Plant growth regulators and Axl and immune checkpoint inhibitors from the edible mushroom Leucopaxillus giganteus

A novel compound, (R)-4-ethoxy-2-hydroxy-4-oxobutanoic acid (1), and six known compounds (2-7) were isolated from the fruiting bodies of the wild edible mushroom Leucopaxillus giganteus. The planar structure of 1 was determined by the interpretation of spectroscopic data analysis. The absolute configuration of 1 was determined by comparing specific rotation of the synthetic compounds. In the plant regulatory assay, the isolated compounds (1-7) and the chemically prepared compounds (8-10) were evaluated their biological activity against the lettuce (Lactuca sativa) growth. Compounds 1 and 3-10 showed the significant regulatory activity of lettuce growth. 1 showed the strongest inhibition activity among the all the compounds tested. In the lung cancer assay, all the compounds were assessed the mRNA expression of Axl and immune checkpoints (PD-L1, PD-L2) in the human A549 alveolar epithelial cell line by RT-PCR. Compounds 1-10 showed significant inhibition activity against Axl and/or immune checkpoint.

Stereochemical Consequences of Vinylpyruvate Hydratase-Catalyzed Reactions

A stereochemical analysis has been carried out on two vinylpyruvate hydratases (VPH), which convert 2-hydroxy-2,4-pentadienoate to 2-keto-4S-hydroxypentanoate in meta-fission pathways. Bacterial strains with this pathway can use aromatic compounds as sole sources of energy and carbon. The analysis was carried out using the 5-methyl and 5-chloro derivatives of 2-hydroxy-2,4-pentadienoate with the enzymes from Pseudomonas putida mt-2 (Pp) and Leptothrix cholodnii SP-6 (Lc). In both organisms, VPH is in a complex with the preceding enzyme in the pathway, 4-oxalocrotonate decarboxylase (4-OD). In D2O, a deuteron is incorporated stereospecifically at the C-3 and C-5 positions of product by both Pp and Lc enzymes. Accordingly, the complexes generate (3S,5S)-3,5-[di-D]-2-keto-4S-hydroxyhexanoate and (3S,5R)-3,5-[di-D]-2-keto-4R-hydroxy-5-chloropentanoate (4R and 5R due to a priority numbering change). The substitution at C-5 (CH3 or Cl) or the source of the enzyme (Pp or Lc) does not change the stereochemical outcome. One mechanism that can account for the results is the ketonization of the 5-substituted dienol to the α,β-unsaturated ketone (placing a deuteron at C-5 in D2O), followed by the conjugate addition of water (placing a deuteron at C-3). The stereochemical outcome for VPH (from Pp and Lc) is the same as that reported for a related enzyme, 2-oxo-hept-4-ene-1,7-dioate hydratase, from Escherichia coli C. The combined observations suggest similar mechanisms for these three enzymes that could possibly be common to this group of enzymes.

Honaucins A-C, potent inhibitors of inflammation and bacterial quorum sensing: synthetic derivatives and structure-activity relationships

Honaucins A-C were isolated from the cyanobacterium Leptolyngbya crossbyana which was found overgrowing corals on the Hawaiian coast. Honaucin A consists of (S)-3-hydroxy-γ-butyrolactone and 4-chlorocrotonic acid, which are connected via an ester linkage. Honaucin A and its two natural analogs exhibit potent inhibition of both bioluminescence, a quorum-sensing-dependent phenotype, in Vibrio harveyi BB120 and lipopolysaccharide-stimulated nitric oxide production in the murine macrophage cell line RAW264.7. The decrease in nitric oxide production was accompanied by a decrease in the transcripts of several proinflammatory cytokines, most dramatically interleukin-1β. Synthesis of honaucin A, as well as a number of analogs, and subsequent evaluation in anti-inflammation and quorum-sensing inhibition bioassays revealed the essential structural features for activity in this chemical class and provided analogs with greater potency in both assays.

Synthesis, structure determination, and biological evaluation of destruxin E

The total synthesis of destruxin E (1) has been achieved for the first time, and the stereochemistry of its chiral center at the epoxide has been determined to be (S). The cyclization precursor 3a was synthesized by solid-phase peptide synthesis. Macrolactonization of 3a utilizing MNBA-DMAPO, followed by formation of the epoxide, then furnished destruxin E. Its diastereomer, epi-destruxin E (2), was also synthesized in the same manner. Furthermore, the biological evaluation indicated that destruxin E exhibits V-ATPase inhibitory activity 10-fold greater than that of epi-destruxin E.

Tetrahydroisoquinoline alkaloids and 2-deoxyribonolactones from Aristolochia arcuata

2-Deoxyribonolactones and four tetrahydroisoquinoline alkaloids were isolated from the acetone extract of the leaves of Aristolochia arcuata Mast., together with pinitol, sequoyitol, glycerol, fructose, sucrose, eupomatenoid-7, salsolinol, and 6,7-dihydroxy-1,1-dimethyl-1,2,3,4-tetrahydroisoquinoline. Their structures were determined on the basis of spectroscopic methods, mainly using 1H, 13C, 15N, and 31P NMR.

The chemical degradation of starch: old reactions and new frontiers

The chemistry of starch degradation is reviewed from the standpoint of the general utility of the reactions and the proposed mechanisms. The limitations and potential of the various chemical transformations are discussed. The reactions discussed include hydrolysis, oxidations, base-catalyzed degradations, halogenations and radiolysis. The potential scope for starch-derived materials in industry is examined. The potential use in the manufacture of fine chemicals is explored.

Structural and stereoisomeric specificity of serum-borne sugar acids related to feeding control by rats

Specificity of chemical structures and stereoisomers among serum-borne short-chain organic acids in rats were assessed for their effects on feeding behavior and humoral factors by infusion into the rat third cerebroventricle. Infusion of glyceric acid (1.0 mumol), 3,4-dihydroxybutanoic acid gamma-lactone (3,4-DB) or 3,4,5-trihydroxypentanoic acid gamma-lactone (2.50 mumol) immediately before the dark phase decreased food intake for, at most, 24 h. These acids did not significantly affect drinking or ambulation. Initial feeding, not necessarily accompanied by periprandial drinking, was induced after infusion of 2,4-dihydroxybutanoic acid gamma-lactone, 2,4,5-trihydroxypentanoic acid gamma-lactone (2,4,5-TP) or exogenous 2,4,5,6-tetrahydroxyhexanoic acid gamma-lactone (2.50 mumol) in the light phase. Of these acids, 3,4-DB most potently suppressed and 2,4,5-TP most potently enhanced feeding. Of these, the 2S,4S-isomer and the 3S-isomer were the most potent of 2,4,5-TP and 3,4-DB, respectively. Only the 2S,4S-isomer of 2,4,5-TP induced hypoglycemia with hyperinsulinemia, whereas opposite effects were produced by the 3S-isomer of 3,4-DB. The results indicate that the positions of the hydroxyl groups on 4-butanolide and the S- and S,S-stereoisomers are important in modulating food intake through the hypothalamus.