Natural Yellow Colors Extracted from Gardenia Fruit (Gardenia jasminoides ELLIS) and Colors Found in Commercial Gardenia Fruit Extract Color-Analysis of Natural Yellow Colors by High Performance Liquid Chromatography-

Abstract

In the previous paper, thin layer and high performance liquid chromatographic methods for the determination of geniposide were reported. In this work, separation and determination of natural colors in gardenia fruit extracts were investigated.Natural colors, crocin and crocetin, and geniposide (which is a contaminant) could be simultaneously separated by reversed-phase high performance liquid chromatography (HPLC) on a Nucleosil 7 C18 column with methyl alcohol-water as the eluant (Fig. 1).The natural yellow colors in gardenia fruit could be extracted with methyl alcohol, 50v/v% aqueous methyl and ethyl alcohols or water. The color intensities (absorbances at 438nm, as crocin) of the extracts became maximum after about 24 hours. Some of the extracts showed a slight loss of colors on subsequent extraction (Fig. 2). The color intensity of the extract with methyl alcohol or 50v/v% aqueous methyl and ethyl alcohols was higher than that of the extract with water, and the ratio of geniposide/color intensity (G/C) in the former extract was 0.4, less than that in the latter extract (Table 2).The color intensity of commercial gardenia fruit extract color was expressed as E1%1cm value at 438nm, as crocin. The values obtained for eighteen samples from different companies were in the range of 4.9 to 175, and the ratios of G/C in 12 of the 18 samples were 0.4-1.6 (Table 3). These results suggested that the samples may have been manufactured by extraction with the above solvents or water.The natural colors in the extract and the samples were analyzed by HPLC. Several peaks (2-4 peaks) besides crocin were detected on the chromatograms, but crocetin was not detected (except in sample Nos. 2 and 11). In sample Nos. 2 and 11, crocin was converted into crocetin during alkaline hydrolysis [Fig. 6 (Sample 2) and Fig. 7 (Sample 2)].The peak which appeared at the retention time of about 20min on HPLC was observed on all the chromatograms (Figs. 3, 4 and 7). The color corresponding to this peak may occur together with crocin in gardenia fruit; its structure might be analogous to those of crocin and crocetin.