Fluorescence of sanguinarine: fundamental characteristics and analysis of interconversion between various forms

Abstract

The quaternary isoquinoline alkaloid, sanguinarine (SG) plays an important role in both traditional and modern medicine, exhibiting a wide range of biological activities. Under physiological conditions, there is an equilibrium between the quaternary cation (SG+) and a pseudobase (SGOH) forms of SG. In the gastrointestinal tract, SG is converted to dihydrosanguinarine (DHSG). All forms exhibit bright fluorescence. However, their spectra overlap, which limited the use of powerful techniques based on fluorescence spectroscopy/microscopy. Our experiments using a combination of steady-state and time-resolved techniques enabled the separation of individual components. The results revealed that (a) the equilibrium constant between SG+ and SGOH is pKa = 8.06, while fluorescence of DHSG exhibited no changes in the pH range 5-12, (b) the SGOH has excitation/emission spectra with maxima at 327/418 nm and excited-state lifetime 3.2 ns, the spectra of the SG+ have maxima at 475/590 nm and excited-state lifetime 2.4 ns. The DHSG spectra have maxima at 327/446 nm and 2-exponential decay with components 4.2 and 2.0 ns, (c) NADH is able to convert SG to DHSG, while there is no apparent interaction between NADH and DHSG. These techniques are applicable for monitoring the SG to DHSG conversion in hepatocytes.

Spectrophotometric study of time stability and acid-base characteristics of chelerythrine and dihydrochelerythrine

“…This study points out that the behavior of chelerythrine and especially its dihydro-derivative in aqueous solutions is more complex than be expected [7,8,10,11].…”

“…Many very extraordinary properties were observed in the frame of detail studies of acidobasic and electrophoretic behavior of sanguinarine (SA) and chelerythrine (CHE) [8][9][10][11] and mainly their dihydroderivatives (dihydrochelerythrine, dihydrosanguinarine, etc., the former being recognized as the first metabolite of detoxification of sanguinarine in rats [2]) in the presence of inert electrolytes [3,4,10,11]. They exhibit very characteristic spectral features that can be used for their direct determination, for studies of their interactions with biomacromolecules using UV-VIS spectrophotometry, fluorimetry, mass spectrometry etc.…”

Fusarium oxysporum homogenates and jasmonate induce limited sanguinarine accumulation in Argemone mexicana cell cultures

“…In E. californica cell cultures a detoxification mechanism involving the enzymatic conversion of sanguinarine to dihydrosanguinarine, its less toxic reduced form, has been described (Weiss et al 2006). Interestingly, although both sanguinarine and its dihydro-derivative display a bright fluorescence, it is possible to discern one or the other given their different spectral properties (Janovská et al 2009). Therefore, the accumulation of sanguinarine and its reduced form in response to the elicitation treatments can be monitored by fluorescence microscopy, either as a green or a blue emission, using the proper combination of optical filters see Methods).…”

The sequential exposure to jasmonate, salicylic acid and yeast extract promotes sanguinarine accumulation in Argemone mexicana cell cultures

“…Sanguinarine displays a characteristic green autofluorescence at 470 nm (Janovská et al 2009). Hence, alkaloid distribution could be analyzed following fluorescence localization in A. mexicana cell cultures.…”