Caffeine Quantity and Phenolic Compounds in a Daily Cup of Coffee and Tea

Coffee is a popular beverage enjoyed by millions of people across the globe. In the last few decades, the health benefits associated with drinking coffee beverages has listed coffee as a functional food. Apart from caffeine, other important bioactive compounds in coffee include chlorogenic acid and their derivatives, theophylline, and theobromine, cafestol, kahweol, tocopherols and trigonelline. The aim of this study was to quantify the caffeine content and identify the most abundant phenolic compounds which may be present in a daily cup of coffee. Since small amounts of caffeine usually remains in the coffee spent (waste product) which may potentially be harnessed for pharmaceutical and nutraceutical purposes, it was also included in the study. Additionally, for comparison purposes black tea leaves were also analysed for their caffeine content. Samples of coffee beans (CB), coffee spent (CS) and tea leaves (TL) were obtained from a Central Queensland University coffee shop in May 2020; no particular brand name or type were associated. A HPLC-DAD analytical method was utilized for caffeine quantification, while comparison to UV spectral data of phenolic standards was explored to tentatively identify the compounds in the sample extracts. No significant difference (p < 0.05) in the caffeine content in the CB and TL was noted (1.7 and 1.9%, respectively). However, a lower caffeine content was noted in CS (0.467 ± 0.062%), as expected. This indicated that about 27.5% caffeine from CB is lost in the CS. UV spectral data of the peaks obtained in the HPLC chromatogram were tentatively identified as glycosides of chlorogenic acid, catechin, chlorogenic acid and caffeine. These results as a proof of concept work suggests that a daily cup of coffee and tea contains reasonable amounts of caffeine and presence of bioactive compounds which offer antioxidant potential and health benefits. Large generation of CS as a by-product in the production of coffee beverage may potentially be utilised as a source of caffeine.