Quantification of Caffeine and 5-Caffeoylquinic Acid (5-Cqa) in Seven European Commercial Coffee (Coffea arabica) Types Using HPLC-PDA

The beneficial biological effects of coffee in the human body are attributed to its bioactive compounds, such as 5-CQA and caffeine. This study aimed to quantify caffeine and 5-CQA levels in seven different types of commercially available roasted coffees with varying intensities: Ristretto Espresso, Viola Espresso, Classico Espresso, Espresso Intense, Forte Lungo, Milano Dolce Gusto, and Decaffeinated Espresso, which are popular in Europe and globally. Three methods were used to prepare coffee extracts: (1) heat refluxing with 40 mL of 60% methanol followed by a 20-fold dilution, (2) hot water extraction (50 mL) using a coffee machine, then diluted to 1000 mL, and (3) hot water extraction (300 mL) with a coffee machine, followed by dilution to 1000 mL. Caffeine and 5-CQA levels were measured using an HPLC-PDA system with an InertSustain Phenyl column, following an isocratic procedure (mobile phase: 7% acetonitrile + 93% water with 0.1% phosphoric acid) at wavelengths of 275 nm and 325 nm for caffeine and 5-CQA, respectively. Methanolic extraction produced higher concentrations of caffeine and 5-CQA than water extraction methods, as these compounds dissolve more readily in methanol. 5-CQA content was the highest (p<0.05) in Decaffeinated Espresso, based on methods 1 (6.32 ± 0.12 mg/g) and 3 (5.70 ± 0.05 mg/g). In method 2, 5-CQA contents in both Decaffeinated Espresso (5.20 ± 0.06 mg/g) and Classico Espresso (5.02±0.05 mg/g) were significantly higher than others. In all extracts, the highest caffeine level was in Milano Dolce Gusto. Caffeine levels in Milano Dolce Gusto across methods 1-3 were 19.1 ± 0.23 mg/g, 14.6 ± 0.1 mg/g, and 18.5 ± 0.17 mg/g, respectively. Based on the caffeine-to-5-CQA ratios observed in methanolic extracts of the seven coffee types (ranging from 0.12 ± 0.00 to 4.69 ± 0.05), we recommend that the Decaffeinated Espresso, which had the lowest ratio, is the most health-beneficial coffee tested in this study.