Effect of preferential solvation and bimolecular quenching reactions on 3OCE in acetonitrile and 1,4-dioxane binary mixtures by optical absorption and fluorescence studies.

Fluorescence quenching and preferential solvation of a coumarin derivative, namely 3-[2-oxo-2-(2-oxo-2H-chromen-3-yl)-ethylidene]-1,3-dihydro-indol-2-one (3OCE), with aniline used as a quencher in solvent mixtures of acetonitrile (AN) and 1,4-dioxane (DX) was carried out at steady state. Suppan's theory of dielectric enrichment was used to understand the nonideality and dielectric enrichment in AN-DX solvent mixtures. The effect of viscosity and dielectric constant variation at room temperature were analyzed. Quenching was characterized using Stern-Volmer plots with an upward curvature. It was found that 3OCE underwent combined static and dynamic quenching that was evident from the quenching rate parameters.

Effect of viscosity and dielectric constant variation on fractional fluorescence quenching analysis of coumarin dye in binary solvent mixtures.

Photo physical properties of fluorescent organic compounds give an immense improved knowledge on characteristics of excited state that is beneficial to devise innovate molecules and understand their performance in particular applications. Coumarin derivatives have been extensively investigated in this regard. This article narrates steady state fluorescence quenching measurements of a coumarin derivative namely 3-hydroxy-3-[2-oxo-2-(3-oxo-3H-benzo[f]chromen-2-yl)-ethyl]-1,3-dihydro-indol-2-one (3HBCD) in a binary mixture of acetonitrile and 1,4-dioxane. Aniline is used as quencher. Fluorescence intensity is large in acetonitrile and decreases as the percentage of 1,4-dioxane in the solvent mixture increases. With modest quencher concentration a deviation towards the x axis is noticed in the Stern-Volmer (S-V) plots. This downward curvature is interpreted as due to the presence of 3HBCD in different conformers in the lowest energy level. Ground state intramolecular hydrogen bonding formation is observed due to the conformational changes in the solute. Figured estimations of various quenching parameters recommend that, while dynamic quenching prompts linearity in S-V plot at lower quencher concentration, increasing quenching efficiency with increasing medium viscosity suggests that reaction is not entirely controlled by material diffusion. Stern-Volmer constant increases with decreasing medium dielectric constant.

Fluorescence of Candida in diagnosis of oral candidiasis.

BACKGROUND: Many pathogenic fungi fluoresce in hematoxylin and eosin stained sections, and Papanicolaou (PAP)-stained smears under ultraviolet illumination. In theory, this phenomenon could aid in the diagnosis of common fungal infections without the delay which is usually associated with special stains. OBJECTIVE: To evaluate the role of fluorescence as a rapid screening technique for oral infections caused by Candida organisms in exfoliative smears of oral candidiasis. MATERIALS AND METHODS: Two smears and one swab were collected from each of 62 clinically diagnosed cases of oral candidiasis. Smears were stained with (PAP) and periodic acid-Schiff stain (PAS). Both smears were evaluated under light microscopy (LM). Later, PAP smears were observed under fluorescent microscopy (PAP-FM). The swab was inoculated on Sabouraud's agar plate. Each technique was evaluated for sensitivity and specificity. RESULTS: It was found that the PAS-stained smears were more reliable for detection of Candida species than other methods (sensitivity = 100%; specificity = 66.7%). The PAP-LM and PAP-FM showed less sensitivity (67.9% and 85.7%) and specificity (66.7% and 33.3%), respectively. Combined results of both light and fluorescent microscopy of PAP (LM + FM) showed increased sensitivity (89.3%) but reduced specificity (16.7%). CONCLUSION: PAP autofluorescence is less sensitive than PAS, still it accentuates the distinct morphological features of Candida.

Pediatric liquid medicaments - Are they cariogenic? An in vitro study.

AIM: Young and chronically sick children receive a variety of oral liquid medications on a routine and regular basis. These pharmaceutical preparations are cariogenic and acidogenic in nature. Hence, the present study was taken up to determine the cariogenic potential of the commonly prescribed pediatric liquid medicaments. MATERIALS AND METHODS: Eight commonly used pediatric liquid medicaments (PLM) were selected and their endogenous pH was measured using a pH electrode meter. The sugar content in them was estimated using High Performance Liquid Chromatography (HPLC). The effect of PLM on Streptococcus mutans was assessed by the ditch plate method. RESULTS: The pH of the liquid medicaments ranged between 6.05 (Salbid(®)) and 7.71 (Theopid(®)). Sucrose was observed in 7 PLM and glucose in 5 PLM. The highest concentration of sucrose was seen in Crocin(®). The lowest concentration of sucrose was seen with Althrocin(®). Both the antibiotic PLMs inhibited the S. mutans growth. Zevit(®) promoted the growth of S. mutans. CONCLUSION: The pH and concentration of sugars of pediatric liquid medicaments can pose as a threat to dental health, especially in chronically sick children, who are on long-term medications.

Synthesis, antitumor, and DNA binding behavior of novel 4-(2-hydroxyquinolin-3-yl)-6-phenyl-5, 6 dihydropyrimidin derivatives in aqueous medium.

This article deals with the synthesis of 4-(2-hydroxyquinolin-3-yl)-6-phenyl-5,6-dihydropyrimidin derivatives (2a-f), on condensation with various aromatic aldehydes and ketones in aqueous ethanolic NaOH solution yielding the corresponding chalcones (3). These chalcones were further reacted with thiourea/urea in the presence of a base, which led to the formation of the titled derivatives (2a-f). The newly synthesized heterocyles were characterized by elemental analysis, FTIR, (1)HNMR, and electronic and mass spectral data. The compounds (2a and 2b) were evaluated for in vitro cyctotoxicity against human breast adenocarcinoma cell (MCF-7). In MTT cytotoxicity studies, both quinolinde derivatives were found most effective. The binding interaction behavior of the compound (2a) and (2d) with calf thymus-DNA (CT-DNA) was studied by electronic spectra, viscosity measurements, and thermal denaturation studies. On binding to CT-DNA, the absorption spectrum underwent bathochromic and hypochromic shifts. The binding constant (K(b)) observed 4.3 x 10(5) M(-1) for (2a), and 3.8 x 10(5) M(-1) for (2d) suggested that compound (2a) binds more strongly with base pairs than (2d).