Determinati on of the stability constant of methylorange/β-cyclodextrin and quercetin/β-cyclodextrin inclusion complexes

Redno uživanje antioksidantov je izjemnega pomena za zdravje človeka, saj ti delujejo kot zaviralci številnih bolezenskih stanj. Vedno zanimivejši postaja naravni antioksidant kvercetin, ki se nevede pogosto znajde na našem dnevnem jedilniku. Kvercetin pa ni znan le po svojih antioksidativnih lastnostih, temveč naj bi deloval tudi protivnetno, preprečeval srčno-žilne bolezni, zniževal krvni tlak itd. Poleg številnih pozitivnih lastnosti ima kvercetin manjšo pomanjkljivost, namreč slabo je topen v vodi. Teoretično smo preučili, da bi tvorba vključitvenega kompleksa kvercetina z β ciklodekstrinom povzročila povečanje stabilnosti in izboljšanje topnosti kvercetina v vodi. Predpostavili smo, kako bi z metodo kompleksacije z izpodrivanjem molekule metiloranža z molekulo kvercetina indirektno določili konstanto stabilnosti brezbarvne molekule kvercetina. β-ciklodekstrin ima zaradi svoje edinstvene strukture sposobnost tvorbe vključitvenega kompleksa še s številnimi drugimi gostujočimi molekulami, med drugim tudi z zelo znanim indikatorjem metiloranžem. Mehanizem tvorbe kompleksa metiloranž/β-ciklodekstrin smo proučevali na osnovi spremembe absorbance raztopine metiloranža. Pripravili smo raztopine s koncentracijo metiloranža 2,5 · 10-5 M in koncentracijo β-ciklodekstrina od 1 · 10-3 M do 5 · 10-3 M. S spektrofotometrično metodo smo v kislem mediju pri 20 °C določili konstanto stabilnosti kompleksa metiloranž/β-ciklodekstrin, ki je znašala (247 ± 22) M-1. Iz absorpcijskih spektrov smo ugotovili, da je sprememba stopnje obarvanosti raztopine sorazmerna s koncentracijo β-ciklodekstrina v raztopini metiloranža. Na podlagi rezultatov sklepamo, da je tvorba kompleksa metiloranž/β-ciklodekstrin izboljšala fizikalno-kemijske lastnosti metiloranža, ter predvidevamo, da bi z eksperimenti potrdili tudi izboljšanje lastnosti kvercetina kot posledico tvorbe vključitvenega kompleksa kvercetin/β ciklodekstrin.The regular consumption of antioxidants is very important for human health as they act as inhibitors for many diseases. There is a growing interest in the natural antioxidant quercetin, which unknowingly occurs frequently in our daily diet. Quercetin is not only known for its antioxidant properties, but is also said to have anti-inflammatory effects, prevent cardiovascular diseases, lower blood pressure, etc. Besides many positive properties, quercetin also has a small disadvantage, namely its poor water solubility. We theoretically investigated that the formation of a quercetin inclusion complex with β-cyclodextrin would lead to an increase in stability and improve the solubility of quercetin in water. We hypothesized that the stability constant of the colorless quercetin molecule would be indirectly determined by the method of complexation by displacing the methyl orange molecule with the quercetin molecule. Due to its unique structure, β-cyclodextrin has the ability to form an inclusion complex with many other host molecules, including the well-known methyl orange indicator. The mechanism of formation of the methyl orange/β-cyclodextrin complex has been studied based on the change in absorbance of the methyl orange solution. Solutions with a concentration of methyl orange 2,5 ˑ 10-5 M and a concentration of β-cyclodextrin from 1 ˑ 10-3 M to 5 ˑ 10-3 M were prepared. The constant (247 ± 22) M-1 of the methyl orange/β-cyclodextrin stability complex was determined in an acidic medium at 20 °C using a spectrophotometric method. From the absorption spectra, we found that the change in the degree of coloration of the solution is proportional to the concentration of β-cyclodextrin in the methyl orange solution. From the results we conclude that the formation of the methyl orange/β-cyclodextrin complex improved the physicochemical properties of methyl orange and we assume that experiments would also confirm the improvement of quercetin properties as a consequence of the formation of the quercetin/β-cyclodextrin inclusion complex