Hydrolysable tannins (HTs) are secondary metabolites from plants, which are roughly classified into gallotannins and ellagitannins having gallic acid and ellagic acid residues respectively attached to the hydroxyl group of glucose by ester linkage. The presence of hexahydroxydiphenoyl and nonahydroxyterphenoyl moieties is considered to render antimicrobial property to HTs. HTs also show considerable synergy with antibiotics. Nevertheless, they have low pharmacokinetic property. The present review presents the scope of HTs as future antimicrobial agent. Copyright © 2016 John Wiley & Sons, Ltd.

Aim/Background:Medicinal plants have ability to resist microorganisms by synthesizing secondary metabolites such as phenols. Rosmarinic acid (RA) is a phenylpropanoid widely distributed in plants and well known as therapeutic and cosmetic agent. Methicillin-resistant Staphylococcus aureus (MRSA) which is resistant to all kinds of β-lactams, threatens even most potent antibiotics. To improve the efficiency of antibiotics against multi-drug resistant bacteria and to reduce the antibiotic dose, the antibacterial activity and the synergistic effect of RA with standard antibiotics against S. aureus and MRSA was investigated.Materials and Methods:Antibacterial activity of RA against S. aureus and a clinical isolate of MRSA was evaluated by agar well diffusion method. Minimum inhibitory concentration (MIC) of RA was determined by broth dilution method. Synergism of RA with various antibiotics against S. aureus and MRSA was studied by broth checkerboard method and time-kill kinetic assay. Effect of RA on microbial surface components recognizing adhesive matrix molecules (MSCRAMM’s) of S. aureus and MRSA was studied using sodium dodecyl sulfate - polyacrylamide gel electrophoresis.Results:MIC of RA was found to be 0.8 and 10 mg/ml against S. aureus and MRSA, respectively. RA was synergistic with vancomycin, ofloxacin, and amoxicillin against S. aureus and only with vancomycin against MRSA. The time-kill analysis revealed that synergistic combinations were a more effective than individual antibiotics. MSCRAMM’s protein expression of S. aureus and MRSA was markedly suppressed by RA + vancomycin combination rather than RA alone.Conclusion:The synergistic effects of RA with antibiotics were observed against S. aureus and MRSA. RA showed inhibitory effect on the surface proteins MSCRAMM’s. Even though RA was shown to exhibit a synergistic effect with antibiotics, the MIC was found to be higher. Thus, further studies on increasing the efficacy of RA can develop it as an adjuvant for antibiotics.

The present study investigated the acute and subacute toxicity of Diakyur, a polyherbal antidiabetic formulation, in experimental animal models. Diakyur contains aqueous extract dry powders of Cassia auriculata, Gymnema sylvestre, Mucuna pruriens, Syzygium jambolanum, Terminalia arjuna, Salacia reticulata, and a crude powder of Cassia javanica. The raw materials were standardized by gravimetric, HPLC and High performance thin layer chromatography (HPTLC) methods for their respective bioactive marker compounds. In an acute toxicity study, Diakyur was administered orally at doses ranging from 100-12800 mg/kg p.o. and the animals were observed for any toxic symptoms up to 72 hr. The results indicated there were no toxic symptoms up to the dose level of 12800 mg/kg p.o. In a subacute toxicity study, Diakyur was tested at the dose of 1600 mg/kg p.o. once daily for 28 days. The animals were sacrificed on the 29th day and various blood biochemical parameters were measured. The liver, kidney, heart, adrenals, pancreas and uterus were processed for histopathological study. The results of the 28 day subacute toxicity study did not show evidence of any changes in body weight, food and water intake, hematological parameters, liver and kidney function tests when compared with the control animals. The vital organs of animals treated with Diakyur for 28 days did not show any histopathological evidence of pathological lesions. From the results it is concluded that Diakyur at the dose of 1600 mg/kg p.o. is safe for longterm treatment in diabetic conditions.

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Two series of 2,4 thiazolidinedione derivatives (T 1 -T 4 ) and (T 5 -T 8 ) containing substituted imidazoles and one series of 5-substituted 2,4-thiazolidinedione derivatives (T 9 -T 12 ) were designed and synthesized. The chemical structures of all the three series of 2,4 thiazolidinedione derivatives have been elucidated by spectral studies (IR, 1 H NMR, 13 C NMR and Mass spectra). The compounds were screened for their anti-bacterial activity against Staphylococcus aureus ATCC-9144, Staphylococcus epidermidis ATCC-155, Escherichia coli ATCC-25922, Pseudomonas aeruginosa ATCC-2853 bacterial species and antifungal activity against Aspergillus niger ATCC-9029, Aspergillus fumigatus ATCC-46645 by the paper disc diffusion technique. The minimum inhibitory concentrations (MICs) of the compounds were also determined by the agar streak dilution method. Among the synthesized compounds methyl-2-(4-((3-(2-methoxy-2-oxoethyl)-2,4-dioxothiazolidine-5-ylidene) methyl)-1H-imidazol-1-yl) acetate (T 2 ), methyl-2-(5-((1-(2-(4-fluorophenylthio)ethyl)-1H-imidazol-4-yl)methylene)-2,4-dioxo thiazolidin-3-yl)acetate (T 4 ) and methyl-2-(2-((3-(2-methoxy-2-oxoethyl)-2,4-dioxothiazolidine-5-ylidene) methyl)-1H-imidazol-1-yl) acetate (T 8 ) were found to possess moderately potent antimicrobial activity with MIC of 1.9, 1.4, 1.6, 0.56, 8.8, 2.3 lg/ml (T 2 ), 3.8, 2.2, 1.6, 2.8, 7.9, 1.7 lg/ml (T 4 ) and 2.7, 3.39, 3.2, 1.4, 8.2, 3.4 lg/ml (T 8 ) against the above mentioned respective strains. All other compounds had shown mild to moderate antibacterial and antifungal activities. ª 2014 Production and hosting by Elsevier B.V. on behalf of King Saud University.