2018, Vol. 16, Special Issue 2
Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/5381
Sirvi
Sirvi 2018, Vol. 16, Special Issue 2 Märksõna "antioxidant activity" järgi
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Kirje Bioactive compounds in herbal infusions(2018) Augšpole, I.; Dūma, M.; Ozola, B.Herbal teas are very popular and known as important source of biologically active compounds. Some of popular Latvian herbal teas: Calendula (Calendula officinalis L.), Matricaria chamomilla (Matricaria chamomilla), Lady's-mantle (Alchemilla vulgaris L.), Jasmine (Jasminum officinale L.), Yarrow (Achillea millefolium L.) and Linden flowers (Tilia spp.) were selected for analysis. This study was carried out with the aim to investigate the effect of extraction time (10, 15, 20 min) on the content of total flavonoids and total phenols as well as antioxidant activity of herbal tea extracts. The infusions were prepared by usual domestic preparation technique using ground air-dried plant materials and boiling deionized water (0.055 µS cm-1 ) for extraction. Content of total flavonoids, total phenols and antioxidant activity was determined spectrophotometrically. Dry matter content was determined in lyophilized herbal infusions. The obtained results indicated that extraction time did not affected the content of biologically active compounds in the herbal infusions significantly (P > 0.05). The highest level of flavonoids was found in Jasmine and Lady's-mantle infusions (average 104.98 ± 9.21 mg quercetin equivalent 100 g -1 and 115.28 ± 5.25 QE mg 100 g -1 respectivelly), while the lowest was determined in Matricaria chamomilla extract – (average 70.10 ± 4.68 QE mg 100 g -1 ). Lady's-mantle tea contained the largest amount of total phenols (average 4126.62 ± 26.24 mg gallic acid equivalents 100g-1 ), the lowest – Calendula tea 1828.04 ± 10.37 mg GAE 100 g -1 ). Data analysis showed a close linear positive correlation between the content of total flavonoids and total phenols in herbal infusions (R2 = 0.872; r = 0.934) with the probability of 99%. In general, all samples tested in this study, demonstrated high level of antioxidant activity (from 75.04 to 91.54 mmol Trolox equivalents 100 g-1 ). Results of the present experiments demonstrated that content of dry matter in analysed herbal teas was significantly different (P < 0.05).Kirje Comparison of phenolic compounds and antioxidant activity of fresh and freeze-dried potatoes(2018) Zarins, R.; Kruma, Z.; Tomsone, L.; Kampuse, S.; Skrabule, I.; Konosonoka, I.H.Potatoes (Solanum tuberosum L.) contain a wide range of compounds with health benefits, and different techniques have been developed for the determination of these compounds. Freeze-drying is a common method for the preservation and preparation of samples for the analyses of bioactive compounds, but it is well known that drying influences the composition of food products. The aim of the current study was to compare phenolic compounds and antioxidant activity of fresh and freeze-dried potatoes. In the experiment 11 cultivar potatoes grown in experimental fields of the Institute of Agricultural Resources and Economics in 2016 were analysed. Potatoes were freeze-dried. Homogenized fresh and freeze-dried samples were extracted with an ethanol/water (80/20 w/w) solution. Total phenolic content (TPC) was determined using the Folin-Ciocalteu method, and the antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH˙) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. The highest TPC and radical scavenging activity were determined in cultivars ‘Peru Purple’ and ‘Blue Congo’ potatoes. Freeze-drying influenced all the tested parameters but more significantly the TPC, and for certain cultivars a reduction of more than 30% was observed. A strong correlation between TPC, DPPH and ABTS in fresh and freeze-dried samples was observed, r = 0.81, r=0.93, r = 0.92, respectively. It could be concluded that the effect of freeze-drying on TPC and antioxidant activity is cultivar dependent.Kirje Effect of germination and extrusion on the phenolic content and antioxidant activity of raw buckwheat (Fagopyrum esculentum Moench)(2018) Beitane, I.; Krumina–Zemture, G.; Sabovics, M.The aim of the research was to determine the total phenolic content, antioxidant activity and phenolic compounds in raw and germinated common buckwheat grain and their extruded products in order to estimate the effect of germination and extrusion on the total phenolic content, antioxidant activity and phenolic compounds in buckwheat. A total of 10 buckwheat samples were analysed, where the raw buckwheat grain was the control sample, four samples were germinated and then extruded. The total phenolic content was determined using the Folin– Ciocalteu assay. The antioxidant activity was determined using a micro plate assay and phenolic compounds with Liquid Chromatography –Time of Flight Mass Spectrometer method. The results showed that germination of buckwheat significantly affected the total phenolic content, antioxidant activity, radical scavenging activity and content of phenolic compounds. The decrease of the total phenolic content, antioxidant activity, radical scavenging activity and the content of some phenolic compounds depended on germination time – 48 h of germination provided greater concentrations at the end of a 24 h germination period, whereas the content of some phenolic compounds like rutin, quercetin and vitexin increased substantially after germination, besides, the increase of phenolic compounds depended on the germination time. In total 26 different phenolic compounds were detected in raw and germinated buckwheat samples and only one compound with an m/z value 385.1282 was unidentified. The data of extrusion revealed a significant decrease of total phenolic content, antioxidant activity, radical scavenging activity and phenolic compounds content in buckwheat samples (P < 0.05). In the extruded buckwheat samples novel phenolic compounds like 4–hydroxybenzoic acid, homovanillic acid, catechin, ferulic acid, and hyperoside were detected.Kirje The possibility of using powdered sea - buckthorn in the development of bakery products with antioxidant properties(2018) Nilova, L.; Malyutenkova, S.The article examines ways of increasing the antioxidant capacity of bakery products (referred to here as BP) by adding powdered peel, powdered seeds, and powdered marc produced from sea - buckthorn berries. Three different versions of BP were developed with the maximum addition of the following powders: from the peel (3%), from the marc (5%) with a sugar content of 14.5%; and from seeds (5%) with a sugar content of 5%, and with a potato flake content of 5%. BPs with the addition of sea - buckthorn powders were bake d at two temperature regimes: 200°C and 220 °C. The content of phenolic compounds, flavonoids, and ascorbic acid were determined for the sea - buckthorn powder, for the crust of BP, and in BP crumbs. The antioxidant activity of BP was determined by the use o f two methods: by chemiluminescence, and by their reaction to the DPPH - radical. Cyclic amides (lactams) were determined in BP crusts and crumbs with the use of the IR spectroscopy method. The AOA of powdered sea buckthorn depended upon the volume of phenol ic compounds and ascorbic acid in them: peel > marc > seeds. The antioxidant properties of BPs decreased in the following order and were aligned the following way: BP with marc > BP with peel > BP with seeds. They displayed higher AOA levels than was calcu lated in theoretical tests, depending upon the volume of powders in the recipe. An increase of the baking temperature led to a loss of phenolic compounds and vitamin C, as well as to the formation of poly lactams. BP baked at the temperature regime of 200 °C displayed the greatest AOA levels.