Study of equilibria in heterogeneous systems of tricyclic antidepressant amitriptyline

Cilj ovog rada bio je proučavanje ravnoteža u heterogenim sistemima tricikličnog antidepresiva amitriptilina (Am) koji sadrže hloride i/ili fosfate. Rastvorljivost Am u uslovima povećane jonske sile određena je pH–Ramp shake–flask metodom. Veća rastvorljivost Am u kiseloj sredini od očekivane, posledica je agregacije – analiza eksperimentalnih podataka pomoću programa pDISOL–XTM ukazuje na verovatno građenje pentamera Am5H5 5+. Kritična micelarna koncentracija i stepen disocijacije agregata određeni su primenom konduktometrijskih titracija. U baznoj sredini primećena je delimična degradacija Am. Eksperimentalno dobijeni podaci o rastvorljivosti biološki aktivnih supstanci i postojećim ravnotežama u heterogenim sistemima važni su u svim fazama dizajna i razvoja lekova.The aim of this work was to study the equilibria in tricyclic antidepressant amitriptyline (Am) heterogeneous systems containing chloride and/or phosphate ions. Solubility of Am in high ionic strength conditions was determined using pH–Ramp shake–flask method.1, 2 Higher solubility of Am than expected in an acidic media is a consequence of self-aggregation – pentamer formation (Am5H5 5+) according to pDISOL–XTM analysis. Critical micelle concentration and the degree of the aggregate dissociation were determined by conductometric titrations. Partial degradation of Am in alkaline suspensions was observed. Experimental studies of solubility as well as the existing equilibria in heterogeneous systems of biologically active compounds are important at all stages of drug design and development

The influence of competing counterions on the solubility of imipramine

Experimental studies of solubility are important in all phases of drug design and development. Solubility data are used to screen out drug-like candidates, biopharmaceutical classification and formulation optimization. The development of oral and parenteral dosage forms can be challenging, especially when drugs are poorly soluble, ionizable, exhibiting pH-dependent solubility and when multiple counterions are present in drug suspension. The influence of different counterions on the existing equilibria and on pH-dependent drug solubility must be defined in such systems. To investigate the effect of multiple ions on the solubility of a model basic drug – tricyclic antidepressant imipramine (Im), we conducted a systematic study of the Im solubility as a function of pH in the presence of both chloride and phosphate ions as well as in chloride-free and phosphate-free suspensions. The pH–Ramp shake–flask method1,2 was used for solubility determination. The computer program pDISOL–X was used for data analysis. It is shown that distinct pH-dependent solubility profiles were obtained in studied systems. Depending on the pH and the total concentration of chloride and/or phosphate ions, Im can precipitate as chloride and phosphate salt or free base. Furthermore, pH values of solid phase transitions (pHmax) varied as well. For instance, pHmax of solid phase transition of (ImH)H2PO4(s) to (ImH)2HPO4(s) change from 5.15 (chloride and phosphate-containing suspensions) to 5.73 (chloride-free suspensions). The intensive self-aggregation of Im in acidic region was suppressed by raising chloride or phosphate ions concentration (Iavg 1.42–1.64 M). In that way, solubility of Im was decreased due to the common-ion effect. This study illustrates the influence of competing counterions on Im solubility and on interconversions in solid phase. Hence, such factors must be taken into account during formulation optimization in drug research

Specific detection of Waitea circinata var. zeae using conventional and real-time PCR

Waitea circinata var. zeae, a pathogen with a relatively narrow host range, has recently been detected in cabbage and oilseed rape in Europe and worldwide. In this study, we developed specific conventional and real-time PCR protocols for direct detection of W. circinata var. zeae from mycelium and diseased plant tissue. The newly developed primer pair zeaefor1/zeaerew1, used in PCR protocols, specifically amplified only target isolates of W. circinata var. zeae when tested against isolates of 11 different binucleate and multinucleate anastomosis groups of Rhizoctonia spp. including AG-A, AG-G, AG-F, AG-U, AG-2-1, AG-2-2, AG-3, AG-4 HGI, AG-4 HGII, AG-4 HGIII, and AG-6 and common soil-borne pathogens. Total of nine previously published primer pairs designed for the detection of various Rhizoctonia spp. were also tested and did not amplify target isolates of W. circinata var. zeae. The detection limit of conventional and real-time PCR protocols was 10–2 and 10–5 (with starting concentration 9.5 ng/µl), respectively, and both methods are the first available tools for direct detection and identification of W. circinata var. zeae from mycelium and diseased oilseed rape seedlings. Both conventional and SYBR-Green-based real-time PCR protocols are cost-effective and provide a solid basis for further investigations of W. circinata var. zeae, particularly in relation to distribution, host range, and epidemiology

Suppression of <i>Monilinia</i> Brown Rot by <i>Bacillus</i> spp. Strains

Brown rot caused by Monilinia spp. is one of the main causes of pre- and postharvest losses in stone and pome fruit production. The use of beneficial microorganisms is considered one of the most promising, safe and effective alternative methods for controlling these pathogens. This study aimed to investigate the antagonistic potential of 33 Bacillus spp. strains, in order to identify the best candidate for brown rot biocontrol. Strains identified as Bacillus amyloliquefaciens B-241 and Bacillus subtilis B-313 and B-358 were chosen for further ex situ studies on detached apple fruit. The efficacy of B-241 (87.1–93.7%) did not differ significantly from a commercially available synthetic fungicide (p > 0.05). The putative mode of action of B. amyloliquefaciens B-241 against Monilinia species is competition for nutrients and antibiosis. The ethyl acetate extract of the strain, applied at 5 and 12.5 mg/mL, was bioactive in vitro and ex situ. A HPLC analysis confirmed the presence of surfactin and bacillomycin D in the extract. However, before developing a shelf-stable product and commercial production, the spectrum and efficacy on a larger scale of the B-241 strain should be determined, and its efficacy in combination with commercial biofungicides and fungicides tested in vivo