Chemical investigation of commercial grape seed derived products to assess quality and detect adulteration

• 21 commercial grape seed extract containing products were analyzed using LC–MS.
• 15 of the 21 were quality challenged, including six samples which were adulterated with high levels of peanut skin extract.
• Non-chromatographic assays now often employed by industry were not able to differentiate adulterated GSE.
• A simple TLC method was developed to quickly detect adulteration of grape seed extract.

Fundamental concerns in quality control arise due to increasing use of grape seed extract (GSE) and the complex chemical composition of GSE. Proanthocyanidin monomers and oligomers are the major bioactive compounds in GSE. Given no standardized criteria for quality, large variation exists in the composition of commercial GSE supplements. Using HPLC/UV/MS, 21 commercial GSE containing products were purchased and chemically profiled, major compounds quantitated, and compared against authenticated grape seed extract, peanut skin extract, and pine bark extract. The antioxidant capacity and total polyphenol content for each sample was also determined and compared using standard techniques. Nine products were adulterated, found to contain peanut skin extract. A wide degree of variability in chemical composition was detected in commercial products, demonstrating the need for development of quality control standards for GSE. A TLC method was developed to allow for rapid and inexpensive detection of adulteration in GSE by peanut skin.