acids and flavonoids. The E_ap and Trolox equivalent antioxidant capacity (TEAC) values were found to correlate for polyphenols, which react with the ABTS cation radical in two steps. Correlation between the half-wave potential (E_1/2) and TEAC was determined for electrochemically irreversible compounds. Mechanisms of the reaction of phenolics on the electrode involving one-and two-electron oxidation are proposed.     

Characterization of plant phenolic compounds by cyclic voltammetry

Phenolic acids and flavonoids were characterized by cyclic voltammetry and total antioxidant activity in the reaction with the ABTS cation radical. Anode peak voltages (Eap) and their pH dependences were determined for the studied phenolic acids and flavonoids. The Eap and Trolox equivalent antioxidant capacity (TEAC) values were found to correlate for polyphenols, which react with the ABTS cation radical in two steps. Correlation between the half-wave potential (Ep/2) and TEAC was determined for electrochemically irreversible compounds. Mechanisms of the reaction of phenolics on the electrode involving one- and two-electron oxidation are proposed.     

Utilization of complex phenolic compounds by Acinetobacter sp.

Summary Acinetobacter sp. utilized the [ring-¹⁴C]dehydropolymer of coniferyl alcohol (DHP) (sp. act. 1.4 × 10⁴ dpm/mg), ¹⁴C-labelled teakwood lignin (sp. act. 2.5 × 10⁴ dpm/mg), guaiacolglyceryl ether, 2-methoxy-4-formylphenoxyacetic acid, p-benzyloxyphenol, dehydrodivanillyl alcohol, dehydrodiisoeugenol, veratrylglycerol--guaiacyl ether, conidendrin, black liquor lignin and indulin as sole carbon sources. The bacterium produced p-coumaric acid, p-hydroxybenzoic acid, vanillic acid, protocatechuic acid and catechol as intermediates from lignins. Acinetobacter sp. produced catechol 1,2-dioxygenase and protocatechuate 3,4-dioxygenase during the degradation of lignins. Correspondence to: A. Mahadevan