Fluorescence quenching of β‐carboline alkaloids in micellar media. A study to select the adequate surfactant to use in analytical techniques

Abstract

The study of fluorescence quenching of the fluorophores allows the localization of the alkaloids (harmane and harmine) in the micelles (SDS, CTAB, Brij-35) to be established. In aqueous micellar solutions (SDS and Brij-35) at pH 13.0, emission corresponding to the neutral or zwitterionic forms can be observed. In the presence of CTAB (pH = 13.0) it was possible to observe the emission of anionic form. These species are not present in buffered aqueous solutions at these pH values. Bromide ion was added to the different surfactant solutions and the quenching effect was studied according to the Stern-Volmer equation. In the presence of SDS the quenching effect is considerably reduced compared to the aqueous solutions without surfactants, while for Brij-35 micelles were similar to those observed in homogeneous aqueous solution. For CTAB micelles a notable fluorescence quenching was observed for the different pH values studied. The fluorescence quenching studies show that the neutral species are associated inside the micelles, instead of the ionic species (cationic, zwitterionic or anionic) remaining on the surface of the micelles. The anionic surface of SDS micelles prevents the quenching effect by anionic quenchers for both neutral and charged species.

Discovery of a Class of Diketopiperazines as Antiprion Compounds

“…Indole, furan, thiophene and benzene derivates 1 j-n were also synthesized to enlarge the chemical diversity of the library. Heteroaromatic b-carboline derivatives 1 o and 1 p were purposely designed with the aim to obtain potential fluorescent probes, owing to the excellent native fluorescence found in carboline systems [38] that has led to their use as probes for biomolecules. [39] To study the importance, if any, of an appropriate planar conformation of 1 a-p, some singly reduced (2 a-d, 2 jk, 2 q) and a saturated derivative (3 d) were also synthesized (structures given in Table 2).…”

Effect of Bile Salt Aggregates on the Prototropic Equilibria of Harmine, a Fluorescent β‐Carboline Alkaloid

“…Scrutiny of literature reports has revealed different prototropic studies of HAR, and other β‐carboline alkaloid analogues in various self‐assembled confined medium. Becker et al.…”

“…Confined environment plays a very crucial role on the photophysics of the fluorophore/drug molecule which has been well explored in the literature . Similarly, various photophysical studies of harmine have been reported in different confined systems like micelles, microemulsions and cyclodextrins ,. Notably, in all these reports the interconversion between the different prototropic forms have been studied mainly as a function of pH and the zwitterionic form has only been observed at basic pH.…”

Jatropha cultivation in southern India: assessing farmers' experiences

“…Indole, furan, thiophene and benzene derivates 1 j – n were also synthesized to enlarge the chemical diversity of the library. Heteroaromatic β‐carboline derivatives 1 o and 1 p were purposely designed with the aim to obtain potential fluorescent probes, owing to the excellent native fluorescence found in carboline systems38 that has led to their use as probes for biomolecules 39. To study the importance, if any, of an appropriate planar conformation of 1 a – p , some singly reduced ( 2 a – d , 2 j – k , 2 q ) and a saturated derivative ( 3 d ) were also synthesized (structures given in Table 2).…”