Submitted to: Near Infrared Spectroscopy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/20/2008
Publication Date: 5/7/2008
Citation: Berhow, M.A., Rayford, W.E., Vaughn, S.F., Palmquist, D.E., Tisserat, B. 2008. Quantification of rosmarinic acid levels by near infrared spectroscopy in laboratory culture grown spearmint plantlets. Journal Near Infrared Spectroscopy. 16:99-104. Interpretive Summary: Rosmarinic acid (RA) is a high value commercial phenolic with a myriad of health applications. RA levels within plantlet leaves can be manipulated by a variety of nutritional and physical treatments in plants grown in lab culture. The large number of experimental samples generated by these experiments made it difficult to quickly and efficiently measure the level of RA by conventional wet analytical methodology. Near infrared (NIR) spectroscopy can be used to measure the levels of a variety of components in whole seeds and dried leaves if a proper calibration curve is prepared. This paper describes the methodology for NIR measurement of RA in dried, powdered spearmint leaves. This methodology was used, along with conventional wet analysis, to show that increasing levels of CO2 produced increased RA concentrations, which correlated with increased growth and morphogenesis.
Technical Abstract: A method for the rapid quantization of rosmarinic acid (RA) in tissues of spearmint using near-infrared (NIR) spectroscopy was developed by correlating with the results of methanol extracts analyzed on a HPLC photo-diode array (PDA) system. NIR and HPLC analyses performed on over 500 samples were used to develop a NIR analytical algorithm. Applying this algorithm resulted in very good calibration statistics for the prediction of RA concentrations in dried powdered samples prepared from the cultured mints. NIR can be used to rapidly and accurately quantitate the levels of this secondary metabolite in plant samples. High positive correlations occur between CO2 levels and spearmint plantlet growth (fresh weight), morphogenetic responses (leaves, roots and shoots) and production of the secondary metabolite rosmarinic acid.