Stability of polyphenols in deep eutectic solvent

Proizvodnjom maslinova ulja nastaje velika količina otpada što predstavlja veliki problem u mediteranskim zemljama koji su najveći prozvođač maslinovog ulja. Osim prijetnje okolišu, otpad koji nastaje u velikim količinama (maslinova komina, lišće te otpadna voda) nakon proizvodnje, vrijedni je izvor antioksidativnih polifenola. Iako je komina masline štetna jer inhibira rasta biljaka, ona u sebi nakon proizvodnje maslinovog ulja, zadržava čak 98 % polifenola koji se izdvojeni mogu koristiti u farmaceutskoj ili kozmetičkoj industriji. Za izdvajanje polifenola se sve češće pojavljuje upotreba prirodnih eutektičkih otapala koje karakterizira netoksičnost, biorazgradivost, nezapaljivost te niska cijena. U ovom radu koristi se prirodno niskotemperaturno eutektičko otapalo (NADES) pripravljeno od tri komponente: jabučne kiseline, fruktoze i glicerola (MaFruGly) s različitim udjelima vode koji omogućavaju uspješnu ekstrakciju fenola. Nakon provedene ekstrakcije praćena je stabilnost izdvojenih polifenola. Dobiveni rezultati pokazuju da je obzirom na smanjenje viskoznosti poželjno dodati veću količinu vode u NADES. Međutim dodatkom više od 50 mas % vode dolazi do degradacije NADES-a, ali i smanjene stabilnosti ekstrakta. Također, veće količine vode pogoduju nastanku gljiva. Dobivanje stabilnih ekstrakata (konstantne koncentracije polifenola i dobre mikrobiološke stabilnosti) otvara mogućnost direktne primjene ekstrakata u kozmetici.The production of olive oils results in a large amount of waste, which is a major problem in the Mediterranean countries that are the largest producers of olive oil. In addition to the threat to the environment, waste generated in large quantities (olive pomace, leaves and waste water) after production, are valuable sources of antioxidant polyphenols. Although olive pomace is harmful because it inhibits plant growth, it retains up to 98 % of polyphenols that can be used in the pharmaceutical or cosmetic industry. For the extraction of polyphenols, the use of natural eutectic solvents is increasingly encountered, characterized by non-toxicity, biodegradability, nonflammability and low price. In this paper a low temperature eutectic solvent is prepared from three components: malic acid, fructose and glycerol (MaFruGly) with different water contents that allow successful extraction of phenols. After the extraction was carried out, the stability of the isolated polyphenols was followed. The results obtained show that, in view of the decrease in viscosity, it is desirable to add a larger amount of water to NADES. However, with the addition of more than 50 % of water, NADES degradation occurs, but also reduces stability of the extract. Also, larger amounts of water favor the emergence of fungus in the samples. Obtaining stable extracts (constant concentration of polyphenols and good microbiological stability) opens the possibility of direct application of extracts in cosmetics