One single standard substance for the simultaneous determination of seven coffee polyphenols in green coffee bean extracts

Coffee polyphenols [1] in green coffee bean extracts (GCBE) have many healthy benefits. These polyphenols called chlorogenic acids included 3-CQA, 4-CQA, 5-CQA, 5-FQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA. Due to the limited availability of reference standards, multi-components analysis is not easy. In this work, the quantitative analysis of multi-components by single reference standard was proposed to simultaneously determine the contents of seven polyphenols in GCBEs by HPLC with Phenomenex Luna C18 column. A gradient elution system was developed for the analysis. The mobile phases consist of A (acetonitrile/water 25:75) and B (acetonitrile/water 10:90). The limit of quantification of 5-CQA was 5 µg. 5-CQA was used as the single standard to determine the content of seven components in GCBEs with relative response factors obtained in this work. Figure 1 shows the chromatograms of standard and sample solutions. The contents of seven polyphenols in different samples collected from the markets were determined with the single standard, 5-CQA. The results were listed in Table 1. In this work, using an easily available single component contained in the GCBEs as reference standard to determine multiple components was a practical option.

Fig. 1: Representative HPLC Chromatograms. a. Standard solution and b. Sample solution of GCBE under the experimental conditions. 1: 3-CQA. 2: 5-CQA. 3: 4-CQA; 4: 5-FQA. 5: 3.4-diCQA. 6: 3.5-diCQA. 7: 4.5-diCQA.

Tab 1: Contents (in percentage) of seven chlorogenic acids in samples of green coffee bean extracts collected in the markets

Compound	1	2	3	4	5	6	7
3-CQA	5.25	6.17	3.66	6.07	2.56	5.12	3.13
5-CQA	18.56	24.24	25.91	27.56	20.67	21.12	25.44
4-CQA	6.67	6.92	6.38	7.96	4.26	10.01	6.53
5-FQA	3.95	4.33	5.87	3.17	5.46	3.29	3.99
3,4-diCQA	2.56	1.92	2.87	1.31	3.52	2.36	2.21
3,5-diCQA	1.92	1.19	2.11	0.82	3.02	1.80	2.28
4,5-diCQA	2.11	1.36	2.47	0.90	3.07	1.94	2.74

References:

[1] Moo-Huchin VM, Moo-Huchin MI, Estada-Leon RJ, Cuevas-Glry L, Estra-Mota IA, Ortiz-Vazquez E, Betancur-Ancona D, Sauri-Duch E. Antioxidant compounds, antioxidant activity and phenolic content in peel from three ropical frits Yucatan, Mexico. Food Chem 2015; 16: 17 – 22