Satureja hortensis L. essential oil causes Acinetobacter baumannii membrane disruption

Essential oils are promising antimicrobial agents against various bacteria, including Acinetobacter baumannii, a highly resistant clinical opportunistic pathogen with an increasing prevalence. The traditional application of the aromatic and medicinal plant Satureja hortensis L. (Lamiaceae) as a natural remedy for the treatment of inflammatory diseases, nausea, diarrhea, and various infectious diseases is well known. The aim of the study was to determine the antimicrobial activity and potential target site for S. hortensis essential oil against A. baumannii. The effect of the essential oil was determined using the microdilution broth method. The determined minimal inhibitory concentration (MIC=1 µl mL-1) showed that S. hortensis essential oil possesses a significant anti-A. baumannii effect. The A. baumannii reference strain ATCC 19606 cells in the exponential growth phase were treated for 3 h at 37 °C with MIC of S. hotensis essential oil and examined by scanning electron microscopy. The electron micrographs highlighted the occurrence of collapsed cells with perforations, cell content leakage, cell debris, but also cell autoaggregation (Fig. 1B). The autoaggregation was further confirmed by an autoaggregation test: untreated cells (Fig. 1A) were partially autoaggregative, while the treated cells were highly autoaggregative, as a result of changes of the cell surface properties. Thus, the essential oil affected the membrane systems of A. baumannii cells, causing structural changes of the bacterial cells. Since A. baumannii strains are susceptible to S. hortensis essential oil, the oil possesses a great potential in the control of growth of this species

A comprehensive method for determining cellular uptake of purine nucleoside phosphorylase and adenylosuccinate synthetase inhibitors by H. pylori

Due to the growing number of Helicobacter pylori strains resistant to currently available antibiotics, there is an urgent need to design new drugs utilizing different molecular mechanisms than those that have been used up to now. Enzymes of the purine salvage pathway are possible targets of such new antibiotics because H. pylori is not able to synthetize purine nucleotides de novo. The bacterium’s recovery of purines and purine nucleotides from the environment is the only source of these essential DNA and RNA building blocks. We have identified formycins and hadacidin as potent inhibitors of purine nucleoside phosphorylase (PNP) and adenylosuccinate synthetase (AdSS) from H. pylori — two key enzymes of the purine salvage pathway. However, we have found that these compounds are not effective in H. pylori cell cultures. To address this issue, we have developed a universal comprehensive method for assessing H. pylori cell penetration by drug candidates, with three alternative detection assays. These include liquid chromatography tandem mass spectrometry, UV absorption, and inhibition of the target enzyme by the tested compound. Using this approach, we have shown that cellular uptake by H. pylori of formycins and hadacidin is very poor, which reveals why their in vitro inhibition of PNP and AdSS and their effect on H. pylori cell cultures are so different. The cell penetration assessment method developed here will be extremely useful for validating the cellular uptake of other drug candidates, facilitating the design of new potent therapeutic agents against H. pylori

Phenolic profiling and bioactivities of fresh fruits and jam of Sorbus species

The purpose of this study was a comprehensive examination of the phenolic profile, the vitamin C content, and the antioxidant, anti-acetylcholinesterase, cytotoxic and antimicrobial activities of extracts and jams of fruits of two edible Sorbus species: well characterized S. aucuparia and two insufficiently explored forms of S. torminalis (torminalis and semitorminalis). Characterisation of 44 phenolics was realized using LC–MS/MS and 15 compounds were confirmed, with chlorogenic acid being the most dominant in S. aucuparia and ferulic acid in both S. torminalis forms. S. aucuparia demonstrated potent antioxidant activity, while that of both S. torminalis forms was moderate. Jam extracts had the highest content of vitamin C. S. aucuparia exhibited some anti-acetylcholinesterase activity, while S. torminalis f. torminalis showed the best antimicrobial activity against Staphylococcus aureus and both forms (torminalis and semitorminalis) possessed the highest activity against Escherichia. coli. The results obtained herein are a great base for further research of edible Sorbus species with the aim of promoting their better usage as nutraceuticals. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172058