A study of the electrochemical activity of some macrolide antibiotics on a gold electrode in a neutral electrolyte

Abstract

The aim of the present study is to present the different reactivity of azithromycin and clarithromycin (pure and commercial) at a gold electrode in neutral electrolyte using cyclic linear sweep voltammetry under the same experimental conditions. A gold electrode was successfully used for the electrochemical qualitative and quantitative determination of azithromycin dihydrate and azithromycin from capsules (Hemomycin®) and for the separation of azithromycin from one of the excipients, lactose monohydrate. The good catalytically activity of the gold electrode was employed only for the qualitative electrochemical determination of pure clarithromycin by appearance of one cathodic and four anodic reactions, which enabled structural changes in this molecule during electrochemical reactions to be studied. Commercial clarithromycin, Clathrocyn® was qualitative determined by one reproducible anodic reaction. The activity of one of the excipients, Avicel, observed as a cathodic peak at different potential from the cathodic peak obtained with pure clarithromicin was used for the determination of its presence in Clathrocyn® tablets. FTIR Analysis showed the apparent changes in structure of pure clarithromycin, as well as in the molecule of clarithromycin in Clathrocyn® tablets. HPLC Analysis showed a significant decrease in the concentration of azithromycin, Hemomycin® clarithromycin and Clathrocyn® after the electrochemical reactions.

U radu su prikazani rezultati ispitivanja elektrohemijske aktivnosti azitromicina i klaritromicina (čiste supstance i komercijalnog farmaceutskog proizvoda) na elektrodi od zlata u neutralnom elektrolitu. HPLC i FTIR spektroskopija su korišćene za analizu elektrolita posle elektrohemijske reakcije. Pokazano je da pod istim eksperimentalnim uslovima azitromicin i klaritromicin ispoljavaju potpuno različito elektrohemijsko ponašanje uslovljeno razlikama u strukturi makrolidnog prstena. Maksimalna vrednost visine jedinog strujnog vrha oksidacije čistog azitromicina i azitromicina u kapsuli Hemomicina® na 0,6 V u 0,05 M NaHCO3 pri 50 mV s-1 je linearna funkcija koncentracije u opsegu 0,235-0,588 mg cm-3 što je omogućilo razvijanje metode za njegovo kvalitativno i kvantitativno određivanje. Razvijena je i metoda za separaciju i kvantitativno određivanje ekscipienta, monohidrata laktoze. Kvalitativno je određen čist klaritromicin detekcijom reproduktivne četiri anodne i jedne katodne reakcije dok je klaritromicin u tableti, Clathrocyn®, kvalitativno određen jednom reproduktivnom anodnom reakcijom. FTIR analiza je pokazala uočljive promene u strukturi molekula klaritromicina. Takođe su uočene i strukturne promene posle ispitivanja klaritromicina u tableti Klatrocina®. HPLC analiza je ukazala na značajno smanjenje koncentracija azitromicina, Hemomicina®, klaritromicina i Klatrocina® u elektrolitu posle elektrohemijskih reakcija.