Didelis dėmesys skiriamas natūralių antioksidantų paieškai ir įvertinimui augalinės kilmės vaistinėse ir maistinėse žaliavose. Mokslinių tyrimų objektais yra didelis skaičius augalų rūšių, ekstraktų, maisto papildų ir vaistinių preparatų. Tiriamųjų darbų našumas ir informatyvumas, be abejonės, priklauso nuo pasirinktų metodų tinkamumo, jautrumo ir efektyvumo. Darbo tikslas yra išvystyti bei įteisinti pokolonėlinę ESC-DPPH metodiką ir ją pritaikyti laisvuosius radikalus surišančių žinomų ir nežinomų junginių, esančių vaistinėje augalinėje žaliavoje, antioksidantinio aktyvumo įvertinimui. ESC išskirstyti junginiai nustatomi UV detektoriumi 275 nm ilgio bangoje; mobili fazė su analitėmis per maišymo trišakį tiekiama į reakcijos kilpą, kur 0,4 ml/min tėkmės greičiu paduodamas DPPH tirpalas. Reakcijos kilpa sujungta su UV/Vis tipo detektoriumi, matuojančiu pratekančio tirpalo absorbciją esant 520 nm bangos ilgiui. Nustatyta, jog Crataegus monogyna lapuose vyraujantis flavonoidas viteksino ramnozidas nepasižymi antioksidantiniu aktyvumu. Reikšmingiausias antioksidantas C. monogyna lapuose ir žieduose yra chlorogeno rūgštis. Didžiausiu antioksidantiniu aktyvumu Origanum vulgare augalinėje žolėje pasižymi rozmarino rūgštis. Achillea millefolium ekstraktuose identifikuotos šios analitės, turinčios radikalus surišantį aktyvumą: chlorogeno rūgštis, luteolin-7-O-gliukozidas, rutinas ir luteolinas. / The most important attention is paid to the search of natural antioxidants and their evaluation in medicinal and food raw materials of plant origin. A number of plants, their extacts, food products and medicinal preparations appear to be objects of scientific research. Effectiveness and informative character of research, undoubtedly, depend on relevance, sensitivity and efficiency of the methods chosen. Aim of this work is development and validation of post column HPLC-DPPH method as well as its application in antioxidant activity evaluation of known and unknown compounds fixing free radicals and existing in medicinal plant raw materials. HPLC separated compounds are identified at wave length of 275 nm and then the mobile phase with analytes flows by mixing tee to the reaction coil, where DPPH reagent solution is supplied. The solution flow rate – 0,4 ml/min. The reaction coil is connected with UV/Vis type detector, which measures absorption of flowing solution at wave length of 520 nm. It was dermined that vitexin rhamnoside, the dominant compound in the leaves of Crataegus monogyna, is not significant radical sacavenger. The most active antioxidant in leaves and the flowers of C. monogyna is chlorogenic acid. The most active antioxidant in Origanum vulgare raw materials is rosmarinic acid. Identified analytes in the extracts of Achillea millefolium that possessed radical scavenging properties were chlorogenic acid, luteolin-7-O-glucoside, rutin and luteolin.

This diploma thesis deals with the development of an HPLC method for the determination of selected compounds participating in enzymatic reaction leading to the formation of gallic acid. The analysed reaction mixture contains the following reagents: shikimic acid, NADP+ and shikimatedehydrogenase (SDH) extracted from parsley; the presumed product of the reaction is gallic acid. Two chromatographic methods for the determination of the above mentioned compounds were developed using C18 HPLC column and porous graphitic carbon Hypercarb column. Molecular absorption spectrometric detection in the UV range was used in all measurements. Separation on the C18 column was found particularly suitable for analysing the composition of the end products of the reaction. Because of the NADP+ and shikimic acid peak overlap it is necessary to observe absorbance at 212 and 260 nm. Shikimic acid and NADP+ can be quantified due to the fact that shikimic acid does not absorb at 260 nm while NADP+ absorb radiation at both wavelengths. Separation via Hypercarb column was found particularly suitable for analysing the process of the reaction; additional products or intermediates can be seen in chromatograms compared to the C18 method. Determination with Hypercarb column is characterized by higher sensitivity and lower limit...