Biodegradation of aromatic carboxylic acids by Pseudomonas mira

Abstract Biodegradation of aromatic acids (ferulic, vanillic and sipapinic acids) by the soil bacterium Pseudomonas mira was studied by high-pressure liquid chromatography. The presence of glucose in the culture medium slowed down the degradation process but did not affect its mechanism. In addition to vanillic acid and hydroquinone, the products of degradation were found to include acetophenone derivatives. Probably, a mechanism capable of shortening the side chain by spontaneous decarboxylation of unstable 3- keto -3-phenylpropionic acid was present, in addition to the elimination of acetic acid via degradation of the cinnamic acid-type compounds.     

Discovery of aromatic amides with triazole-core as potent reversal agents against P-glycoprotein-mediated multidrug resistance

P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) is a major impediment for clinical cancer therapy. 19 novel aromatic amides with triazole-core as MDR reversal agents were designed and synthesized via click chemistry to reverse MDR. Among them, compound 42 was identified as the most promising candidate with high potency (EC₅₀ = 78.1 ± 5.4 nM), low cytotoxity (SI > 1282) and persistent duration in reversing doxorubicin (DOX) resistance in K562/A02 cells. 42 also enhanced the potency of other P-gp associated cytotoxic agents with different structures. In further study, remarkably increased intracellular accumulation of Rh123 and DOX in K562/A02 cells was achieved by compound 42, while CYP3A4 activity had no change by compound 42. These results indicate that compound 42 as a relatively safe modulator of P-gp-mediated MDR has good potential for further development.     

On the inhibition of muscle membrane chloride conductance by aromatic carboxylic acids

25 aromatic carboxylic acids which are analogs of benzoic acid were tested in the rat diaphragm preparation for effects on chloride conductance (G(Cl)). Of the 25, 19 were shown to reduce membrane G(Cl) with little effect on other membrane parameters, although their apparent K(i) varied widely. This inhibition was reversible if exposure times were not prolonged. The most effective analog studied was anthracene-9-COOH (9-AC; K(i) = 1.1 x 10(-5) M). Active analogs produced concentration-dependent inhibition of a type consistent with interaction at a single site or group of sites having similar binding affinities, although a correlation could also be shown between lipophilicity and K(i). Structure-activity analysis indicated that hydrophobic ring substitution usually increased inhibitory activity while para polar substitutions reduced effectiveness.

These compounds do not appear to inhibit G(Cl) by altering membrane surface charge and the inhibition produced is not voltage dependent. Qualitative characteristics of the I-V relationship for Cl(-) current are not altered. Conductance to all anions is not uniformly altered by these acids as would be expected from steric occlusion of a common channel. Concentrations of 9-AC reducing G(Cl) by more than 90 percent resulted in slight augmentation of G(I). The complete conductance sequence obtained at high levels of 9-AC was the reverse of that obtained under control conditions. Permeability sequences underwent progressive changes with increasing 9-AC concentration and ultimately inverted at high levels of the analog. Aromatic carboxylic acids appear to inhibit G(Cl) by binding to a specific intramembrane site and altering the selectivity sequence of the membrane anion channel.

     

Permeation of aromatic carboxylic acids across lipid bilayers: the pH-partition hypothesis revisited

According to the pH-partition hypothesis the charged species of organic compounds do not contribute to lipid bilayer permeation as they generally show negligible partitioning into n-octanol. With this assumption, membrane permeation is related to the molar fraction of the neutral species at a particular pH. A recently developed permeation assay permits us to directly determine pH-dependent permeation of aromatic carboxylic acids. Tb(3+)-loaded liposomes are incubated with aromatic carboxylic acids and upon excitation at the absorption wavelength of the acid, permeation kinetics can be measured as an increase in Tb(3+) luminescence. The anions of the tested acids permeated egg phosphatidylcholine membranes only 12 (2-hydroxynicotinic acid), 66 (salicylic acid), and 155 (dipicolinic acid) times slower than the net neutral species. The anions, therefore, controlled the total permeation already at 1-2 pH units above their pK(a). These results indicate that in contrast to the expectations of the pH-partition hypothesis, lipid bilayer permeation of an acidic compound can be completely controlled by the anion at physiological pH.     

Discovery of benzothiazole amides as potent antimycobacterial agents

From a high throughput screening of commercially available libraries against nontuberculous mycobacteria and Mycobacterium tuberculosis, numerous hits were identified with moderate activity. Extensive medicinal chemistry optimization has led to a series of potent benzothiazole amide antimycobacterial agents. Replacement of the adamantyl group with cyclohexyl derivatives and further development of this series resulted in an advanced lead compound, CRS400393, which demonstrated excellent potency and a mycobacteria-specific spectrum of activity. MIC values ranged from 0.03 to 0.12?μg/mL against Mycobacterium abscessus and other rapid-grower NTM, and 1–2?μg/mL against Mycobacterium avium complex. The preliminary mechanism of action studies suggested these agents may target MmpL3, a mycobacterial mycolic acid transporter. The series has demonstrated in vivo efficacy in a proof of concept mouse model of M. abscessus infection.     

An experimental study of Yersinia in plants]

Y. enterocolitica and Y. pseudotuberculosis have been experimentally found to penetrate into plants (cabbage, salad, pea, oat) from infected soil and water and to remain in different plant organs (roots, seeds, leaves) up to 30 days (the term of observation). The processes of S-R dissociation in Yersinia cultures isolated from plants, as well as changes in some enzymatic properties, have been established. In the test on Infusoria the cytotoxic action of strains isolated from plants has been noted. The possible role of plants in carrying pathogenic bacteria from the soil to the surface ecological systems and the subsequent infection of animals and humans is discussed.     

Characterization of Sphingomonas aldehyde dehydrogenase catalyzing the conversion of various aromatic aldehydes to their carboxylic acids

Natural products represent an important source of drugs in a number of therapeutic fields, e.g. antiinfectives and cancer therapy. Natural products are considered as biologically validated lead structures, and evolution of compounds with novel or enhanced biological properties is expected from the generation of structural diversity in natural product libraries. However, natural products are often structurally complex, thus precluding reasonable synthetic access for further structure-activity relationship studies. As a consequence, natural product research involves semisynthetic or biotechnological approaches. Among the latter are mutasynthesis (also known as mutational biosynthesis) and precursor-directed biosynthesis, which are based on the cellular uptake and incorporation into complex antibiotics of relatively simple biosynthetic building blocks. This appealing idea, which has been applied almost exclusively to bacteria and fungi as producing organisms, elegantly circumvents labourious total chemical synthesis approaches and exploits the biosynthetic machinery of the microorganism. The recent revitalization of mutasynthesis is based on advancements in both chemical syntheses and molecular biology, which have provided a broader available substrate range combined with the generation of directed biosynthesis mutants. As an important tool in supporting combinatorial biosynthesis, mutasynthesis will further impact the future development of novel secondary metabolite structures.     

An experimental study of the antidepressive properties of captopril]

Captopril, as well as amitriptyline, was shown to enhance apomorphine-induced stereotype in mice. At doses, which failed to modify the effect of apomorphine, both substances reversed the inhibitory action of sulpiride and haloperidol on stereotypical behaviour. Treatment with captopril (25 mg/kg) did not modify the open-field behaviour, but significantly reduced the immobility in the forced swim test (20 mg/kg) Dopaminergic link was suggested to be involved in the CNS effect of captopril.     

Effect of radiosensitizing agents on electron transport systems

Experiments have been carried out to study the interaxtion between chemical radiosensitizing agents and model electron transport systems. Using an NAD(P)H:O2 oxidoreductase enzyme as such a model, it was demonstrated that radiosensitizers can act as intermediates in the transfer of electrons from NADH to O2, even in the presence of classical inhibitors of electron transport, with anefficiency related to both their redox potentials and their radiosensitizing abilities. This work which was further confirmed in mammalian mitochondria and microsomes as well as in a cultured cell system indicated that these sensitizers can accept electrons from a variety of organelle systems. This action was shown to be related to the concentration of reduced pyridine nucleotides present both in vivo and in vitro. Of the electron-affinic agents tested, those whose redox potential was more negative than -0.39 V may possibly serve as better radiotherqpeutic mediators.     

Synthesis,SAR study and biological evaluation of novel pyrazolo[1,5-a]pyrimidin-7-yl phenyl amides as anti-proliferative agents

Checkpoint deficiency of malignant cells can be exploited in cancer drug discovery. Compounds that selectively kill checkpoint-deficient cells versus checkpoint-proficient cells can be utilized to preferentially target tumor cells, while sparing normal cells. The protein p21^{Wafl/Cipl/Sdi1} (hereafter referred to as p21) inhibits progression of the cell cycle by inhibiting the activity of G1 kinases (cyclin D/cdk4 and cyclin E-cdk2) and the G2 kinase (cyclin B/cdkl) in response to DNA damage or abnormal DNA content. The expression of p21 is often low in human cancer cells due to frequent loss of the upstream activator, p53, and is associated with poor prognosis in some cancer patients. Using an isogenic pair of cell lines, HCT116 (p21+/+) and 80S14 (p21?/?), we have disclosed previously a novel series of pyrazolo[1,5-a]pyrimidines that preferentially kill the p21-deficient cells. We will present the synthesis, biological activities and SAR study of a series of pyrazolo[1,5-a]pyrimidines with an optimized phenyl amide moiety at the C-7 position. The mechanism of action of these compounds will also be discussed.     

Amperometric study of the inhibitory effect of carboxylic acids on tyrosinase

A tyrosinase-modified Pt electrode, based on physical entrapment of the enzyme in agar–agar gel, was constructed and used to investigate the inhibitory effect of six carboxylic acids. At an applied potential of −50 mV versus saturated calomel electrode (SCE), the bioelectrode develops a fast, steady state response, linearly correlated with the phenol concentration up to 10 mg/l, with a sensitivity of 3.7 nA l/mg. A kinetic analysis of the amperometric response to phenol, recorded in the absence and in the presence of carboxylic acids (benzoic, 3-bromobenzoic, 4-ethylbenzoic, acetic, phenylacetic, 2-naphthylacetic acids), revealed that for the first four compounds the inhibition process corresponds to an uncompetitive one. Using the Lineweaver–Burk linearization the inhibition constants as well as the inhibition coefficients were calculated for the strong inhibitors: benzoic, 3-bromobenzoic, 4-ethylbenzoic and acetic acids.     

Oxidation of heterocyclic and aromatic aldehydes to the corresponding carboxylic acids by Acetobacter and Serratia strains

Conversion of heterocyclic and aromatic aldehydes to the corresponding carboxylic acids was carried out using Acetobacter rancens IFO3297, A. pasteurianus IFO13753 and Serratia liquefaciens LF14. IFO3297 produced 110 g 2-furoic acid l(-1) from furfural with a 95% molar yield. 5-Hydroxymethyl-2-furancarboxylic acid was produced from the corresponding aldehyde by using whole cells LF14. IFO13753 and LF14 both converted isophthalaldehyde, 2,5-furandicarbaldehyde, 2,5-thiophenedicarbaldehyde and 2,2' biphenyldicarbaldehyde to the corresponding formylcarboxylic acid with 86-91% molar yields.     

An acridinium sulphonylamide as a new chemiluminescent label for the determination of carboxylic acids in liquid chromatography

The synthesis of a new acridinium sulphonylamide label for the liquid chromatographic determination of carboxylic acids is described. The label 10-methyl-N-(p-tolyl)-N-(p-iodoacetamidobenzenesulphonyl)-9-acridinium carboxamide iodide is synthesized from 9-acridinecarboxylic acid by a seven-step reaction. Ibuprofen, used as test compound, is coupled to the reactive iodoacetamide group of the label by means of an alkylation reaction in dry acetonitrile for 20 min at 50°C in the presence of 18-crown-6 and potassium carbonate as base catalyst. The reaction mixture is injected into a liquid chromatographic system with chemiluminescence detection. Separation is performed on a Zorbax C₁₈ column with acetonitrile-water-tetrahydrofuran (39:57:4, v/v/v) containing 10 mmol/L TBABr and 0.035% H₂O₂ as the mobile phase at a flow rate of 1.0 ml/min. Chemiluminescence detection is achieved by the post-column addition of 200 mmol/L potassium hydroxide dissolved in methanol–water (1:1, v/v) at a flow rate of 20 μL/min. The detection limit (S/N = 3) of derivatized ibuprofen is 60 pg (3 pg injected). © 1998 John Wiley & Sons, Ltd.