Asian Pacific Journal of Tropical Biomedicine

415-423

Authors: Chandran Govindasamy, KNS Sirajudeen

Objective: To investigate the effect of alpha-lipoic acid (ALA) supplementation on systolic blood pressure (SBP), renal oxidant-antioxidant status and renal damage in spontaneously hypertensive rats (SHR) and SHR administered with Nω-nitro-L-arginine methyl ester (L-NAME). Methods: Male rats were divided into four groups (SHR, SHR+ALA, SHR+L-NAME, SHR+ALA+L-NAME). The respective group of rats was administered with ALA (100 mg/ kg/day) from age 4 weeks to 28 weeks and L-NAME (25 mg/kg/day) from age 16 weeks to 28 weeks. SBP was measured every two weeks and twenty four hour urine was collected at 4 weeks, 16 weeks and 28 weeks for estimation of protein, creatinine and N-acetyl-β-D-glucosaminidase. At the end of 28 weeks, rats were sacrificed and blood and kidneys collected for assessment of blood creatinine, kidney thiobarbituric acid reactive substances, protein carbonyls, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, glutathione disulfide, glutathione, total antioxidant status and nitric oxide as well as histopathological examination. Results: ALA supplementation significantly reduced SBP of SHR and SHR+L-NAME rats when compared to their respective non-supplemented groups. Renal oxidant status markers including thiobarbituric acid reactive substances and protein carbonyls were significantly reduced on SHR and SHR+L-NAME rats supplemented with ALA at 28 weeks as well as ALA supplementation significantly increased renal antioxidants including superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, glutathione and glutathione/ glutathione disulfide ratio at 28 weeks. No significant change in nitric oxide levels was observed between the ALA supplemented and non-supplemented groups. Renal dysfunction was ameliorated on ALA supplementation as evidenced by significant reduction in urine protein levels, N-acetyl-β-D-glucosaminidase activity and significant increase of creatinine clearance in SHR and SHR+L-NAME at 28 weeks. Renal histopathological examination showed that ALA supplementation prevented vascular damage in SHR and ameliorated glomerular damage in SHR+L-NAME at 28 weeks. Conclusions: ALA has hypotensive and renoprotective effects on both SHR and SHR+L-NAME, which could be due to its ability to ameliorate oxidative stress in the kidneys.

434-442

Authors: Carola A Torres, Mario A Sturla, Ana M Romero, María A Judis

Objective: To identify and isolate phenolic compounds from Cuspidaria convoluta, and to evaluate their antibacterial activity and synergistic effect with antibiotics. Methods: The crude extract was prepared by maceration with methanol (5%). The dry extract was suspended in water and fractionated successively. The most active extract was selected by its antibacterial activity and its total phenol content was determined by spectrophotometry and by HPLC-MS/MS. Bioactive fractions of the most active extract were separated by column chromatography and evaluated by bioautography. Isolated compounds were identified. Minimum inhibitory concentration (MIC) of these compounds was determined by microdilution broth method, and synergism with antibiotics (ampicillin, gentamicin and oxacillin) was tested by checkerboard and time-kill assays. Results: Coumaric acid, catechin/epicatechin, and luteolin were purified and identified from the extract. There was an increase in the antibacterial activity of antibiotics when they were combined with these compounds. The combination of luteolin and ampicillin had the most potent antibacterial activities. The MICs of oxacillin for each of methicillin-resistant Staphylococcus aureus strains were reduced between 4 and 8-fold when these strains were coincubated with sub-MIC (≤ ½ MIC) levels of these compounds, demonstrating that the combination had synergistic effect for all cases. Conclusions: Cuspidaria convoluta contains important pharmacologically active substances that can be used to improve antibiotic efficacy.