Pycnogenol® and Ginkgo biloba extract: effect on peroxynitrite-oxidized sarcoplasmic reticulum Ca2+-ATPase

The effect of two natural standardized plant extracts, Pycnogenol® and EGb 761, on sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity and posttranslational modifications induced by peroxynitrite was investigated to assess their possible protective role. EGb 761 was found to have a protective effect on SERCA activity in the concentration range of 5–40 µg/ml. On the other hand, Pycnogenol® caused a decrease of SERCA activity at concentrations of 25 µg/ml. EGb 761 did not prevent protein carbonyl formation upon oxidation with peroxynitrite. On the contrary, Pycnogenol® at the concentrations of 5 and 10 µg/ml significantly decreased the level of protein carbonyls by 44% and 54%, respectively. Neither Pycnogenol® nor EGb 761 exerted a protective effect against thiol group oxidation.The plant extracts studied modulated peroxynitrite-injured SERCA activity by different ways and failed to correlate with posttranslational modifications. Their effect seems to be associated with their ability to change SERCA conformation rather than by their antioxidant capacity

General toxicity assessment of the novel aldose reductase inhibitor cemtirestat

Cemtirestat, 3-mercapto-5H-[1,2,4]-triazino[5,6-b]indole-5-acetic acid was recently designed and patented as a highly selective and efficient aldose reductase inhibitor endowed with antioxidant activity. The aim of the present study was to assess the general toxicity of cemtirestat using in silico predictions, in vitro and in vivo assays. ProTox-II toxicity prediction software gave 17 “Inactive” outputs, a mild hepatotoxicity score (0.52 probability) along with a predicted LD50 of 1000 mg/kg. Five different cell lines were used including the immortalized mouse microglia BV-2, the primary human fibroblasts VH10, the insulinoma pancreatic β-cells INS-1E, the human colon cancer cells HCT116 and the human immortalized epithelial endometrial cell lines HIEEC. In contrast to the clinically used epalrestat, cemtirestat showed remarkably low cytotoxicity in several different cell culture viability tests such as MTT proliferation assay, neutral red uptake, BrdU incorporation, WST-1 proliferation assay and propidium iodide staining followed by flow cytometry. In a yeast spotting assay, the presence of cemtirestat in incubation of Saccaromyces cerevisiae at concentrations as high as 1000 µM did not affect cell growth rate significantly. In the 120-day repeated oral toxicity study in male Wistar rats with daily cemtirestat dose of 6.4 mg/kg, no significant behavioral alterations or toxicological manifestations were observed in clinical and pathological examinations or in hematological parameters. In summary, these results suggest that cemtirestat is a safe drug that can proceed beyond preclinical studies