1. Evaluating hop extract concentrations found in commercial beer to inhibit Streptococcus mutans biofilm formation
Eric R Gregory, Renad F Bakhaider, Grace F Gomez, Ruijie Huang, Elizabeth A S Moser, Richard L Gregory J Appl Microbiol. 2022 Sep;133(3):1333-1340. doi: 10.1111/jam.15632. Epub 2022 Jun 5.
Aims: The purpose of this study was to compare the effect of hop extracts with diverse β-acid concentrations on Streptococcus mutans biofilm formation. Methods and results: Ten different hop extracts, with α-acid concentrations similar to those found in commercial beer products and β-acid concentrations ranging from 2.6 to 8.1%, were added to distilled water to make standardized concentrations. S. mutans isolates were treated with hop extract dilutions varying from 1:2 to 1:256. The minimum inhibitory, minimum bactericidal and minimum biofilm inhibitory concentrations were determined and the optical density was evaluated. Live/dead staining confirmed the bactericidal effects. Biofilm formation of several strains of S. mutans was significantly inhibited by hop extract dilutions of 1:2, 1:4, 1:8, 1:16 and 1:32. Strong negative correlations were observed between α- and β-acid concentrations of the hop extracts and S. mutans total growth and biofilm formation. Conclusions: The use of hop extracts prepared similarly to commercial beer decreased S. mutans biofilm formation. Significance and impact of the study: The inclusion of hops in the commercial beer products may provide beneficial health effects. Further studies are warranted to determine an effect in vivo on the development of dental caries.
2. Fluorescent probes for monitoring myeloperoxidase-derived hypochlorous acid: a comparative study
Karolina Pierzchała, et al. Sci Rep. 2022 Jun 3;12(1):9314. doi: 10.1038/s41598-022-13317-8.
MPO-derived oxidants including HOCl contribute to tissue damage and the initiation and propagation of inflammatory diseases. The search for small molecule inhibitors of myeloperoxidase, as molecular tools and potential drugs, requires the application of high throughput screening assays based on monitoring the activity of myeloperoxidase. In this study, we have compared three classes of fluorescent probes for monitoring myeloperoxidase-derived hypochlorous acid, including boronate-, aminophenyl- and thiol-based fluorogenic probes and we show that all three classes of probes are suitable for this purpose. However, probes based on the coumarin fluorophore turned out to be not reliable indicators of the inhibitors' potency. We have also determined the rate constants of the reaction between HOCl and the probes and they are equal to 1.8 × 104 M-1s-1 for coumarin boronic acid (CBA), 1.1 × 104 M-1s-1 for fluorescein based boronic acid (FLBA), 3.1 × 104 M-1s-1 for 7-(p-aminophenyl)-coumarin (APC), 1.6 × 104 M-1s-1 for 3'-(p-aminophenyl)-fluorescein (APF), and 1 × 107 M-1s-1 for 4-thiomorpholino-7-nitrobenz-2-oxa-1,3-diazole (NBD-TM). The high reaction rate constant of NBD-TM with HOCl makes this probe the most reliable tool to monitor HOCl formation in the presence of compounds showing HOCl-scavenging activity.
3. Lewis Acid-Catalyzed 2,3-Dihydrofuran Acetal Ring-Opening Benzannulations toward Functionalized 1-Hydroxycarbazoles
Shaoren Yuan, Gabriel Guerra Faura, Hailey E Areheart, Natalie E Peulen, Stefan France Molecules. 2022 Nov 30;27(23):8344. doi: 10.3390/molecules27238344.
The development of a Lewis acid-catalyzed, intramolecular ring-opening benzannulation of 5-(indolyl)2,3-dihydrofuran acetals is described. The resulting 1-hydroxycarbazole-2-carboxylates are formed in up to 90% yield in 1 h. The dihydrofuran acetals are readily accessed from the reactions of enol ethers and α-diazo-β-indolyl-β-ketoesters. To highlight the method's synthetic utility, a formal total synthesis of murrayafoline A, a bioactive carbazole-containing natural product, was undertaken.
