The Laboratory Notebook
Answering important questions about quality.
By Robert Green
Resveratrol is currently a hot item in the nutraceuticals market because of the “buzz” surrounding several studies suggesting it may play a role in cancer prevention and contain “anti-aging” properties, among other things. In this column, we address some technical questions about resveratrol, but the discussion is also relevant to many botanicals and what you need to know to be sure you get the analytical services you need.
Q. I have a grape skin product that I sent to a lab asking for resveratrol content. The results seem low. I noticed the analytical report states that the quantity measured was of “trans resveratrol.” Are the terms “resveratrol” and “trans resveratrol” synonymous? If not, could this be the reason the reported results are low?
A. The answers are “no” and “maybe.” But let’s start at the beginning.
If there has been one theme running through this column over the years it is that when requesting analytical work you must be an educated consumer. While our work is scientific and can be very technical, it is not beyond the understanding of everyone in the industry. In order for you to get what you want from an analytical lab, you have to know what to ask for. As so poignantly stated by Yogi Berra many years ago, “If you don’t know where you are going, you might wind up someplace else.”
Many products to be tested are simple, like vitamin C. If you want vitamin C tested, all you need do is ask for it. However, this is not the case with many botanicals. For them, the item to be tested may not be one single component but a composite of many. A good example is soy iso-flavones. There are 12 of them. Some labs test three of them, some four and some six. The result of “total isoflavones” is the sum of those tested. Obviously, if lab “A” tests six and lab “B” tests only three (and assuming the sample contains all six) the results of lab A will be higher than that of lab B. (Can’t you already see a fight erupting between those two labs when both analyses are correct.) Now, that does not necessarily mean that lab B did anything wrong; it just means that the procedure it em-ployed measures only three. The lesson is that what is tested is crucial information the client needs to know. Some labs disclose which analytes are being tested on its pricing sheet; for others you have to ask. We go one step further and list on the analytical report the analytes measured and provide the total at the bottom, that way there is no confusion as to what was and was not included.
Now to your situation. Resveratrol comes in two forms—cis and trans. These are called isomers, which are compounds with the same molecular formula but different chemical structures. Some say only the trans isomer is biologically active and the cis does nothing; some say both are important. Some even say the cis may actually be harmful. As an analytical lab we do not opine on the pros and cons of the resveratrol isomers, we tell you how much of each is in your product.
Analytical labs generally tailor their service offerings to the most commonly requested tests and those tests are usually as basic as possible to get the job done. This is as it should be. If a lab’s clientele is only interested in certain analytes there is no reason to determine and charge for an analysis of other analytes. When you submit your sample to a laboratory requesting a resveratrol analysis, unless otherwise requested, the lab is going to perform that test according to its procedure. In the case of resveratrol, many times the trans value is the only component the lab is measuring. This means that the reported resveratrol number will be the trans value only. However, if there is something specific that you hope to find from this analysis, like the cis and trans values, do not assume that is what you are going to get—you have to ask for it.
On that note, the reason why the standard test may not automatically include the cis and trans values is because that is a more complex analysis that requires special attention. When you request the identification and quantification of cis and trans resveratrol, the lab is obviously looking for two analytes instead of one. As you may remember from past columns, the more things you wish to identify and quantify in a sample, the more complex the analysis, and the more it will cost you. In this case, the extraction procedure is the same for the cis and trans-resveratrol since they are similar. However, the instrument method is different because it needs to qualify and quantify two closely related items.
This takes us to the analytical standard. In order to quantify the cis and trans isomers, you need an analytical standard for each. The commercially available standard for resveratrol is found in the trans form; the cis form is not commercially available. If a laboratory wants to quantify the cis, then it must develop a cis standard.
As for whether adding the cis value will greatly improve your overall resveratrol value (and you want the total of the two), it may indeed. As with all samples and all analytes, it completely depends on your sample. If you have significant cis, want that value included and the lab is looking only for trans, your total resveratrol value will be adversely affected. Conversely, if your specification calls for trans only you would want to be sure that an analytical report with an amount for total resveratrol does not include the amount of any cis present.
When it comes to analytical testing, you need to educate yourself on your product and how it should be tested if you want the process to work for you. The subject may appear daunting, but even a quick Internet search may alert you to potential issues you may en-counter with your product so you can take proactive steps with your lab to prevent them. Your analytical lab should be willing to walk you through the various permutations. After all, it is your product and your money.NW