title: Isolation of a new phlorotannin, a potent inhibitor of carbohydrate-hydrolyzing enzymes, from the brown alga Sargassum patens.
abstract: Ethanol extracts from 15 kinds of marine algae collected from the coast of the Noto Peninsula in Japan were examined for their inhibitory effects on human salivary α-amylase. Four extracts significantly suppressed the enzyme activity. An inhibitor was purified from the extract of  Sargassum patens . The compound was a new phloroglucinol derivative, 2-(4-(3,5-dihydroxyphenoxy)-3,5-dihydroxyphenoxy) benzene-1,3,5-triol (DDBT), which strongly suppressed the hydrolysis of amylopectin by human salivary and pancreatic α-amylases. The 50% inhibitory activity (IC(50)) for α-amylase inhibition of DDBT (3.2 μg/mL) was much lower than that of commercially available α-amylase inhibitors, acarbose (26.3 μg/mL), quercetagetin (764 μg/mL), and α-amylase inhibitor from  Triticum aestivum  (88.3 μg/mL). A kinetic study indicated that DDBT was a competitive α-amylase inhibitor with a K(i) of 1.8 μg/mL. DDBT also inhibited rat intestinal α-glucosidase with an IC(50) value of 25.4 μg/mL for sucrase activity and 114 μg/mL for maltase activity. These results suggest that DDBT, a potent inhibitor of carbohydrate-hydrolyzing enzymes, may be useful as a natural nutraceutical to prevent diabetes.
authors.affiliation: Department of Food Science, Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, Ishikawa, Japan. konishi@ishikawa-pu.ac.jp
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Kawamura-Konishi
authors.forename: Natsuko
authors.initials: N
authors.lastname: Watanabe
authors.forename: Miki
authors.initials: M
authors.lastname: Saito
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nakajima
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sakaki
authors.forename: Takane
authors.initials: T
authors.lastname: Katayama
authors.forename: Toshiki
authors.initials: T
authors.lastname: Enomoto
mesh_terms: D000818:Animals; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D006801:Humans; D007564:Japan; D007700:Kinetics; D055292:Pancreatic alpha-Amylases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D000459:Phaeophyceae / Q000737:chemistry*; D051381:Rats; D055291:Salivary alpha-Amylases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D044647:Sargassum / Q000737:chemistry*
chemical_list: D004791:Enzyme Inhibitors; D055292:Pancreatic alpha-Amylases; D055291:Salivary alpha-Amylases