Supramolecular cyclodextrin complexes of hydroxy-indoles applied as protectors of fluorescence

BRACAMONTE A.G., VEGLIA A. V.

Quebec

Congreso; CSC, Canadien society for chemistry 2013; 2013

Hydroxy-indoles, as serotonin (5-hydroxytryptamine, 5HT) and 5-hydroxy-3-indolyl acetic acid (5HIA) are metabolites of tryptophan. It is well known that the fluorescence emission of indole compounds is affected by the media showing fluorescence quenching in basic and acid conditions. The study of these processes is particularly important for analytical determinations in such media. In the present work we analyzed the cyclodextrin effect on the fluorescence emission of 5HT and its main metabolite (5HIA) in acid and alkaline media. From Stern-Volmer plots, quenching constants (KQ) were determined in the presence and absence of b-cyclodextrin (bCD) and hydroxypropyl-b-cyclodextrin (HPbCD), in water at 25.0 ºC. In both media a decrease in the values of KQ was measured in the presence of CDs, as compared with their absence. In acid media, the decrease was: (36-39) % with bCD and (50-54) % with HPbCD for 5HIA and 5HT respectively. In basic media, with the neutral receptors, these values are 69-29 % with bCD and 56-43 % with HPbCD for 5HIA and 5HT respectively. Also, a complete quenching inhibition produced by ionized cyclodextrins was determined for both substrates. The results showed a net protective fluorescence quenching effect due to the guest inclusion into the cyclodextrin.Q) were determined in the presence and absence of b-cyclodextrin (bCD) and hydroxypropyl-b-cyclodextrin (HPbCD), in water at 25.0 ºC. In both media a decrease in the values of KQ was measured in the presence of CDs, as compared with their absence. In acid media, the decrease was: (36-39) % with bCD and (50-54) % with HPbCD for 5HIA and 5HT respectively. In basic media, with the neutral receptors, these values are 69-29 % with bCD and 56-43 % with HPbCD for 5HIA and 5HT respectively. Also, a complete quenching inhibition produced by ionized cyclodextrins was determined for both substrates. The results showed a net protective fluorescence quenching effect due to the guest inclusion into the cyclodextrin.