Rubusuaviins A-F, Monomeric and Oligomeric Ellagitannins from Chinese Sweet Tea and Their α-Amylase Inhibitory Activity Rubusuaviins A-F, Monomeric and Oligomeric Ellagitannins from Chinese Sweet Tea and Their α-Amylase Inhibitory Activity

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-β-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 α-amylase activity by rubusuaviins and related ellagitannins was compared. Ellagitannins with β-galloyl groups at the glucose C-1 positions showed stronger inhibition compared with the α-galloyl and desgalloyl compounds. The molecular weight of these compounds was not important for the inhibition of α-amylase activity.

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-β-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 α-amylase activity by rubusuaviins and related ellagitannins was compared. Ellagitannins with β-galloyl groups at the glucose C-1 positions showed stronger inhibition compared with the α-galloyl and desgalloyl compounds. The molecular weight of these compounds was not important for the inhibition of α-amylase activity.