Carlson M, Thompson R D
U.S. Food and Drug Administration, Minneapolis, MN 55401, USA.
J AOAC Int. 1998 Jul-Aug;81(4):691-701.
Herbal preparations derived from the dried seeds of guaraná (Paullinia cupana) have become a popular nutritional supplement used for stimulatory purposes. Once considered a drug substance in the United States, guaraná currently is classified as a food additive and dietary supplement. The pharmacological activity of guaraná-containing products is primarily due to methylxanthine alkaloids. For guaraná preparations, methylxanthine levels and, more significantly, the presence of several polyphenol compounds (i.e., catechins) provide phytochemical markers of authenticity. Methylxanthines and polyphenols are extracted from sample matrix with a heated phosphate buffer-methanol solution, the cooled extract is filtered, and the extract is injected into the liquid chromatographic (LC) system. A Nova-Pak C18 column eluted with phosphate buffer-methanol mobile phase (pH = 3.50) and monitored at 272 nm gave satisfactory resolution for the methylxanthines theobromine, theophylline, caffeine and the polyphenols (+)-catechin and (-)-epicatechin. Twenty-four products including dried seeds, dried paste, seed powders, tablets, and capsule formulations were assayed and conclusions were drawn about their authenticity. The LC system responded linearly to methylxanthines over the 100-fold range in concentration from 0.043 to 4.30 micrograms/mL for theobromine and caffeine and from 0.041 to 4.10 micrograms/mL for theophylline. Precision data for the 3 methylxanthines obtained from 10 different products (n = 5) gave relative standard deviation (RSD) values of 1.18-15.52% within a concentration range of 0.01-52.28 mg/g. Recoveries of methylxanthines from fortified products varied from 87.5 to 120.0%. The response for catechins was linear over a 200-fold range in concentration of 0.05-10.0 micrograms/mL. Precision data from 5 products (n = 5) gave RSD values of 1.08-5.54% within a concentration range of 0.34-32.65 mg/g. Recoveries from these products ranged from 87.7 to 109.7%. Results and chromatographic profiles for 14 commercial products in solid dosage form indicate that a number of these products may not contain authentic guaraná as an active ingredient or contain less than the declared quantity of guaraná. The proposed procedure also was applied to 2 carbonated soft drinks and a sample of maté.
源自瓜拉那（巴西香可可）干燥种子的草药制剂已成为一种用于刺激目的的流行营养补充剂。瓜拉那在美国曾被视为药物，目前被归类为食品添加剂和膳食补充剂。含瓜拉那产品的药理活性主要归因于甲基黄嘌呤生物碱。对于瓜拉那制剂，甲基黄嘌呤含量，更重要的是几种多酚化合物（即儿茶素）的存在提供了真实性的植物化学标志物。用加热的磷酸盐缓冲液 - 甲醇溶液从样品基质中提取甲基黄嘌呤和多酚，冷却后的提取物过滤后注入液相色谱（LC）系统。用磷酸盐缓冲液 - 甲醇流动相（pH = 3.50）洗脱并在272 nm处监测的Nova - Pak C18柱对甲基黄嘌呤可可碱、茶碱、咖啡因以及多酚（+） - 儿茶素和（ - ） - 表儿茶素给出了令人满意的分离度。对包括干燥种子、干燥膏剂、种子粉末、片剂和胶囊制剂在内的24种产品进行了分析，并就其真实性得出结论。LC系统对甲基黄嘌呤在浓度范围为0.043至4.30微克/毫升的可可碱和咖啡因以及0.041至4.10微克/毫升的茶碱的100倍范围内呈线性响应。从10种不同产品（n = 5）获得的3种甲基黄嘌呤的精密度数据在浓度范围为0.01至52.28毫克/克内给出相对标准偏差（RSD）值为1.18 - 15.52%。从强化产品中回收甲基黄嘌呤的回收率在87.5%至120.0%之间。儿茶素在浓度范围为0.05至10.0微克/毫升的200倍范围内呈线性响应。来自5种产品（n = 5）的精密度数据在浓度范围为0.34至32.65毫克/克内给出RSD值为1.08 - 5.54%。从这些产品中的回收率在87.7%至109.7%之间。14种固体剂型商业产品的结果和色谱图表明，这些产品中有许多可能不含有正宗的瓜拉那作为活性成分，或者所含瓜拉那的量低于宣称的量。所提出的方法也应用于2种碳酸软饮料和一份马黛茶样品。
