SummaryIntroduction: Fireweed (Epilobium angustifolium (L.) Holub) is a common weed growing on meadows, roadside and agricultural wasteland, creating vast, rapidly spreading fields.Objective: The aim of the study was to evaluate the antioxidant activity of extracts from fresh fireweed, harvested at three ripening stages.Methods: Analysis of antioxidative activity was carried out by DPPH, ABTS and FRAP methods. Total polyphenol and total flavonoid content were also determined. Plant material was extracted using ultra-sound-assisted green extraction technique with methanol, ethanol and isopropanol at different concentrations and water.Results: The highest antioxidant activity evaluated by DPPH, ABTS and FRAP was found for the extracts prepared in 70% ethanol. The highest content of total polyphenols were observed in extracts in 70% ethanol, whereas the highest content of flavonoids extracts in undiluted methanol.Conclusion:Epilobium angustifolium harvested at fruit ripening stage seems to be a valuable source of antioxidants.

Introduction: Hop (Humulus lupulus L.) is a common plant in Europe, with many beneficial health effects. In addition to the use in brewing, hops are a valuable source of active substances used in conventional and folk medicine, such as humulones and lupulones, as well as antioxidants, including phenolic compounds.Objective: The aim of the study was to evaluate and compare the antioxidant activity of alcoholic extracts of fresh hop leaves collected in 2017 and 2018. Material and methods:The raw material consisting of fresh hop leaves was extracted using ultrasoundassisted extraction. Methyl, ethyl and isopropyl alcohol at three concentrations were used as extractants. The antioxidant activity of extracts was determined using DPPH and FRAP methods. Total phenolic content was evaluated using the Folin-Ciocalteu technique. Results:All the extracts showed antioxidant potential as well as the phenolic content. Regardless of the harvesting year and methods of evaluation, the highest antioxidant activity and the total polyphenol content were observed for extracts prepared in undiluted methanol, obtained during one hour lasting extraction. Conclusion:The results of the studies have suggested that hop leaves can be a potential source of healthpromoting antioxidants.

Background. The supplementation of antioxidants, in particular those of plant origin, may help to prevent the development of diseases caused by oxidative stress. Therefore, it is important to study plants for their antioxidant contents. Up to now, only a few reports on the antioxidant activity of different varieties and parts of grapefruit have been published. Therefore, the aim of this study was to evaluate the antioxidant potential of different parts and varieties of grapefruit. Moreover, the impact of different extraction parameters on the activity of the obtained extracts was estimated. Materials and methods. Extracts of albedo, flavedo and flesh from three varieties of grapefruit-red, white and sweetie-were obtained using ultrasound-assisted extraction (time-5, 10, 15 and 30 minutes; solventsdistilled water as well as 20, 40, 70 and 96% (v/v) ethanol). The samples were evaluated using the DPPH, ABTS, FRAP and Folin-Ciocalteu methods. Results. The extracts of peel (in particular, those of albedo) showed higher antioxidant potential than the samples of flesh. In the majority of cases, the highest potential in the group of flesh and flavedo extracts was observed in the sweetie samples. The highest activity in the group of albedo samples was found in the white grapefruit extracts. Parameters such as the type of solvent and the extraction time had an impact on the antioxidant activity of the obtained extracts. Conclusion. Grapefruit, in particular their peels, could be valuable sources of natural antioxidants. However, more detailed studies on the antioxidant properties of the studied plants are required.

Summary Introduction: Antioxidants, isolated from different plant parts, are widely used due to their ability to prevent the development of so-called oxidative stress. Sea buckthorn (Hippophae rhamnoides L.) is one of the plants with expected antioxidant properties. Objective: The aim of the study was to evaluate the antioxidant activity of ethanolic, methanolic and acetonic extracts of H. rhamnoides leaves, ripe and unripe fruits obtained by ultrasound-assisted extraction. Methods: To estimate the antioxidant potential of the extracts the DPPH, FRAP, ABTS and Folin-Ciocalteu methods were applied. Moreover, the influence of the extrahent, as well as extraction time, on this activity was evaluated. Results: Sea buckthorn leaf extracts showed higher activity, contrary to the fruit extracts. Moreover, higher activity of ripe fruit extracts compared to unripe material extracts was found. To obtain the highest content of antioxidants in the extracts, ultrasound-assisted extraction for 60 min with methanol should be applied. Conclusions: The presented in vitro results could lead to the conclusion that H. rhamnoides seems to be a valuable source of antioxidants to be applied in various branches of industry.

Background. The search for new sources of natural antioxidants is very important because many diseases are caused by oxidative stress. Fruit which contain antioxidants are an important part of a healthy diet. The aim of this study was to evaluate the antioxidant activity of extracts of both the fresh and frozen peel and the flesh of Garcinia mangostana L. Materials and methods. The extracts from the fresh and frozen peel and the flesh of mangosteen were prepared by ultrasound-assisted extraction using 20%, 40%, 70% and 96% (v/v) ethanol for 15, 30 or 60 minutes. The antioxidant potential was evaluated by the DPPH, ABTS, CUPRAC, FRAP and FIC methods, whereas the total phenolic content was measured using the Folin-Ciocalteu (F-C) technique. The contents of anthocyanins and flavonoids in the peel extracts were also determined. Results. In most cases, the highest antioxidant activity was observed in the fresh peel samples. It was higher than the antioxidant potential of the frozen peels and the fresh and frozen flesh. The ultrasound-assisted extraction, in particular those lasting 30 or 60 minutes and using ethanol in concentrations higher than 20% (v/v), seemed to be an effective extraction process. Conclusion. The obtained results suggest that G. mangostana, in particular its peels, could be a valuable source of antioxidants. The extraction parameters, such as the time or solvent concentration, as well as the type of plant material, had an impact on the tested properties of the extracts. However, more detailed studies on the antioxidant activity of the studied plants are required.