Antistaphylococcal and biofilm inhibitory activities of acetyl-11-keto-β-boswellic acid from Boswellia serrata

<p>Abstract</p> <p>Background</p> <p>Boswellic acids are pentacyclic triterpenes, which are produced in plants belonging to the genus <it>Boswellia</it>. Boswellic acids appear in the resin exudates of the plant and it makes up 25-35% of the resin. β-boswellic acid, 11-keto-β-boswellic acid and acetyl-11-keto-β-boswellic acid have been implicated in apoptosis of cancer cells, particularly that of brain tumors and cells affected by leukemia or colon cancer. These molecules are also associated with potent antimicrobial activities. The present study describes the antimicrobial activities of boswellic acid molecules against 112 pathogenic bacterial isolates including ATCC strains. Acetyl-11-keto-β-boswellic acid (AKBA), which exhibited the most potent antibacterial activity, was further evaluated in time kill studies, postantibiotic effect (PAE) and biofilm susceptibility assay. The mechanism of action of AKBA was investigated by propidium iodide uptake, leakage of 260 and 280 nm absorbing material assays.</p> <p>Results</p> <p>AKBA was found to be the most active compound showing an MIC range of 2-8 μg/ml against the entire gram positive bacterial pathogens tested. It exhibited concentration dependent killing of <it>Staphylococcus aureus </it>ATCC 29213 up to 8 × MIC and also demonstrated postantibiotic effect (PAE) of 4.8 h at 2 × MIC. Furthermore, AKBA inhibited the formation of biofilms generated by <it>S. aureus </it>and <it>Staphylococcus epidermidis </it>and also reduced the preformed biofilms by these bacteria. Increased uptake of propidium iodide and leakage of 260 and 280 nm absorbing material by AKBA treated cells of <it>S aureus </it>indicating that the antibacterial mode of action of AKBA probably occurred via disruption of microbial membrane structure.</p> <p>Conclusions</p> <p>This study supported the potential use of AKBA in treating <it>S. aureus </it>infections. AKBA can be further exploited to evolve potential lead compounds in the discovery of new anti-Gram-positive and anti-biofilm agents.</p

Tandem Catalysis by Lipase in a Vinyl Acetate-Mediated Cross-Aldol Reaction

The lipase Novozym435 (0.6% w/w) was used in tandem with organocatalysts in a first vinyl/isopropenyl acetate-mediated aldol reaction. The reaction was facilitated through the lipase-catalyzed in situ generation of acetaldehyde/acetone. The importantfeatures of the present methodology include the mild and facile reaction conditions, regenerability of the lipase, comparatively high yields and minimal side product formation

Boswellic acids: a group of medicinally important compounds

This review, containing over 276 references, covers the progress made in the chemistry and bioactivity of this important group of triterpenoids. Though initially known for their anti-inflammatory and antiarthritic activities through a unique 5-LO inhibition mechanism, boswellic acids have recently attained significance due to their anti-cancer properties. The phytochemistry and chemical modifications, including mechanism of action, are discussed

Synthesis of Biaryls via Benzylic C–C Bond Cleavage of Styrenes and Benzyl Alcohols

A metal-free oxidative coupling of styrenes and benzyl alcohols with arenes has been developed for the synthesis of biaryls. The reaction features a conspicuous benzylic C–C bond cleavage of styrenes and benzyl alcohols. The reaction with both substrates proceeds through a common aldehydic intermediate formed through oxidative C–C bond cleavage of alkene and oxidation of benzyl alcohols. The reaction proceeds efficiently over a broad range of substrates with excellent functional group tolerance

A facile approach towards enantiomerically pure masked β-amino alcohols

b-Amino alcohols are bioactive molecules, used also as catalysts in asymmetric C–C bond formation. While asymmetric synthesis has been the preferred route for their preparation, there was always been a need to develop a facile methodology involving environmentally friendly transformations. Masked amines in the form of phthalimide alcohols, prepared via a fast coupling reaction in an ionic liquid as a reusable reaction media together with reduction and an efficient biocatalytic resolution, offer a green methodology for enantiomerically pure products(ee . 99%, 50 g L21)

2,3-Unsaturated Allyl Glycosides as Glycosyl Donors for Selective α-Glycosylation

In the presence of NBS and a catalytic amount of a Lewis acid, 2,3-unsaturated allyl glycosides [6-(allyloxy)-3,6-dihydro-2-(hydroxymethyl)-2H-pyran-3-ol] have been successfully used as versatile glycosyl donors for the stereoselective R-glycosylation of a variety of alcohols comprising sensitive functions such as acetonide, keto, nitro, and ester in 50�90% yields. The methodology offers an equally facile alternative to 4-pentenyl replacement in unsaturated sugars

A general metal-free approach for the stereoselective synthesis of C-glycals from unactivated alkynes

A novel metal-free strategy for a rapid and α-selctive C-alkynylation of glycals was developed. The reaction utilizes TMSOTf as a promoter to generate in situ trimethylsilylacetylene for C-alkynylation. Thanks to this methodology, we can access C-glycosides in a single step from a variety of acetylenes , i.e., arylacetylenes and most importantly aliphatic alkynes

Lipase-catalyzed Separation of Geometrical Isomers: Geraniol 13Nerol

The substrate/lipase ratio as well as pH of the buffer medium played important roles in the resolution of geometrical isomeric mixture of geraniol 13nerol. Based on the results, an immobilized lipase from Pseudomonas fluorescens (PFL) was found effective in selective transesterifications whereas Pseudomonas sp. Lipase (PSL) was found to be useful in hydrolyzing the esters