title: Quantitation of curcuminoids in curcuma rhizome by near-infrared spectroscopic analysis.
abstract: This study investigated a nondestructive and rapid quantitation method for the curcuminoids, including curcumin, demethoxycurcumin, and bisdemethoxycurcumin, present in turmeric using near-infrared (NIR) spectroscopy and multivariate statistics. In the second derivatives of the NIR spectra of turmeric samples, two characteristic absorptions of curcuminoids were detected around 1700 and 2300-2320 nm. Partial least-squares regression (PLS-R) analysis was applied to the NIR spectra obtained from 34 turmeric samples, and PLS models for the quantitation of curcumin, demethoxycurcumin, bisdemethoxycurcumin, and total curcuminoid contents in the pulverized turmeric samples were constructed. Combination usage of the Standard Normal Variate (SNV) and second derivatives was obviously superior to other preprocessing methods. The lowest root mean squared error of cross-validation (RMSECV) values were detected at 6, 6, 6, and 6 PLS factors, for the quantitative subjects curcumin, demethoxycurcumin, bisdemethoxycurcumin, and total curcuminoid contents. It was clarified that the prediction of the composition by PLS-R analysis showed high correlation with the results of HPLC quantitations.
authors.affiliation: Division of Pharmacognosy, Department of Medicinal Resources, Institute of Natural Medicine, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan. ktanaka@inm.u-toyama.ac.jp
authors.forename: Ken
authors.initials: K
authors.lastname: Tanaka
authors.forename: Yosiaki
authors.initials: Y
authors.lastname: Kuba
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Sasaki
authors.forename: Fumiko
authors.initials: F
authors.lastname: Hiwatashi
authors.forename: Katsuko
authors.initials: K
authors.lastname: Komatsu