Abstract
Thirteen polyphenolics were isolated from fresh pods of Caesalpinia pulcherrima using various methods of column chromatography. The structures of these polyphenolics were elucidated as gallic acid (1), methyl gallate (2), 6-O-galloyl-d-glucoside (3), methyl 6-O-galloyl-β-d-glucoside (4), methyl 3,6-di-O-galloyl-α-d-glucopyranoside (5), gentisic acid 5-O-α-d-(6′-O-galloyl)glucopyranoside (6), guaiacylglycerol 4-O-β-d-(6′-O-galloyl)glucopyranoside (7), 3-methoxy-4-hydroxyphenol 1-O-β-d-(6′-O-galloyl) glucopyranoside (8), (+)-gallocatechin (9), (+)-catechin (10), (+)-gallocatechin 3-O-gallate (11), myricetin 3-rhamnoside (12), and ampelopsin (13). All isolated compounds were tested for their antioxidant activities in the 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, and peroxynitrite radicals scavenging assays. Among those compounds, 11, 12, and 2 exhibited the best DPPH-, hydroxyl-, and peroxynitrite radical-scavenging activities, respectively. Compound 7 is a new compound, and possesses better scavenging activities towards DPPH but has equivalent hydroxyl radical scavenging activity when compared to BHT. The paper is the first report on free radical scavenging properties of components of the fresh pods of Caesalpinia pulcherrima. The results obtained from the current study indicate that the free radical scavenging property of fresh pods of Caesalpinia pulcherrima may be one of the mechanisms by which this herbal medicine is effective in several free radical mediated diseases.
Highlights
Reactive oxygen species (ROS), major free radicals generated in many redox processes [1], often induce oxidative damage to biological molecules, such as carbohydrates, lipids, proteins, and DNA.Many serious diseases and accelerated aging, including cardiovascular diseases, inflammation, and neurodegenerative diseases are caused by biomolecular degeneration, followed by the initiation and propagation of oxidative chain reactions [2,3]
By comparison to the previous literature, compounds 1~6 and 8~13 were identified as known compounds including two simple polyphenols, gallic acid (1) [33] and methyl gallate (2) [34]; three gallotannins of 6-O-galloylD-glucoside (3) [35,36], methyl 6-O-galloyl-α-D-glucoside (4) [37], and methyl 3,6-di-O-galloyl-α-Dglucopyranoside (5) [36]; two phenol glycoside gallates of gentisic acid 5-O-α-D-(6'-O-galloyl) glucopyranoside (6) [38] and 3-methoxy-4-hydroxyphenol 1-O-β-D-(6'-O-galloyl) glucopyranoside
Its infrared (IR) spectrum indicated the presence of a hydroxyl group
Summary
Reactive oxygen species (ROS), major free radicals generated in many redox processes [1], often induce oxidative damage to biological molecules, such as carbohydrates, lipids, proteins, and DNA. It has been suggested that antioxidant compounds may prevent aging by scavenging free radicals and delaying or preventing oxidation of biological molecules [4]. Caesalpinia pulcherrima Swartz (Leguminosae) is a commonly used medicinal herb in Taiwan. Different parts of this herb are used in common remedies to treat a number of disorders including menoxenia, pyrexia, bronchitis, wheezing, and malarial infection. Isolated compounds from published studies on the C. pulcherrima. The MeOH/CH2Cl2 (1:1) crude extracts from flower and leaf parts of C. pulcherrima have been evaluated by the DPPH (1,1-diphenyl-2-picrylhydrazyl)-scavenging method [23]. The antioxidant potential of the isolated compounds was evaluated by DPPH-, hydroxyl-, and peroxynitrite-scavenging assay methods
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