|Harnly, James - Jim|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/3/2011
Publication Date: 12/3/2011
Citation: Lin, L., Harnly, J.M., Zhang, R., Chen, H., Fain, Z. 2011. A general approach to quantification of hydroxycinnamic acid derivatives and flavones, flavonols, and their glycosides by UV spectrophotometry. Journal of Agricultural and Food Chemistry. 60:544-553. Interpretive Summary: Both identificantion and quantification of dietary polyphenols is very important for the estimation of their daily intake and determination of their contribution to human health benefits. This paper introduces a general method that uses a readily available, inexpensive compound as a standard for the quantification of all the phenolic compounds that are based on a hydroxycinnamic structure using UV absorption spectrophotometry. The concept presented in this paper will allow quantification of the polyphenols in foods in a more accurate, convenient, efficient, and cheaper manner. This method will allow for the determination of the concentrations of an increased number of polyphenols in foods and will facilitate studies on their impact on human health.
Technical Abstract: A general method was developed for the quantification of hydroxycinnamic acid derivatives and flavones, flavonols, and their glycosides based on the UV molar relative response factors (MRRF) of the standards. Each of these phenolic compounds contains a cinnamoyl structure and has a maximum absorbance (lamda-max) for Band I within a spectral interval of 320-370 nm. MRRF values were measured for 5 separate groups at 5 different wavelengths and then normalized between groups based on rutin. The five groups were hydroxycinnamic acids and their derivatives (326 nm), apigenins (336 nm), luteolins (348 nm), flavonol glycosides at the 3 and 7 position (354 nm), and flavonol aglycones and flavonol glycosides at other than the 3 and 7 positions (368 nm). Using MRRF values, a series of 5 standards can be used to quantify the polyphenols in each group or a single standard such as rutin can be used to quantify the phenolics in all 5 groups. The quantification of these polyphenols in two teas and Erigeron breviscapus whole plant was used as examples.