Background: Green, black and yellow tea leaves are rich in phenolic compounds that are known for their antioxidant activity thus beneficial effect on human health. In practice, different methods are used to determine antioxidant activity. The objective of this study was to determine content of phenols, flavonoids and tannins, as well as antioxidant activity of tea leaves. Results: Green, yellow and black tea leaves (intact and pulverised leaves) were used for extraction by methanol or acidified methanol. Spectrophotometric methods were used for determination of selected parameters. Antioxidant activity was determined in extracts and pulverised tea leaves by application of 2,2-diphenyl-1-picrilhydrazyl (DPPH) and 2,2′azinobis-(3-ethylbenzthiazoline-6-sulphonic acid (ABTS) free radicals. For determination of antioxidant activity of the pulverised leaves, 'QUENCHER' method was used. The method is based on the direct treatment of dry sample with free radicals. Extracts obtained by extraction of pulverised tea leaves with acidified methanol had the highest phenolic content (3.823, 4.226 and 6.829 g/kg for green, black and yellow tea, respectively). In methanol extracts, phenol content decreased in order yellow > green > black tea and, in acidified methanol extracts, yellow > black > green tea, regardless of particle size of tea leaves for extraction. Flavonoid and tannin contents followed the same tendency as phenol content. The highest antioxidant activity had acidified methanol extracts of pulverised tea leaves, regardless of used method (DPPH and ABTS). Results of antioxidant activity obtained with 'QUENCHER' method were compared with results of acidified methanol extracts. Green and yellow tea had higher antioxidant activity when 'QUENCHER' method was used in contrast to the black tea where higher antioxidant activity was determined in extract. Conclusions: Particle size and extraction solvent had high influence on total phenolic compounds, total flavonoid and tannin content as well as on antioxidant activity. Also, antioxidant activity of samples highly depended on used free radicals and sample preparation prior their application.

Antimicrobial activity of Usnea barbata especially against bacteria involved in pathogenesis of various skin conditions has been well documented in literature. Nevertheless, there are no papers dealing with formulation of its isolates into topical preparations for treatment of skin infections. In present study, alkyl polyglucoside (APG)-based vehicle was developed as carrier of U. barbata CO 2 -supercritical extract (U-SE) that demonstrated the best antimicrobial potential in preliminary screening. For comparison, chosen extract in the same concentration and using the same procedure was incorporated into a pharmacopoeial vehicle. Comparative evaluation of physicochemical stability, efficiency and safety proved APG-based vehicle to possess certain preferential features as carrier of U-SE compared to the reference one, composing a topical formulation with potential clinical relevance in treatment of skin infections.

Recently, research efforts have been directed toward medicinal plants and their extracts, as important sources of natural antioxidant. Lots of biologically active compounds are responsible for the antioxidant effects of yarrow-Achillea millefilium L. extracts. The aim of our study was to determine which of the process parameters of pressure enhanced solvent extraction of Millefolii herba is significant for its efficiency and weather there are interactions between the examined parameters. Compression time, decompression time and the number of cycles were identified as independent variables, while the content of total flavonoids, tannins and total polyphenols were selected as dependent variables. For obtaining the extract of M. herba, rich in antioxidative ingredients, compression time should be set on its higher level (2.0 min), decompression time on its lower level (1.30 min) and the number of cycles on its higher level (99).