Application of chiral stationary phases for the separation of vitamin A acetate isomers.

The separation of vitamin A acetate isomers is essential for quality assurance of e.g. nutrition supplements, cosmetics, and pharmaceutical ingredients. High performance liquid chromatography (HPLC) is currently the most suitable analytical method for tackling this challenging separation task. However, the existing methods based on normal phase chromatography (NPC) are poorly reproducible due to the typical disadvantages of NPC, such as long equilibration times and fluctuation in retention factors. A new reversed phase method developed in our labs allows the separation of the isomers applying a chiral stationary phase (CSP). This phase consists of an immobilized polysaccharide which can be used in every chromatographic mode. However, they are not typically used in reversed phase mode. Through the screening of various stationary phases with different polysaccharide based chiral selectors, the choice of the ideal stationary phase could be confirmed, allowing to draw conclusions about the retention mechanism. The CSP Chiralpak IG-3 was found to be the most suitable among the examined. Regarding the separation mechanism, the spatial helical structure of the polysaccharide derivatives was confirmed to be of particular significance. In addition to the stationary phase, the mobile phase was tested for optimization regarding composition, gradient parameters as well as temperature using chromatographic method optimization software for the sake of method robustness.

Carboxymethyl potato starch hydrogels encapsulated cyclodextrin metal-organic frameworks for enantioselective loading of S-naproxen and its programmed release.

A natural polysaccharide-based vehicle is facilely prepared for enantioselective loading of S-naproxen (S-NPX) and its programmed release. Cyclodextrin metal-organic frameworks (CD-MOF) are synthesized through the coordination of K+ with γ-cyclodextrin (γ-CD). Compared with R-NPX, the CD-MOF preferably combines with S-NPX, which can be confirmed by the thermodynamic calculations. The S-NPX loaded CD-MOF (CD-MOF-S-NPX) is grafted with disulfide bond (-S-S-) to improve its hydrophobicity, and the loaded S-NPX is further encapsulated in the chiral cavity of γ-CD by carboxymethyl potato starch (CPS) hydrogels. The intermolecular hydrogen bonding of the CPS hydrogels is prone to be destroyed in mildly basic media (∼pH 8.0), resulting in the swelling of the hydrogels; the -S-S- linkage in the vehicle can be cleaved in the presence of glutathione (GSH), leading to the collapse of the CD-MOF. Therefore, the programmed release of S-NPX can be achieved. Also in this work, the release kinetics is investigated, and the results indicate that the release of S-NPX is controlled by the Higuchi model.

C- and N-Phosphorylated Enamines-An Avenue to Heterocycles: NMR Spectroscopy.

The review presents extensive data (from the works of the author and literature) on the structure of C- and N-chlorophosphorylated enamines and the related heterocycles obtained by multipulse multinuclear 1H, 13C, and 31P NMR spectroscopy. The use of phosphorus pentachloride as a phosphorylating agent for functional enamines enables the synthesis of various C- and N-phosphorylated products that are heterocyclized to form various promising nitrogen- and phosphorus-containing heterocyclic systems. 31P NMR spectroscopy is the most convenient, reliable and unambiguous method for the study and identification of organophosphorus compounds with different coordination numbers of the phosphorus atom, as well as for the determination of their Z- and E-isomeric forms. An alteration of the coordination number of the phosphorus atom in the phosphorylated compounds from 3 to 6 leads to a drastic screening of the 31P nucleus from about +200 to -300 ppm. The unique structural features of nitrogen-phosphorus-containing heterocyclic compounds are discussed.

Understanding of formation and change of chiral aroma compounds from tea leaf to tea cup provides essential information for tea quality improvement.

Abundant secondary metabolites endow tea with unique quality characteristics, among which aroma is the core component of tea quality. The ratio of chiral isomers of aroma compounds greatly affects the flavor of tea leaves. In this paper, we review the progress of research on chiral aroma compounds in tea. With the well-established GC-MS methods, the formation of, and changes in, the chiral configuration of tea aroma compounds during the whole cycle of tea leaves from the plant to the tea cup has been studied in detail. The ratio of aroma chiral isomers varies among different tea varieties and finished teas. Enzymatic reactions involving tea aroma synthases and glycoside hydrolases participate the formation of aroma compound chiral isomers during tea tree growth and tea processing. Non-enzymatic reactions including environmental factors such as high temperature and microbial fermentation involve in the change of aroma compound chiral isomers during tea processing and storage. In the future, it will be interesting to determine how changes in the proportions of chiral isomers of aroma compounds affect the environmental adaptability of tea trees; and to determine how to improve tea flavor by modifying processing methods or targeting specific genes to alter the ratio of chiral isomers of aroma compounds.

Leaf cuticular waxes of wild-type Welsh onion (Allium fistulosum L.) and a wax-deficient mutant: Compounds with terminal and mid-chain functionalities.

Plant cuticles cover aerial organs to limit non-stomatal water loss and protect against insects and pathogens. Cuticles contain complex mixtures of fatty acid-derived waxes, with various chain lengths and diverse functional groups. To further our understanding of the chemical diversity and biosynthesis of these compounds, this study investigated leaf cuticular waxes of Welsh onion (Allium fistulosum L.) wild type and a wax-deficient mutant. Leaf waxes were extracted with chloroform, separated using thin layer chromatography (TLC), and analyzed using gas chromatography-mass spectrometry (GC-MS). The extracts contained typical wax compound classes found in nearly all plant lineages but also two uncommon compound classes. Analyses of characteristic MS fragmentation patterns followed by comparisons with synthetic standards identified the latter as very-long-chain ketones and primary ketols. The ketols were minor compounds, with chain lengths ranging from C28 to C32 and carbonyls mainly on C-18 and C-20 in wild type wax, and a C28 chain with C-16 carbonyl in the mutant. The ketones made up 70% of total wax in the wild type, consisting mainly of C31 isomers with carbonyl group on C-14 or C-16. In contrast, the mutant wax comprised only 4% ketones, with chain lengths C27 and C29 and carbonyls predominantly on C-12 and C-14, respectively. A two-carbon homolog shift between wild type and mutant was also observed in the primary alcohols (a major wax compound class), whilst alkanes exhibited a four-carbon shift. Overall, the compositional data shed light on possible biosynthetic pathways to wax ketones that can be tested in future studies.

Production of Two Isomers of Sphaeralcic Acid in Hairy Roots from Sphaeralcea angustifolia.

The Sphaeralcea angustifolia plant is used as an anti-inflammatory and gastrointestinal protector in Mexican traditional medicine. The immunomodulatory and anti-inflammatory effects have been attributed to scopoletin (1), tomentin (2), and sphaeralcic acid (3) isolated from cells in suspension cultures and identified in the aerial tissues of the wild plant. The hairy roots from S. angustifolia established by infecting internodes with Agrobacterium rhizogenes were explored to produce active compounds based on biosynthetic stability and their capacity to produce new compounds. Chemical analysis was resumed after 3 years in these transformed roots, SaTRN12.2 (line 1) produced scopoletin (0.0022 mg g-1) and sphaeralcic acid (0.22 mg g-1); instead, the SaTRN7.1 (line 2) only produced sphaeralcic acid (3.07 mg g-1). The sphaeralcic acid content was 85-fold higher than that reported for the cells in the suspension cultivated into flakes, and it was similar when the cells in suspension were cultivated in a stirring tank under nitrate restriction. Moreover, both hairy root lines produced stigmasterol (4) and ß-sitosterol (5), as well as two new naphthoic derivates: iso-sphaeralcic acid (6) and 8-methyl-iso-sphaeralcic acid (7), which turned out to be isomers of sphaeralcic acid (3) and have not been reported. The dichloromethane-methanol extract from SaTRN7.1 hairy root line had a gastroprotective effect on an ulcer model in mice induced with ethanol.

Quality Analysis of Canola and Mustard Oil Using Fluorescence Spectroscopy.

The potential of Fluorescence spectroscopy has been utilized for the quality analysis of canola and mustard oil along with the effect of heating on their molecular composition has been investigated. Laser diode at 405 nm has been employed directly to oil surface to excite both oil type samples and their emission spectra has been recorded by an in-house developed Fluorosensor. The emission spectra of both oil types unveiled that they contain carotenoids, isomers of vitamin E and chlorophylls that exhibit their fluorescence at 525 and 675/720 nm, and these can be used as markers for their quality assurance. Fluorescence spectroscopy is a fast, reliable and non-destructive analytical technique for the quality assessment of both oil types. Moreover, the effect of temperature on their molecular composition has been investigated by heating them at 110, 120, 130, 140, 150, 170, 180 and 200 °C, each sample for 30 min which was done because both oils are used for cooking and frying. On heating, the deterioration of carotenoids and isomers of vitamin E in both oil types occurred with an increase in the oxidised products. However, it was found that up to 150 °C, both oil types can be used safely for cooking/frying purpose where they do not lose much of their valuable ingredients and up to 180 °C for deep frying, both oils can be used with less deterioration and after that both deteriorated much due to rapid increase of the oxidized products. The portable Fluorosensor, therefore, proved as an excellent device for quality screening of edible oils based on carotenoids and vitamin E.

Polyacetylene Isomers Isolated from Bidens pilosa L. Suppress the Metastasis of Gastric Cancer Cells by Inhibiting Wnt/ß-Catenin and Hippo/YAP Signaling Pathways.

(E)-7-Phenyl-2-hepten-4,6-diyn-1-ol (1) and (Z)-7-Phenyl-2-hepten-4,6-diyn-1-ol (2) are isomeric natural polyacetylenes isolated from the Chinese medicinal plant Bidens pilosa L. This study first revealed the excellent anti-metastasis potential of these two polyacetylenes on human gastric cancer HGC-27 cells and the distinctive molecular mechanisms underlying their activities. Polyacetylenes 1 and 2 significantly inhibited the migration, invasion, and adhesion of HGC-27 cells at their non-toxic concentrations in a dose-dependent manner. The results of a further mechanism investigation showed that polyacetylene 1 inhibited the expressions of Vimentin, Snail, ß-catenin, GSK3ß, MST1, YAP, YAP/TAZ, and their phosphorylation, and upregulated the expression of E-cadherin and p-LATS1. In addition, the expressions of various downstream metastasis-related proteins, such as MMP2/7/9/14, c-Myc, ICAM-1, VCAM-1, MAPK, p-MAPK, Sox2, Cox2, and Cyr61, were also suppressed in a dose-dependent manner. These findings suggested that polyacetylene 1 exhibited its anti-metastasis activities on HGC-27 cells through the reversal of the EMT process and the suppression of the Wnt/ß-catenin and Hippo/YAP signaling pathways.

Comparative Analysis of Physical and Chemical Properties of Differently Obtained Zn-Methionine Chelate with Proved Antibiofilm Properties (Part II).

The previously demonstrated activity of aqueous solutions of methionine and zinc salts against biofilms of uropathogenic bacteria prompted us to investigate the structure and properties of zinc methionine complex obtained from such solutions. The paper presents the analysis results of zinc coordination complexes with methionine obtained by synthesis (0.034 mol of L-methionine, 0.034 mol of NaOH, 40 mL of H2O, 0.017 mol ZnSO4, 60 °C) and simple crystallization from water solution (25 mL of a solution containing 134 mmol/L L-methionine, 67 mmol/L ZnSO4, pH = 5.74, I = 0.37 mmol/L, crystallization at room temperature during more than two weeks). IR spectral analysis and X-ray diffraction showed the structural similarity of the substances to each other, in agreement with the data described in the literature. DSC confirmed the formation of a thermally stable (in the range from -30 °C to 180 °C) chelate compound in both cases and indicated the possible retention of the polymorphic two-dimensional structure inherent in L-methionine with the temperature of phase transition 320 K. The crystallized complex had better solubility in water (100 to 1000 mL per 1.0 g) contra the synthesized analog, which was practically insoluble (more than 10 000 mL per 1.0 g). The results of the solubility assessment, supplemented by the results of the dispersion analysis of solutions by the dynamic light scattering method indicated the formation of zinc-containing nanoparticles (80 nm) in a saturated water solution of a crystallized substance, suggesting the crystallized substance may have higher bioavailability. We predicted a possibility of the equivalent existence of optically active cis and trans isomers in methionine-zinc solutions by the close values of formation enthalpy (-655 kJ/mol and -657 kJ/mol for cis and trans forms, respectively) and also illustrated by the polarimetry measurement results (∆α = 0.4°, pH = 5.74, C(Met) = 134 mmol/L; the concentration of metal ion gradually increased from 0 to 134 mmol/L). The obtained results allowed us to conclude that the compound isolated from the solution is a zinc-methionine chelate with the presence of sulfate groups and underline the role of the synthesis route for the biopharmaceutical characteristics of the resulting substance. We provided some quality indicators that it may be possible to include in the pharmacopeia monographs.

Lutein Isomers: Preparation, Separation, Structure Elucidation, and Occurrence in 20 Medicinal Plants.

Lutein and its cis-isomers occur in a lot of plants, including a variety of flowers. In this study, lutein isomers were produced via iodine-catalyzed isomerization, and four cis-isomers (9Z-, 9'Z-, 13Z-, and 13Z') were isolated by means of column chromatography and semipreparative HPLC. The structures of the 9'Z- and 13'Z-isomers were elucidated via NMR measurements. These compounds were used as standards for the HPLC-DAD-MS determination of the carotenoid composition of the flowers of 20 plant species, in which lutein and its geometrical isomers are the main components. The flowers showed great variation in their cis- and trans-lutein content, and also in the presence or absence of other carotenoids, such as violaxanthin, neoxanthin, ß-cryptoxanthin, and ß-carotene. Some of the investigated flowers were found to be rich sources of lutein without zeaxanthin.

Flavor components detection and discrimination of isomers in Huaguo tea using headspace-gas chromatography-ion mobility spectrometry and multivariate statistical analysis.

Aroma components are one of the crucial factors in dynamic processes analysis, quality control, and origin traceability. Various categories of Huaguo Tea possessed different taste due to the generation of aroma. In this study, a comprehensive analysis of volatiles was conducted for five popular Huaguo Tea samples (Lemon Slices, Bitter Gourd Slices, Citri Reticulatae Pericarpium, Red Lycium Barbarum, and Black Lycium Barbarum) via gas chromatography-ion mobility spectrometry (GC-IMS) combining with multivariate statistical strategies. Comparison analysis was achieved with the properties of visually and intuitively by drawing of topography plots. A total of one hundred and eighty volatiles were distinguished. Aliphatic isomers were identified simultaneously by fingerprint spectra. Alcohols, aldehydes, esters, and ketones were the most abundant volatiles in Huaguo Tea samples. To characterize the Huaguo Tea precisely and establish an analysis model for their classification, multivariate statistical analysis was applied to distinguish different Huaguo Tea. Satisfied discrimination was obtained by principal component analysis (PCA) and orthogonal partial least squares discrimination analysis (OPLS-DA) based on the HS-GC-IMS results with the robustness parameter (R2Y) of 99.4%, and prediction ability parameter (Q2) of 98.6%, respectively. The results provide a theoretical basis for aroma discrimination, isomer identification, and categories analysis of Huaguo Tea.

Structured lipids produced from palm-olein oil by interesterification: A controllable lipase-catalyzed approach in a solvent-free system.

Palm olein (POL) was modified by enzymatic interesterification with different degrees of acyl migration in a solvent-free packed bed reactor. The fatty acid and acylglycerol composition, isomer content, thermodynamic behavior, and relationship between crystal polymorphism, solid fat content (SFC), crystal microstructure, and texture before and after modification were studied. We found that the increase in sn-2 saturation interesterification was not only due to the generated tripalmitin (PPP) but also caused by acyl migration, and the SFC profiles were changed accordingly. The emergence of high melting point acylglycerols was an important factor accelerating the crystallization rate, further shortening the crystallization induction time, leading to the formation of large crystal spherulites, thereby reducing the hardness. The transformation from the ß' to the ß form occurred during post-hardening during storage. The isomer content also affected the physicochemical properties of the modified POL.

Characterization of ginsenoside structural isomers from mixtures using in situ methylation with direct analysis in real-time ionization tandem mass spectrometry.

Characterization of structural isomers of bioactive molecules is important for recognizing their functions, but it has been challenging due to their highly similar structures. As the main bioactive constituents of Panax ginseng, ginsenosides have different structural isomers attributed to the aglycone structure and glycosylation sites as well as stereochemistry of sugar groups attached. This work demonstrated a simple and robust in situ methylation reaction with tetramethylammonium hydroxide (TMAH) using ambient ionization source of direct analysis in real time (DART) to characterize saponin structural isomers. The DART ion source provides favorable conditions to methylate hydroxyl groups of ginsenoside instantaneously with TMAH, and it can ionize the methylated products at the same time. Methylated ginsenoside stereoisomers even with subtle structure differences generated very different mass signals from full-scan MS and tandem MS. High-resolution mass spectrometry aided the assignment of molecular structures of the various precursor and fragment ions from different ginsenosides, which provided structural information for both the aglycone skeleton and the sugar moieties in ginsenosides. The presented method was successfully used for the identification of ginsenosides in Panax ginseng, and saponin isomers were characterized without the need for chromatographic separation and/or tedious offline sample pretreatment.

Assessment of the antioxidant activities of representative optical and geometric isomers of astaxanthin against singlet oxygen in solution by a spectroscopic approach.

Astaxanthin (AST) is a natural antioxidant and has been widely applied as a food supplement. While astaxanthin has many isomers, there are few studies comparing its physicochemical properties. In this work, we were concerned about their antioxidant activities against external oxidative stresses, and specifically, the singlet oxygen (1O2) quenching capacities of the representative optical and geometric isomers of astaxanthin were examined. Methylene blue (MB) was used as the photosensitizer to produce 1O2, and 1,3-diphenylisobenzofuran (DPBF) was used to probe 1O2. Our results showed that the 1O2 quenching capacities of the optical isomers, including 3S,3'S, 3R,3'S, and 3R,3'R all-trans-astaxanthin, are identical. In contrast, the 1O2 quenching capacity of cis-astaxanthin is higher than that of all-trans-astaxanthin. As such, this work provides an effective spectroscopic approach to assessing the antioxidant activities of various forms of astaxanthin against singlet oxygen, and demonstrates the remarkable difference among the geometric isomers.

Isomeric lipid signatures reveal compartmentalized fatty acid metabolism in cancer.

The cellular energy and biomass demands of cancer drive a complex dynamic between uptake of extracellular FAs and their de novo synthesis. Given that oxidation of de novo synthesized FAs for energy would result in net-energy loss, there is an implication that FAs from these two sources must have distinct metabolic fates; however, hitherto, all FAs have been considered part of a common pool. To probe potential metabolic partitioning of cellular FAs, cancer cells were supplemented with stable isotope-labeled FAs. Structural analysis of the resulting glycerophospholipids revealed that labeled FAs from uptake were largely incorporated to canonical (sn-) positions on the glycerol backbone. Surprisingly, labeled FA uptake also disrupted canonical isomer patterns of the unlabeled lipidome and induced repartitioning of n-3 and n-6 PUFAs into glycerophospholipid classes. These structural changes support the existence of differences in the metabolic fates of FAs derived from uptake or de novo sources and demonstrate unique signaling and remodeling behaviors usually hidden from conventional lipidomics.

Conduction of a chemical structure-guided metabolic phenotype analysis method targeting phenylpropane pathway via LC-MS: Ginkgo biloba and soybean as examples.

The phenylpropane pathway (PPP) is one of the most extensively investigated metabolic routes. This pathway biosynthesizes many important active ingredients such as phenylpropanoids and flavonoids that affect the flavor, taste and nutrients of food. How to elucidate the metabolic phenotype of PPP is fundamental in food research and development. In this study, we designed a structural periodical table filled with 103 metabolites produced from PPP. All of them especially the 62 structural isomers were qualified and quantified with high resolution and sensitivity via multiple reaction mode in liquid chromatography tandem triple quadrupole mass spectrometry. Ginkgo biloba and soybean were used as samples for the practical application of this method: The delicate spatial-temporal metabolic balance of PPP from ginkgo biloba has been first elucidated; It is first confirmed that the salt and draught stresses could redirect the biosynthesis trend of PPP to produce more isoflavones in soybean leaves.

Free, soluble conjugated and insoluble bonded phenolic acids in Keemun black tea: From UPLC-QQQ-MS/MS method development to chemical shifts monitoring during processing.

Phenolic acids, including benzoic acid and hydroxycinnamic acid derivatives, are the main compounds of black tea. An efficient and accurate analytical method to quantify ten phenolic acids was established and validated by ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-QQQ-MS/MS). The chemical shifts during the processing of Keemun black tea were analyzed and the phenolic acids were quantified. Compared with fresh tea leaves, after processing, the contents of free phenolic acids, including gallic acid, salicylic acid, p-coumaric acid, and ferulic acid, increased markedly. Still, the contents of soluble conjugated phenolic acids, including p-coumaroylquinic acid isomers and chlorogenic acid isomers, decreased. Furthermore, the total contents of lignin, and insoluble bonded phenolic acids decreased. The adduct of (-)-epigallocatechin gallate and 3-caffeoylquinic acid was detected in tea samples, and its content increased highly after fermentation. The developed and validated analytical method can be used to monitor the manufacturing process of black tea.

[Evaluation and optimization of content determination method of Chrysanthemi Flos in Chinese Pharmacopoeia].

This study discovered that the resolution of 3,5-O-dicaffeoylquinic acid(isochlorogenic acid A) in the content determination method of Chrysanthemi Flos in Chinese Pharmacopoeia(ChP)(2020 edition) was poor, which affected accurate quantification. We tested the method in ChP with chromatographic columns of seven brands to clarify the problems in the existing method, optimized the chromatographic conditions by adjusting the mobile phase composition and elution ratio and replacing the chromatographic column packing, and carried out the reproducibility assay for the new method. The two methods were compared for the content determination results of Chrysanthemi Flos prepared from six different varieties. As evaluated by the resolution based on different chromatographic columns of seven brands, the existing method failed to separate isochlorogenic acid A and isochlorogenic acid D well. The peaks of the two components were not completely separated on three chromatographic columns, and isochlorogenic acid A and isochlorogenic acid D generated a co-effluent peak in the other four columns. Isochlorogenic acid A and isochlorogenic acid D could be completely separated under the optimized chromatographic conditions. The difference in the peak areas of isochlorogenic acid A+isochlorogenic acid D obtained by the optimized method and the method in ChP was not significant, with deviation less than 3.0%, which further proved that the result measured by the method in ChP was the co-effluent of isochlorogenic acid A and isochlorogenic acid D. The optimized method can ensure the accurate quantification of isochlorogenic acid A. The existing content determination method of Chrysanthemi Flos has the problem of poor resolution. It is recommended to revise the chromatographic conditions for the content determination method of Chrysanthemi Flos to improve the resolution of isochlorogenic acid A and ensure its accurate quantification.

Research progress on conjugated linoleic acid bio-conversion in Bifidobacterium.

Conjugated linoleic acid (CLA), a group of 18 carbon conjugated dienoic acids, has been considered a promising food supplement owing to its various physiological benefits to human health. Owing to a high isomer selectivity of the product and a simple isolation and purification process, microbial CLA has become a research hotspot. Many food-grade bacteria such as Lactobacillus and Bifidobacterium have been reported to possess CLA-production ability. Particularly, Bifidobacterium has high bio-conversion rate and enhanced CLA production, and is one of the best and most promising CLA producers among microorganisms. Consequently, this article aimed to review the current knowledge about Bifidobacterium CLA producers, the complex factors regulating CLA production in Bifidobacterium, the role of CLA production in Bifidobacterium, and the potential mechanism underlying Bifidobacterium CLA production. In summary, the above information offers novel insights into the production of food-grade CLA as well as the rational design of health-promoting fermented foods or synbiotics.

WCK 1152, WCK 1153: Discovery and structure activity relationship for the treatment of resistant pneumococcal and staphylococcal respiratory infections.

Novel antibacterial agents needed constantly to counter the ever emergent resistance development to commercially available drugs; one of the effective synthetic antibacterial classes is fluoroquinolone (FQ). This study includes structure activity relationship based design and synthesis of novel fluoroquinolone molecules active against resistant pathogens bearing mutations of DNA gyrase and/or topoisomerase IV which also express efflux pumps. Here, series of compounds were prepared by treating 1-cyclopropyl-6,7-difluoro-8-methoxy-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid as a core with various 4-substituted-3,3-dialkyl piperidines as side chains, through conventional synthetic approaches. Subsequently, antibacterial activities of these fluoroquinolones were examined against Streptococcus pneumoniae, SPN 5844 (Moxi resistant DNA gyrase and topo IV mutant) and SPN 706 (FQ efflux positive). The current manuscript covers >50 examples of fluoroquinolone NCEs, amongst 20 NCEs have shown MIC in the range of (0.4 to >6.25 µg/ml) for SPN 5844 and (0.1-12.5 µg/ml) for SPN 706 strains. During the course of this study; WCK 919, comprising two chiral isomers; WCK 1152 and WCK 1153 were emerged as lead among the different series synthesized. Advance studies suggested either WCK 1152 or WCK 1153 are the worthy candidates for further clinical developments for respiratory infections caused by resistant pneumococci and staphylococci. However, on the basis of in house preclinical work, WCK 1152 had been selected for phase-1 domestic clinical trials.