Two new antidiabetic xanthones from the twigs of Garcinia oblongifolia.

Two new xanthones, oblongixanthones I (1) and J (2), and seven known compounds (3-9), were isolated from an EtOAc extract of the twigs of Garcinia oblongifolia. Their structures were elucidated using spectroscopic methods, mainly 1 D and 2 D NMR. The antidiabetic effects of the two new compounds were evaluated using α-glucosidase and PTP1B inhibition assays. Both compounds displayed strong inhibition towards α-glucosidase with IC50 values of 258.7 ± 49.3 and 187.1 ± 27.5 µM, respectively (compared with acarbose, IC50 = 900.0 ± 3.0 µM) and moderate effects against PTP1B with IC50 values of 93.9 ± 12.3 and 64.1 ± 5.8 µM, respectively (compared with RK682, IC50 = 4.4 ± 0.3 l µM).

In vitro and in silico antioxidant and α-glucosidase inhibitory potential of compounds isolated from Garcinia gaudichaudii.

Nine compounds including a new one, garcichaudiic acid (1), were isolated from the bark of G. gaudichaudii and their structures were characterized mainly by 1 D and 2 D NMR experiments. The antioxidant capacity of the isolated compounds was determined using DPPH radical scavenging assay and the anti-hyperglycemic activity was assessed by measuring the inhibitory effect against α-glucosidase. Among them, compound 4 showed higher antioxidant activity than the positive control, ascorbic acid, while both compounds 1 and 7 exhibited more significant α-glucosidase inhibitory activity than the reference drug acarbose. Molecular docking analysis of the bioactive compounds was also performed to examine the binding modes and key interactions with the catalytic site.

Chemical constituents of Aglaia elaeagnoidea and Aglaia odorata and their cytotoxicity.

Two new rocaglamides, 8b-O-5-oxohexylrocaglaol (1) and elaeagnin (2), together with twelve known compounds, were isolated from the bark of Aglaia elaeagnoidea and the whole tree of A. odorata. Their structures were determined using spectroscopic methods, mainly 1D and 2D NMR. Cytotoxic activity against HepG2 human liver cancer cells of the isolated compounds was evaluated in vitro using the SRB assay. Three rocaglamide derivatives, dehydroaglaiastatin (13), 8b-O-5-oxohexylrocaglaol (1) and rocaglaol (5), exhibited significant effects with IC50 values of 0.69, 4.77 and 7.37 µM, respectively.

Synthesis of novel oligomeric anionic alkyl glycosides using laccase/TEMPO oxidation and cyclodextrin glucanotransferase (CGTase)-catalyzed transglycosylation.

Modification of alkyl glycosides, to alter their properties and widen the scope of potential applications, is of considerable interest. Here, we report the synthesis of new anionic alkyl glycosides with long carbohydrate chains, using two different approaches: laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation of a long-carbohydrate-chain alkyl glycoside and cyclodextrin glucanotransferase (CGTase)-catalyzed elongation of anionic alkyl glycosides. The laccase/TEMPO oxidation of dodecyl ß- d-maltooctaoside proceeded efficiently with the formation of aldehyde and acid products. However, depolymerization occurred to a large extent, limiting the product yield and purity. On the other hand, CGTase-catalyzed coupling/disproportionation reactions with α-cyclodextrin and dodecyl ß- d-maltoside diuronic acid (DDM-2COOH) or octyl ß- d-glucuronic acid (OG-COOH) as substrates gave high conversions, especially when the CGTase Toruzyme was used. It was found that pH had a strong influence on both the enzyme activity and the acceptor specificity. With non-ionic substrates (dodecyl ß- d-maltoside and octyl ß- d-glucoside), Toruzyme exhibited high catalytic activity at pH 5-6, but for the acidic substrates (DDM-2COOH and OG-COOH) the activity was highest at pH 4. This is most likely due to the enzyme favoring the protonated forms of DDM-2COOH and OG-COOH, which exist at lower pH (pKa about 3).

Efficient laccase/TEMPO oxidation of alkyl glycosides: Effects of carbohydrate group and alkyl chain length.

Alkyl glycosides with long hydrophobic chains have attractive surfactant properties, but their wider application is hampered by their low solubility in water. Here, a route to increased solubility by introduction of carboxyl groups via laccase/TEMPO oxidation is presented. The oxidation pathways for dodecyl ß-maltoside and hexadecyl ß-maltoside were studied in detail. Close to full conversion was achieved for both substrates and conditions were found under which the diacid products dominated, with only minor amounts of under-oxidized and over-oxidized products. Dodecyl ß-maltoside oxidation was improved to give a yield of 85 % of the diacid derivative. Interestingly, in spite of low substrate solubility the oxidation of hexadecyl ß-maltoside was very efficient in aqueous medium, due to the higher solubility of the products. Addition of organic cosolvents did not provide additional advantages. The method is promising for producing soluble anionic derivatives of alkyl glycosides in an environmentally friendly and efficient way.

Chemoenzymatic synthesis of the pH responsive surfactant octyl ß-D-glucopyranoside uronic acid.

Methodology was developed to expand the range of benign alkyl glycoside surfactants to include also anionic types. This was demonstrated possible through conversion of the glycoside to its carboxyl derivative. Specifically, octyl ß-D-glucopyranoside (OG) was oxidised to the corresponding uronic acid (octyl ß-D-glucopyranoside uronic acid, OG-COOH) using the catalyst system T. versicolor laccase/2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and oxygen from air as oxidant. The effects of oxygen supply methodology, concentrations of laccase, TEMPO and OG as well as reaction temperature were evaluated. At 10 mM substrate concentration, the substrate was almost quantitatively converted into product, and even at a substrate concentration of 60 mM, 85% conversion was reached within 24 h. The surfactant properties of OG-COOH were markedly dependent on pH. Foaming was only observed at low pH, while no foam was formed at pH values above 5.0. Thus, OG-COOH can be an attractive low-foaming surfactant, for example for cleaning applications and emulsification, in a wide pH range (pH 1.5-10.0).

Cytotoxic limonoids from the bark of Walsura cochinchinensis.

Three new limonoids, walsucochinones A-C (1-3), along with eight known compounds, were isolated from an ethyl acetate extract of the bark of Walsura cochinchinensis. Their structures were determined using spectroscopic techniques, mainly 1-D and 2-D NMR. The ethyl acetate extract showed cytotoxic activity against MCF-7 human breast cancer cells and cytotoxicity of the isolated compounds were evaluated in vitro using the SRB assay. Walsucochinone C (3) exhibited the most active effect with IC50 value of 16.4 ±â€¯0.2 µM.