Investigation On The Chemical Constituents And Bioactivities Of Red Maple And Blueberry Flower

Chemical constituents and DPPH free radical scavenging and a-glucosidase inhibition activities of red maple and blueberry flower were investigated in this paper. A total of55different compounds including twenty-one gallic acid derivatives, twenty flavonoids, ten phenylpropanoids, one coumarin and three lignans were isolated and identified. All of their structures were extensively identified by the combination of physicochemical properties, UV spectrum, infrared spectrum, NMR spectrum (including2D NMR) and high-resolution mass spectrum. Among those isolated compounds, eleven were new compounds. Biological activities tests indicated most compounds showed very stronger DPPH free radical scavenging activity, and some gallic acid derivatives and Flavonol glycosides showed powerful a-glucosidase inhibition activity. The structure-activity relationship (SAR) of gallic acid derivatives, flavonoids and phenylpropanoids were briefly discussed. The detailed contents and results of this paper are briefly as follows:A total of twenty-seven compounds were isolated and purified by the combination of column chromatography of Silica gel coupled with macroporous resin, Sephadex LH-20, RP-ODS and preparative HPLC chromatography from red maple stem. They are five new compounds, including maplexin A (2), maplexin B (3), maplexin C (5), maplexin D (6) and maplexin E (12), respectively. Other twenty-two compounds are known, including Ginnalin C (1), Ginnalin B (4), Ginnalin A (7),3,6-di-O-galloyl-1,5-anhydro-D-glucitol (8),3-Methoxy-4-hydroxyphenol-1-O-P-D-(6'-O-galloyl)-glucopyranoside (17), catechin (18), epicatechin (19), epicatechin-3-O-gallate (20), procyanidins A6(21), procyanidins A2(22), quercetin-3-O-a-L-rhamnoside (23), quercetin-3-O-3"-galloyl-rhamnoside (24), quercetin-3-O-2"-galloyl-rhamnos-ide (25), Nortrachelogenin-8'-O-β-D-glucopyranoside (26),7,8-dihydroxy-6-methoxycoumarin (27), phloridzin (28), gallic acid (29), methyl gallate (30),3,4-dihydroxy-5-methoxybenzoic acid methyl ester (31), methyl syringate (32), methyl vanillate (33) and3,5-dihydroxy-4-methoxybenzoic acid (34).A total of twelve compounds were isolated and identified from red maple bark. They are six new compounds, including maplexin F (9), maplexin G (10), maplexin H (11), maplexin I (13), rubrumosides A (14) and rubrumosides B (16). Other six compounds are known, including nymphaeoside A (15) and the same five compounds as isolated from red maple stem:Ginnalin C (1), Ginnalin B (4), Ginnalin A (7), gallic acid (29) and methyl vanillate (33), respectively. In short, thirty-four compounds were isolated and identified from red maple and eleven were new compounds. Compounds15,17,21,22,26,28,31and34were isolated from the family of Aceraceae for the first time, and compounds1,4,7,8,20,24,25,32and33were isolated from the plant for the first time.All of the isolated compounds from red maple were tested for their a-glucosidase inhibition and DPPH free radical scavenging activities. New compounds Maplexins E-I all showed powerful a-glucosidase inhibitory activity with range of the IC507.9-16.1μM. All of the compounds except26,31-34showed very strong DPPH free radical scavenging activity with range of the IC507.7-77.5μM. Analysis the relationship of the structure of gallic acid derivatives and the a-glucosidase inhibitory activity, which suggested that the a-glucosidase inhibitory activities of these gallotannins were influenced by both the number and positions of the galloyl groups. Compounds1-4, which possess one galloyl group each, did not show any activity in this assay, while compounds5-8, which possess two galloyl groups each, showed moderate a-glucosidase inhibitory activity. While maplexin E-I (9-13), which contained three galloyl groups, showed powerful a-glucosidase inhibitory activity.A total of twenty-one compounds including ten phenylpropanoids and eleven flavonoids, were isolated and purified from blueberry flower. The compounds were identified from their nuclear magnetic resonance (NMR) and mass spectral data as5-O-caffeoylshikimic acid (35),5-O-Caffeoylquinic acid (36),5-O-Caffeoylquinic acid methyl ester (37),3,5-dicaffeoylquinic acid methyl ester (38), Methyl caffeate (39),5-O-coumaroylquinic acid (40),5-O-coumaroylquinic methyl ester (41), trans-cinnamic acid methyl ester (42), Rosin (43),2'-O-β-D-Glucosylrosine (44), quercetin-3-O-β-D-glucoside (45), quercetin-3-O-β-D-galactoside (46), quercetin-3-O-α-L-arabinopyranoside (47), myricetin-3-O-β-D-glucoside (48), myricetin-3-O -β-D-galactoside (49), quercetin-3-O-(6"-O-coumaroyl)-β-D-glucoside (50), quercetin-3-O-(2"-O-coumaroyl)-β-D-glucoside (51), kaempferol-3-O-(6"-O-coumaroyl)-β-D-glucoside (52) and other three are phenylpropanoid-substituted catechins (53-55).All of the isolated compounds from blueberry flower were tested for their α-glucosidase inhibition and DPPH free radical scavenging activities. All of the flavonoids showed powerful a-glucosidase inhibitory activity with range of the IC5028.9-137.5μM, while the phenylpropanoids showed very weak activity, only3,5-dicaffeoylquinic acid methyl ester (38) showed good activity with the IC5099.9μM. All of the compounds except40-44and52showed very strong DPPH free radical scavenging activity with range of the IC507.8-59.4μM. Analysis the relationship of the structure and the DPPH free radical scavenging activity, which suggested that the DPPH free radical scavenging activities were influenced by the number of the hydroxy groups.