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27 pages, 3961 KiB

Open AccessFeature PaperArticle

Floridoside Phosphotriester Derivatives: Synthesis and Inhibition of Human Neutrophils’ Oxidative Burst

by Luís Pinheiro, Catarina Cipriano, Filipe Santos, Patrícia Máximo, Eduarda Fernandes, Marisa Freitas and Paula S. Branco

Molecules 2025, 30(13), 2850; https://doi.org/10.3390/molecules30132850 - 3 Jul 2025

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Abstract

Floridoside (2-O-D-glycerol-α-D-galactopyranoside) is a natural product typically found in red algae. It serves as the algae’s carbon reserve and is produced as a protective response against osmotic and heat stress. Both floridoside and its acylated derivatives have been associated with modulating redox homeostasis and inflammatory responses. Therefore, we aimed to evaluate whether the newly synthesized floridoside phosphotriesters (1b–1d, 1f–1h) and acylated floridoside derivative (1e) can modulate the oxidative burst in stimulated human neutrophils. Synthetic strategies included the glycosylation of the thioglycoside donor with glycerol derivatives, having NIS/TfOH as the promoter. Phosphorylation was achieved with POCl₃ in the presence of pyridine. The compounds were analysed for their cytotoxicity, with 1b and 1h being cytotoxic at 50 μM, while the others showed no cytotoxicity in the tested concentrations. The detection of the neutrophils’ oxidative burst was performed using multiple probes [luminol, aminophenyl fluorescein (APF), and Amplex Red (AR)] to evaluate reactive species levels. Compound 1e prevented the oxidative burst in activated human neutrophils (IC₅₀ = 83 ± 7 μM). All the other tested compounds were ineffective in inhibiting APF and AR oxidation under the present experimental conditions. These findings highlight the potential of floridoside-based derivatives as candidates for targeting inflammatory pathways. Full article

(This article belongs to the Section Bioorganic Chemistry)

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17 pages, 7802 KiB

Open AccessArticle

Alterations in Carbohydrate Quantities in Freeze-Dried, Relative to Fresh or Frozen Maize Leaf Disks

by Lynnette M. A. Dirk, Tianyong Zhao, John May, Tao Li, Qinghui Han, Yumin Zhang, Mohammad R. Sahib and Allan Bruce Downie

Biomolecules 2023, 13(1), 148; https://doi.org/10.3390/biom13010148 - 11 Jan 2023

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Abstract

For various reasons, leaves are occasionally lyophilized prior to storage at −80 °C and preparing extracts. Soluble carbohydrate identity and quantity from maize leaf disks were ascertained in two separate years using anion exchange HPLC with pulsed electrochemical detection. Analyses were made from disks after freezing in liquid nitrogen with or without subsequent lyophilization (both years) or directly after removal from plants with or without lyophilization (only in the second year). By adding the lyophilizing step, galactose content consistently increased and, frequently, so did galactoglycerols. The source of the galactose increase with the added lyophilizing step was not due to metabolizing raffinose, as the raffinose synthase (rafs) null mutant leaves, which do not make that trisaccharide, also had a similar increase in galactose content with lyophilization. Apparently, the ester linkages attaching free fatty acids to galactoglycerolipids of the chloroplast are particularly sensitive to cleavage during lyophilization, resulting in increases in galactoglycerols. Regardless of the galactose source, a systematic error is introduced for carbohydrate (and, most likely, also chloroplast mono- or digalactosyldiacylglycerol) amounts when maize leaf samples are lyophilized prior to extraction. The recognition of lyophilization as a source of galactose increase provides a cautionary note for investigators of soluble carbohydrates. Full article

(This article belongs to the Section Biomacromolecules: Carbohydrates)

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15 pages, 4625 KiB

Open AccessArticle

Identification and Characterization of a Thermostable GH36 α-Galactosidase from Anoxybacillus vitaminiphilus WMF1 and Its Application in Synthesizing Isofloridoside by Reverse Hydrolysis

by Jialing Wang, Xuefei Cao, Weihao Chen, Jiaxing Xu and Bin Wu

Int. J. Mol. Sci. 2021, 22(19), 10778; https://doi.org/10.3390/ijms221910778 - 5 Oct 2021

Cited by 14 | Viewed by 2533

Abstract

An α-galactosidase-producing strain named Anoxybacillus vitaminiphilus WMF1, which catalyzed the reverse hydrolysis of d-galactose and glycerol to produce isofloridoside, was isolated from soil. The α-galactosidase (galV) gene was cloned and expressed in Escherichia coli. The galV was classified into the GH36 family with a molecular mass of 80 kDa. The optimum pH and temperature of galV was pH 7.5 and 60 °C, respectively, and it was highly stable at alkaline pH (6.0–9.0) and temperature below 65 °C. The specificity for p-nitrophenyl α-d-galactopyranoside was 70 U/mg, much higher than that for raffinose and stachyose. Among the metals and reagents tested, galV showed tolerance in the presence of various organic solvents. The kinetic parameters of the enzyme towards p-nitrophenyl α-d-galactopyranoside were obtained as K_m (0.12 mM), V_max (1.10 × 10⁻³ mM s⁻¹), and K_cat/K_m (763.92 mM⁻¹ s⁻¹). During the reaction of reverse hydrolysis, the enzyme exhibited high specificity towards the glycosyl donor galactose and acceptors glycerol, ethanol and ethylene glycol. Finally, the isofloridoside was synthesized using galactose as the donor and glycerol as the acceptor with a 26.6% conversion rate of galactose. This study indicated that galV might provide a potential enzyme source in producing isofloridoside because of its high thermal stability and activity. Full article

(This article belongs to the Section Macromolecules)

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