Isolation and Characterization of Lactic Acid Bacteria From "Trites" Having the Ability to Produce α-Glucosidase Inhibitors

Alpha-glucosidase inhibitors are one of the therapies used for treating type 2 diabetes by inhibiting the absorption of carbohydrates in the gastrointestinal tract. In addition to antimicrobial activity, some probiotic species show α-glucosidase inhibitor activity, making them potential alternative therapies for type 2 diabetes. This study aimed to characterize probiotics from "trites," a traditional food from North Sumatra, Indonesia, that exhibit α-glucosidase inhibition, potentially useful for type 2 diabetes treatment. The probiotic potential of the isolates was evaluated through antagonistic activity, acid tolerance, bile tolerance, and susceptibility to antimicrobial agents. α-Glucosidase inhibition was tested with acarbose as a control. The best-performing isolate, LBSU8, was identified as Pediococcus acidilactici through 16S rRNA gene sequencing. Gene analysis using genome sequencing for LBSU8 revealed antimicrobial secondary metabolites, including RiPPs, polyketide, and NRP, while capsular polysaccharide might contribute to its antidiabetic activity. Though no specific α-glucosidase inhibitory secondary metabolites were identified, enzymes like dTDP-glucose 4,6-dehydratase, transketolase, and glucose-1-phosphate thymidylyltransferase may contribute to this activity. P. acidilactici LBSU8 shows potential as an alternative diabetes therapy in the food and drug industries. Further studies are needed to elucidate the exact mechanism behind its α-glucosidase inhibitory activity and to explore its efficacy in clinical settings.

Advancement in chiral heterocycles for the antidiabetic activity

For the synthesis and development of pharmaceuticals, chirality is an important structural component. Chiral heterocyclic compounds have annoyed the interest of synthetic chemists who are working to create useful and efficient techniques for these molecules. As indicated by the expanding number of chiral drugs created in the last two decades, the link between chirality and pharmacological activity has become more important in the pharmaceutical and biopharmaceutical industries. Approximately 65% of currently used drugs are chiral, and many of them are promoted as racemates in many circumstances. There are a growing number of new chiral heterocyclic compounds with important biological properties and intriguing uses in medical chemistry and drug discovery. In this study, we review current breakthroughs in chiral heterocycles and their different physiological activities that have been published in the last year (from 2010 to early 2023). This study focuses on the current trends in the use of chiral heterocycles in drug design and the creation of several powerful and competent candidates for diabetic illnesses.

Chemoselective Nozaki-Hiyama-Takai-Kishi and Grignard reaction: short synthesis of some carbahexopyranoses

A common, divergent, efficient, stereoselective and short approach for the total syntheses of some carbahexopyranoses namely, MK7607, (-)-gabosine A, (-)-conduritol E, (-)-conduritol F, 6a-carba-β-d-fructopyranose and other carbasugars using chemoselective Grignard or Nozaki-Hiyama-Takai-Kishi (NHTK) reactions and RCM. Herein, the Grignard and NHTK reactions are able to differentiate the reactivity difference between lactol or lactolacetate and aldehyde of 2 & 6 under given conditions to give the desired skeleton chemoselectivity.

Glycomimetics for the inhibition and modulation of lectins

Carbohydrates are essential mediators of many processes in health and disease. They regulate self-/non-self- discrimination, are key elements of cellular communication, cancer, infection and inflammation, and determine protein folding, function and life-times. Moreover, they are integral to the cellular envelope for microorganisms and participate in biofilm formation. These diverse functions of carbohydrates are mediated by carbohydrate-binding proteins, lectins, and the more the knowledge about the biology of these proteins is advancing, the more interfering with carbohydrate recognition becomes a viable option for the development of novel therapeutics. In this respect, small molecules mimicking this recognition process become more and more available either as tools for fostering our basic understanding of glycobiology or as therapeutics. In this review, we outline the general design principles of glycomimetic inhibitors (Section 2). This section is then followed by highlighting three approaches to interfere with lectin function, i.e. with carbohydrate-derived glycomimetics (Section 3.1), novel glycomimetic scaffolds (Section 3.2) and allosteric modulators (Section 3.3). We summarize recent advances in design and application of glycomimetics for various classes of lectins of mammalian, viral and bacterial origin. Besides highlighting design principles in general, we showcase defined cases in which glycomimetics have been advanced to clinical trials or marketed. Additionally, emerging applications of glycomimetics for targeted protein degradation and targeted delivery purposes are reviewed in Section 4.

Biocatalytic synthesis of chiral five-membered carbasugars intermediates utilizing CV2025 ω-transaminase from Chromobacterium violaceum

(S)-4-(Hydroxymethyl)cyclopent-2-enone is a key intermediate in the synthesis of chiral five-membered carbasugars, which can be used to synthesize a large number of pharmacologically relevant carbocyclic nucleosides. Herein, CV2025 ω-transaminase from Chromobacterium violaceum was selected based on substrate similarity to convert ((1S,4R)-4-aminocyclopent-2-enyl)methanol to (S)-4-(hydroxymethyl)cyclopent-2-enone. The enzyme was successfully cloned, expressed in Escherichia coli, purified and characterized. We show that it has R configuration preference in contrast with the conventional S preference. The highest activity was obtained below 60 °C and at pH 7.5. Cations Ca²⁺ and K⁺ enhanced activity by 21% and 13%, respectively. The conversion rate reached 72.4% within 60 min at 50 °C, pH 7.5, using 0.5 mM pyridoxal-5'-phosphate, 0.6 μM CV2025, and 10 mM substrate. The present study provides a promising strategy for preparing five-membered carbasugars economically and efficiently.

A Synthetic Approach to Several C7-Carbasugars via a Key Intramolecular Morita-Baylis-Hillman Reaction

A new synthetic strategy for C7-carbasugars is developed via an intramolecular Morita-Baylis-Hillman reaction, in which a substituted dial precursor prepared from d-mannose cyclizes smoothly in the presence of DMAP to afford polyhydroxylated cyclohex-1-enecarbaldehyde with good yield. By employment of the cyclization products as key intermediates, the first syntheses of carbasugar ester 1 and epicorepoxydon A, as well as practical syntheses of epoxydines B and C, (-)-MK7607, (-)-streptol, and (-)-gabosine E are achieved.

Synergy of R-(-)carvone and cyclohexenone-based carbasugar precursors with antibiotics to enhance antibiotic potency and inhibit biofilm formation

The widespread use of antibiotics in recent decades has been a major factor in the emergence of antibiotic resistances. Antibiotic-resistant pathogens pose increasing challenges to healthcare systems in both developing and developed countries. To counteract this, the development of new antibiotics or adjuvants to combat existing resistance to antibiotics is crucial. Glycomimetics, for example carbasugars, offer high potential as adjuvants, as they can inhibit metabolic pathways or biofilm formation due to their similarity to natural substrates. Here, we demonstrate the synthesis of carbasugar precursors (CSPs) and their application as biofilm inhibitors for E. coli and MRSA, as well as their synergistic effect in combination with antibiotics to circumvent biofilm-induced antibiotic resistances. This results in a biofilm reduction of up to 70% for the CSP rac-7 and a reduction in bacterial viability of MRSA by approximately 45% when combined with the otherwise ineffective antibiotic mixture of penicillin and streptomycin.

Biosynthesis of cyclitols

Review covering up to 2021Cyclitols derived from carbohydrates are naturally stable hydrophilic substances under ordinary physiological conditions, increasing the water solubility of whole molecules in cells. The stability of cyclitols is derived from their carbocyclic structures bearing no acetal groups, in contrast to sugar molecules. Therefore, carbocycle-forming reactions are critical for the biosynthesis of cyclitols. Herein, we review naturally occurring cyclitols that have been identified to date and categorize them according to the type of carbocycle-forming enzymatic reaction. Furthermore, the cyclitol-forming enzymatic reaction mechanisms and modification pathways of the initially generated cyclitols are reviewed.

Current Synthetic Approaches to the Synthesis of Carbasugars from Non-Carbohydrate Sources

Carbasugars are a group of carbohydrate derivatives in which the ring oxygen is replaced by a methylene group, producing a molecule with a nearly identical structure but highly different behavior. Over time, this definition has been extended to include other unsaturated cyclohexenols and carba-, di-, and polysaccharides. Such molecules can be found in bacterial strains and the human body, acting as neurotransmitters (e.g., inositol trisphosphate). In science, there are a wide range of research areas that are affected by, and involve, carbasugars, such as studies on enzyme inhibition, lectin-binding, and even HIV and cancer treatment. In this review article, different methods for synthesizing carbasugars, their derivatives, and similar cyclohexanes presenting comparable characteristics are summarized and evaluated, utilizing diverse starting materials and synthetic procedures.

Synthesis of novel seven-membered carbasugars and evaluation of their glycosidase inhibition potentials

Here, we report the synthesis of five novel seven-membered carbasugar analogs. We adopted a chiral-pool strategy starting from the cheap and readily available d-mannitol to synthesize these ring-expanded carbasugars. Apart from several regioselective protecting group manipulations, these syntheses involved Wittig olefination and ring-closing metathesis as the key steps. We observed an unprecedented deoxygenation reaction of an allylic benzyl ether upon treatment with H₂/Pd during the synthesis. Preliminary biological evaluation of the carbasugars revealed that these ring expanded carbasugars act as inhibitors of various glycosidases. This study highlights the importance of the synthesis of novel ring expanded carbasugars and their biological exploration.

Here, we report the synthesis of five novel seven-membered carbasugar analogs.

Actinomycetes from the Red Sea Sponge Coscinoderma mathewsi: Isolation, Diversity, and Potential for Bioactive Compounds Discovery

The diversity of actinomycetes associated with the marine sponge Coscinoderma mathewsi collected from Hurghada (Egypt) was studied. Twenty-three actinomycetes were separated and identified based on the 16S rDNA gene sequence analysis. Out of them, three isolates were classified as novel species of the genera Micromonospora, Nocardia, and Gordonia. Genome sequencing of actinomycete strains has revealed many silent biosynthetic gene clusters and has shown their exceptional capacity for the production of secondary metabolites, not observed under classical cultivation conditions. Therefore, the effect of mycolic-acid-containing bacteria or mycolic acid on the biosynthesis of cryptic natural products was investigated. Sponge-derived actinomycete Micromonospora sp. UA17 was co-cultured using liquid fermentation with two mycolic acid-containing actinomycetes (Gordonia sp. UA19 and Nocardia sp. UA 23), or supplemented with pure mycolic acid. LC-HRESIMS data were analyzed to compare natural production across all crude extracts. Micromonospora sp. UA17 was rich with isotetracenone, indolocarbazole, and anthracycline analogs. Some co-culture extracts showed metabolites such as a chlorocardicin, neocopiamycin A, and chicamycin B that were not found in the respective monocultures, suggesting a mycolic acid effect on the induction of cryptic natural product biosynthetic pathways. The antibacterial, antifungal, and antiparasitic activities for the different cultures extracts were also tested.

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

In this review we present relevant and recent applications of porphyrin derivatives as photocatalysts in organic synthesis, involving both single electron transfer (SET) and energy transfer (ET) mechanistic approaches. We demonstrate that these highly conjugated photosensitizers show increasing potential in photocatalysis since they combine both photo- and electrochemical properties which can substitute available metalloorganic photocatalysts. Batch and continuous-flow approaches are presented highlighting the relevance of enabling technologies for the renewal of porphyrin applications in photocatalysis. Finally, the reaction scale in which the methodologies were developed are highlighted since this is an important parameter in the authors' opinion.

Remarkable Effect of [Li(G4)]TFSI Solvate Ionic Liquid (SIL) on the Regio- and Stereoselective Ring Opening of α-Gluco Carbasugar 1,2-Epoxides

Carba analogues of biologically relevant natural carbohydrates are promising structures for the development of future drugs endowed with enhanced hydrolytic stability. An open synthetic challenge in this field is the optimization of new methodologies for the stereo- and regioselective opening of α-gluco carbasugar 1,2-epoxides that allow for the preparation of pseudo mono- and disaccharides of great interest. Therefore, we investigated the effect of Lewis acids and solvate ionic liquids (SILs) on the epoxide ring opening of a model substrate. Of particular interest was the complete stereo- and regioselectivity, albeit limited to simple nucleophiles, toward the desired C(1) isomer that was observed using LiClO4. The results obtained with SILs were also remarkable. In particular, Li[NTf2]/tetraglyme ([Li(G4)]TFSI) was able to function as a Lewis acid and to direct the attack of the nucleophile preferentially at the pseudo anomeric position, even with a more complex and synthetically interesting nucleophile. The regioselectivity observed for LiClO4 and [Li(G4)]TFSI was tentatively ascribed to the formation of a bidentate chelating system, which changed the conformational equilibrium and ultimately permitted a trans-diaxial attack on C(1). To the best of our knowledge, we report here the first case in which SILs were successfully employed in a ring-opening process of epoxides.

Gram-scale carbasugar synthesis via intramolecular seleno-Michael/aldol reaction

Carbasugars represent an important category of natural products possessing a broad spectrum of biological activities. Lots of effort has been done to develop gram scale synthesis. We are presenting a new approach to gram scale synthesis of the carbasugar skeleton via intramolecular seleno-Michael/aldol reaction. The proposed strategy gave gram amounts of 6-hydroxy shikimic ester in a tandem process in 36% overall yield starting from d-lyxose. We have attempted to demonstrate the synthetic utility of 6-hydroxyshikimic acid derivatives by covering the important synthetic modifications and related applications, namely synthesis of protected (-)-gabosine E, (-)-MK7606, (-)-valienamine and finally unprotected methyl (-)-shikimate.

Biosynthesis and production of quercitols and their application in the production of pharmaceuticals: current status and prospects

(-)-vibo-Quercitol is a deoxyinositol (1L-1,2,4/3,5-cyclohexanepentol) that occurs naturally in low concentrations in oak species, honeydew honey, and Gymnema sylvestre. The author's research group recently reported that (-)-vibo-quercitol and scyllo-quercitol (2-deoxy-myo-inositol, 1,3,5/2,4-cyclohexanepentol), a stereoisomer of (-)-vibo-quercitol, are stereoselectively synthesized from 2-deoxy-scyllo-inosose by the reductive reaction of a novel (-)-vibo-quercitol 1-dehydrogenase in Burkholderia terrae and of a known scyllo-inositol dehydrogenase in Bacillus subtilis, respectively. The author's research group therefore identified two enzymes capable of producing both stereoisomers of deoxyinositols, which are rare in nature. (-)-vibo-Quercitol and scyllo-quercitol are potential intermediates for pharmaceuticals. In this review, the author describes the biosynthesis and enzymatic production of quercitols and myo-inositol stereoisomers and their application in the production of potential pharmaceuticals.

C-5a-substituted validamine type glycosidase inhibitors

A series of N-alkyl derivatives of the D-galactosidase inhibitor 1,4-di-epi-validamine featuring lipophilic substituents at position C-5a was prepared and screened for their glycosidase inhibitory properties. Products turned out selective for β-galactosidases as well as β-glucosidases.