Anti-Infective Agents - Volume 10, Issue 1, 2012

s The emergence of new bacterial strains with multiple resistances may lead to the emergence of new hospitalacquired infections that result in high mortality. Research on new antiinfectives must therefore be continued and all possible strategies should be explored. Screening of plant extracts as well as secondary metabolites, aiming to highlight the presence of new compounds with antimicrobial activity is a potential source of more effective drugs. In this paper we report the antibacterial and hemolytic activities of the ethyl acetate fraction and compounds 1 (8-formyl-3',5-dihydroxy-7- methoxy-6-methylflavanone) and 2 (3&apos-formyl-3,4',6'-trihydroxy-2'-methoxy-5'-methylchalcone) isolated from Piper montealegreanum, which have not shown any previous biological study. The ethyl acetate fraction from Piper montealegreanum showed antibacterial activity against Gram positive (B. subtilis) and Gram negative (E. coli and P. aeruginosa) resistant to ampicillin at lower concentrations showing no cytotoxic effect against human erythrocytes (A, B and O), and is therefore a potential broad-spectrum antibacterial agent. Both the flavanone and the chalcone showed antibacterial activity against P. aeruginosa resistant to ampicillin, which means that they can be used as narrow–broad antibacterial agents.

Synthesis and in vitro anti-tubercular activity against Mycobacterium tuberculosis H37Ra and H37Rv of a number of 3-hydroxy[2,3-c][1]benzopyran-6(H)-ones 1a-f and 3-Benzyl-8-hydroxy-1,2,3,4-tetrahydro-chromeno[3,4- c]pyridin-5-ones 8a-c has been reported. Few of the compounds exhibited anti–tubercular activity with MIC as low as 3.12 μg/ml in virulent and avirulent strains.

As skin is an integumentary organ of the body, it acts as the portal of entry for extraneous substances for their effective topical and transdermal delivery. Possessing various advantages, it has the limitation of low permeability of drugs across it, limiting the efficacy of drugs. Therefore, various carrier systems have been developed to enhance the permeation to the deep tissues. Most recently, ethosomes have been developed as efficient vesicles to deliver the drug into deep strata of the epidermis. A large number of drugs belonging to various therapeutic categories have been incorporated in these vesicles. These systems exhibited enhanced permeability to treat deep infections of the skin, initiating a new era in vesicular research for topical drug delivery. Various reports show promising future of ethosomes for topical, transdermal and dermal delivery of various antimicrobial agents more effectively, to treat skin diseases and providing better in vivo profiles thus suggesting the need of the clinical testing of these carriers for their widespread utility. So, to assess its safety and efficacy various preclinical and clinical studies were conducted. The present review focuses on the preclinical and clinical aspect of delivery of various antimicrobial agents such as antifungal, antibacterial and antiviral agents through ethosomal vesicular carriers illustrating enhanced safety and efficacy by designing these carriers.

The development of antimicrobial agents to treat infections has been one of the most notable medical achievements of the past century. Despite the growing list of azoles, their clinical value has been limited by their relatively high risk of toxicity and the emergence of drug resistance. This necessitates the development of more effective broad spectrum antimicrobials with fewer side effects. We previously described the design and synthesis of some new azole derivatives in both imidazole and triazole groups. Here we selected 30 analogues of them in 4 different categories (imidazoles (1), benzimidazoles (2), triazoles (3) and benztriazoles (4)) and investigated their antibacterial activity against different species of gram positive and gram negative microorganisms. Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, Bacillus subtilis as gram positive and Escherichia coli, Salmonella typhi, Shigella sonnei, Pseudomonas aeroginosa and Proteus vulgaris as gram negative bacteria were chosen. Disc plate method and serial dilution assay were used to establish the minimum inhibitory concentration of the above compounds. The results show compounds 1-dodecyl- 2-methyl-1H-imidazole (1g), 2-(1H-1-imidazolyl)-1-cyclohexanol (1a) and 2-(2-methyl-4-nitro-1H-1-imidazolyl)-1- cyclohexanol (1o) had desirable antibacterial activity on both gram positive and gram negative species. Compounds 1- trityl-1H-benzo (d) imidazole (2a) and 1-octyl-1H-1,2,4-triazole (3b) had higher effect for gram positive and gram negative bacteria respectively. Compounds 2-methyl-1- nonyl-1H-imidazole (1f) and 1-butyl-2-methyl-;4-nitro-1H-imidazole (1l) had moderate activity for gram negative bacteria.

Recurrent HCV is universal after liver transplantation in patients viremic at the time of transplantation and leads to cirrhosis in up to 30% of patients by five years. Once cirrhosis develops, the risk of hepatic decompensation is 42% per year. This has led to recurrent HCV emerging as an important yet controversial indication for liver retransplantation and a renewed interest in the role of anti-viral therapies. Despite encouraging results with pegylated interferon and ribavirin in the non-transplant HCV population, these findings have not translated to transplant recipients where viral eradication is frequently unsuccessful for genotype 1 patients (<40%). Rejection although rare, remains a concern and the use of stimulating factors controversial. The lack of effective therapies, severe side effects and reports of hepatic decompensation despite HCV eradication raises the question of whether these patients should be treated with interferon-based therapies. Clinical trials of newer antivirals are urgently required in these patients who are at risk of rapid development of cirrhosis.

Flavonoids comprise a group of naturally occurring compounds that are known by their biological properties. Antiviral, antibacterial, antifungal, and antimycobacterial activities were analyzed. The results were discussed in terms of the bioactivity tested, and the structure-activity relationship (SAR), bidimensional (2D)- and three-dimensional (3D)- quantitative structure-activity relationship (QSAR) studies carried out on flavones, flavanones, chalcones, and some biflavonoids.

In silico methods have been used to identify five different classes of compounds as inhibitors of the essential Plasmodium falciparum enzyme lactate dehydrogenase (LDH). The molecules were assayed for in vitro antimalarial activity in both cell- and enzyme-based inhibition models. 5-Bromo-2-hydroxypyridine-3-carboxylic acid 19 is the most active with IC50 of 3.5 nM for chloroquine sensitive and 5 nM for resistant strains of Plasmodium falciparum, compared to 11 nM and 100 nM for the standard chloroquine. In LDH-enzyme inhibition assays the leading compounds are 5, 10, 18 and 19. Docking studies and the 3D-QSAR technique - CoRIA have been used to identify key binding elements between the molecules and residues in the LDH active site. A bifurcated salt bridge that associates the carboxylate group on the molecules with the guanidino group in the side chain of both Arg109 and Arg171 along with π-stack of the heterocycle with the pyridine ring of the cofactor NAD+, are the prime interactions. In silico ADME/toxicity studies also suggest these molecules have favorable pharmacokinetic and toxicity profiles.

In the present study, some novel Schiff's bases of 4-methyl-2-thiazolamine were synthesized by condensation of 2-amino-4-methylthiazole with different substituted aromatic aldehydes. Structures of newer Schiff's bases were established on the basis of IR, 1HNMR, Mass spectral data and elemental analyses. All the synthesized compounds were obtained in good yields and high purity. The antimicrobial activity of the synthesized compounds was preliminarily evaluated by paper disc diffusion technique. The minimum inhibitory concentrations (MIC) of the compounds were also determined by tube dilution method. All the compounds showed antibacterial activity at the tested dose against four different strains of Gram positive and Gram negative bacteria but were considerably less when compared to the reference standard drug ciprofloxacin. Among the synthesized compounds 2a, 2b, 2c, 2d exhibited to some extent better activity against all the tested strains. The antifungal activity was also found to be considerably less than that of the standard drug ketoconazole for all the synthesized compounds.