| 學者對石榴營養補給品標準的疑慮 |
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學者對石榴營養補給品標準的疑慮 根據一份對於市場上流通的產品的研究報導指出: 對石榴抽出物營養補給品的標準化於鞣花酸本身並不能準確的代表他們抗氧化的活性，並會誤導消費者對健康的益處。一份對市面上27種補給品的研究發現,鞣花酸本身並不能代表石榴多酚的抗氧化性。並更進一步的指出從低成本提煉出的鞣花酸也會有誤導性的抗氧化成效。在27個被檢測的營養補給品中,只有五個有顯著的石榴丹寧酸，17個的主要化學成分為鞣花酸含有微量或無法辨識的石榴丹寧酸，另外有五個則不含鞣安酸或丹寧。 可水解性的丹寧酸(石榴素punicalin和石榴鞣punicalagins)是抗氧化物的一個很重要的指標，在石榴汁裡占有90%的抗氧化活性。這些單寧酸會在腸道中水解並分解成鞣花酸進入血液，接著再代謝成尿石素。尿石素是在石榴汁或是萃取物裡一種很重要的氧化劑。然而，在商業標準裡，鞣花酸才是石榴抽出物的化學成分標準。所以，以鞣花酸含量來當作石榴粹出營養補給品的標準並不能準確的保證石榴營養品的可靠性。 專家選擇市面上的營養補充品來測試它們的抗壞血酸等效(AAE) 和五倍子酸等值(GAE)。石榴素、石榴鞣還有鞣花酸的含量是透過高壓液相層析法(HPLC)來分析的，而抗氧化的活性則是採用"Trolox 等效抗氧化能力分析法"來測定。
Study questions pomegranate supplement standardization Standardizing pomegranate extract supplements to ellagic acid alone could be inaccurately representing their antioxidant activity and misleading consumers as to their health benefits, according to a study of commercially available products. Researchers at the University of California tested 27 pomegranate supplements in the form of capsules, tablets and softgels to determine their phytochemical profiles beyond their content of ellagic acid. Their findings, published in the Journal of Agricultural and Food Chemistry, demonstrated that ellagic acid alone does not represent pomegranate polyphenols. Furthermore, the addition of ellagic acid from other less expensive sources could be misleadingly boosting the perception of antioxidant activity without increasing tannin levels, said the researchers. Antioxidant activity Hydrolyzable tannins (punicalin and punicalagins) are a key indicator of antioxidants, thought to account for almost 90 percent of the antioxidant activity of pomegranate juice. These tannins are hydrolyzed in the intestinal tract and lead to sustained blood levels of ellagic acid. The ellagic acid is then metabolized to urolithins, which are also thought to account for some of the biological activities associated with pomegranate juice or extract consumption. However, it is the content of ellagic acid which is largely used as the chemical marker for the commercial standardization of pomegranate supplements. The researchers tested the commercial supplement products chosen for the study to determine total polyphenol content, using both gallic acid equivalent (GAE) and ellagic acid equivalent (EAE) assays. Punicalagins, punicalin, and ellagic acid contents were determined by HPLC, whereas antioxidant capacity was measured using the Trolox equivalent antioxidant capacity (TEAC) assay.
No authenticity guarantee “Of the 27 supplements tested, only five had the typical pomegranate tannin profile by HPLC, 17 had ellagic acid as the predominant chemical with minor or no detectable pomegranate tannins, and five had no detectable tannins or ellagic acid,” said the researchers.
“Therefore, standardization of pomegranate extract supplements based on their ellagic acid content does not guarantee pomegranate supplement authenticity.” In addition, they highlighted that this method of standardization means that supplements can be adulterated with ellagic acid from less expensive sources, such as chestnut bark. David Winston, president and founder of extract supplier Herbalist & Alchemist, agreed that this type of adulteration occurs in the supplements industry. “Many companies buy raw materials from the least expensive source, but are they really getting what they think they are getting?” he said. “It is very important to know the supplier of raw material, especially with powders. Adequate botanical ID and chemical testing (if organoleptic testing is not adequate) are essential. (…) Having a C of A is not enough. Reputation and careful quality control are the hallmarks of reputable and reliable suppliers and manufacturers,” said Winston. President and COO of pomegranate extract supplier Cyvex, Matt Phillips, said the data in the study does not demonstrate that the pomegranate extracts standardized for ellagic acids were adulterated with ellagic acid from other sources. “For the pomegranate extracts standardized for punicalagins, TLC identification might be used as an identity test. For extracts standardized for ellagic acid, identification of the source is much more difficult and this might be an area which needs future work,” he said. The researchers concluded that more research is needed to assess the health impact of substituting ellagic acid for the complex mix of phytochemicals in a pomegranate extract dietary supplement. 資料來源: ‘Absence of Pomegranate Ellagitannins in the Majority of Commercial Pomegranate Extracts: Implications for standardization and Quality Control’
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