Ruthenium Chloride—Induced Oxidative Cyclization of Trans-Resveratrol to (±)-ε-Viniferin and Antimicrobial and Antibiofilm Activity Against Streptococcus pneumoniae

Abstract

Polyphenol ε-viniferin ( 2 ) is a protective phytochemical found in several plant families. Here, we report a simple and effective method for the synthesis of (±)-ε-viniferin ( 2 ) as major product and (±)-(E)-ω-viniferin ( 3 ) as a minor product. Synthesized viniferin compounds and standard viniferin were analyzed for antibacterial and antibiofilm activity against Gram-positive bacteria Streptococcus pneumoniae . The minimum inhibitory concentrations (MICs) of (±)-ε-viniferin ( 2 ) and standard viniferin were 20 µm. However, the MICs of (±)-(E)-ω-viniferin ( 3 ) and compound 8 were 40 µm. Although viniferin significantly (p < 0.05) reduced pre-established in vitro biofilms and killed bacteria within the biofilm, it was unable to prevent biofilm formation at sub-MIC concentrations. The time kill experiment revealed that viniferin killed bacteria and reduced 2.8 log 10 bacteria at 2 × MIC concentration after 24 h. Scanning electron microscope (SEM) analysis and live/dead biofilm staining of pre-established biofilms revealed that viniferin treatment disrupts membrane integrity of biofilm bacteria. Crystal violet absorption, total protein, and DNA and RNA release revealed that viniferin alters bacterial cell permeability, eventually killing bacteria.

Organocatalytic enantioselective synthesis of dihydronaphthofurans and dihydrobenzofurans: reaction development and insights into stereoselectivity

“…Among the inorganic bases tested, K 2 CO 3 and Cs 2 CO 3 enhanced the reaction rate, while the enantioselectivity decreased drastically (40% ee in 60 min and 26% ee in 10 min, entries 8 and 9, respectively). A drastic change has been observed in the reaction rates using organic bases compared to inorganic ones (entries [10][11][12][13]. DABCO afforded the best result, with 92% chemical yield and a 65% ee value in 2 h. In the solvent screening studies, the DHN formation reaction was carried out with 5 mol% of organocatalyst VI with one equivalent of the base DABCO (entries [14][15][16][17][18][19][20][21][22][23].…”

“…They may also possess anti-viral, anti-tumor, and anti-fungal properties as in the case of bicunningines A and B, 11 (±)-ε-viniferin, 12 (−)-ephedradine A, 13 toxol, 13 and (±)-lawsonicin (Fig. 1).…”

“…Compounds possessing a fundamental DHF core are of great importance in pharmaceutical and agrochemical chemistry. [11][12][13][14][15] Drugs used to treat many diseases such as hernia, arthritis, and carcinoma have DHN and DHB motifs.…”

Stilbenoids: A Natural Arsenal against Bacterial Pathogens

“…However, further studies are required to elucidate the mechanism of action, since it did not appear to be related to virulence factors production, including pyocyanin, rhamnolipid, and pyochelin by P. aeruginosa [111]. In another study [112], (±)-ε-viniferin along with its stereoisomer (±)-E-ω-viniferin, the hydrogenated and the penta-methylated analogues (Figure 16), was tested on different S. pneumonia strains. (±)-ε-Viniferin was found to be the most active compound with an MIC value of 20 µM even on antibiotic-resistant strains.…”

“…Moreover, (±)-ε-viniferin inhibited bacteria and planktonic cells growth under biofilm, without a bactericidal effect. SEM analysis, crystal violet (CV) absorption assay, significantly increased release of total protein and genetic material (DNA and RNA), all supported alteration and lysis of bacteria cell membrane, thus suggested as the target of (±)-ε-viniferin [112]. δ-Viniferin and pallidol (Figure 16) were investigated for their antibacterial activity in several studies.…”