Antihyperglycemic activities

A number of mushrooms, including Agaricus subrufescens, Grifola frondosa, Pleurotus ostreatus, and Cordyceps, have antihyperglycemic activity in vivo. Grifola frondosa creates alpha glucosidase inhibitor compounds.[61] Ternatin is an antihyperglycemic cyclic heptapeptide isolated from Trametes versicolor. Cyclic peptides (or cyclic proteins) are polypeptide chains whose amino and carboxyl termini are themselves linked together with a peptide bond that forms a circular chain. A number of cyclic peptides have been discovered in nature and they can range anywhere from just a few amino acids in length, to hundreds. Cyclic peptides can be classified according to the types of bonds that comprise the ring. Homodetic cyclic peptides, such as cyclosporine A, are those in which the ring is composed exclusively of normal peptide bonds (i.e. between the alpha carboxyl of one residue to the alpha amine of another). Cyclic isopeptides contain at least one non-alpha amide linkage, such as a linkage between the side chain of one residue to the alpha carboxyl group of another residue, as in microcystin and bacitracin. Cyclic depsipeptides, such as aureobasidin A and HUN-7293, have at least one lactone (ester) linkage in place of one of the amides. Some cyclic depsipeptides are cyclized between the C-terminal carboxyl and the side chain of a Thr or Ser residue in the chain, such as kahalalide F, theonellapeptolide, and didemnin B. Bicyclic peptides such as the amatoxins amanitin and phalloidin contain a bridging group, generally between two of the side chains. In the amatoxins, this bridge is formed as a thioether between the Trp and Cys residues. Other bicyclic peptides include e hinomycin, triostin A, and Celogentin C. There are a number of cyclic peptide hormones which are cyclized through a disulfide bond between two cysteines, as in somatostatin and oxytocin. The processes by which cyclic peptides are formed in cells are not yet fully understood. One interesting property of cyclic peptides, however, is that they tend to be extremely resistant to the process of digestion, enabling them to survive intact in the human digestive tract. This trait makes cyclic peptides attractive to designers of protein-based drugs that may be used as scaffolds which, in theory, could be engineered to incorporate any arbitrary protein domain of medicinal value, in order to allow those components to be delivered orally. This is especially important for delivery of other proteins that would be destroyed without such implementation. Alpha-glucosidase inhibitors are oral anti-diabetic drugs used for diabetes mellitus type 2 that work by preventing the digestion of carbohydrates (such as starch and table sugar). Carbohydrates are normally converted into simple sugars (monosaccharides), which can be absorbed through the intestine. Hence, alpha-glucosidase inhibitors reduce the impact of carbohydrates on blood sugar. Examples of alpha-glucosidase inhibitors include: Acarbose- Precose Miglitol - Glyset Voglibose Even though the drugs have a similar mechanism of action, there are subtle differences between acarbose and miglitol. Acarbose is an oligosaccharide, whereas miglitol resembles a monosaccharide. Miglitol is fairly well absorbed by the body, as opposed to acarbose. Moreover, acarbose inhibits pancreatic alpha-amylase in addition to alpha-glucosidase.