Unusual fernane and gammacerane glycosides from the aerial parts of Spergula fallax

A review of the fernane-type triterpenoids as anti-fungal drugs

Human fungal pathogens could cause a broad plethora of infections in both the immunocompetent and immunocompromised host. Fungal infections have become important causes of morbidity and mortality in recent years, the current arsenal of anti-fungal therapies was restricted. Ibrexafungerp was a novel, highly bioavailable glucan synthase inhibitor formulated for both intravenous and oral administration being developed by Scynexis; it was also the first novel anti-fungal drug class approved in more than 20 years. Ibrexafungerp was one semi-synthetic derivative of enfumafungin, a natural product isolated from fungi. This review reported the discovery of enfumafungin and ibrexafungerp, their anti-fungal mechanism, summed up 63 fernane-type triterpenoids from natural products, including 49 from plants, 9 from fungi and 5 from lichen. In addition, the review summarized the progress of enzymes responsible for the biosynthesis of type II fernane triterpenoid (enfumafungin skeleton) and type I fernane triterpenoid (polytolypin skeleton). The good example kept our confidence up for searching for new leading compounds and discovering drugs from fungi.

Morusacerane: A new gammacerane triterpenoid from the trunk of Morus Alba linn. with α-glucosidase inhibitory activity

This phytochemistry investigation on the trunk of Morus alba L. resulted in the isolation of three triterpenoids, including a new gammacerane triterpenoid - morusacerane (1); along with two known compounds of betulinic acid (2) and ursolic acid (3). The structure elucidation was thoroughly conducted based on 1D, 2D-NMR and HRESIMS spectra, followed by a comparison with existing literatures. The evaluation on α-glucosidase inhibitory exhibited the great potential of the application of these isolated compounds in diabetes treatments. The results show that morusacerane (1), betulinic acid (2), and ursolic acid (3) demonstrate the strong inhibitory with the IC50 values of 106.1, 11.12, and 7.20 μM, respectively. All of these compounds interacted well with the allosteric site enzyme α-glucosidase MAL32 through H-bonds and hydrophobic interaction.

High-sensitivity qualitative and quantitative analysis of human, bovine and goat milk glycosphingolipids using HILIC-MS/MS with internal standards

Glycosphingolipids (GSLs) in human milk regulate the immune system, support intestinal maturation, and prevent gut pathogens. The structural complexity and low abundance of GSLs limits their systematic analysis. Here, we coupled the use of monosialoganglioside 1-2-amino-N-(2-aminoethyl) benzamide (GM1-AEAB) derivatives as internal standards with HILIC-MS/MS to qualitatively and quantitatively compare GSLs in human, bovine, and goat milk. One neutral glycosphingolipid (GB) and 33 gangliosides were found in human milk, of which 22 were newly detected and three were fucosylated. Five GB and 26 gangliosides were identified in bovine milk, of which 21 were newly discovered. Four GB and 33 gangliosides were detected in goat milk, 23 of them newly reported. GM1 was the main GSL in human milk; whereas disialoganglioside 3 (GD3) and monosialogangloside 3 (GM3) were dominant in bovine and goat milk, respectively; N-acetylneuraminic acid (Neu5Ac) was detected in >88 % of GSLs in bovine and goat milk. N-hydroxyacetylneuraminic acid (Neu5Gc)-modified GSLs were 3.5 times more abundant in goat than in bovine milk; whereas GSLs modified with both Neu5Ac and Neu5Gc were 3 times more abundant in bovine than in goat milk. Given the health benefits of different GSLs, these results will facilitate the development of custom-designed human milk-based infant formula.

Biosynthetic characterization of the antifungal fernane-type triterpenoid polytolypin for generation of new analogues via combinatorial biosynthesis

Fernane-type triterpenoids are a small group of natural products mainly found in plants and fungi with a wide range of biological activities. Polytolypin is a representative fernane-type triterpenoid from fungi and possesses potent antifungal activity. So far, biosynthesis of fungal-derived fernane-type triterpenoids has not been characterized, which hinders the expansion of their structural diversity using biosynthetic approaches. Herein, we identified the biosynthetic gene cluster of polytolypin and elucidated its biosynthetic pathway through heterologous expression in Aspergillus oryzae NSAR1, which involves a new triterpene cyclase for the biosynthesis of the hydrocarbon skeleton motiol, followed by multiple oxidations via three P450 enzymes. Moreover, two new triterpene cyclases for the biosynthesis of two other fernane-type skeletons isomotiol and fernenol were identified from fungi, and were individually co-expressed with the three P450 enzymes involved in polytolypin biosynthesis. These studies led to the generation of 13 fernane-type triterpenoids including eight new compounds, and two of them showed stronger antifungal activity towards Candida albicans FIM709 than polytolypin.

Electrospray ionization mass spectrometry characterization of ubiquitous minor lipids and oligosaccharides in milk of the camel (Camelus dromedarius) and their inhibition of oxidative stress in human plasma

The aim of this study was to characterize minor lipids in methanol fraction extracted from raw camel milk after loading it on a water-preconditioned short C18 open column and fractionating with a gradient of methanol/water. The C18 column showed high fractionation efficiency of minor lipids, such as glycosphingolipids, lipopolysaccharides, or oligosaccharides, when compared with other constituents, in particular polysaccharides, proteins, and free fatty acids. Liquid chromatography electrospray ionization tandem mass spectrometry in negative ion mode was used to identify 21 new glycosphingolipids, lipopolysaccharides, and oligosaccharides. Electrospray ionization tandem mass spectrometry was qualified to provide relevant data for recognizing the molecular mass, glycosylation sequences, and structure of saccharide moieties for the revealed compounds. The sequence of combinations of one selected lipopolysaccharide, which was considered the backbone of the remaining lipopolysaccharides, was confirmed in a density functional theory study. The obtained results showed that the tested fraction is a rich source of glycosphingolipids, lipopolysaccharides, and oligosaccharides with antioxidant activity.

Triterpenoids

Covering 2014. Previous review: Nat. Prod. Rep., 2017, 34, 90-122 This review covers the isolation and structure determination of triterpenoids reported during 2014 including squalene derivatives, lanostanes, holostanes, cycloartanes, cucurbitanes, dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes, serratanes, isomalabaricanes and saponins; 374 references are cited.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly- saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.