Clinical Pharmacokinetics of Green Coffee Bean Extract
Coffee (Coffea arabica, Rubiaceae) beans are used in many cultures across the globe to brew the popular caffeinated beverage. Caffeine and coffee have been linked with reduced incidence of metabolic syndrome and diabetes, lower serum triglycerides, better athletic performance, and improved memory and attention. Other than caffeine, antioxidant compounds such as chlorogenic acids (CGA) may underlie coffee’s benefits, as some studies report similar results for decaffeinated coffee. Among coffee CGAs, 5-CQA comprises about 35% of CGAs in roasted coffee and 56-62% in green coffee beans. One serving of coffee provides 20-675 mg CGAs, depending on the type of roast, preparation, serving size, and many other factors.
CGAs, like most polyphenolic compounds, are not well absorbed in the human body but are broken down or metabolized to smaller units in the gut. Coffee CGAs are differentially absorbed and/or metabolized in humans, with large individual variation. It has been suggested the presence of plant polyphenols in combination with caffeine may offer additional health benefits. Using a post intake study period of four hours (240 minutes) to conform to earlier studies of coffee and caffeine, the authors compared a natural coffee extract and a standard synthetic caffeine product to investigate the relative activity and kinetics of CGAs in combination with caffeine in a small randomized, double-blind, two-period crossover trial.
Sixteen healthy male participants were enrolled and randomized to receive one dose of either 60 mg botanically sourced caffeine (product 1) derived from 480 mg green coffee bean extract (Applied Food Sciences, Inc.; Austin, Texas) or 60 mg synthetic US Pharmacopoeia standard caffeine (product 2) during two study sessions, crossing over to the other product for the second session. Sessions were separated by at least five days. Participants did not consume caffeine or caffeinated products for at least 24 hours before sessions. They fasted for at least 10 hours before each session. They were given their respective test substances in an 8 oz. liquid form, in identical bottles, and instructed to drink it within five minutes, then to add 2 oz. of water to the bottle, swish it, and drink that as well. Blood was collected one hour before dosing and at 0.25, 0.5, 0.75, 1.0, 1.5, 2.0, 2.5, 3.0, and 4.0 hours post-dosing. Determinations were made of blood levels of 3-, 4-, and 5-CQA and of serum caffeine (as methylxanthine). Caffeine has a mean half-life of about five hours and a time to maximum plasma concentration (tmax) of ~60 minutes. Endpoints included maximum plasma concentration (Cmax), tmax, and area under the curve (AUC0-4 h) over the four-hour study period. Blood pressure and heart rate were also measured about one hour before dosing and about four hours after dosing as a safety monitoring measure. Fifteen participants completed the study.
CGAs were only analyzed, using high-pressure liquid chromatography (HPLC), from blood samples taken in connection with the intake of product 1. Caffeine was analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Controls included blank human serum, where endogenous interference occurred, and blank bovine serum albumin, with no interference seen. There were no statistically significant differences in age, body mass index, vital signs, or metabolic parameters between participants in either group during the study. No AEs were reported or observed. For all CGAs analyzed, increases from baseline serum levels are steep, peaking at about one hour after ingestion. For both 3- and 4-CQA, tmax was reached at a mean of about one hour (range, 0.75-4.0 h). For 5-CQA, tmax was slightly longer (mean, 1.5 h [0.75-2.5 h]). Total CQAs also had a tmax of one hour (0.75-4.0 h). 3-CQA had a Cmax almost double that of either 4- or 5-CQA (11.4±4.52 ng/mL vs. 6.84±3.13 and 7.20±3.66 ng/mL, respectively). AUC directly correlated to the dosing of each of the CQA compounds in the standardized green coffee bean extract. 3-CQA was also most-absorbed of the CGAs analyzed. At the end of four hours, all three CQAs remained at serum levels above baseline. While other studies have reported different results in terms of relative CGA absorption, it is clear that these compounds are readily absorbed and bioavailable in humans. Pharmacokinetic markers for caffeine did not differ significantly between study groups, indicating once again the chemical identity of botanically-sourced and synthetic caffeine.
No conflicts of interest were mentioned.
Morton K, Knight K, Kalman D, Hewlings S. A prospective randomized, double-blind, two-period crossover pharmacokinetic trial comparing green coffee bean extract–a botanically sourced caffeine–with a synthetic USP control. Clin Pharmacol Drug Dev. November 2018;7(8):871-879. doi: 10.1002/cpdd.451.