| Abstract | Cilj je ovog završnog rada bio procijeniti doprinos proteina, aromatskih aminokiselina, fenolnih kiselina i flavonoida apsorbanciji otopina meda u ultraljubičastom području. U tu svrhu je 14 različitih uzoraka meda (3 meda kadulje, 3 lipe, 3 medljikovca, 3 meda bagrema i 2 meda kestena) podvrgnuto razdvajanju sastavnih molekula primjenom gel filtracije na Sephadexu G-25 superfine, pri čemu su prikupljene frakcije analizirane na intenzitet apsorbancije pri 230, 260, 280 i 340 nm. Analizom elucijskih profila ustanovljeno je da se UV-aktivne molekule meda skupljaju u frakcijama od 3 do čak 20 mL i to ovisno o botaničkoj vrsti meda, pri čemu se različite botaničke vrste meda međusobno razlikuju kako po obliku krivulja elucije, tako i broju i intenzitetu detektiranih vrhova apsorbancije. Najviši intenziteti apsorbancije pronađeni su pri valnoj duljini od 230 nm, nakon čega slijedi valna duljina od 260 nm, potom 280 nm, dok su najčešće najniže vrijednosti apsorbancije postignute pri 340 nm. Izuzetak su činili lipov i kestenov med kod kojih su vrlo visoke vrijednosti apsorbancije zabilježene i pri 340 nm. Mjerenje intenziteta apsorbancije otopina čistih proteina, aromatskih aminokiselina, te odabranih predstavnika fenolnih kiselina i polifenola, pokazalo je da se intenziteti apsorbancije pri 230, 260 i 280 nm mogu pripisati prisutnosti proteina, aromatskih aminokiselina, fenolnih kiselina i flavonoida, a intenziteti apsorbancije pri 340 nm prisutnosti specifičnih molekula poput klorogenske, kavene i trans-ferulinske kiseline, te kvercetina i rutina. Razdjeljivanje molekula umjetnog meda gel filtracijom na Sephadexu G-25 superfine pokazalo je da su proteini glavni čimbenik UV-aktivnosti meda zabilježene od 3 do 6 frakcije, dok se UV-aktivnost meda od 7 do 20 frakcije može pripisati prisutnosti aromatskih aminokiselina, fenolnih kiselina i flavonoida. Na temelju izračuna površina ispod krivulje može se zaključiti da se apsorbancija otopina meda u ultraljubičastom području prije svega može pripisati sadržaju niskomolekularnih komponenti meda poput fenolnih kiselina, flavonoida i aromatskih aminokiselina, dok se utjecaj molekula molekulske mase veće od 5000 Da, poput proteina, Maillardovih produkata i melanoidina na apsorbanciju otopina meda najviše zamjećuje pri 230 nm. |
| Abstract (english) | The present study aimed to estimate contribution of proteins, aromatic amino acids, phenolic acids and flavonoids to the UV-absorbance of honey solution. In this respect, 14 different honey samples (3 of sage, 3 of lime, 3 of black locust, 3 of honeydew honey, and 2 of chestnut honey) were separated by gel filtration on Sephadex G-25 superfine and collected fractions analysed on absorbance intensity at wavelength of 230, 260, 280 and 340 nm. Chromatographic profiles of UV-active compounds of examined honeys showed that honeys of different botanical origin differentiate in the shape, as well as in number and intensity of detected peaks. UV-active molecules of examined honeys were collected between third up to 20th fraction, which were dependent on honey botanical origin. Recorded absorbance intensity of chromatographic curves, were in the most cases as follows A230 nm > A260nm > A280nm > A340 nm, with the exception of lime and chestnut honeys where significant contribution of UV-active compound at 340 nm were found. Analysis of absorbance intensity of solutions of pure compounds reported to be present in honey (proteins, 3 aromatic amino acids, selected 6 phenolic acids and 2 flavonoids) revealed that absorbance intensity recorded at 230, 260 and 280 nm could be mainly attributed to the presence of proteins, aromatic amino acids, phenolic acids and flavonoids, while absorbance intensity at 340 nm to the presence of specific molecules such as chlorogenic, caffeic and trans-ferulic acid, as well as quercetin and rutin. Separation of artificial honey by gel filtration on Sephadex G-25 superfine, followed by concomitant UV-measurement at 230, 260, 280 and 340 nm, and quantitative determination of proteins, reactive amino groups and total polyphenols, revealed that UV-absorption recorded in fractions from 3rd to 6th mL originate from proteins, while those one from 7th up to 20th mL from combined UV-absorptivity of aromatic amino acids, phenolic acids and flavonoids. Based on abovementioned, as well as on the area under the curve calculation of examined honeys, it can be concluded that majority of UV-absorbance of examined honeys can be attributed to the presence of low molecular weight compounds, such as phenolic acids, flavonoids and aromatic amino acids. However, in the case of UV-absorbance at 230 nm, contribution of molecules of molecular mass greater than 5000 Da, such as proteins, melanoidins and Maillard products cannot be neglected. |
