Structural studies of an arabinoxylan isolated from Litsea glutinosa (Lauraceae)

Anti-hyperglycemic and anti-hyperlipidemia effects of the alkaloid-rich extract from barks of Litsea glutinosa in ob/ob mice

The present study investigated the anti-hyperglycemic and anti-hyperlipidemia effects of the alkaloid-rich extract from Litsea glutinosa barks (CG) in ob/ob mice. CG was orally administrated (50, 100 and 200 mg/kg) to ob/ob mice for 4 weeks. Parameters of glucose metabolism, hepatotoxicity, hyperlipidemia and inflammation were measured. CG was chemically characterized using UPLC-QTOF-MS. CG dose-dependently decreased body and fat weights without reducing average food intake. CG (100–200 mg/kg) significantly reduced the serum levels of fasting glucose, glycosylated hemoglobin (HbAlc) and glycosylated serum protein (GSP). CG increased insulin sensitivity as manifested by decreased fasting serum insulin, reduced homeostasis model assessment-estimated insulin resistance (HOMA-IR) and improved oral glucose tolerance. CG also alleviated dyslipidemia, ameliorated liver steatosis, increased the activity of serum lipase and alleviated inflammation. The activities of liver pyruvate kinase and glucokinase as well as liver content of glycogen were increased after CG treatment. CG was rich in alkaloids and eight main alkaloids were identified, many of which had been demonstrated to possess adequate anti-diabetic activities. These results suggest that the alkaloid-rich extract of CG possesses potential anti-hyperglycemic and anti-hyperlipidemic effects and can be utilized as an effective agent for the treatment of type 2 diabetes.

Arabinoxylan from Mucilage of Tomatoes (Solanum lycopersicum L.): Structure and Antinociceptive Effect in Mouse Models

Tomato is a known functional food due to its content of bioactive compounds. Herein, polysaccharides were extracted from mucilage of tomatoes, and a purified fraction (PTOK) was analyzed by sugar composition, methylation, and NMR spectroscopy analysis. The results showed the presence of an arabinoxylan, having (1→4)-linked β-d-Xylp units in the main chain, which carried a low proportion of branching (∼5.6%), at O-2 and O-3 position, with side chains constituted by single Araf or Xylp units. Intraperitoneal administration of the arabinoxylan in mice significantly reduced the number of abdominal constrictions induced by 0.6% acetic acid and the inflammatory phase of nociception induced by 2.5% formalin, indicating that it had an antinociceptive effect on inflammatory pain models, amplifying the biological role displayed by arabinoxylans in the diet. Furthermore, this study reports the presence of an arabinoxylan in a dicotyledon plant, and also it is the first study of polysaccharides from mucilage of tomatoes.

Cytotoxicity potentials of eleven Bangladeshi medicinal plants

Various forms of cancer are rising all over the world, requiring newer therapy. The quest of anticancer drugs both from natural and synthetic sources is the demand of time. In this study, fourteen extracts of different parts of eleven Bangladeshi medicinal plants which have been traditionally used for the treatment of different types of carcinoma, tumor, leprosy, and diseases associated with cancer were evaluated for their cytotoxicity for the first time. Extraction was conceded using methanol. Phytochemical groups like reducing sugars, tannins, saponins, steroids, gums, flavonoids, and alkaloids were tested using standard chromogenic reagents. Plants were evaluated for cytotoxicity by brine shrimp lethality bioassay using Artemia salina comparing with standard anticancer drug vincristine sulphate. All the extracts showed potent to moderate cytotoxicity ranging from LC50 2 to 115 µg/mL. The highest toxicity was shown by Hygrophila spinosa seeds (LC50 = 2.93 µg/mL) and the lowest by Litsea glutinosa leaves (LC50 = 114.71 µg/mL) in comparison with standard vincristine sulphate (LC50 = 2.04 µg/mL). Among the plants, the plants traditionally used in different cancer and microbial treatments showed highest cytotoxicity. The results support their ethnomedicinal uses and require advanced investigation to elucidate responsible compounds as well as their mode of action.

XAX1 from glycosyltransferase family 61 mediates xylosyltransfer to rice xylan

Xylan is the second most abundant polysaccharide on Earth and represents an immense quantity of stored energy for biofuel production. Despite its importance, most of the enzymes that synthesize xylan have yet to be identified. Xylans have a backbone of β-1,4-linked xylose residues with substitutions that include α-(1→2)-linked glucuronosyl, 4-O-methyl glucuronosyl, and α-1,2- and α-1,3-arabinofuranosyl residues. The substitutions are structurally diverse and vary by taxonomy, with grass xylan representing a unique composition distinct from dicots and other monocots. To date, no enzyme has yet been identified that is specific to grass xylan synthesis. We identified a xylose-deficient loss-of-function rice mutant in Os02g22380, a putative glycosyltransferase in a grass-specific subfamily of family GT61. We designate the mutant xax1 for xylosyl arabinosyl substitution of xylan 1. Enzymatic fingerprinting of xylan showed the specific absence in the mutant of a peak, which was isolated and determined by (1)H-NMR to be (β-1,4-Xyl)(4) with a β-Xylp-(1→2)-α-Araf-(1→3). Rice xax1 mutant plants are deficient in ferulic and coumaric acid, aromatic compounds known to be attached to arabinosyl residues in xylan substituted with xylosyl residues. The xax1 mutant plants exhibit an increased extractability of xylan and increased saccharification, probably reflecting a lower degree of diferulic cross-links. Activity assays with microsomes isolated from tobacco plants transiently expressing XAX1 demonstrated xylosyltransferase activity onto endogenous acceptors. Our results provide insight into grass xylan synthesis and how substitutions may be modified for increased saccharification for biofuel generation.

Assignment of structures to oligosaccharides produced by enzymic degradation of a beta-D-glucan from barley by 1H- and 13C-n.m.r. spectroscopy

The structures of one tri-(1), two tetra-(2 and 3), and one hexa-saccharide (4) produced by treatment of barley flour, after removal of the starch components, with a fungal beta-D-glucanase (Finizyme) have been assigned on the basis of 1H- and 13C-n.m.r. data as follows: beta-D-Glcp-(1----3)-beta-D-Glcp-(1----4)-D-Glcp (1), beta-D-Glcp-(1----4)-beta-D-Glcp-(1----3)-beta-D-Glcp-(1----4)-D-Glcp (2), beta-D-Glcp-(1----3)-beta-D-Glcp-(1----4)-beta-D-Glcp-(1----4)-D-Glcp (3), and beta-D-Xylp-(1----4)-[alpha-L-Araf-(1----3)]-[alpha-L-Ara f-(1----2)-beta-D-Xylp-(1----4)-beta-D-Xylp- (1----4)-D-Xylp (4).