Synthesis of digalactosyl diacylglycerols and their structure–inhibitory activity on human lanosterol synthase

Chemical Inhibition of Sterol Biosynthesis

Cholesterol is an essential molecule of life, and its synthesis can be inhibited by both genetic and nongenetic mechanisms. Hundreds of chemicals that we are exposed to in our daily lives can alter sterol biosynthesis. These also encompass various classes of FDA-approved medications, including (but not limited to) commonly used antipsychotic, antidepressant, antifungal, and cardiovascular medications. These medications can interfere with various enzymes of the post-lanosterol biosynthetic pathway, giving rise to complex biochemical changes throughout the body. The consequences of these short- and long-term homeostatic disruptions are mostly unknown. We performed a comprehensive review of the literature and built a catalogue of chemical agents capable of inhibiting post-lanosterol biosynthesis. This process identified significant gaps in existing knowledge, which fall into two main areas: mechanisms by which sterol biosynthesis is altered and consequences that arise from the inhibitions of the different steps in the sterol biosynthesis pathway. The outcome of our review also reinforced that sterol inhibition is an often-overlooked mechanism that can result in adverse consequences and that there is a need to develop new safety guidelines for the use of (novel and already approved) medications with sterol biosynthesis inhibiting side effects, especially during pregnancy.

Regulatory science of natural products

Foods and pharmaceuticals play key roles in public health and welfare and ensuring that these products meet their quality assurance standards is a top priority in health and medical care. Quality assurance of natural products is essential in pharmaceutical sciences because the outset of a medicine is a natural, crude drug. Regulatory science underpins scientific regulations and is closely related to the quality assurance of foods and pharmaceuticals to ensure their safety and efficacy. During my time at the National Institute of Health Sciences, Japan, from 1986 to present, the regulatory science of natural products has been my main research focus. This review discusses 24 studies related to the regulatory science of natural food additives, 26 related to foods, 23 related to borderline products, 16 related to illicit psychotropic mushrooms, plants, and agents, and 57 related to herbal medicines. In later sections, the regulatory science for ethical Kampo products with new dosage forms and herbal medicines that use Kampo extracts as active pharmaceutical ingredients are discussed. My experience from the early twenty-first century in research projects on the bioequivalence of Kampo products and the development of ephedrine alkaloid-free Ephedra Herb extract demonstrate that regulatory science is crucial for developing new drugs.

Stereoselective Synthesis of Diglycosyl Diacylglycerols with Glycosyl Donors Bearing a β-Stereodirecting 2,3-Naphthalenedimethyl Protecting Group

Diglycosyl diacylglycerols (DGDGs) are major components of Gram-positive bacterial plasma membranes and are involved in the immune response systems. The chemical synthesis of DGDGs has been highly demanded, as it will allow the elucidation of their biological functions at the molecular level. In this study, we have developed a novel β-stereodirecting 2,3-naphthalenedimethyl (NapDM) protecting group that is orthogonal to protecting groups commonly used in oligosaccharide synthesis. The NapDM group can be easily cleaved under TFA-mediated acidic conditions. Futhermore, we demonstrated the application of this protecting group to an acyl protecting-group-free strategy by utilizing the NapDM group for the synthesis of DGDGs. This strategy features the use of the β-stereodirecting NapDM group as an acid-cleavable permanent protecting group and late-stage glycosylation of monoglycosyl diacylglycerol acceptors, enabling the stereoselective synthesis of three different bacterial DGDGs with unsaturated fatty acid chain(s).

Anti-Inflammatory Activity of Glycolipids and a Polyunsaturated Fatty Acid Methyl Ester Isolated from the Marine Dinoflagellate Karenia mikimotoi

A new monogalactosyldiacylglycerol (MGDG), a known monogalactosylmonoacylglycerol (MGMG) and a known polyunsaturated fatty acid methyl ester (PUFAME) were isolated from the marine dinoflagellate Karenia mikimotoi. The planar structure of the glycolipids was elucidated using mass spectroscopy (MS) and nuclear magnetic resonance (NMR) analyses and comparisons to the known glycolipid to confirm its structure. The MGDG was characterized as 3-O-β-D-galactopyranosyl-1-O-3,6,9,12,15-octadecapentaenoyl-2-O-tetradecanoylglycerol 1. The MGMG and PUFAME were characterized as (2S)-3-O-β-D-galactopyranosyl-1-O-3,6,9,12,15-octadecapentaenoylglycerol 2 and Methyl (3Z,6Z,9Z,12Z,15Z)-octadeca-3,6,9,12,15-pentaenoate 3, respectively. The isolation of the PUFAME strongly supports the polyunsaturated fatty acid (PUFA) fragment of these glycolipids. The relative configuration of the sugar was deduced by comparisons of ³J_HH values and proton chemical shifts with those of known glycolipids. All isolated compounds MGDG, MGMG and PUFAME 1-3 were evaluated for their antimicrobial and anti-inflammatory activity. All compounds modulated macrophage responses, with compound 3 exhibiting the greatest anti-inflammatory activity.

Convergent Synthesis of Digalactosyl Diacylglycerols

Efficient convergent chemical syntheses of digalactosyl diacylglycerols (DGDGs), which have both a galactose-galactose α(1→6)-linkage and a galactose-glycerol β-linkage along with a diacylglycerol containing various kinds of fatty acids, have been accomplished. In order to achieve a concise synthesis, we chose to use allylic protective groups as permanent protective groups. We have also achieved α- and β-selective glycosylations for the respective linkages with high yields as the key steps.

Total synthesis of a cyclopropane-fatty acid α-glucosyl diglyceride from Lactobacillus plantarum and identification of its ability to signal through Mincle

We report a concise synthesis of glycolipid GL1 from Lactobacillus plantarum commencing from methyl α-d-glucopyroside. A Jacobsen hydrolytic kinetic resolution is used to generate a diastereomerically-pure glycidyl glucoside that was elaborated to the diglyceride by stepwise brominolysis, acylation with oleoyl chloride, and bromide-substitution by the tetrabutylammonium salt of 9S,10R-dihydrosterculic acid. GL1 and analogues were shown to signal through the glycolipid pattern recognition receptor Mincle.

Total synthesis and structure-activity relationship of glycoglycerolipids from marine organisms

Glycoglycerolipids occur widely in natural products, especially in the marine species. Glycoglycerolipids have been shown to possess a variety of bioactivities. This paper will review the different methodologies and strategies for the synthesis of biological glycoglycerolipids and their analogs for bioactivity assay. In addition, the bioactivities and structure-activity relationship of the glycoglycerolipids are also briefly outlined.

Galactolipids from Bauhinia racemosa as a new class of antifilarial agents against human lymphatic filarial parasite, Brugia malayi

Bioassay guided fractionation of ethanolic extract of the leaves of Bauhinia racemosa led to the isolation of galactolipid and catechin class of the compounds (1-7) from the most active n-butanol fraction (F4). Among the active galactolipids, 1 emerged as the lead molecule which was active on both forms of lymphatic filarial parasite, Brugia malayi. It was found to be better than the standard drug ivermectin and diethylcarbamazine (DEC) in terms of dose and efficacy.

Chemoenzymatic synthesis and antimicrobial activity evaluation of monogalactosyl diglycerides

Monogalactosyl diglycerides with medium to long fatty acid acyl chains, were prepared and examined for antimicrobial activity against Gram positive, Gram negative bacteria and fungi. The study of their in vitro antimicrobial activity confirms the significant activity of some monogalactosyl diacylglycerol analogues and establishes for the galactose series that the 1,2-disubstitution and the octanoyl chain are the proper structural features for the maximum activity.

Chemoenzymatic synthesis and in vitro studies on the hydrolysis of antimicrobial monoglycosyl diglycerides by pancreatic lipase

Monoglucosyl and monogalactosyl diglycerides (MGDGs) with medium-long length acyl chains, identified as active components in Euphorbiaceae, were synthesized. They were examined for antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. MGDGs with two octanoyl groups at both 1- and 2-positions showed the most potent activity. The stereoselectivity of pancreatic lipase was investigated in vitro where the preference for the 1 position in MGDGs is strictly related to the length of the acyl chains.

Chemoenzymatic synthesis and antimicrobial activity evaluation of monoglucosyl diglycerides

Monoglucosyl diglycerides with medium-long length fatty acid acyl chains were prepared and examined for antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. The study of their in vitro antimicrobial activity confirms the significant activity of some monoglucosyl diacylglycerol analogues and establishes for the glucose series that the 1,2-disubstitution and the octanoyl chain are the proper structural features for the maximum activity.

Syntheses of an α-d-Gal-(1→6)-β-d-Gal diglyceride, as lipase substrate

Two different routes were explored to afford 3-O-(6-O-alpha-D-galactopyranosyl-beta-D-galactopyranosyl)-1,2-di-O-dodecanoyl-sn-glycerol. In the first one, the key step was the glycosylation of the 3-O-(2,3,4-tri-O-benzyl-beta-D-galactopyranosyl)-1,2-O-isopropylidene-sn-glycerol acceptor with 2-pyridyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-galactopyranoside as the donor. In the second one, the key step was the coupling of 2,3,4-tri-O-acetyl-6-O-(2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl)-D-galactopyranosyl trichloroacetimidate donor with 1,2-O-isopropylidene-sn-glycerol. Even though the number of steps was the same in both pathways, the first one afforded a better overall yield (12.4%) than the second one (6.5%). This eight-step synthesis allowed the preparation of the expected glycolipid, which was used as substrate for recombinant GPLRP2 galactolipase using the monomolecular film technique.