Draženka Komes

Phenolic content and antioxidative capacity of green and white tea extracts depending on extraction conditions and the solvent used

The efficiencies of different solvents in the extraction of phenolics from bagged and loose leaves of white and green tea, after different extraction times, as well as the antioxidative capacity of the obtained extracts, were investigated. The developed HPLC method has the potential to separate and determinate 17 phenolics widely distributed in plants, but in investigated tea extracts only four catechins and traces of three flavonols and one flavone were separated and detected based on comparison with authentic standards. The extraction efficiency of phenolics depended strongly on the time of extraction and the solvents used. The extraction of catechins from green tea was significantly affected by the form (bagged or loose) of the tea, whereas this effect was shown not to be statistically significant for white tea. Green tea was a richer source of phenolics than was white tea. The extraction of phenolics from white tea by water could be accelerated by the addition of lemon juice. Aqueous ethanol (40%) was most effective in the prolonged extraction of catechins. The antioxidative capacity of the investigated tea extracts correlated with their phenolic content.

Comparative study of polyphenols and caffeine in different coffee varieties affected by the degree of roasting.

The bioactive composition of coffee, as one of the most popular beverages in the world, has attracted interest as a potential source of beneficial bioactive compounds, especially polyphenols and caffeine. Since the content of these compounds is affected by the processing conditions, the objective of this study was to determine the content of polyphenolic compounds and caffeine in four different coffee varieties: Minas and Cioccolatato (Coffea arabica), and Cherry and Vietnam (Coffea canephora syn. Coffea robusta), roasted by three varying degrees (light, medium and dark). The content of the polyphenolic compounds and the antioxidant capacity of coffees were determined using UV/Vis spectrophotometric methods, while the content of chlorogenic acid derivatives was determined using HPLC analysis. The caffeine content was determined by means of two spectrophotometric methods, as well as HPLC analysis. Additionally, raw caffeine was also obtained by an isolation procedure with chloroform. Cherry coffee, a variety of C. canephora exhibited the highest overall content of total phenols (42.37mg GAE/g), followed by Minas coffee, while Cioccolatato contained the lowest TPC (33.12mg GAE/g). Cherry coffee also exhibited the highest content of individual classes of polyphenols (flavan-3-ols, procyanidins and tannins), while the highest content of chlorogenic acid (CQA) derivatives was determined in Minas and Cioccolatato coffees (C. arabica). The highest content of total and individual polyphenolic compounds was determined in coffees roasted in both light and medium roasting conditions, which was also observed for the content of CQA derivatives and antioxidant capacity of roasted coffees. The highest caffeine content in the coffee samples was determined by employing the HPLC analysis (0.06-2.55%). Light roasted Cherry coffee contained the highest overall content of caffeine among all coffees, which exhibited a decrease with intensified roasting.

Diversity of aroma patterns in wild and cultivated Fragaria accessions

Plant breeders are interested in strawberry species as donors of volatile compounds in breeding programmes because of the diversity and intensity of wild strawberry aroma. Therefore, the topic of this paper is the prospective analysis of four accessions of four wild strawberry accessions in comparison to a standard cultivar of Fragaria × ananassa Duch. by using human sensory, gas chromatography mass spectrometry (GCMS) and gas chromatography–olfactometry (GCO). The wild species have higher aroma intensities compared with the cultivated one. The flavour quality differs significantly. Semiquantitative GC analysis revealed that F. × ananassa cv. ‘Elsanta’ has the lowest content of volatile compounds whereas Fragaria moschata L. ‘Cotta’ has the highest. The aroma impressions, measured by GCO, support the findings of GCMS analyses. The nasal impact frequency (NIF)-profiles of the wild types are more manifold and of higher intensities than those of the cultivated F. × ananassa cv. ‘Elsanta’ which corresponds with the overall flavour impression when tasting the fresh fruits.

Phenolic composition and antioxidant properties of some traditionally used medicinal plants affected by the extraction time and hydrolysis.

INTRODUCTION Polyphenolic phytochemicals in traditionally used medicinal plants act as powerful antioxidants, which aroused an increasing interest in their application in functional food development. OBJECTIVE The effect of extraction time (5 and 15 min) and hydrolysis on the qualitative and quantitative content of phenolic compounds and antioxidant capacity of six traditionally used medicinal plants (Melissa officinalis L., Thymus serpyllum L., Lavandula officinalis Miller, Rubus fruticosus L., Urtica dioica L., and Olea europea L.) were investigated. METHODOLOGY The content of total phenols, flavonoids, flavan-3-ols and tannins was determined using UV/Vis spectrophotometric methods, while individual phenolic acids, flavones and flavonols were separated and detected using HPLC analysis. Also, to obtain relevant data on the antioxidant capacity, two different assays, (2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging and ferric reducing/antioxidant power (FRAP) assays were used. RESULTS The extraction efficiency of phenolics, as well as the antioxidant capacity of plant extracts, was affected by both prolonged extraction and hydrolysis. The overall highest content of phenolic compounds was determined in hydrolyzed extract of blackberry leaves (2160 mg GAE/L), followed by the non-hydrolyzed extract of lemon balm obtained after 15 min of extraction (929.33 mg GAE/L). The above extracts also exhibited the highest antioxidant capacity, while extracts of olive leaves were characterized with the lowest content of phenolic compounds, as well as the lowest antioxidant capacity. The highest content of rosmarinic acid, as the most abundant phenolic compound, was determined in non-hydrolyzed extract of lemon balm, obtained after 15 min of extraction. Although the hydrolysis provided the highest content of polyphenolic compounds, longer extraction time (15 min) was more efficient to extract these bioactives than shorter extraction duration (5 min). CONCLUSION The distribution of detected phenolic compounds showed a wide variability with regard to their botanical origin. Examined medicinal plants showed to be a valuable supplement to a daily intake of bioactive compounds.

Bioactive composition and antioxidant potential of different commonly consumed coffee brews affected by their preparation technique and milk addition.

Coffee is one of the most popular beverages in the world, prepared and consumed in many different ways. Taste, aroma and composition of the coffee brew vary depending on the preparation method. Therefore, this study investigates the effect of different brewing methods on the polyphenol and methylxanthine composition and antioxidant capacity of thirteen different coffee brews. The content of total phenols and flavonoids was determined spectrophotometrically and the content of chlorogenic acid derivates (3-CQA, 4-CQA and 5-CQA) and caffeine using the high performance liquid chromatography (HPLC-PDA). Antioxidant capacity of coffee brews was evaluated by using the ABTS (2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)) and FRAP (ferric-reducing antioxidant power) assays. Instant coffee brews showed the highest values in content of total phenols, chlorogenic acid derivates, caffeine and antioxidant capacity, which significantly decreased by milk addition. The antioxidant capacity of coffee brews was in compliance with the total phenol content and content of chlorogenic acid derivates.

Improving the controlled delivery formulations of caffeine in alginate hydrogel beads combined with pectin, carrageenan, chitosan and psyllium

Alginate-based blends consisting of carrageenan, pectin, chitosan or psyllium husk powder were prepared for assessment of the best formulation aimed at encapsulation of caffeine. Alginate-pectin blend exhibited the lowest viscosity and provided the smallest beads. Alginate-psyllium husk blend was characterised with higher viscosity, yielding the largest bead size and the highest caffeine encapsulation efficiency (83.6%). The release kinetics of caffeine indicated that the porosity of alginate hydrogel was not reduced sufficiently to retard the diffusion of caffeine from the beads. Chitosan coated alginate beads provided the most retarded release of caffeine in water. Morphological characteristics of beads encapsulating caffeine were adversely affected by freeze drying. Bitterness intensity of caffeine-containing beads in water was the lowest for alginate-psyllium beads and chitosan coated alginate beads. Higher sodium alginate concentration (3%) for production of hydrogel beads in combination with psyllium or chitosan coating would present the most favourable carrier systems for immobilization of caffeine.

Comparison of Conventional and Ultrasound Assisted Extraction Techniques of Yellow Tea and Bioactive Composition of Obtained Extracts

Yellow tea is the least investigated type of tea (Camellia sinensis), therefore, this study is focused on characterization of bioactive content of yellow tea extracts as well as application of inovative extraction techniques (ultrasound bath and probe) compared to conventional extraction, in water and aqueous ethanol media. Comparison of obtained extracts was based on total flavonoid (TFC) and nonflavonoid (TNC) content, HPLC analysis of individual polyphenols and methylxanthines, and antioxidant capacity. The highest TFC was detected in extracts obtained by ultrasound probe assisted extraction in aqueous ethanol as an extraction medium and the lowest in extracts obtained by ultrasound bath extraction (water and aqueous ethanol) with a trend of increase with prolonged extraction time. Conventional extraction was successful when combined with 75% aqueous ethanol as an extraction medium. Results of HPLC analysis and antioxidant capacity assays were generally in compliance with these results. This study proves that ultrasound probe extraction could succesfully be used for extraction of polyphenols and methylxanthines from yellow tea.

Physical, bioactive and sensory quality parameters of reduced sugar chocolates formulated with natural sweeteners as sucrose alternatives

In this study, sugar alcohols, dietary fibers, syrups and natural sweeteners were used as sucrose alternatives in the production of reduced sugar chocolates (50% of cocoa parts) with enhanced bioactive profile. Formulated chocolates were evaluated for their physical (particle size distribution, texture) and sensory properties, sugar composition, polyphenolic compounds content and antioxidant capacity. All produced reduced sugar chocolates ensured >20% lower calorific value than conventional chocolate (prepared with sucrose). Formulated chocolates containing stevia leaves and peppermint exhibited the best sensory properties (especially with regard to mouthfeel, sweetness and herbal aroma), as well as the highest polyphenolic content and antioxidant capacity. Particle size and hardness of chocolates increased in comparison to conventional chocolate, in particular when the combination of fructose and isomalt or lactitol was used. The bioactive profile of produced chocolates was enriched with phenolic acids, flavone (luteolin and apigenin) and flavonol (quercetin) derivatives, which were not identified in control chocolate.

The Bioactive Potential of Red Raspberry (Rubus idaeus L.) Leaves in Exhibiting Cytotoxic and Cytoprotective Activity on Human Laryngeal Carcinoma and Colon Adenocarcinoma

In this article, the bioactive potential of red raspberry leaves, a by-product of this widely spread plant, mostly valued for its antioxidant-rich fruits, was determined. The polyphenolic profile and antioxidative properties of red raspberry leaf extract were determined and examined for potential biological activity. Cytotoxic effect, antioxidative/prooxidative effect, and effect on total glutathione concentration were determined in human laryngeal carcinoma (HEp2) and colon adenocarcinoma (SW 480) cell lines. SW 480 cells are more susceptible to raspberry leaf extract in comparison with HEp2 cells. The antioxidative nature of raspberry leaf extract was detected in HEp2 cells treated with hydrogen peroxide, as opposed to SW 480 cells, where raspberry leaf extract induced reactive oxygen species formation. Raspberry leaf extract increased total glutathione level in HEp2 cells. This effect was reinforced after 24 hours of recovery, indicating that induction was caused by products formed during cellular metabolism of compounds present in the extract. Comparison of the results obtained on these two cell lines indicates that cellular response to raspberry extract will depend on the type of the cells that are exposed to it. The results obtained confirmed the biological activity of red raspberry leaf polyphenols and showed that this traditional plant can supplement the daily intake of valuable natural antioxidants, which exhibit beneficial health effects.

Phytochemical Attributes of Four Conventionally Extracted Medicinal Plants and Cytotoxic Evaluation of Their Extracts on Human Laryngeal Carcinoma (HEp2) Cells

The bioactive composition and cytotoxic and antioxidative/prooxidative effects of four medicinal plants: yarrow (Achillea millefolium L.), hawthorn (Crataegus oxyacantha L.), ground ivy (Glechoma hederacea L.), and olive (Olea europea L.) on human laryngeal carcinoma cell line (HEp2) were investigated. Water extracts of these plants obtained by infusion, maceration, and decoction were characterized for their polyphenol content and antioxidant capacity. Based on the extraction efficiency of polyphenols, the final extracts were obtained whose polyphenolic profile, polysaccharides, mineral content, and cytoprotective activities were determined. The overall highest content of polyphenols and antioxidant capacity was determined in hawthorn, followed by yarrow and ground ivy, and the lowest in olive leaves extract. Phytochemical screening revealed the presence of phenolic acids, as the most abundant bioactive compounds, followed by flavonoids, flavons, and flavonols. All examined medicinal plants reduced the cell viability and reactive oxygen species formation in a dose- and time-dependent manner. Ground ivy and yarrow containing a high content of phenolic acids and polysaccharides were more efficient to decrease the cell survival when compared to olive leaf and hawthorn. Experiments confirmed the importance of polyphenolic composition rather than content of investigated plants and revealed a relationship between the polyphenolic and polysaccharide contents and antioxidant/prooxidant characters of medicinal plants.