Fu Caili, Loo Alvin Eng Kiat, Chia Fiona Ping Ping, Huang Dejian
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Republic of Singapore.
J Agric Food Chem. 2007 Sep 19;55(19):7689-94. doi: 10.1021/jf071166n. Epub 2007 Aug 23.
Oligomeric proanthocyanidins were extracted from mangosteen pericarps and fractionated by a Sephadex LH-20 column to give 0.66% yield (dry matter). (13)C and (1)H NMR signals showed the presence of predominantly procyanidins together with a few prodelphinidin units along with small amounts of stereoisomers of afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin. Depolymerization with benzylmercaptan resulted in epicatechin thioether as the major product, and the mean degree of polymerization was determined to be 6.6. The electron spray ionization-mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectra revealed the dominant B type oligomers with mainly epicatechin units and with a small amount of A type oligomers. The isolated proanthocyanidins are potent peroxyl radical scavengers as evidenced by the high oxygen radical scavenging capacity at 1.7 x 10 (4) micromol TE/g, much higher than that of pine bark and grape seed extracts.
从山竹果皮中提取低聚原花青素,并通过葡聚糖LH - 20柱进行分离,得到0.66%的产率(干物质)。碳-13和氢-1核磁共振信号表明,主要存在原花青素,同时伴有少量原花青定单元,以及少量阿福豆素/表阿福豆素、儿茶素/表儿茶素和没食子儿茶素/表没食子儿茶素的立体异构体。与苄硫醇进行解聚反应,主要产物为表儿茶素硫醚,测得平均聚合度为6.6。电喷雾电离质谱和基质辅助激光解吸/电离飞行时间质谱显示,主要为以表儿茶素单元为主的B型低聚物,同时含有少量A型低聚物。分离得到的原花青素是有效的过氧自由基清除剂,其高氧自由基清除能力为1.7×10⁴微摩尔TE/克,远高于松树皮提取物和葡萄籽提取物。