Identifikacija in kvantifikacija polifenolnih spojin v ekstraktih tujerodnih dresnikov Fallopia japonica, F. sachalinensis in F. x bohemica - Korenčan, Martina (M. Korenčan, 2018)
V raziskavi smo preučevali razlike v vsebnostih antioksidantov v različnih tkivih japonskega dresnika (Fallopia japonica), sahalinskega dresnika (F. sachalinensis) in njunega križanca, češkega dresnika (F. x bohemica). Pripravili smo etanolne ekstrakte različnih tkiv vseh treh taksonov z ekstrakcijo v vodni kopeli (50 °C) s stresanjem in z ultrazvočno ekstrakcijo. Najvišjo antioksidativno učinkovitost (AOU) smo z metodo ABTS določili v olupkih korenin japonskega dresnika, in sicer 3 mmol/g, izraženo kot ekvivalent troloksa, najnižjo pa v steblih japonskega dresnika, 0,23 mmol/g. Merili smo tudi prooksidativno aktivnost vzorcev, kjer smo zelo visoko sposobnost redukcije Fe3+ železovih ionov določili v olupkih korenin in socvetjih vseh treh taksonov, in sicer približno 2 mmol/g, izraženo kot ekvivalent askorbinske kisline. Z metodo tekočinske kromatografije visoke ločljivosti (HPLC) smo določili prisotnost resveratrola, polidatina, katehina in epikatehina v tkivih vseh treh taksonov dresnikov. Cvet češkega dresnika je najbogatejši vir resveratrola (476 µg/g), olupek korenine japonskega dresnika pa polidatina (23,5 mg/g). Vrednosti celo presegajo vrednosti resveratrola in polidatina v rdečem grozdju. Katehina smo največ določili v korenikah sahalinskega dresnika (13,3 mg/g), epikatehina pa v socvetjih češkega dresnika (27,1 mg/g). Preverjali smo tudi stabilnost resveratrola in polidatina v odvisnosti od temperature in časa. Izkazalo se je, da sta obe spojini stabilni do 48 ur pri temperaturi do 60 °C. Izsledki raziskav bi bili lahko v pomoč pri razvoju novih prehranskih dopolnil. Differences between antioxidant capacity of Japanese knotweed (Fallopia japonica), Sakhalin knotweed (F. sachalinensis) and their hybrid Czech knotweed (F. x bohemica) were examined in this research. We prepared ethanol extracts of different tissues by extraction in water bath and by ultrasonic extraction. We measured antioxidant capacity (AOC) with ABTS method. The highest AOC was detected in rhizome sheaths of Japanese knotweed, 3 mmol TEAC/g, while the lowest was detected in stems of Japanese knotweed, 0,23 mmol TEAC/g. Prooxidant activity was determined by reduction of Fe3+ and the highest ability to reduce iron ions was determined in rhizome sheaths and flowers of all taxons (about 2 mmol of ascorbic acid equivalent). The presence of resveratrol, polydatin, catechin and epicatechin was detected by a HPLC/DAD system in all taxons of knotweed, and content of each was quantified. Czech knotweed flower is the richest source of resveratrol (476 µg/g),while Japanese knotweed rhizome sheaths are the richest source of polydatine (23,3 mg/g) and has even exceeded values of the mentioned polyphenols in red grapes. The reachest source of catechin (13,3 mg/g) are Sakhalin knotweed rhizomes, and epicatechin (27,1 mg/g) flowers of Czech knotweed. Finally, we examined stability of resveratrol and polydatine as a function of temperature and time. It turned out, that both compounds are stable up to 48 hours at temperatures up to 60 °C. Outcomes of this research may help to develop new dietary supplements.