Scopelophila cataractae is a rare moss that grows on copper-containing soils. S. cataractae protonema was grown on basal MS medium containing copper. A starch-degrading activity was detected in homogenates of the protonema, after successive extraction with phosphate buffer and buffer containing 3 M LiCl. Buffer-soluble extract (BS) and LiCl-soluble extract (LS) readily hydrolyzed amylopectin to liberate only glucose, which shows that α-glucosidase (EC 3.2.1.20) in BS and LS hydrolyzed amylopectin. The Km value of BS for maltose was 0.427. The Km value of BS for malto-oligosaccharide decreased with an increase in the molecular mass of the substrate. The value for maltohexaose was 0.106, which is about four-fold lower than that for maltose. BS was divided into two fractions of α-glucosidase (BS-1 and BS-2) by isoelectric focusing. The isoelectric points of these two enzymes were determined to be 4.36 (BS-1) and 5.25 (BS-2) by analytical gel electrofocusing. The two enzymes readily hydrolyzed malto-oligosaccharides. The two enzymes also hydrolyzed amylose, amylopectin and soluble starch at a rate similar to that with maltose. The two enzymes readily hydrolyzed panose to liberate glucose and maltose (1 : 1), and the Km value of BS for panose was similar to that for maltotriose, whereas the enzymes hydrolyzed isomaltose only weakly. With regard to substrate specificity, the two enzymes in BS are novel α-glucosidases. The two enzymes also hydrolyzed β-limit dextrin, which has many α-1,6-glucosidic linkages near the non-reducing ends, more strongly than maltose, which shows that they do not need a debranching enzyme for starch digestion. The starch-degrading activity of BS was not inhibited by p-chloromercuribenzoic acid or α-amylase inhibitor. When amylopectin was treated with BS and LS in phosphate buffer, pH 6.0, glucose, but not glucose-1-phosphate, was detected, showing that the extracts did not contain phosphorylase but did contain an α-glucosidase. These results show that α-glucosidases should be capable of complete starch digestion by themselves in cells of S. cataractae.
An approximately threefold increase in glycogenolytic activity of the neutral α-1,4-glucosidase and a twofold increase in the same activity of the acid isoform have been found in extracts of anaplastic astrocytoma and glioblastoma multiforme tumors of brain tissue. "Maltase activity" of the respective enzymes increased by 60-80% in both kinds of tumor extracts. However a significant decrease in α-amylase and almost complete disappearance of phosphorylase activities have also been found in both kinds of tumors.
Macroalgae from Fucus genus are a valuable source of bioactive components as they are abundant in complex polysaccharides, fatty acids and polyphenols. In this work, the biological activity and chemical composition of extracts and fractions obtained from endemic Fucus virsoides J. Agardh species collected in the summer and in the fall were investigated. From dichloromethane:methanol (1:1) extract three fractions were made: petroleum-ether, ethyl-acetate and n-butanol. The aim of the study was to examine the influence of the seasonal variations on algal composition and activity. The significant seasonal variation in content and biological activity of Fucus virsoides samples was found. Fall extract and fractions exerted higher cytotoxic effects on cancer cell lines in comparison with summer extract and fractions. The examined extracts and fractions showed higher cytotoxic activity towards cancer cells compared to normal fibroblast MRC5 cells. Morphological evaluation and cell cycle distribution analysis demonstrated their proapoptotic activity in human cervical adenocarcinoma HeLa cells. Fall extract and fractions better suppressed the migration and tube formation of EA.hy926 cells in comparison with summer extract and fractions. Fall extract and fractions were more potent in inhibition of α-glucosidase enzymatic activity. Ethyl-acetate fractions, from both seasons, exhibited the best antibacterial and antifungal activity on all tested bacteria and fungi. In conclusion, the two fall fractions ethyl-acetate and petroleum-ether rich in polyphenols and polyunsaturated fatty acids, were the most active and exhibited prominent anticancer and anti-α-glucosidase activities.
There has been an enormous interest in the development of alternative medicines for type 2 diabetes, specifically screening for phytochemicals with the ability to delay or prevent glucose absorption. The goal of the present study was to provide in vitro evidence for potential inhibition of α-glucosidase and α-amylase enzymes, followed by a confirmatory in vivo study on rats to generate a stronger biochemical rationale for further studies on the ethanolic extract of Andrographis paniculata and andrographolide. The extract showed appreciable α-glucosidase inhibitory effect in a concentration-dependent manner (IC50=17.2±0.15 mg/ml) and a weak α-amylase inhibitory activity (IC50=50.9±0.17 mg/ml). Andrographolide demonstrated a similar (IC50=11.0±0.28 mg/ml) α-glucosidase and α-amylase inhibitory activity (IC50=11.3±0.29 mg/ml). The positive in vitro enzyme inhibition tests paved way for confirmatory in vivo studies. The in vivo studies demonstrated that A. paniculata extract significantly (P<0.05) reduced peak blood glucose and area under curve in diabetic rats when challenged with oral administration of starch and sucrose. Further, andrographolide also caused a significant (P<0.05) reduction in peak blood glucose and area under the curve in diabetic rats. Hence α-glucosidase inhibition may possibly be one of the mechanisms for the A. paniculata extract to exert antidiabetic activity and indicates that AP extract can be considered as a potential candidate for the management of type 2 diabetes mellitus.
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