Quality control is a key factor in making sure green tea dietary supplement products pack the same antioxidant punch as green tea leaves used for brewing beverages, according to U.S. Department of Agriculture (USDA) scientists.
Green tea-based dietary supplements have gained popularity in the U.S. market in recent years. But when it comes to sipping green tea versus taking the dietary supplement form, the better choice relative to health is unknown.
Scientists with USDA's Agricultural Research Service (ARS) in Beltsville, Md., studied the differences between phytochemicals in green tea dietary supplements and green tea leaves used for brewing beverages. ARS is USDA's principal intramural scientific research agency.
Chemist Pei Chen, with the ARS Beltsville Human Nutrition Research Center, headed the study. Chen and colleagues Jianqhao Sun and Long-Ze Lin analyzed extractions of 20 commercially available green tea dietary supplement products and eight dry green tea leaf samples. They compared the chemical constituents of the samples using an analytical technique called "HPLC/MS." This technique can separate one chemical constituent from another in a complex matrix. The technique also has the ability to identify and quantify chemical constituents accurately.
The study demonstrated that phytonutrients called flavonol glycosides were degraded and that another phytonutrient called catechin had oxidized during manufacturing and storage for many of the green tea supplement samples studied. They also found some additives in the supplements that were not listed on the labels. Brand names were not disclosed in the published study, but the researchers noted that most major dietary supplement manufacturers were represented.
The researchers concluded that although there are fine green tea dietary supplement products, there is no way for the consumer to know the qualities of those products from reading the labels. In addition, the consumer may ingest other botanical extracts unintentionally, and the quality of those green tea products varies significantly. The 2011 study was published in the Journal of AOAC International.
The U.S. Food and Drug Administration issued “current good manufacturing practices” that require all botanical ingredients in supplements to be identified. To answer the increased demands for valid analytical methods, Harnly chaired an expert review panel that established “Guidelines for Validation of Botanical Identification Methods” for AOAC International (Association of Analytical Communities)—a nonprofit association dedicated to excellence in analytical methods.
Organic and Traditional Differences
Switching to fresh fruit, the BHNRC “Rio Red Grapefruit” study showed that MS fingerprinting, when combined with a pattern-recognition method called “ANOVA-PCA,” could clearly establish that there are chemical differences between grapefruit samples in terms of growing year, harvest time, and farming method (conventional or organic).
For the study, Harnly and Chen studied samples of Rio Red grapefruit furnished by Gene Lester of the ARS Food Quality Laboratory, also in Beltsville. The grapefruits were grown using conventional and organic cultivation methods. They were harvested at three growing phases (early, mid, and late season) during 2005 and 2006. The juices were analyzed by mass spectrometry with no separation of the molecules. The overlapping mass spectra of all the molecules, or the “spectrometric fingerprint,” is very complex and, like human fingerprints, is analyzed by looking at the overall pattern.
ANOVA-PCA was used to determine whether a distinction could be made between the two cultivation methods and the three harvest dates (growing phases) by analyzing the MS spectral fingerprints of the grapefruit juices. The analysis showed that the chemical patterns of the fingerprints were statistically different among the farming modes, growing years, and times of harvest, regardless of the MS method used.
The results are important in demonstrating that conventional and organic products have different chemical compositions, although it is unknown at this time if these differences have significance to consumers. The 2010 study was published in the Journal of Agricultural and Food Chemistry.
Let’s Not Forget Herbals
American ginseng is one of the most commonly used herbal medicines in the world. But discriminating between ginsengs grown in different countries is difficult using traditional methods. Chen headed a study involving MS fingerprints and pattern-recognition analysis methods to discriminate between American ginseng grown in the United States and that grown in China. They studied 15 American ginseng samples grown in Wisconsin and 25 samples grown in China. The MS fingerprints, representing the chemical compositions of the samples, made it possible to distinguish between samples grown in the two different locations.
This research is part of Human Nutrition, an ARS national program (#107) described atwww.nps.ars.usda.gov.
James Harney and Pei Chen are with the USDA-ARS Food Composition and Methods Development Laboratory, 10300 Baltimore Ave., Beltsville, MD 20705-2350; (301) 504-8569, ext. 261 [Harnly], (301) 504-8144, ext. 238 [Chen].
"Digital Detectives Decipher Ingredients" was published in the April 2012 issue of Agricultural Research magazine.
