Michał Sójka

The structure, occurrence and biological activity of ellagitannins: a general review.

The present paper deals with the structure, occurrence and biological activity of ellagitannins. Ellagitannins belong to the class of hydrolysable tannins, they are esters of hexahydroxydiphenoic acid and monosaccharide (most commonly glucose). Ellagitannins are slowly hydrolysed in the digestive tract, releasing the ellagic acid molecule. Their chemical structure determines physical and chemical properties and biological activity. Ellagitannins occur naturally in some fruits (pomegranate, strawberry, blackberry, raspberry), nuts (walnuts, almonds), and seeds. They form a diverse group of bioactive polyphenols with anti-inflammatory, anticancer, antioxidant and antimicrobial (antibacterial, antifungal and antiviral) activity. Furthermore, they improve the health of blood vessels. The paper discusses the metabolism and bioavailability of ellagitannins and ellagic acid. Ellagitannins are metabolized in the gastrointestinal tract by intestinal microbiota. They are stable in the stomach and undergo neither hydrolysis to free ellagic acid nor degradation. In turn, ellagic acid can be absorbed in the stomach. This paper shows the role of cancer cell lines in the studies of ellagitannins and ellagic acid metabolism. The biological activity of these compounds is broad and thus the focus is on their antimicrobial, anti-inflammatory and antitumor properties. Ellagitannins exhibit antimicrobial activity against fungi, viruses, and importantly, bacteria, including antibiotic-resistant strains such as methicillin-resistant Staphylococcus aureus.

Composition and properties of purified phenolics preparations obtained from an extract of industrial blackcurrant (Ribes nigrum L.) pomace

Summary An extract obtained from industrial blackcurrant pomace was purified and fractionated on an RP C18 column, resulting in three phenolics preparations of different composition. The phenolics in the preparations were quantified by HPLC, their anti-oxidant capacity was determined, and the preparations were subjected to HPLC-MS analysis in order to identify the bioactive compounds present. The purified preparations selected for study were an anthocyanin-rich preparation, a myricetin and quercetin glycosides-containing preparation, and an aglycon-containing preparation. All three preparations were characterised by having a high content of polyphenols. The anthocyanin-rich preparation was the most concentrated in polyphenols [> 50% (w/w)], followed by the aglycon-containing preparation [> 20% (w/w)], and finally the glycosides-containing preparation [> 9% (w/w)]. The preparations were also characterised by their high anti-oxidant capacity, which was > 3,100 µM TEAC g−1 (TEAC = Trolox Equivalent Anti-oxidant Capacity) for all preparations. The HPLC-MS study confirmed that the anthocyanin-rich preparation was composed of the following anthocyanins: delphinidin-3-glucoside, delphinidin-3-rutinoside, cyanidin-3-glucoside, and cyanidin-3-rutinoside. The aglycon preparation contained four aglycons, of which myricetin and quercetin were predominant, and kaempferol and isorhamnetin were present in lower amounts. The glycosides-containing preparation was found to be the most interesting, since it contained myricetin, quercetin, kaempferol, and isorhamnetin glycosides. Myricetin and quercetin galactosides were also detected in blackcurrant extract for the first time. Moreover, the presence of nitrile-containing compounds, two acylated anthocyanins, and one auron-type compound was detected.

Antifungal Activity of Lactobacillus sp. Bacteria in the Presence of Xylitol and Galactosyl-Xylitol

Lactic acid fermentation is a natural method of antimicrobial food protection. Antagonistic activity of Lactobacillus sp. bacteria, taking part in this process, is directed mainly against the same or other microorganisms. In this work we determine the impact of the presence of xylitol and galactosyl-xylitol on the antagonistic activity of 60 Lactobacillus sp. strains against indicator molds (Alternaria alternata, Alternaria brassicicola, Aspergillus niger, Fusarium latenicum, Geotrichum candidum, and Mucor hiemalis) and yeasts (Candida vini). We used double-layer method to select antifungal strains of Lactobacillus bacteria and poisoned medium method to confirm their fungistatic properties. Additionally, we examined the inhibition of Alternaria brassicicola by Lactobacillus paracasei ŁOCK 0921 cultivated with xylitol or galactosyl-xylitol directly on wild cherries. The presence of xylitol and its galactosyl derivative led to increase of spectrum of antifungal activity in most of the studied plant-associated lactobacilli strains. However, no single strain exhibited activity against all the indicator microorganisms. The antifungal activity of Lactobacillus bacteria against molds varied considerably and depended on both the indicator strain and the composition of the medium. The presence of xylitol and galactosyl-xylitol in the growth medium is correlated with the antifungal activity of the studied Lactobacillus sp. bacteria against selected indicator molds.

Characterisation of the chemical composition of scab-resistant apple pomaces.

Summary Pomaces obtained during the production of cloudy or clear juice from scab-resistant apple cultivars (28 harvested in 2006, and 23 harvested in 2007) were studied as a source of nutritionally important components. It was shown that the average yield of pomace during the production of cloudy juice was 6.4% (w/w), and 4.9% (w/w) for clear juice pressing. The average total dietary fibre (TDF) contents were 48.4% (w/w) and 52.4% (w/w) for cloudy and clear juice pomaces, respectively. Ten pomaces from cloudy apple juice production, and 12 obtained from clear juice production, contained ≥ 2,000 mg kg−1 of polyphenols.‘Ariwa’ and ‘Rajka’ are apple cultivars suitable for juice production and their pomaces are characterised by having high contents of TDF [50.9% (w/w) and 51.1% (w/w), respectively], with aboveaverage polyphenol and quercetin glycoside concentrations. The mean contents of quercetin glycosides for pomaces from all apple cultivars was 994 mg kg−1 after clear juice production, and 908.2 mg kg−1 after cloudy juice production. ‘Topaz’, which became a popular commercial apple cultivar in Europe, was the best source of health-promoting components. Its pomace was the richest source of polyphenols among all 28 cultivars studied. It contained ≥ 2,000 mg kg−1 quercetin glycosides in both its clear and cloudy juice pomaces.

Transfer and Mass Balance of Ellagitannins, Anthocyanins, Flavan-3-ols, and Flavonols during the Processing of Red Raspberries (Rubus idaeus L.) to Juice

The putative health benefits of raspberries and raspberry-based products are potentially attributable to the presence of polyphenolic compounds, such as ellagitannins, anthocyanins, flavanols, and flavonols. Their content in the products of raspberry processing into juice may be affected by the fruit cultivar, technological process parameters, and the properties of the polyphenolics themselves. The objective of the study was to investigate the composition and quantity of the above polyphenolics in raspberries and the products of their processing (that is, juice and press cake, including its seed and seedless fractions). The study also examined the relationship between the molecular mass of ellagitannins and their transfer to juice. The average percentage contributions of ellagitannins, anthocyanins, flavanols, and flavonols to total polyphenolics in the fruits were 64.2%, 17.1%, 16.9%, and 1.8%, respectively. Analysis of raspberry products showed that the dominant compounds in juice were anthocyanins, with 65.1% contribution to total polyphenolics, while in raspberry press cake, they were tannins (98.0%, mainly ellagitannin including lambertianin C and sanguiin H-6). As shown by our mass-balance calculations, on average, 68.1% of ellagitannins and 87.7% of flavanols were retained in press cake, especially in its seedless fraction. In addition, a significant negative correlation was found between the molecular mass of ellagitannins and their transfer to juice. An increase in molecular mass from 1568 to 2805 Da resulted in a more than 10-fold decrease in ellagitannin transfer.

Ellagitannins and Flavan-3-ols from Raspberry Pomace Modulate Caecal Fermentation Processes and Plasma Lipid Parameters in Rats

Raspberry pomace is a source of polyphenols, which nutritional and health promoting properties are not sufficiently known. The aim of this 8-weeks study was to scrutinize if raspberry extracts (REs) with different ellagitannins to flavan-3-ols ratios might favorably affect the caecal fermentation processes and blood lipid profile in rats. Forty male Wistar rats were fed with a standard diet or its modification with two types of REs (E1 and E2) characterized by different ratios of ellagitannins to flavan-3-ols (7.7 and 3.1 for E1 and E2, respectively) and added to a diet at two dosages of polyphenolic compounds (0.15 and 0.30% of a diet; L and H treatments, respectively). Irrespective of polyphenols dietary level, both REs reduced the activity of bacterial β-glucuronidase, increased production of butyric acid in the caecum and reduced triacylglycerols in blood plasma. The E1 treatment at both dosages caused more effective reduction in the concentration of ammonia and elevated acetate level in the caecal digesta than E2. On the other hand, only the E2 treatment lowered value of the atherogenic index when compared with control group. When comparing dosages of REs, a higher one was more potent to reduce the activity of bacterial β-glucosidase, β-, α-galactosidase and lowered value of the HDL profile in plasma. To conclude, REs may favorably modulate the activity of the caecal microbiota and blood lipid profile in rats; however, the intensity of these effects may be related to the dosages of dietary polyphenols and to their profile, e.g., ellagitannins to flavan-3-ols ratio.

Effects of Dietary Addition of a Low-Pectin Apple Fibre Preparation on Rats

Abstract The aim of this study was to scrutinise if the dietary addition of a low-pectin fibre preparation obtained from apple pomace, the by-product of apple concentrate processing, is able to favourably affect the gut metabolism, antioxidant status and blood bio-markers of the organism, as it takes place when apple fibre is present in the diet as an unprocessed ingredient. The nutritional experiment was performed on rats allocated to 2 groups of 10 animals each and fed for 2 weeks with either a control cellulose-containing diet or an experimental low-pectin apple fibre-containing diet. To induce metabolic disorders a diet rich in saturated fat and fructose was used in both diet-specific groups. The dietary apple fibre preparation (AFP) significantly reduced the activity of sucrase and maltase in the mucosa of the small intestine. In the caecal digesta, the dietary AFP significantly increased bacterial α-glucosidase and α-galactosidase activity, whereas bacterial β-glucuronidase activity was significantly reduced. Also, the content of short chain fatty acids in the caecal digesta was significantly increased after the AFP supplementation. In the blood serum, the dietary AFP significantly reduced the glucose concentration, and decreased the ratio of total cholesterol to HDL cholesterol. In conclusion, the tested dietary AFP is still able to favourably affect the gut metabolism and can also ameliorate blood glucose concentration, which seems to be related to the inhibition of mucosal disaccharidase activities. However, the analysed preparation has no influence on the antioxidant status of the organism and may trigger adverse effects on cholesterol metabolism.

Ellagitannins from Rubus idaeus L. Exert Geno- and Cytotoxic Effects against Human Colon Adenocarcinoma Cell Line Caco-2

Ellagitannins possess several biological activities, including anticancer properties. The goal of the present study was to investigate the cyto- and genotoxic activities of a red raspberry ellagitannin preparation (REP) in the concentration range of 2.5-160 μg/mL, as well as that of the main individual raspberry ellagitannins, sanguiin H-6 (SH-6, 12.8-256 μM) and lambertianin C (LC, 9.3-378 μM), against human colon adenocarcinoma cell line Caco-2. The ellagitannin concentrations used in the study correspond to those found in foodstuffs containing raspberry fruit. REP, SH-6, and LC exhibited strong concentration-dependent genotoxic properties, inducing DNA damage ranging from 7.3 ± 1.3 to 56.8 ± 4.3%, causing double-strand breaks and oxidation of DNA bases. At IC50 (124 μg/mL) the REP affected the nuclear morphology and induced the apoptosis of Caco-2 cells. Because the REP has been found to possess chemopreventive activity, it can be used as a natural food additive to enhance the health benefits of foodstuffs.

Naringenin Schiff base: antioxidant activity, acid–base profile, and interactions with DNA

A Schiff base derived from naringenin (NTSC) and its complex with Cu(II) ([Cu(H3L)(OAc)]·H2O, Cu(II)–NTSC) have been synthesized and characterized by physicochemical and spectroscopic methods. EPR studies confirmed that nitrogen, oxygen, and sulfur are the donor atoms bound to Cu(II) in the complex. The geometry of the complex has been modelled using DFT methods. Furthermore, naringenin and NTSC were used for the formation of Cu(II) complexes in solution, for comparison of biological activities. Antioxidant studies confirmed better radical scavenging activity of both NTSC and its Cu(II) complex compared to naringenin. The interaction of these compounds with calf thymus DNA was monitored by UV–Vis spectroscopy.

Ellagitannins from Raspberry (Rubus idaeus L.) Fruit as Natural Inhibitors of Geotrichum candidum

The paper presents the chemical characteristics of ellagitannins isolated from raspberry (Rubus idaeus L.) fruit and their in vitro and in situ antifungal activity against Geotrichum candidum ŁOCK 0511. The study investigated a complex preparation containing various raspberry ellagitannins at a concentration of 86% w/w, as well as pure lambertianin C and sanguiin H-6. The ellagitannin preparation was obtained by extracting raspberry press cake and purifying the extract using Amberlite XAD resin, while individual compounds were isolated by means of preparative HPLC. The complex preparation was analyzed for the content of ellagitannins, anthocyanins, and flavan-3-ols using HPLC and LC-MS. The antifungal activity of the complex ellagitannin preparation and the isolated ellagitannins was determined for the strain Geotrichum candidum. The MIC and MFC values (10.0 mg/mL and 30.0 mg/mL, respectively) were found to be the same for lambertianin C, sanguiin H-6, and the complex ellagitannin preparation. The fungistatic activity of the studied ellagitannin preparation at a concentration of 10 mg/mL, as determined by the poisoned medium method, was 65.2% following 6 day incubation of Geotrichum candidum, with the linear growth rate of only 16.2 mm/day. The corresponding parameters for the control sample were 0% and 56 mm/day, respectively. The study demonstrated both in vitro and in situ antifungal activity of raspberry ellagitannins against Geotrichum candidum.