Synthesis and elucidation of absolute stereochemistry of salaprinol, another thiosugar sulfonium sulfate from the ayurvedic traditional medicine Salacia prinoides

Copper-Catalyzed Asymmetric Sulfonylative Desymmetrization of Glycerol

Glycerol is the main side product in the biodiesel manufacturing process, and the development of glycerol valorization methods would indirectly contribute the sustainable biodiesel production and decarbonization. Transformation of glycerol to optically active C3 units would be one of the attractive routes for glycerol valorization. We herein present the asymmetric sulfonylative desymmetrization of glycerol by using a CuCN/(R,R)-PhBOX catalyst system to provide an optically active monosulfonylated glycerol in high efficiency. A high degree of enantioselectivity was achieved with a commercially available chiral ligand and an inexpensive carbonate base. The optically active monosulfonylated glycerol was successfully transformed into a C3 unit attached with differentially protected three hydroxy moieties. In addition, the synthetic utility of the present reaction was also demonstrated by the transformation of the monosulfonylated glycerol into an optically active synthetic ceramide, sphingolipid E.

The chemistry and biology of natural ribomimetics and related compounds

Natural ribomimetics represent an important group of specialized metabolites with significant biological activities. Many of the activities, e.g., inhibition of seryl-tRNA synthetases, glycosidases, or ribosomes, are manifestations of their structural resemblance to ribose or related sugars, which play roles in the structural, physiological, and/or reproductive functions of living organisms. Recent studies on the biosynthesis and biological activities of some natural ribomimetics have expanded our understanding on how they are made in nature and why they have great potential as pharmaceutically relevant products. This review article highlights the discovery, biological activities, biosynthesis, and development of this intriguing class of natural products.

Peptidoglycan-inspired autonomous ultrafast self-healing bio-friendly elastomers for bio-integrated electronics

Elastomers are essential for stretchable electronics, which have become more and more important in bio-integrated devices. To ensure high compliance with the application environment, elastomers are expected to resist, and even self-repair, mechanical damage, while being friendly to the human body. Herein, inspired by peptidoglycan, we designed the first room-temperature autonomous self-healing biodegradable and biocompatible elastomers, poly(sebacoyl 1,6-hexamethylenedicarbamate diglyceride) (PSeHCD) elastomers. The unique structure including alternating ester-urethane moieties and bionic hybrid crosslinking endowed PSeHCD elastomers superior properties including ultrafast self-healing, tunable biomimetic mechanical properties, facile reprocessability, as well as good biocompatibility and biodegradability. The potential of the PSeHCD elastomers was demonstrated as a super-fast self-healing stretchable conductor (21 s) and motion sensor (2 min). This work provides a new design and synthetic principle of elastomers for applications in bio-integrated electronics.

Elongation of the side chain by linear alkyl groups increases the potency of salacinol, a potent α-glucosidase inhibitor from the Ayurvedic traditional medicine "Salacia," against human intestinal maltase

Four chain-extended analogs (12a-12d) and two related de-O-sulfonated analogs (13a and 13c) by introducing alkyl groups (a: R = C₃H₇, b R = C₆H₁₃, c: R = C₈H₁₇, d: R = C₁₀H₂₁) to the side chains of salacinol (1), a natural α-glucosidase inhibitor from Ayurvedic traditional medicine "Salacia", were synthesized. The α-glucosidase inhibitory activities of all the synthesized analogs were evaluated in vitro. Against human intestinal maltase, the inhibitory activities of 12a and 13a with seven-carbon side chain were equal to that of 1. In contrast, analogs (12b-12d, and 13c) exhibited higher level of inhibitory activity against the same enzyme than 1 and had equal or higher potency than those of the clinically used anti-diabetics, voglibose, acarbose, and miglitol. Thus, elongation of the side chains of 1 was effective for specifically increasing the inhibitory activity against human intestinal maltase.

Anil Kumar N, Sharopov F, Ramírez-Alarcón K, Ruiz-Ortega A, Abdulmajid Ayatollahi S, Valere Tsouh Fokou P, Kobarfard F, Amiruddin Zakaria Z, Iriti M, Taheri Y, Martorell M, Sureda A, N. Setzer W, Durazzo A, Lucarini M, Santini A, Capasso R, Adrian Ostrander E, -ur-Rahman A, Iqbal Choudhary M, C. Cho W, Sharifi-Rad J. Antidiabetic Potential of Medicinal Plants and Their Active Components

Diabetes mellitus is one of the major health problems in the world, the incidence and associated mortality are increasing. Inadequate regulation of the blood sugar imposes serious consequences for health. Conventional antidiabetic drugs are effective, however, also with unavoidable side effects. On the other hand, medicinal plants may act as an alternative source of antidiabetic agents. Examples of medicinal plants with antidiabetic potential are described, with focuses on preclinical and clinical studies. The beneficial potential of each plant matrix is given by the combined and concerted action of their profile of biologically active compounds.

Recent Progress in the Construction of Natural De-O-Sulfonated Sulfonium Sugars with Antidiabetic Activities

A group of sulfonium salts equipped with a polyhydroxylated side-chain structure have been isolated and identified as potent α-glycosidase inhibitors. Consequently, they have become an attractive target in diverse research disciplines, including organic synthesis, drug discovery, and chemical biology. To this end, the development of practical and effective synthetic strategies, especially for more bioactive de-O-sulfonated sulfonium salts, is a significant research area in organic synthesis. An ideal synthetic methodology should provide easily accessible intermediates with high chemical stability for the key coupling reaction to diastereoselectively construct the sulfonium cation center. This minireview summarizes recently developed strategies applied in the construction of natural de-O-sulfonated sulfonium sugars: 1) acid-catalyzed de-O-sulfonation of sulfonium sulfate inner salts, 2) a coupling reaction between side-chain fragments containing leaving groups and a thiosugar, 3) a coupling reaction between side-chain fragments containing epoxide structures and a thiosugar, and 4) a two-step sequential S_N 2 nucleophilic substitution between side-chain fragments containing thiol groups and a diiodide derivative.

Ajothiolanes: 3,4-Dimethylthiolane Natural Products from Garlic ( Allium sativum)

Stereoisomers of 5-(2-allylsulfinyl)-3,4-dimethylthiolane-2-ol, a family of 3,4-dimethylthiolanes of formula C₉H₁₆O₂S₂ we name ajothiolanes, were isolated from garlic ( Allium sativum) macerates and characterized by a variety of analytical and spectroscopic techniques, including ultraperformance liquid chromatography (UPLC), direct analysis in real time-mass spectrometry (DART-MS), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Ajothiolanes were found to be spectroscopically identical to a family of previously described compounds named garlicnins B_1-4 (C₉H₁₆O₂S₂), whose structures we demonstrate have been misassigned. 2D ¹³C-¹³C NMR incredible natural abundance double quantum transfer experiments (INADEQUATE) were used to disprove the claim of nine contiguous carbons in these compounds, while X-ray absorption spectroscopy (XAS) along with computational modeling was used to disprove the claim that these compounds were thiolanesulfenic acids. On the basis of the similarity of their NMR spectra to those of the ajothiolanes, we propose that the structures of previously described, biologically active onionins A_1-3 (C₉H₁₆O₂S₂), from extracts of onion ( Allium cepa) and Allium fistulosum, and garlicnin A (C₁₂H₂₀O₂S₄), from garlic extracts, should also be reassigned, in each case as isomeric mixtures of 5-substituted-3,4-dimethylthiolane-2-ols. We conclude that 3,4-dimethylthiolanes may be a common motif in Allium chemistry. Finally, we show that another garlic extract component, garlicnin D (C₇H₁₂O₂S₃), claimed to have an unprecedented structure, is in fact a known compound from garlic with a structure different from that proposed, namely, 2( E)-3-(methylsulfinyl)-2-propenyl 2-propenyl disulfide.

Mutagenicity and antimutagenicity of Salacia crassifolia (mart. Ex. Schult.) G. Don. evaluated by Ames test

Abstract Salacia crassifolia (Mart. Ex. Schult.) G. Don. is a bush which belongs to Celastraceae family and occurs specially in Brazilian Cerrado. Its leaves, stem, seeds and fruits are popularly used for several medicinal purposes, such as antitumoral, antirheumatic, anti-inflammatory and antimicrobial. In this study, the mutagenic and antimutagenic activities of S. crassifolia stem bark fractions (hexane, ethyl acetate and hydroalcoholic) were evaluated by the Ames mutagenicity assay in Salmonella typhimurium TA98 and TA100 strains. By the obtained results, all S. crassifolia fractions did not significantly increase the number of prototrophic revertants for histidine (His+) in both S. typhimurium strains tested (p > 0.05), suggesting absence of mutagenicity. Regarding antimutagenicity, the fractions ethyl acetate and hydroalcoholic significantly decreased the number of His+ revertants colonies induced by positive control for strain TA98 (p < 0.05), demonstrating protection against mutagenicity induced by 4-nitroquinolile1-oxide, whereas the hexane fraction did not show antimutagenic effect in this strain. In the TA100 strain, all fractions of S. crassifolia protected DNA against the harmful action of sodium azide, and the hexane fraction exhibited the greatest protection in this work. Thus, it’s possible conclude that the fractions of S. crassifolia tested in this study could be used in chemoprevention.

Aspects of extraction and biological evaluation of naturally occurring sugar-mimicking sulfonium-ion and their synthetic analogues as potent α-glucosidase inhibitors from Salacia: a review

A review of the selective inhibitory activities of sulfonium compounds ofSalaciaagainst intestinal α-glucosidases, structural features important for effective inhibition and the toggling approach for controlling starch digestion and glucose release.

A Fortuitously Straightforward Synthesis of 4-Acetoxy-2-Propyltetrahydrothiophene

4-Acetoxy-2-propyltetrahydrothiophene was synthesised from 1-hepten-4-ol by a three-step route involving epoxidation and mesylation to 1,2-epoxy-4-heptyl mesylate and then reaction with thioacetate. An acetoxylated cyclic product was formed instead of the expected thioacetate, and a mechanism for its formation using an intramolecular transesterification is proposed.

Salacinol and related analogs: new leads for type 2 diabetes therapeutic candidates from the Thai traditional natural medicine Salacia chinensis

The antidiabetic effect of a hot water extract of stems of Salacia chinensis (SCE) was evaluated in vivo in KK-A^y mice, a typical type 2 diabetes mellitus mice model. Administration of CE-2 dietary feed containing 0.25 and/or 0.50% of SCE for three weeks to KK-A^y mice significantly suppressed the elevation of both blood glucose and HbA1c levels without significant changes in body weight or food intake. Glucose tolerance was improved by administration to KK-A^y mice for 27 days of AIN93M purified dietary feed containing 0.12% of SCE. No suppressive effect with respect to HbA1c level was observed when AIN93M/Glc dietary feed in which all digestible glucides were replaced with glucose was administered with SCE. Thus, α-glucosidase inhibitory activity approved as the mechanism of action of the antidiabetic effect of SCE by in vitro investigation was reconfirmed also in in vivo studies. Evaluation of the α-glucosidase inhibitory activity of the active constituents, salacinol (1), kotalanol (3), and neokotalanol (4), by employing human α-glucosidases revealed that these compounds inhibited them as potently (IC₅₀ = 3.9–4.9 μM for maltase) as they inhibited rat small intestinal α-glucosidase. The principal sulfonium constituents (1–4) were highly stable in an artificial gastric juice. In addition, 1–4 were hardly absorbed from the intestine in an experiment using the in situ rat ligated intestinal loop model. The results indicate that these sulfoniums are promising leads for a new type of anti-diabetic agents.

Evaluation of Salacia species as anti-diabetic natural resources based on quantitative analysis of eight sulphonium constituents: a new class of α-glucosidase inhibitors

INTRODUCTION

Stems and roots of Salacia genus plants have been used in Ayurveda as a specific remedy for early stage diabetes. Previous investigations identified four sulphonium sulphates, that is, salacinol (1), kotalanol (3), ponkoranol (5) and salaprinol (7), as the compounds responsible for the anti-diabetic activity. Their desulphonates (2, 4, 6 and 8) were also isolated as active constituents. Two separate quantitative analytical protocols, that is, for 1 and 3 and for 2 and 4, have been developed recently.

OBJECTIVE

To: validate the two analytical protocols with respect to all eight sulphoniums; evaluate the quality of a variety of Salacia samples collected in different geographical regions, that is, Thailand, Sri Lanka and India; and determine their distribution in each part of the plant, that is, stems/roots, leaves and fruits.

METHODS

Analyses of four sulphonium sulphates in 32 Salacia extracts were carried out on an Asahipak NH2P-50 column, and those of the corresponding desulphonates were conducted on an Inertsil ODS-3 column.

RESULTS

Neokotalanol (4) was the major constituent in Salacia samples from Thailand, whereas 1 was the primary constituent in extracts of the stems/roots of plants from Sri Lanka and India. These sulphoniums were only present in trace amounts in leaves and fruits of the plants.

CONCLUSION

Two analytical protocols were successfully applied to analyse 32 Salacia samples, and revealed that sulphoniums (1-8) had characteristic distributions due to the plant part and/or due to geographical region.

Structure, histochemistry and phytochemical profile of the bark of the sobol and aerial stem of Tontelea micrantha (Celastraceae - Hippocrateoideae)

The bark of the underground stem of Tontelea micrantha (Mart. ex. Schult.) A. C. Sm., a native Brazilian Cerrado species, is used in folk medicine for treating kidney ailments. The structures of the underground and the aerial stems were examined and their barks were analyzed for the presence of secondary metabolites. Bark fragments were processed according to conventional techniques in plant anatomy and their chemical compositions examined using histochemical and phytochemical tests, thin layer chromatography, and high-efficiency liquid chromatography. The underground stem is a sobol with unusual cambial activity. Laticifers that secrete terpenoids were present in the cortex and phloem of both organs and can contribute to the identification of the species in field. Druses were present in both barks, but mono-crystals were only observed in the sobol. Tannins, flavonoids, alkaloids, and terpenoids occurred in both types of bark, but carotenoids were only detected in the sobol. The similarities between these two organs indicate that the aerial stem bark has potential medicinal use and represents a plausible alternative to harvesting the sobol, which could contribute to the preservation of natural populations of this species.

Isolation, structure identification and SAR studies on thiosugar sulfonium salts, neosalaprinol and neoponkoranol, as potent α-glucosidase inhibitors

Two hitherto missing members of sulfonium salts family in Salacia genus plants as a new class of α-glucosidase inhibitors, neoponkoranol (7) and neosalaprinol (8), were isolated from the water extracts, and their structures were unambiguously identified. For further SAR studies on this series of sulfonium salts, several epimers of 7 and 8 were synthesized, and their inhibitory activities against rat small intestinal α-glucosidases were evaluated. Among them, 3'-epimer of 7 was found most potent in this class of molecules, and revealed as potent as currently used antidiabetics, voglibose and acarbose.

Quantitative analysis of neosalacinol and neokotalanol, another two potent α-glucosidase inhibitors from Salacia species, by LC-MS with ion pair chromatography

A quantitative analytical method for the highly polar sulfonium pseudo-sugar constituents neosalacinol (3) and neokotalanol (4), another two potent α-glucosidase inhibitors isolated from Ayurvedic traditional medicine Salacia species, was developed by employing an ion pair reagent upon chromatographic separation. The optimum conditions for separation and detection of these two constituents were achieved on an ODS column (3-µm particle size, 2.1-mm i.d. × 100 mm) with 5 mM undecafluorohexanoic acid-MeOH (99:1, v/v) as the mobile phase and using MS equipped with an electrospray ionization source. More than ten samples of Salacia from different origins were analyzed, and the results indicated that the assay was reproducible and precise and could be readily utilized for evaluation of α-glucosidase inhibitory activity of Salacia species. By combining this assay with the quantitative analytical method previously developed for salacinol (1) and kotalanol (2), a more precise and strict evaluation of α-glucosidase inhibitory activities of extracts from Salacia species (R = 0.959 for maltase and 0.795 for sucrase) was achieved.

Towards the elusive structure of kotalanol, a naturally occurring glucosidase inhibitor

This Highlight describes the detailed approach used to determine the absolute stereochemistry of the stereogenic centers in the acyclic side chain of kotalanol, a naturally occurring glucosidase inhibitor isolated from the plant Salacia reticulata. The plant extract itself is used in Ayurvedic medicine for the treatment of Type 2 diabetes. We highlight the syntheses of proposed candidates based on structure-activity relationships, the total synthesis of kotalanol, and crystallographic studies of kotalanol and its de-O-sulfonated derivative complexed with recombinant human maltase glucoamylase (MGA), a critical intestinal glucosidase involved in the breakdown of glucose oligomers into glucose.

Sulfonium-ion glycosidase inhibitors isolated from Salacia species used in traditional medicine, and related compounds

A novel class of naturally-occurring glycosidase inhibitors, having sulfonium sulfate structures, has been isolated as bioactive components from Indian plants, belonging to the Salacia genus in the family Celastraceae, and used in Ayurvedic medicine for the treatment of type-2 diabetes. Thus far, five such sulfonium salts, namely, salacinol, kotalanol, salaprinol, ponkoranol and de-O-sulfonated kotalanol, have been isolated from this plant species. These structurally unique zwitterionic glycosidase inhibitors have received much attention due to their therapeutic potential in the treatment of type-2 diabetes. We recently reported a review article which focused mainly on salacinol and related analogues. The present review presents an update on the remaining four compounds from this class of glycosidase inhibitors, with respect to their isolation, glucosidase inhibitory activities, and synthesis. In addition, progress towards the stereochemical structure elucidation of kotalanol, through synthesis of analogues, is described. Review with 42 references.

Facile synthesis of de-O-sulfated salacinols: revision of the structure of neosalacinol, a potent alpha-glucosidase inhibitor

Facile synthesis of de-O-sulfated salacinols (3) was developed by employing the coupling reaction of an epoxide, 1,2-anhydro-3,4-di-O-benzyl-D-erythritol (9) with 2,3,5-tri-O-benzyl-1,4-dideoxy-1,4-epithio-D-arabinitol (10) as the key reaction. The reported structure of a potent alpha-glucosidase inhibitor named neosalacinol (8), isolated recently from Ayurvedic medicine Salacia oblonga, was proved incorrect, and revised to be de-O-sulfated salacinol formate (3c) by comparison of the spectroscopic properties with those of the authentic specimen synthesized. Discrepancies and confusion in the literature concerning the NMR spectroscopic properties of salacinol (1) have also been clarified.