Constituents of Amomum tsao-ko and their radical scavenging and antioxidant activities |
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Authors: | Teresita S Martin Hiroe Kikuzaki Masashi Hisamoto Nobuji Nakatani |
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Affiliation: | (1) Faculty of Human Life Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi, 558-8585 Osaka, Japan |
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Abstract: | Constituents of the fruit of Amomum tsao-ko were investigated following a preliminary screening of the antioxidant activity of several extracts of the fruit of this
plant that showed that the dichloromethane extract and the ethyl acetatesoluble and water-soluble fractions of the 70% aqueous
acetone extract had higher activity than α-tocopherol and butylated hydroxytoluene (BHT). Eleven compounds were isolated from
the ethyl acetate-soluble fraction, and their structures were elucidated as (+)-hannokinol (1), meso-hannokinol (2), (+)-epicatechin (3), (−)-catechin (4), β-sitosterol (5), β-sitosterol 3-O-glucoside (6), 2,6-dimethoxyphenol (7), protocatechualdehyde (8), protocatechuic acid (9), vanillic acid (10), and p-hydroxybenzoic acid (11) based on mass and various nuclear magnetic resonance (NMR) spectroscopic techniques. This is the first isolation of epicatechin
and catechin from the genus Amomum. The radical scavenging activity of the isolated compounds was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and colorimetric
and electron spin resonance (ESR) analyses. The antioxidant activity of the compounds was also determined based on the oxidative
stability index (OSI). The catechins and catechol derivatives showed strong activities in both the DPPH radical scavenging
activity and antioxidant activity assays. |
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Keywords: | Amomum tsao-ko antioxidant BHT catechin DPPH epicatechin ESR oxidative stability index (OSI) radical scavenging α -tocopherol |
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