Tannic Fractions Research Articles

Sensory variability associated with anthocyanic and tannic fractions isolated from red wines

Tannins and anthocyanins are important modulators of the intrinsic quality of red wines, playing a major role in consumer preference and appreciation. Tannins are chiefly responsible for the astringency in wines although their role in eliciting different astringent subqualities is still relatively unknown. On the other hand, the sensory contribution of anthocyanic fractions is even less clear. The main aim of the present study was to assess whether anthocyanic fractions from red wine elicit specific mouthfeel and taste attributes that differ from their tannin counterparts, and to evaluate the contribution of anthocyanic and tannic fractions to taste and mouthfeel of red wines. Isolation of tannin (Ftannin) and anthocyanin (Fantho) fractions from 20 wines involved reversed-phase semipreparative liquid chromatography followed by solid phase extraction. The 40 derived fractions subsequently underwent sensory characterisation using a labelled sorting task and a rate-K attributes method. Bitterness and dryness were the salient attributes differing among the sensory spaces of both Fantho and Ftannin. Likewise, other independent and non-correlated mouthfeel dimensions differed for both Fantho (“grainy” and mouthcoating”) and Ftannin (“gummy”). A significant linear model predicting wine dryness from the “dry” intensity of Fantho and Ftannin was obtained, with tannic fractions presenting a higher contribution than anthocyanic fractions. These results not only confirmed that tannins have a major implication in red wine dryness but also unequivocally demonstrated a relevant implication of certain anthocyanins in this attribute. In contrast, bitterness of the original wines could not be directly related to the bitterness perceived in any of the two groups of fractions. The addition of an extremely bitter anthocyanic fraction to wines only increased bitterness in certain wines, suggesting that bitterness in wines may result from perceptual interactions and that some wines contain strong bitterness suppressors.

The role of extracts from Eugenia uniflora L. against metal stress in eukaryotic and prokaryotic models

This study aims to verify the chelating, antioxidant and cytoprotective activities of Eugenia uniflora in a eukaryotic and prokaryotic model. Ethanolic extract, as well as tannic and flavonoid fractions, were prepared from samples obtained from the species which were analyzed by LC-MS. The antioxidant activity through the FRAP method showed that the tannic fraction had the lowest EC50. The suggested compounds identified in the extract and fractions were quercetin and the derivatives, myricetin, gallic acid, vanillic acid, quinic acid and catechin. Regarding the flavonoid fraction, a reduction in the fungicidal effect was observed. When the ethanolic extract was assayed in the presence of mercury chloride, all fractions showed a cytoprotection in relation to this metal. The sub-allelopathic concentration used was 64 μg/mL. The flavonoid fraction showed cytoprotective activity against aluminum for caulicles and radicles, whereas for the mercury against the radicles at all concentrations. Meanwhile the tannic fraction against aluminum showed a better development in the size of the radicles, the mercury there were differences in the sizes of the radicles and caulicles. The results demonstrated in this work indicate that natural products of Eugenia uniflora are promising sources of natural products with antioxidant and chelating activity.

Phytotoxicity reduction of the mercury chloride effect by natural products from Eugenia jambolana Lam.: A new strategy against the toxic metal pollution

The objective of this work was to evaluate the antioxidant, metal chelating and cytoprotective activity of the Eugenia jambolana Lam. extract, as well as of its flavonoid and tannic fractions, against the action of Mercury Chloride (HgCl2). Flavonoids were quantified and an LC-MS chromatographic analysis was performed to identify secondary metabolites. Fe2+ and Fe3+ chelation tests and antioxidant activity were carried out using the FRAP method. Microbiological tests were performed by microdilution to determine the Minimum Inhibitory Concentration (MIC). From these results the Minimum Bactericidal (MBC) and Minimum Fungicide Concentration (MFC) were evaluated. The allelopathy and cytoprotection assays were performed using eukaryotic and prokaryotic models. The results revealed the presence of phenolic acids and flavonoids in the E. jambolana extract and fractions. The sub-allelopathic concentration (64 μg/mL) was used and the results demonstrated the E. jambolana potential cytoprotective effect against mercury chloride.

Psidium guajava bioactive product chemical analysis and heavy metal toxicity reduction

The present study had as its objective to verify the Psidium guajava var. Pomifera L. chelating, antioxidant and cytoprotective effects against mercury and aluminum. The ethanolic extract, tannic and flavonoid fractions were subjected to LC-MS analysis. The Ferric Reducing Antioxidant Power (FRAP) and ferric ion reduction demonstrated a present antioxidant activity. The fungicidal and bactericidal activity of these metals were established. After determining the sub-allelopathic doses, germination tests using Lactuca sativa were performed. Quercetin and its derivatives were the main compounds identified in the extract and the fractions. Mercury chloride significantly reduced the bactericidal effect of the flavonoid fraction (p < 0.001). None of the fractions were cytoprotective against mercury or aluminum in the fungal model assays. Using a sub-allelopathic concentration (64 μg/mL), the ethanolic extract, flavonoid and tannic fractions were found to be cytoprotective against aluminum for radicles, however only the tannic fraction was cytoprotective for caulicles. These data suggest that natural P. guajava products are promising cytoprotective compound sources. This activity may be related to the antioxidant effect of secondary metabolites, mainly flavonoids. Our results point to a potential for environmental intervention product and technique development aimed at mitigating contamination by toxic metals such as mercury and aluminum.

Analysis by UPLC-MS-QTOF and antifungal activity of guava (Psidium guajava L.)

Psidium guajava L. is a plant widely used for food and in folk medicine all over the world. Studies have shown that guava leaves have antifungal properties. In this study, Flavonoid and Tannic fractions were tested to investigate their chemical composition and antifungal potential in vitro.21 compounds in the two fractions, presenting a higher content of phenolic compounds. The antifungal assays were performed against Candida albicans, Candida tropicalis and Candida krusei by microdilution to determine the IC50 and the cell viability curve. Minimal Fungicidal Concentration(MFC) and the inhibitory effects of the association of the fractions with Fluconazole, as well as the assays used to verify any morphological changes were performed in microculture chambers based on the concentrations from the microdilution. The IC50 of the isolated fractions and the fractions associated with each other were calculated, varying from 69.29 to 3444.62 μg/mL and the fractions associated with fluconazole varied from 925.56 to 1.57 μg/mL, it was clear that the association of the natural product with the antifungal presented a synergism. The fractions affected pleomorphism capacity and have a potential antifungal activity as they caused fungal inhibition in isolated use, potentiated the action of Fluconazole, reducing its concentration and impeding morphological transition, one of the virulence factors of the genus.

Anti-Trypanosoma, anti-Leishmania and cytotoxic activities of natural products from Psidium brownianum Mart. ex DC. and Psidium guajava var. Pomifera analysed by LC–MS

Neglected diseases are those that are prevalent in developing countries, even with a rich biodiversity. These diseases still persist because of the lack of scientific studies, government negligence or failures of the public health system. This study aims to identify the composition of extracts and fractions from Psidium brownianum and Psidium guajava through LC–MS, to evaluate its in vitro anti-parasitic and cytotoxic activity against Trypanosoma cruzi, Leishmania brasiliensis and L. infantum epismastigote and promastigote forms, as well as mammalian cells. The results showed the presence of chemical constituents in the two Psidium species as quercetin, myricetin and gallic acid derivatives. The P. brownianum extract and fractions showed low toxicity at all tested concentrations and all samples were effective at the concentration of 1000μg/mL against the parasites, with the extract being the most efficient against the L. infantum promastigote form. The ethanolic extract, and the flavonoid and tannic fractions, from P. guajava showed low toxicity for the fibroblasts. All samples showed effectiveness at the highest concentration tested and the extract was more effective against the promastigote forms tested. The results showed that the species Psidium brownianum and Psidium guajava demonstrated an anti-parasitic activity against the T. cruzi, L. brasiliensis and L. infantum parasite cell lines indicating these species as an alternative therapy given their efficacy in the in vitro assays performed, opening the possibility for new biological studies to further this knowledge through in vivo assays.

LC–MS characterization, anti-kinetoplastide and cytotoxic activities of natural products from Eugenia jambolana Lam. and Eugenia uniflora

ObjectiveTo evaluate the trypanocidal, leishmanicidal and cytotoxic activity of Eugenia jambolana (E. jambolana) and Eugenia uniflora (E. uniflora) extracts and fractions. MethodsThe products were characterized by LC–MS. Antiparasitic assays were performed and cytotoxicity was evaluated in fibroblastos. In vitro assays were performed using spectrophotometric evaluation. All assays were performed in thrice. ResultsThe results showed that the extracts and the tannic fraction from E. jambolana inhibited 100% of the epimastigote lines. The ethanolic extract was the most efficient in all concentrations tested against the three parasite strains. In the cytotoxicity assay the flavonoid fraction showed low toxicity. All E. uniflora samples showed cytotoxicity at the highest concentration tested, but the extract showed no toxic effect on the fibroblasts at the lowest concentration. The flavonoid and tannic fractions were more efficient against Leishmania braziliensis promastigotes compared to the extract. However, the extracts and the tannic fraction were more effective against Leishmania infantum strains. The effect on epimastigote cells was observed at all concentrations tested, with all E. uniflora samples. However, the samples were more effective at the highest concentration, where there was inhibition in 100% of the Trypanosoma cruzi strains. ConclusionsThe species E. jambolana and E. uniflora presented antiparasitic activity against all tested parasite strains, indicating that these species can serve as an alternative therapy as they were efficient in the tests performed. The E. uniflora extract and the E. jambolana flavonoid fraction presented a low cytotoxicity, opening the floor for new biological studies.

Changes in tannins, ascorbic acid and sugar content in astringent persimmons during on-tree growth and ripening and in response to different postharvest treatments

Changes in tannins, ascorbic acid and sugars in astringent persimmons ‘Rojo Brillante’ and ‘Kaki Tipo’ were investigated during fruit maturation and after postharvest treatments. Soluble tannins exhibited a significant initial increment, followed by a marked constant decrease that led to values between 0.2 and 0.3 g/100 g fresh weight (FW) in the last stage of maturity studied. During the entire period monitored, insoluble tannins represented the minor component of the total tannic fraction, accounting for 9–27% (Rojo Brillante) and 17–32% (Kaki Tipo) of total tannins; levels of insoluble tannins were comparable to or higher than the soluble tannins in softer fruits. Total vitamin C decreased from 0.18–0.20 to about 0.08 g/100 g FW during fruit development owing to fruit growth rather than to degradation processes. Total sugars increased from about 4 g/100 g FW at the early stage of fruit development to 17 g/100 g FW after reaching the commercial stage of maturity. Glucose and fructose increased during the entire period monitored, while sucrose reached a maximum and then gradually decreased, probably owing to a strong invertase activity. Antiradical activities were significantly related to the corresponding tannic fraction. In both ‘Rojo Brillante’ and ‘Kaki Tipo’, postharvest treatment with CO 2 was more effective than with ethylene in reducing soluble tannin concentration (0.031–0.067 and 0.220–0.262 g/100 g FW, respectively).

Purification of Ellagic Acid by UF Membranes

Ellagic acid (2, 3, 7, 8-tetrahydroxy(1)benzopyrano(5, 4, 3-cde)(1)benzopyran-5, 10-dione) was selected as a model pollutant which is present in the tannic fraction of cork processing wastewater. The ultrafiltration of aqueous ellagic acid solutions through three membranes was studied in tangential UF laboratory equipment. Two of the membranes were polyethersulfone (Biomax10K and Biomax5K, with MWCO of 10000 and 5000 Da, respectively), and the third made of regenerated cellulose (Ultracel5K, with MWCO of 5000 Da). The water hydraulic permeability was evaluated for each membrane. The evolution of the permeate flow rate with processing time was followed, and the influence of the main operating variables (feed flow rate, trans-membrane pressure and nature of the membranes) on the permeate flux was also established. According to the hypothesis of the film theory, the intrinsic and apparent rejection coefficients, as well as the mass transfer coefficients, were also determined, and the values obtained were discussed as a function of the operating conditions used.

Removal of Phenolic Compounds in Water by Ultrafiltration Membrane Treatments

The ultrafiltration (UF) of aqueous solutions containing mixtures of three phenolic compounds (gallic acid, acetovanillone, and esculetin) was studied in a tangential UF laboratory system. These substances were selected as model pollutants present in the tannic fraction of the cork processing wastewaters. The two membranes used were a polyethersulfone membrane (Biomax5KTM) and a regenerated cellulose membrane (Ultracel5KTM), both with a molecular weight cut-off (MWCO) of 5000 Da. Previous experiments for the characterization of the membranes led to values for the water hydraulic permeability of 70.3 and 18.1 L/h · m2 · bar for the Biomax5K and Ultracel5K membranes, respectively. During the UF experiments, the permeate flow rate remained almost constant with processing time and the evolution of the pollutants concentrations varied depending on the nature of the membranes and the substances. The influence of the main operating variables (tansmembrane pressure and feed flow rate) on the permeate flux was established, and values for the apparent and intrinsic rejection coefficients were evaluated. Cork processing wastewater UF experiments were also conducted under similar operating conditions to those applied to the ultrapure water solutions. Removals of chemical oxygen demand, aromatic and tannic contents, and color were determined in these experiments, and the elimination of the three model compounds in the wastewater was also followed, with the evaluation of their apparent rejection coefficients.

Polyphenols susceptible to migrate from cork stoppers to wine

Cork polyphenols susceptible to migrate into wine were studied in ten different types of natural and agglomerated cork stoppers, made of one and several pieces. Both low molecular weight polyphenols (LMWP) and ellagitannins (ET) were analysed by HPLC. Moreover, the molecular weight distribution was determined in tannic fractions. The LMWP gallic, protocatechuic, vanillic, caffeic, ferulic and ellagic acids; vanillin, protocatechuic, coniferilic and sinapic aldehydes, aesculetin and aescopoletin; and the ET castalagin, grandinin, vescalagin and roburin E were evaluated in all the samples. These LMWP and ET, found also in oak wood in different concentrations, play an important role in wine ageing. Although natural cork stoppers yielded, in general, higher amounts of polyphenols than agglomerated cork stoppers, no significant differences were found among the different types of cork stoppers.

Free radical scavenging effect of anthocyanins in red wines

Free radicals are extremely harmful to living organisms in that, they attack different constituents of the cell, leading to acceleration of the ageing process and sometimes even its destruction, or if the DNA is affected, irreversible malfunctions. It is now widely recognised that the phenolic compounds of wine have very high free radical scavenging potential. The aim of this paper is to determine which of these phenolic compounds are responsible for the strong free radical scavenging potential of red wines. In order to do so, a red wine was fractionated into phenolic fractions. After extraction and purification of these compounds from the wine, we have measured their free radical scavenging activities using an enzymatic method. The anthocyanic fraction showed a high free radical scavenging power in relation to the other tannic fractions. In order to explain this phenomenon, some pure anthocyanins were studied and a relationship between their free radical scavenging activity and their molecular structure was suggested.

Chemical Characterization of Reproduction Cork from Spanish Quercus Suber

The chemical composition of Quercus suber reproduction cork was studied in planks from three different trees at different stages of their industrial processing and in samples collected in seven locations in the three main Spanish production areas. Extracts in chloroform, methanol and water, neùtral and acid fractions of waxes, suberin, lignin, holocellulose and pentosans, and polyphenols (low molecular weight polyphenols and tannins), were quantified. Suberin was the main component in all the samples, followed by lignin and holocellulose in lower concentrations. The most affected variables throughout the industrial processing were: lignin, chloroform and water extracts and the acid fraction of waxes. These variables did not allow one to distinguish the studied trees, which are differentiated by the percentages of methanol extracts, the tannic fraction of polyphenols, the free of suberin residue and the holocellulose content. Four variables were selected as those which provided the greatest discrimination among provenances: methanol extract, low molecular weight polyphenols, desuberinized residue and acid fraction of waxes. However, the studied populations can not be clearly distinguished by their chemical composition and no relationship was found between geographical proximity of their provenances and chemical resemblance.