title: Rubusuaviins A-F, monomeric and oligomeric ellagitannins from Chinese sweet tea and their alpha-amylase inhibitory activity.
abstract: Six new ellagitannins herein, rubusuaviins A-F, were isolated from the aqueous acetone extract of Chinese sweet tea (Tien-cha, dried leaves of Rubus suavissimus S. LEE) together with seven known tannins. Rubusuaviin A was characterized as 1-O-galloyl-2,3-O-(S)-HHDP-4,6-O-(S)-sanguisorboyl-beta-D-glucopyranose. Rubusuaviins B, C, and E are dimeric, trimeric, and tetrameric ellagitannins, respectively, in which the sanguisorboyl groups were connected ellagitannin units. Rubusuaviins D and F were desgalloyl derivatives of rubusuaviins C and E, respectively. The inhibition of alpha-amylase activity by rubusuaviins and related ellagitannins was compared. Ellagitannins with beta-galloyl groups at the glucose C-1 positions showed stronger inhibition compared with the alpha-galloyl and desgalloyl compounds. The molecular weight of these compounds was not important for the inhibition of alpha-amylase activity.
authors.affiliation: Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Haizhou
authors.initials: H
authors.lastname: Li
authors.forename: Takashi
authors.initials: T
authors.lastname: Tanaka
authors.forename: Ying-Jun
authors.initials: YJ
authors.lastname: Zhang
authors.forename: Chong-Ren
authors.initials: CR
authors.lastname: Yang
authors.forename: Isao
authors.initials: I
authors.lastname: Kouno
mesh_terms: D002236:Carbohydrate Conformation; D002681:China; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D047348:Hydrolyzable Tannins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013056:Spectrophotometry, Ultraviolet; D013662:Tea / Q000737:chemistry*; D000516:alpha-Amylases / Q000037:antagonists & inhibitors*