Authors:W. Zielenkiewicz, I. Terekhova, M. Wszelaka-Rylik, and R. Kumeev
Calorimetry, densimetry, 1H NMR and UV–vis spectroscopy were used to characterize inclusion complex formation of hydroxypropylated α- and β-cyclodextrins
with meta- and para-aminobenzoic acids in aqueous solutions at 298.15 K. Formation of more stable inclusion complexes between para-aminobenzoic acid and cyclodextrins was observed. The binding of aminobenzoic acids with hydroxypropyl-α-cyclodextrin was
found to be enthalpy-governed owing to the prevalence of van der Waals interactions and possible H-binding. Complex formation
of hydroxypropyl-β-cyclodextrin with both acids is mainly entropy driven. The increased entropy contribution observed in this
case is determined by dehydration of solutes occurring during the revealed deeper insertion of aminobenzoic acids into the
cavity of hydroxypropyl-β-cyclodextrin. By comparing complex formation of aminobenzoic acids with native and substituted cyclodextrins
it was found that the availability of hydroxypropyl groups slightly influenced the thermodynamic parameters and did not change
the binding mode or driving forces of interaction.
A particularly rapid HPTLC method has been established for chromatographic separation and quantification of
-aminobenzoic acid (PABA) in complex dietary supplement tablets. After chromatography, PABA was determined by spectrodensitometry at 270 nm. PABA spots were then visualized by a novel staining procedure involving the
coupling reaction after spraying with 8-hydroxyquinoline in situ on the chromatographic plates. After visualization, spectrodensitometric analysis was repeated at 500 nm. Linearity, intermediate precision, sensitivity, accuracy, and precision were compared for both methods. Results from tablet analysis were verified with the modified
Mixed complexes of the type: Zn(Hsal)2(2-MeHim)2, Zn(Han)2(2-MeHim)2, Cd(Hsal)2(2-MeHim)2, Cd(Han)2(2-MeHim)2, where Hsal=OHC6H4COO−, Han=NH2C6H4COO−, 2-MeHim=2-methylimidazol) have been synthesized and characterized by IR spectroscopic and X-ray diffraction studies. Single-crystal
X-ray structure of Cd(Hsal)2(2-MeHim)2 has been obtained. Thermal behaviour of the compounds was investigated by thermal analysis (TG, DTG, DTA). A coupled TG-MS
system was used to analyse the principal volatile products of complexes. Thermal decomposition pathways have been postulated.
Authors:Nourrudin W. Ali, Nada S. Abdelwahab, Maha M. Abdelrahman, Badr A. El-Zeiny, and Salwa I. Tohamy
Three accurate, sensitive, simple, and precise spectrophotometric methods along with thin-layer chromatography (TLC)–densitometric method were developed, optimized, and validated for the determination of folic acid in the presence of its two impurities (photodegradation products), namely, pteroic acid and para-aminobenzoic acid. Method A is the ratio difference spectrophotometric method (RDSM) which depends on measuring the difference value in the ratio spectrum, where the difference between 291 and 313 nm was used for the determination of folic acid, while the difference between 305 and 319 nm was selected for the estimation of para-aminobenzoic acid; on the other hand, pteroic acid can be determined using the first derivative of ratio spectra spectrophotometric method at 262 nm. Method B is the double-divisor spectrophotometric method (DDSM); this method is based on using the ratio spectrum obtained by the division of the spectrum of ternary mixture by the spectrum of binary mixture containing two of the three mentioned components, and in this method, folic acid, para-aminobenzoic acid, and pteroic acid were measured at 242, 313, and 258 nm, respectively. Method C is the mean-centering of ratio spectra spectrophotometric method (MCR); in this method, folic acid, para-aminobenzoic acid, and pteroic acid can be measured using the mean-centered second ratio spectra amplitudes at 317–318 (peak to peak), 264–265 (peak to peak), and 232 nm, respectively. Lastly, method D is a TLC‒densitometric one that depends on the separation and quantification of the mentioned components on TLC silica gel 60 F254 plates, using methanol‒ iso-propanol‒water‒acetic acid (9:0.5:0.5:0.2, by volume) as the developing system, followed by densitometric measurement of the separated bands at 280 nm. Method validation was carried N.W. Alia, N.S. Abdelwahaba, M.M. Abdelrahmana, and S.I. Tohamy, Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Beni-Suef University, Alshaheed Shehata Ahmed Higazy St., 62514, Beni-Suef, Egypt; and B.A. El-Zeiny, Pharmaceutical Analytical Chemistry Department, Faculty of Pharmacy, Cairo University, Kasr EL-Aini Street, ET 11562, Cairo, Egypt. *E-mail: email@example.com out according to the International Conference on Harmonisation (ICH) guidelines, and the proposed methods were successfully applied to the analysis of folic acid in pharmaceutical formulations, where no interference from additives has been found. The results obtained by the proposed methods were statistically compared with those obtained by the official reversed-phase high-performance liquid chromatography (RP-HPLC) method, in which no significant difference was observed.
The thermal stabilities of thorium(IV) salts of ortho-, meta- and para-hydroxy- and aminobenzoic acids were studied. The salts were prepared as hydrated compounds with general formula Th(OH)2(R-C6H4COO)2·nH2O, wereR = OH or NH2, andn = 2, 3 or 4, while the salt of 3-aminobenzoic acid was anhydrous. On heating, the salts undergo dehydration in two or three steps and di(R-benzoato)dihydroxothorium(IV) or di(2-hyroxybenzoato)oxothorium(IV) is then transformed directly to ThO2.
Authors:Mónika Magony, Ildikó Kákonyi, Anna Gara, P. Rapali, Katalin Perei, K. Kovács, and G. Rákhely
A bacterium capable to grow on sulfanilic acid as sole carbon, nitrogen and sulfur source has been isolated. A unique feature of this strain is that it contains the full set of enzymes necessary for the biodegradation of sulfanilic acid. Taxonomical analysis identified our isolate as
SA1 sp. The biodegradation pathway of sulfanilic acid was investigated at the molecular level. Screening the substrate specificity of the strain disclosed its capacity to degrade six analogous aromatic compounds including
-aminobenzoic acid. Moreover, the strain was successfully used for removal of oil contaminations.
SA1 seemed to use distinct enzyme cascades for decomposition of these molecules, since alternative enzymes were induced in cells grown on various substrates. However, the protein patterns appearing upon induction by sulfanilic acid and sulfocatechol were very similar to each other indicating common pathways for the degradation of these substrates. Cells grown on sulfanilic acid could convert
-aminobenzoic acid to some extent and vice versa. Two types of ring cleaving dioxygenases were detected in the cells grown on various substrates: one preferred protocatechol, while the other had higher activity with sulfocatechol. This latter enzyme, named as sulfocatechol dioxygenase was partially purified and characterized.
Authors:Yi Changhou, Jin Jannan, Zhang Shuyuan, Wang Ketai, Zhang Dayuan, and Zhou Maolun
An organic compound labelled by using radioastatine was conjugated to a protein.211At reacts with the diazo-compound of para-aminobenzoic acid to yield para-astatobenzoic acid, which is separated by ether extraction and high performance liquid chromatography (HPLC) and then conjugated with IgG and bovine serum albumin (BSA) via an acylation reaction. The results of the animal experiments have shown that the211At-carbon bond is stable in vivo and the conjugate contains at least 40% of the initial activity of211At. Astatine-211 labelled proteins have also been prepared by direct oxidation with hydrogen peroxide or Chloramine-T. The separation of labelled proteins by Sephadex chromatography is very effective. The structure of proteins affects the labelling results and the yield of211At-BSA labelled by oxidation with hydrogen peroxide can be increased up to 96.4%.