Rapid Quantification of Nobiletin and Tangeretin in Citrus Peel Extractions by Raman Spectroscopy

Nobiletin and tangeretin were the most abundant polymethoxyflavones in citrus fruits, especially in the peels. Quantification of these two flavones in citrus peels was traditionally conducted by using High-Performance Liquid Chromatography (HPLC) method. In this study, Raman spectroscopy was utilized to achieve rapid quantification of nobiletin and tangeretin in citrus peels after simple solvent extraction and chromatographic separation. Powdered sample were examined nondestructively without further sample preparation. The relative nobiletin contents in the sample after solvent extraction and the sample after chromatographic separation were estimated to be 35.1±0.8 % and 91.7±0.9 %,respectively, in a few seconds. The Raman result was comparable to the HPLC result (42.4±2.2 % and 91.1±0.5 %). This study demonstrated the great capacity of Raman spectroscopy to simply, rapidly and accurately quantify the molecular content in a mixture.