Anticoagulant-active sulfated arabinogalactan from Chaetomorpha linum: Structural characterization and action on coagulation factors

A sulfated polysaccharide from the green alga Chaetomorpha linum, designated CLS4, was isolated by water extraction, anion-exchange and size-exclusion chromatography. Chemical and spectroscopic analyses demonstrated that CLS4 was a sulfated arabinogalactan, which was constituted by (1→6)-β-d-galactopyranose and (1→5)-α-l-arabinofuranose residues with sulfate groups at C-2/ C-3 of (1→5)-α-l-arabinofuranose and C-2/C-4 of (1→6)-β-d-galactopyranose. CLS4 possessed strong anticoagulant activity in vitro or in vivo as evaluated by activated partial thromboplastin time and thrombin time assays. CLS4 largely inhibited the activities of the coagulation factors XII, XI, IX and VIII. CLS4 was a potent thrombin inhibitor mediated by antithrombin III (ATIII) or heparin cofactor II, and it also effectively stimulated the factor Xa inhibition by potentiating ATIII. Moreover, CLS4 had a high thrombolytic activity in vitro as assessed by clot lytic rate assay. The results suggested that CLS4 could be a promising source of anticoagulant agent.

Behavior of 3-isobutyl-2-methoxypyrazine biosynthesis related to proposed precursor and intermediate in wine grape

Although 3-alkyl-2-methoxypyrazines (MPs) are very important flavor compounds in grape and wine, the metabolic pathway of these compounds has not been fully elucidated, and only a few studies have focused on it to date. In this study, we performed in situ incorporation of the proposed precursor (l-Leu) and the key intermediate (2-amino-4-methylpentanamide; AMPA) of 3-isobutyl-2-methoxypyrazine (IBMP) biosynthesis into Cabernet Sauvignon clusters. The IBMP content and the expression levels of key related genes were monitored. IBMP content decreased shortly after l-Leu or AMPA treatment, but subsequently increased significantly, with raised levels of O-methyltransferase genes (VvOMT1 and VvOMT3) in the berries between veraison and maturation. We speculate that l-Leu may be a precursor of IBMP biosynthesis and that AMPA may be a key intermediate.

Epiberberine, a natural protoberberine alkaloid, inhibits urease of Helicobacter pylori and jack bean: Susceptibility and mechanism

In our previous study, Rhizoma Coptidis extract was found to exert more potent inhibitory effect than its major component berberine towards urease from Helicobacter pylori (HPU) and jack bean (JBU). In continuation of our work, the present study was designed to further comparatively investigate the urease inhibitory activities of five major protoberberine alkaloids in Rhizoma Coptidis, namely berberine, palmatine, coptisine, epiberberine, jateorhizine to identify the bioactive constituent, and illuminate the potential mechanism of action. Results indicated that the five protoberberine alkaloids acted as concentration-dependent inactivators of urease with IC₅₀ values ranging between 3.0 and 5087μM for HPU and 2.3->10,000μM for JBU, respectively. Notably, epiberberine (EB) was found to be the most potent inhibitor against both ureases with IC₅₀ values of 3.0±0.01μM for HPU and 2.3±0.01μM for JBU, which was more effective than the standard urease inhibitor, acetohydroxamic acid (83±0.01μM for HPU and 22±0.01μM for JBU, respectively). Further kinetic analysis revealed that the type of EB inhibition against HPU was slow-binding and uncompetitive, with K_i of 10.6±0.01μM, while slow-binding and competitive against JBU with K_i of 4.6±0.01μM. Addition of thiol reagents, such as l-cysteine, glutathione and dithiothreitol, significantly abolished the inhibition, while Ni²⁺ competitive inhibitors, boric acid and sodium fluoride, synergetically inhibited urease with EB, indicating the obligatory role of the active site sulfhydryl group for the inhibition. In addition, binding of EB with the urease proved to be reversible, as about 65% and 90% enzymatic activity of HPU and JBU, respectively, could be restored by dithiothreitol application. These findings highlighted the potential role of Rhizoma Coptidis protoberberine alkaloids, especially EB, as a lead urease inhibitor in the treatment of diseases associated with ureolytic bacteria. Thus, EB had good potential for further development into a promising therapeutic approach for the treatment of urease-related diseases.

N-terminal 5-mer peptide analog P165 of amyloid precursor protein inhibits UVA-induced MMP-1 expression by suppressing the MAPK pathway in human dermal fibroblasts

Exposure to ultraviolet (UV) radiation leads to a progressive increase in dermal damage through the degradation of collagen, which is mediated by matrix metalloproteinases (MMPs). UV radiation alters the intracellular signaling events that regulate the elaboration of MMPs. Our previous study showed that P165, the N-terminal 5-mer peptide analog of amyloid precursor protein, exerts a protective effect on ultraviolet A (UVA)-induced loss of collagen type I in human dermal fibroblasts (HDFs) by inhibiting the generation of intracellular reactive oxygen species and MMP-1. In this study, we focused on specific signal transduction pathways to elucidate the possible photoprotective mechanisms of P165 in controlling MMP-1 inhibition. Results from western blot analyses indicated that pretreatment with P165 dose-dependently inhibited UVA-induced phosphorylation of extracellular regulated protein kinases (ERK), c-Jun N-terminal kniase (JNK), p38 mitogen-activated protein kinases (MAPKs), and the phosphorylation of their downstream targets c-Jun and c-Fos. The photoprotective effects of P165 were further demonstrated in collagen type I secretion and cellular senescence induced by UVA irradiation. These findings suggest that P165 exerts photoprotective activity in UVA-treated HDFs by regulating MMP-1 generation. This activity may be mediated by inhibiting the MAPK signaling pathways. Thus, P165 is a potential agent for the prevention of skin photoaging.