Metabolism of food phenolic acids by Lactobacillus plantarum CECT 748

Phenolic acids account for almost one third of the dietary phenols and are associated with organoleptic, nutritional and antioxidant properties of foods. This study was undertaken to assess the ability of Lactobacillus plantarum CECT 748^T to metabolize 19 food phenolic acids. Among the hydroxycinnamic acids studied, only p-coumaric, caffeic, ferulic and m-coumaric acids were metabolized by L. plantarum. Cultures of L. plantarum produced ethyl and vinyl derivatives from p-coumaric and caffeic acids, 4-vinyl guaiacol from ferulic acid, and 3-(3-hydroxyphenyl) propionic acid from m-coumaric acid. Among the hydroxybenzoic acids analysed, gallic acid and protocatechuic acid were decarboxylated to pyrogallol and catechol, respectively. Inducible enzymes seem to be involved, at least in m-coumaric and ferulic acid metabolism, since cell-free extracts from cultures grown in the absence of these phenolic acids were unable to metabolize them. Further work is needed for the identification of the enzymes involved, since the knowledge of the metabolism of phenolic compounds is an important issue for the food industry.     

Effect of phenolic acids on glucose and organic acid metabolism by lactic acid bacteria from wine

The influence of phenolic (p-coumaric, caffeic, ferulic, gallic and protocatechuic) acids on glucose and organic acid metabolism by two strains of wine lactic acid bacteria (Oenococcus oeni VF and Lactobacillus hilgardii 5) was investigated. Cultures were grown in modified MRS medium supplemented with different phenolic acids. Cellular growth was monitored and metabolite concentrations were determined by HPLC-RI. Despite the strong inhibitory effect of most tested phenolic acids on the growth of O. oeni VF, the malolactic activity of this strain was not considerably affected by these compounds. While less affected in its growth, the capacity of L. hilgardii 5 to degrade malic acid was clearly diminished. Except for gallic acid, the addition of phenolic acids delayed the metabolism of glucose and citric acid in both strains tested. It was also found that the presence of hydroxycinnamic acids (p-coumaric, caffeic and ferulic) increased the yield of lactic and acetic acid production from glucose by O. oeni VF and not by L. hilgardii 5. The results show that important oenological characteristics of wine lactic acid bacteria, such as the malolactic activity and the production of volatile organic acids, may be differently affected by the presence of phenolic acids, depending on the bacterial species or strain.     

Study of the inhibitory activity of phenolic compounds found in olive products and their degradation by Lactobacillus plantarum strains

Lactobacillus plantarum is the main species responsible for the spontaneous fermentation of Spanish-style green olives. Olives and virgin oil provide a rich source of phenolic compounds. This study was designed to evaluate inhibitory growth activities of nine olive phenolic compounds against four L. plantarum strains isolated from different sources, and to explore the L. plantarum metabolic activities against these phenolic compounds. None of the nine compounds assayed (oleuropein, hydroxytyrosol, tyrosol, as well as vanillic, p-hydroxybenzoic, sinapic, syringic, protocatechuic and cinnamic acids) inhibited L. plantarum growth at the concentration found in olive products. Oleuropein and tyrosol concentrations higher than 100 mM were needed to inhibit L. plantarum growth. On the other hand, sinapic and syringic acid showed the highest inhibitory activity since concentrations ranging from 12.5 to 50 mM inhibited L. plantarum growth in all the strains analyzed. Among the nine compounds assayed, only oleuropein and protocatechuic acid were metabolized by L. plantarum strains grown in the presence of these compounds. Oleuropein was metabolized mainly to hydroxytyrosol, while protocatechuic acid was decarboxylated to catechol. Metabolism of oleuropein was carried out by inducible enzymes since a cell-free extract from a culture grown in the absence of oleuropein was unable to metabolize it. Independent of their isolation source, the four L. plantarum strains analysed showed similar behaviour in relation to the inhibitory activity of phenolic compounds, as well as their ability to metabolize these compounds.     

Synergistic and suppressive effects of dietary phenolic acids and other phytochemicals from cereal extracts on nuclear factor kappa B activity

In this study the combinatorial action of the main phenolic acids (ferulic, caffeic, p-coumaric and sinapic acids) found in extracts of free (ME) and bound phenolic acids (HE) from oat, barley and wheat flour on the modulation of NF-κB activity was investigated. The results show that combination of phenolic acids in low concentrations (<0.1 μg/ml) has a significant synergistic, or enhanced effect, on NF-κB activity, while their combination in high concentrations (0.3–70 μg/ml) helps to suppress the strong effect obtained by individual solutions of ferulic and p-coumaric acids. The modulation of NF-κB activity observed by HE extracts is the effect of combinatorial action of the phenolic acids present therein, while the modulation of NF-κB activity observed with ME extracts is the result of combinatorial action of phenolic acids together with other phenolic compounds present in the extracts. These results increase the knowledge about the health promoting effect from cereal consumption and dietary phenolic acids.     

Characterisation of calamansi (Citrus microcarpa). Part I: Volatiles,aromatic profiles and phenolic acids in the peel

Volatile compounds in the peel of calamansi (Citrus microcarpa) from Malaysia, the Philippines and Vietnam were extracted with dichloromethane and hexane, and then analysed by gas chromatography–mass spectroscopy/flame ionisation detector. Seventy-nine compounds representing >98% of the volatiles were identified. Across the three geographical sources, a relatively small proportion of potent oxygenated compounds was significantly different, exemplified by the highest amount of methyl N-methylanthranilate in Malaysian calamansi peel. Principal component analysis and canonical discriminant analysis were applied to interpret the complex volatile compounds in the calamansi peel extracts, and to verify the discrimination among the different origins. In addition, four common hydroxycinnamic acids (caffeic, p-coumaric, ferulic and sinapic acids) were determined in the methanolic extracts of calamansi peel using ultra-fast liquid chromatography coupled to photodiode array detector. The Philippines calamansi peel contained the highest amount of total phenolic acids. In addition, p-Coumaric acid was the dominant free phenolic acids, whereas ferulic acid was the main bound phenolic acid.     

Screening of representative cider yeasts and bacteria for volatile phenol-production ability

Representative cider microorganisms (47 yeast strains and 16 bacterial strains) were studied for their ability to produce volatile phenols in a synthetic medium simulating cider conditions and supplemented with the necessary precursors. The various strains were tested for cinnamoyl esterase activity and only Lactobacillus collinoides were able to hydrolyse chlorogenic acid. Phenolic acid decarboxylase (PAD) activities were observed for 6 yeasts and 4 bacterial species allowing them to produce vinylphenols from hydroxycinnamic acids. On the other hand, 4 bacterial species exhibited phenolic acid reductase (PAR) activities leading to the formation of hydroxyphenylpropionic acids. Brettanomyces/Dekkera anomala and L. collinoides were able to produce 4-ethylcatechol (4-EC) and 4-ethylphenol (4-EP) from caffeic and p-coumaric acid, respectively, indicating that both species exhibit PAD and vinylphenol reductase (VPR) activities. In the experimental conditions used, the production of ethylphenols by L. collinoides was faster than the one observed for D. anomala.     

The analysis of phenolic constituents in glabrous canaryseed groats

Nineteen glabrous canaryseed samples, comprising brown- and yellow-coloured seeds, were investigated to determine the nature of phenolic constituents present. Total phenolic content (TPC) was determined, using the Folin–Ciocalteau assay. Flavonoid and phenolic acid compositions were determined, using high performance liquid chromatographic and mass spectrometric (LC–MS/MS) techniques. TPC ranged from 174 to 209 mg/100 g for canaryseed wholemeal samples. The canaryseed bran contained twice as much TPC as the wholemeal. The brown- and yellow-coloured whole canaryseeds exhibited the same flavonoid profiles. LC–MS/MS analysis showed that the canaryseed acetone extract was rich in flavonoid glycosides, with the bran being mainly composed of O-pentosyl isovitexin and the flour having a compound at m/z 468. No proanthocyanidins were detected in the 19 samples. Ferulic acid was the dominant phenolic acid, followed by caffeic and p-coumaric acids. The wholemeal obtained from the brown-coloured group had significantly higher contents of ferulic (>196 mg/kg) and caffeic (>96 mg/kg) acids in comparison to the yellow-coloured canaryseed group. The latter had ferulic and caffeic acids at levels less than 165 and 78 mg/kg, respectively, with one exception which had relatively higher levels (190 and 94 mg/kg). Whilst canaryseed flour contained significantly very low levels of ferulic acid (22–34 mg/kg), the bran was enriched in ferulic (593–766 mg/kg), caffeic (304–452 mg/kg) and p-coumaric (119–142 mg/kg) acids.     

Characterization of the phenolic acid profile and in vitro bioactive properties of white beetroot products

The impact of boiling, baking and fermentation treatment on the phenolic acid profile, antioxidant capacity (AC) and angiotensin-1 converting enzyme (ACE) activity of white beetroot was investigated. The phenolic acids were analysed by liquid chromatography–mass spectrometry (micro-HPLC-MS/MS), while AC and ACE were determined by in vitro assays. Phenolic acids concentration was between 87.55 and 100.98 ng g⁻¹ d.m. Ferulic and p-coumaric acids were the main compounds among the nine phenolic acids identified. Boiling increased the phenolic acid content by 3%; however, baking and fermentation reduced the level of these acids by approximately 6% and 11%, respectively. A significant positive correlation was observed between the results of all AC assays and sinapic and caffeic acid content. The ACE inhibitory activity of white beetroot products may be attributable to the combined effect of the syringic, 4-hydroxybenzoic, ferulic and p-coumaric acids. Our study indicates that white beetroot as a novel product may be a valuable source of phenolic acids and functional properties.     

Localization of phenolic acids and antioxidant activity in sorghum kernels

White and red of sorghum grains were sequentially pearled into 11 pearling fines and the corresponding 11 pearled kernels to study the localization of phenolic acids within sorghum grains. All fractions were analyzed for phenolic acids content by HPLC and antioxidant capacity by FRAP assays. Four phenolic acids identified in all fractions were caffeic, p-coumaric, ferulic, and sinapic acids. Data showed that the distribution of phenolic acids and antioxidant capacity in two sorghum genotypes was heterogeneous. Around 60% of the phenolic acids and the antioxidant capacity were recovered in the initial three pearling fine fractions that constituted about 20% surface removal. The concentrations of the phenolic acids decreased significantly with sequential pearling. Significant correlation between total phenolic acids and antioxidant capacity was observed with all fractions except for the first pearling fines from the red sorghum.     

Effect of lactic acid fermentation on antioxidant properties and phenolic acid contents of oyster (<Emphasis Type="Italic">Pleurotus ostreatus</Emphasis>) and chanterelle (<Emphasis Type="Italic">Cantharellus cibarius</Emphasis>) mushrooms

Fruiting bodies of Pleurotus ostreatus (oyster) and Cantharellus cibarius (chanterelle) mushrooms underwent acid fermentation using 3 strains of lactic acid bacteria (LAB) as starter cultures. Polyphenol contents, antioxidant activities, and phenolic acid contents in fresh, blanched, and fermented mushrooms were investigated. Fruiting bodies of oyster mushrooms exhibited higher total phenolic contents than chanterelle mushrooms. Blanching caused a decrease in polyphenol contents and antioxidant activities in both mushroom types. No important differences were observed in total phenolic compound contents (measured using Folin-Ciocalteau reagent) in mushrooms using different LAB strains. Lactobacillus plantarum was the most useful microorganism for lactic acid fermentation of fruiting bodies for reduction of the pH value. The highest concentrations of single phenolic acids: gallic, homogentisic, and ferulic acids were present in mushrooms fermented using L. plantarum.     

Sugars, organic acid and phenolic compounds of Ziziphus mauritiana Fruit

This study was conducted to identify soluble sugars, non-volatile acids and phenolic compounds in Ziziphus mauritiana fruit. Soluble sugars in Ziziphus mauritiana fruit were qualitatively determined by TLC. The sugars identified to be present in Ziziphus mauritiana were galactose, fructose and glucose. TLC was also used for qualitative analysis of phenolic compounds; five spots of phenolic compounds were observed. Only two of the observed spots were identified using the R_f values of the standards that were available. The two phenolic compounds identified by TLC were caffeic acid and p-coumaric acid. Phenolic compounds were also quantified using HPLC. Twelve peaks of phenolic compounds were detected. Among these, p-hydroxybenzoic acid, caffeic, ferulic acid and p-coumaric acid were the most abundant with concentrations of 365.94, 30.76, 19.64 and 19.28 mg/kg dry mass respectively, whereas vanillic acid was the least abundant with a concentration of 2.52 mg/kg. The organic acids were qualitatively analysed by PC and citric acid, malonic acid and malic acid were identified in the Ziziphus mauritiana fruit.     

Antioxidative activity of phenolic acids on triacylglycerols and fatty acid methyl esters from olive oil

The autoxidation of kinetically pure triacylglycerols and methyl esters of olive oil (TGOO and MEOO) in the presence of four different concentrations of p-coumaric, ferulic and caffeic acids at 100 °C was studied. It was established that effectiveness and strength of the phenolic acids were greater in MEOO than in TGOO. In both lipid substates the molecules of phenolic acids participate in one side-reaction (with hydroperoxides). The rate constants of this reaction in TGOO and in MEOO are practically the same. The phenolic acids take part in chain initiation. The rate of this reaction for ferulic and caffeic acids has equal values in TGOO and in MEOO, whereas for p-coumaric acid it is twice as high in TGOO than in MEOO. The radicals of the phenolic acids participate in one reaction of chain propagation (with the lipid substrate) both in triacylglycerols and in methyl esters of olive oil. Comparison with the data published recently for sunflower oil triacylglycerols and methyl esters demonstrates the strong influence of the unsaturation type and degree of the lipid system on the kinetics and mechanism of the antioxidative action of the phenolic acids.     

Phytochemical profiles and inhibitory effect on free radical-induced human erythrocyte damage of Dracaena draco leaf: A potential novel antioxidant agent

The present study reports for the first time the metabolite profile and antioxidant activity of aqueous extract obtained from Dracaena draco L. leaf. Volatiles profile was determined by HS-SPME/GC-IT-MS, with 34 compounds being identified, distributed by distinct chemical classes: 2 alcohols, 5 aldehydes, 16 carotenoid derivatives and 8 terpenic compounds. Carotenoid derivative compounds constituted the most abundant class in leaf (representing 45% of total identified compounds). Phenolics profile was determined by HPLC/DAD and 9 constituents were identified: 2 hydroxycinnamic acid derivatives – 5-O-caffeoylquinic and 3,5-O-dicaffeoylquinic acids; 4 hydroxycinnamic acids – caffeic, p-coumaric, ferulic and sinapic acids and 3 flavonol glycosides – quercetin-3-O-rutinoside, kaempferol-3-O-glucoside and kaempferol-3-O-rutinoside. The most abundant phenolic compound is quercetin-3-O-rutinoside (representing 50.2% of total polyphenols). Organic acids composition was also characterised, by HPLC–UV and oxalic, citric, malic and fumaric acids were determined. Oxalic and citric acids were present in higher amounts (representing 47%, each). The antioxidant potential of this material was assessed by the ability to protect against free radical-induced biomembrane damage, using human erythrocyte as in vitro model. Leaf extract strongly protected the erythrocyte membrane from haemolysis (IC₅₀ of 39 ± 11 μg/ml), in a time- and concentration-dependent manner. This is the first report showing that D. draco leaf is a promising antioxidant agent.     

Phenolic acids in the jute plant (corchorus capsularis)

The bark and the stem of unretted jute plant (Corchorus capsularis) were found to contain various free, glycosidic and ester-linked phenolic acids. From an 80% aqueous ethanol extract, p-coumaric, ferulic, caffeic, vanillic and p-hydroxybenzoic acids were identified and quantified. p-Coumaric acid, the major component, and β-sitosterol were isolated and characterised.     

Content of flavonols and selected phenolic acids in strawberries and Vaccinium species: influence of cultivar,cultivation site and technique

The amounts of flavonols (quercetin, myricetin and kaempferol) and phenolic acids (ellagic, p-coumaric, caffeic and ferulic acids) were analysed in six strawberry cultivars and in the berries of genus Vaccinium (four blueberry cultivars, wild bilberry, wild bog whortleberry). Differences between strawberries from organic vs. conventional cultivation were investigated and the influence of geographical origin on phenolic compounds of strawberries and blueberries was studied. Three different extraction and hydrolysis procedures together with two HPLC methods with diode-array UV/vis detection were used. The varietal differences in the total content of the phenolics analysed were larger among the cultivated blueberries (from 4.4 to 9.2 mg/100 g, fresh weight) than among the strawberry cultivars (from 42.1 to 54.4 mg/100 g). Some regional differences were observed in the phenolic contents in blueberries and strawberries. Compared to conventional cultivation techniques, organic cultivation had no consistent effect on the levels of phenolic compounds in strawberries.     

Effect of grape polyphenols on lactic acid bacteria and bifidobacteria growth: resistance and metabolism

Food polyphenols are able to selectively modify the growth of susceptible micro-organisms. This study describes the effect of a flavan-3-ol enriched grape seed extract (GSE) on the growth of several lactic acid bacteria (LAB) and bifidobacteria and the ability of the resistant strains to metabolize these compounds. Streptococcus thermophilus, Lactobacillus fermentum, Lactobacillus acidophilus and Lactobacillus vaginalis strains showed a remarkable sensitivity to the phenolic extracts assayed, including a GSE fraction consisting mainly in (+)-catechin and (−)-epicatechin (GSE-M). On the other hand, Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus bulgaricus strains reached maximal growth with the GSE fractions, including a rich-oligomeric (GSE-O) fraction. Within bifidobacteria, Bifidobacterium lactis BB12 showed the highest sensitivity to the phenolic extracts assayed, whereas Bifidobacterium breve 26M2 and Bifidobacterium bifidum HDD541 reached maximum growth in presence of GSE-O and GSE-M fractions. Metabolism of flavan-3-ols by LAB and bifidobacteria resistant strains was investigated in vitro. The results revealed that only L. plantarum IFPL935 was able to metabolize the polyphenols studied by means of galloyl-esterase, decarboxylase and benzyl alcohol dehydrogenase activities that led to the formation of gallic acid, pyrogallol and catechol, respectively. An unknown metabolite that does not exhibit a phenolic-acid-type structure was also detected, which suggests a new enzyme activity in L. plantarum IFPL935 able to degrade flavan-3-ol monomers.     

The distribution of phenolic acids in pumpkin’s hull-less seed,skin, oil cake meal,dehulled kernel and hull

The phenolic acids in whole hull-less seed, its skin and oil cake meal, dehulled kernel and hull of pumpkin (Cucurbita pepo) were separated into free, esterified and insoluble-bound forms, which were then identified and quantified by high-performance liquid chromatography with a photodiode array detector. In all samples, protocatechuic, p-hydroxybenzoic, vanillic, trans-p-coumaric, ferulic, trans-sinapic acids and p-hydroxybenzaldehyde were quantified. Caffeic acid was present in all samples except in hulls, while syringic acid was not detectable only in skin and oil cake meal. p-Hydroxybenzoic acid was the dominant phenolic compound in all investigated samples, with 34.7%, 52.0%, 51.4%, 67.4% and 51.8% found in hull-less seed, oil cake meal, skin, dehulled kernels and hulls, respectively, based on total phenolic acid content. Most phenolic acids were present in bound (esterified and insoluble) form, from 50.6% in skin to 84.1% in hull-less seed.     

Changes in phenolic composition and antioxidant activity of white wine during bottle storage: Accelerated browning test versus bottle storage

Polyphenol content, antioxidant activity, reducing power, colour and changes during storage over nine months in bottles and after accelerated browning were studied in selected Hellenic varietal white wines. The following phenolic compounds were identified in the wines: Caftaric, coutaric, fertaric, ferulic, caffeic, p-coumaric and gallic acids, (+)-catechin and (−)-epicatechin. The results showed that the contents of most of the phenols diminished with time, with the exception of caffeic, ferulic and p-coumaric acids. Antioxidant activity increased with storage whereas reducing power remained significantly unaffected. Accelerated browning did not significantly alter the concentrations of tartaric acid esters but it increased the concentrations of the hydroxycinnamic and gallic acids. (+)-Catechin concentration was not affected while (−)-epicatechin decreased. Antioxidant activity did not show any significant change but reducing power was reduced after the end of the browning test. As for the absorbance at 420 nm, it remained unchanged during storage, but it was significantly increased after accelerated browning.     

Interactions of p-coumaric,caffeic and ferulic acids and their styrenes with model lipid membranes

The influence of the p-coumaric, caffeic and ferulic phenolic acids, and their corresponding styrenes, on structural properties of a model lipid membrane was investigated by differential scanning calorimetry and fluorimetry. The phenolic acids were seen to have smaller effects, compared to their styrenes, on the temperature and enthalpy of the main phase transition (gel-to-liquid) of extruded large unilamellar liposomes prepared from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine lipids. A slight thermal and enthalpy destabilisation of the liposomes was seen with the phenolic acids at a lipid:acid molar ratio of 1:1. In contrast, their styrenes had higher destabilisation effects on the enthalpy of the phase transition. For fluorescence spectroscopy with 1,6-diphenyl-1,3,5-hexatriene as the membrane probe, the polarisation measurements showed that the styrenes, which are less polar than their corresponding acids, had greater effects on lipid membrane structure. The correlations between the structural properties of these compounds and their effects on membrane structure are discussed.