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This review is an effort to summarize recent developments in synthesis of O -glycosides and N -, C -glycosyl molecules with promising antidiabetic potential. Articles published after 2000 are included. First, the O -glycosides used in the treatment of diabetes are presented, followed by the N -glycosides and finally the C -glycosides constituting the largest group of antidiabetic drugs are described. Within each group of glycosides, we presented how the structure of compounds representing potential drugs changes and when discussing chemical compounds of a similar structure, achievements are presented in the chronological order. C -Glycosyl compounds mimicking O -glycosides structure, exhibit the best features in terms of pharmacodynamics and pharmacokinetics. Therefore, the largest part of the article is concerned with the description of the synthesis and biological studies of various C -glycosides. Also N -glycosides such as N -(β- d -glucopyranosyl)-amides, N -(β- d -glucopyranosyl)-ureas, and 1,2,3-triazolyl derivatives belong to the most potent classes of antidiabetic agents. In order to indicate which of the compounds presented in the given sections have the best inhibitory properties, a list of the best inhibitors is presented at the end of each section. In summary, the best inhibitors were selected from each of the summarizing figures and the results of the ranking were placed. In this way, the reader can learn about the structure of the compounds having the best antidiabetic activity. The compounds, whose synthesis was described in the article but did not appear on the figures presenting the structures of the most active inhibitors, did not show proper activity as inhibitors. Thus, the article also presents studies that have not yielded the desired results and show directions of research that should not be followed. In order to show the directions of the latest research, articles from 2018 to 2019 are described in a separate Sect. 5 . In Sect. 6 , biological mechanisms of action of the glycosides and patents of marketed drugs are described.

Acireductone dioxygenase (ARD) is an intriguing enzyme from the methionine salvage pathway that is capable of catalysing two different oxidation reactions with the same substrate depending on the type of the metal ion in the active site. To date, the structural information regarding the ARD-acireductone complex is limited and possible reaction mechanisms are still under debate. The results of joint experimental and computational studies undertaken to advance knowledge about ARD are reported. The crystal structure of an ARD from Homo sapiens was determined with selenomethionine. EPR spectroscopy suggested that binding acireductone triggers one protein residue to dissociate from Fe , which allows NO (and presumably O ) to bind directly to the metal. Mössbauer spectroscopic data (interpreted with the aid of DFT calculations) was consistent with bidentate binding of acireductone to Fe and concomitant dissociation of His88 from the metal. Major features of Fe vibrational spectra obtained for the native enzyme and upon addition of acireductone were reproduced by QM/MM calculations for the proposed models. A computational (QM/MM) study of the reaction mechanisms suggests that Fe promotes O-O bond homolysis, which elicits cleavage of the C1-C2 bond of the substrate. Higher M /M redox potentials of other divalent metals do not support this pathway, and instead the reaction proceeds similarly to the key reaction step in the quercetin 2,3-dioxygenase mechanism.

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