Evaluation of method for extraction of antioxidants from Black crowberry (Empetrum nigrum) - Stegovec, Iztok (I. Stegovec, 2021)
Black crowberry is a procumbent shrub, adapted to the harsh conditions found in the north. The berries are similar to blueberries, darker in colour with a distinct astringent taste and rich in bioactive compounds. Our aim was to evaluate three different organic solvents (ethanol, methanol, acetone) at different concentrations on extraction of these compounds, spectrophotometrically assess the total phenolics, and evaluate their thermal stability. We chose the 70% acetone, and repeated the extraction on store-bought berries and the sample we picked in the wild. We determined the total phenolic and total monomeric anthocyanin content, measured antioxidant capacity and determined the sugar content. We confirmed our hypothesis, that extractions with different solvents differ, but overthrew our claim that the 70% ethanol extraction would be the most efficient. We confirmed our hypothesis that the extracts with bioactive compounds vary in stability at different temperatures and pH values. We determined, that with increasing temperature, the activation energy decreases and the rate of the reactions increases. The results show that most likely a two step process is taking place, which points to a possibility of separating the bioactive compounds using different temperatures. For determination of exact parameters, needed for such separation, and its final confirmation, further analyses are required. Črna mahunica je pritalno jagodičevje, prilagojeno za preživetje v bolj ekstremnih razmerah na severu kontinentov. Obrodi majhne, borovnicam podobne jagode, ki so temnejše, skoraj črne in zelo trpke. Jagode so bogate z bioaktivnimi spojinami, še posebej z antioksidanti. Namen magistrskega dela je bil določiti najbolj učinkovito topilo izmed treh organskih topil (etanol, metanol, aceton) z različnimi koncentracijami, spektrofotometrično določiti skupne fenolne spojine in ovrednotiti njihovo toplotno stabilnost. Za nadaljnje analize smo izbrali 70 % aceton in postopek ekstrakcije ponovili na jagodah kupljenih v trgovini, in na vzorcu nabranem v naravi. Spektrofotometrično smo določili vsebnost skupnih fenolov, vsebnost monomernih antocianov, antioksidativno učinkovitost in vsebnost sladkorjev. Potrdili smo hipotezo, da se ekstrakcije z različnimi topili razlikujejo po uspešnosti, vendar ovrgli hipotezo, da bo najuspešnejša ekstrakcija s 70 % etanolom. Potrdili smo hipotezo, da so ekstrahirane spojine drugače stabilne pri različnih temperaturah in pH vrednostih. Določili smo znižanje aktivacijske energije in povečanje hitrosti razkroja s povišanjem temperature. Rezultati kažejo na dvostopenjski razpad, kar namiguje na možnost ločbe nekaterih spojin z uporabo različnih temperatur. Za določitev točnih parametrov, potrebnih za tako ločitev, in dokončno potrditev so potrebne nadaljnje analize.