Syntheses and Properties of Two Heterocyclically Substituted Hypericin Derivatives: 10,11-Dibenzothiazolyl-10,11-didemethylhypericin and 10,11-Dibenzoxazolyl-10,11-didemethylhypericin

Summary. The syntheses of the two heterocyclically substituted title hypericin derivatives were achieved starting either from 6-benzothiazolyl-tri-O-methyl-6-demethylemodin or 6-benzoxazolyl-tri-O-methyl-6-demethylemodin. The use of microwave assisted synthesis for the preparation of these anthraquinone synthons and the chemical as well as photochemical properties of the corresponding unique hypericin derivatives, which might constitute new photodynamic therapy agents, are reported. The tautomeric and stereochemical aspects of these hypericin derivatives were investigated by means of semiempirical calculations (AM1).     

9,12-Dibenzothiazolylhypericin and 10,11-Dibenzothiazolyl-10,11-didemethylhypericin: Photochemical Properties of Hypericin Derivatives Depending on the Substitution Site

Investigating the properties of similar but regioselectively differently substituted hypericin derivatives, 9,12-dibenzothiazolylhypericin was synthesized and compared with the recently prepared 10,11-analogue. A significant difference in the ability to generate singlet oxygen and/or reactive oxygen species and different absorption spectra of these two derivatives were observed.     

Syntheses,Photochemical Properties,and Tautomerism of Intramolecularly <Emphasis Type="Italic">Friedel-Crafts</Emphasis> Acylated Hypericin Derivatives

Summary. Intramolecularly Friedel-Crafts acylation carried out on the hypericin moiety provided a new class of 9,12-dicarbonyl substituted hypericin derivatives as potential candidates for photodynamic therapy (PDT). Focusing on cyclopentanone and cyclohexanone condensed derivatives, investigations concerning the chemical and photochemical properties as well as the tautomerism of these compounds were performed.     

9,12-Dibenzothiazolylhypericin and 10,11-Dibenzothiazolyl-10,11-didemethylhypericin: Photochemical Properties of Hypericin Derivatives Depending on the Substitution Site

Summary. Investigating the properties of similar but regioselectively differently substituted hypericin derivatives, 9,12-dibenzothiazolylhypericin was synthesized and compared with the recently prepared 10,11-analogue. A significant difference in the ability to generate singlet oxygen and/or reactive oxygen species and different absorption spectra of these two derivatives were observed.     

Visualisation of polysaccharide fouling on microporous membrane using different characterisation techniques

Although many studies assessed fouling behaviour in microporous membrane processes like membrane bioreactors (MBRs), in situ or direct observation of the fouling layer has not yet been possible. The observation of the fouling layer resulting from the filtration of model solutions allowed better understanding of MBR fouling intensity and mechanisms. In this study, alginate has been used as a model for polysaccharide (one of the main foulants in MBRs). Three visualisation techniques, confocal laser scanning microscopy (CLSM), environmental scanning electron microscopy (ESEM), and direct observation (DO) have been tested to observe the alginate fouling. The work presented in this paper revealed the advantages and limitations of each technique used for this specific application. Although no coating is required for this technique, ESEM allowed distinct non-destructive observation of clean membrane. However, the lack of structure in the alginate fouling layer limited the use of this technique for fouled membranes. While CLSM requires the use of expensive fluorescent markers, DO appeared as the most promising technique for direct and in situ observation of MBR fouling. DO of alginate/bentonite and alginate/bacteria solutions revealed the creation of a well-structured dual fouling system (bentonite-concentrated layer of 50 μm embedded and covered by a concentration polarisation of alginate greater than 240 μm) on the surface of hollow fibre membrane.     

Approximate solutions of fractional Zakharov–Kuznetsov equations by VIM

This paper presents the approximate analytical solution of a fractional Zakharov–Kuznetsov equation with the help of the powerful variational iteration method. The fractional derivatives are described in the Caputo sense. Several examples are given and the results are compared to exact solutions. The results show that the variational iteration method is very effective, convenient and simple to use.     

Syntheses, Photochemical Properties, and Tautomerism of Intramolecularly Friedel-Crafts Acylated Hypericin Derivatives

Intramolecularly Friedel-Crafts acylation carried out on the hypericin moiety provided a new class of 9,12-dicarbonyl substituted hypericin derivatives as potential candidates for photodynamic therapy (PDT). Focusing on cyclopentanone and cyclohexanone condensed derivatives, investigations concerning the chemical and photochemical properties as well as the tautomerism of these compounds were performed.     

Variational iteration method for fractional heat- and wave-like equations

This paper applies the variational iteration method to obtaining analytical solutions of fractional heat- and wave-like equations with variable coefficients. Comparison with the Adomian decomposition method shows that the VIM is a powerful method for the solution of linear and nonlinear fractional differential equations.     

Syntheses and Properties of Two Heterocyclically Substituted Hypericin Derivatives: 10,11-Dibenzothiazolyl-10,11-didemethylhypericin and 10,11-Dibenzoxazolyl-10,11-didemethylhypericin

The syntheses of the two heterocyclically substituted title hypericin derivatives were achieved starting either from 6-benzothiazolyl-tri-O-methyl-6-demethylemodin or 6-benzoxazolyl-tri-O-methyl-6-demethylemodin. The use of microwave assisted synthesis for the preparation of these anthraquinone synthons and the chemical as well as photochemical properties of the corresponding unique hypericin derivatives, which might constitute new photodynamic therapy agents, are reported. The tautomeric and stereochemical aspects of these hypericin derivatives were investigated by means of semiempirical calculations (AM1).