Chlorogenic Acid: A Comprehensive Reference
1. Identity and Chemical Characterization
Chemical Names and Classification
Chlorogenic acid (CGA) is an ester of caffeic acid and quinic acid, belonging to the group of polyphenols commonly found in the human diet, especially in coffee, tea, fruits, vegetables, and numerous medicinal plants. Also known as coffee tannic acid and 3-caffeoylquinic acid, it is a water-soluble polyphenolic phenylacrylate compound produced by plants through the shikimic acid pathway during aerobic respiration. Its molecular formula is C16H18O9. Its hemihydrate is a white needle-like crystal or slightly yellow needle-like crystal, hardly soluble in organic solvents such as chloroform, ether, and benzene, and readily soluble in polar solvents such as methanol, ethanol, and acetone.
Isomers and Structural Variants
According to the different binding sites and numbers of caffeoyl quinic acid, there are ten kinds of chlorogenic acid isomers composed of mono-caffeoyl quinic acid and dicaffeoyl quinic acid, namely: 1-caffeoylquinic acid, 3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, 1,3-dicaffeoylquinic acid, 1,4-dicaffeoylquinic acid, 1,5-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic acid. Among these, 5-O-caffeoylquinic acid (5-CQA) is the most abundant form in plant-based foods and beverages.
Natural Sources
CGA is a natural plant extract with a vast array of sources, present in honeysuckle, potato, cork, eucommia leaves, chrysanthemum, strawberry, mango, blueberries, mulberry leaves, and green coffee. Diverse plant families are known to contain chlorogenic acids in different tissues, including various health-promoting foods, such as vegetables, grapes, apples, pears and citrus fruits, and commonly consumed beverages (coffee, green tea, and wine). In medicinal plant resources, Lonicera japonica Thunb. and Eucommia ulmoides Oliv. have been identified as species with high accumulation of CGA.
Research indicates that coffee is the main contributor to daily CGA intake, with a single 200 mL cup containing approximately 50–150 mg of CGAs. The content of chlorogenic acid in coffee beans is easily affected by external factors such as variety, growth environment (soil quality, climate, latitude, humidity), and roasting process, especially temperature. Compared with the instability of coffee beans, there is a fairly high concentration of chlorogenic acid in coffee leaves, and the content of young leaves is higher than that of mature leaves, even up to three times the difference.
Common Forms and Preparations as a Supplement
CGA is commercially available primarily as green coffee bean extract (GCBE), standardized to a defined percentage of chlorogenic acids. It is also encountered in the form of purified powders (as the isolated compound) and as components of multi-ingredient nutraceutical formulations. The chlorogenic acids family is the most widely distributed botanical drug in the phenolic acid group and is also commonly found in various traditional Chinese medicine (TCM) extracts.
2. Traditional and Historical Use
Traditional Chinese Medicine (TCM)
Traditional Chinese medicine (TCM) and Ayurveda traditions have pharmacologically used many plant species with a high content of chlorogenic acids. The most prominent source plant in TCM is Lonicera japonica (Japanese honeysuckle, known as Jin Yin Hua or "Gold-Silver Flower"). It has been a widely-used traditional Chinese medicine for about 3,000 years. Its main Chinese medicinal usage is to dispel the heat-evil, to treat diseases like upper-respiratory tract infections, carbuncles, and pneumonia. In TCM, it is considered a "cooling" herb, often included in formulas for its potential to "clear heat" and "remove toxins."
Ren Dong Teng (the honeysuckle stem, Lonicera japonica) was historically used during the Tang Dynasty to treat epidemic fevers and heat-related illnesses. In Traditional Chinese Medicine, it is known for "clearing heat and unblocking the channels," making it valuable for both external and internal inflammation. The herb's main active compounds — including chlorogenic acid, luteolin, and other flavonoids — demonstrate broad antibacterial, antiviral, anti-inflammatory, antioxidant, and immunomodulatory activities, providing a modern pharmacological basis for its traditional heat-clearing and detoxifying uses.
CGA is widely found in higher dicotyledonous plants, ferns, and many Chinese medicine plants, which enjoy the reputation of "plant gold."
Coffee-Related Traditional Use
Although coffee leaf tea has only gradually appeared in recent years, people have used the leaves of coffee trees to make tea-like beverages for hundreds of years, especially in major coffee-growing areas such as Sumatra, Ethiopia, Sudan, and Jamaica. Coffee leaves have been commonly used to make infusions in many coffee-producing countries such as Ethiopia and South Sudan.
Scientific Isolation
The first isolation of chlorogenic acid dates back to the early 1900s by chemists studying coffee chemistry in Europe. Around mid-century, researchers realized it contributed to flavor and bitterness in coffee, and by the 1980s, nutrition scientists began exploring its potential metabolic benefits.
3. Key Constituents and Active Compounds
Chlorogenic acid itself is the principal bioactive compound of interest, but it is important to understand that the CGA family comprises multiple structurally related esters. 5-caffeoylquinic acid (5-CQA) and 3,5-dicaffeoylquinic acid (3,5-DCQA) are the major chlorogenic acids found in coffee by-products.
Upon ingestion, CGA is metabolized into its component parts. Chlorogenic acid is not hydrolyzed in the stomach and the small intestine, but is absorbed in the stomach in its intact form and as hydrolyzed forms such as caffeic acid and (iso)ferulic acids in the small intestine. Once reaching the cecum, chlorogenic acid is hydrolyzed into caffeic acid and further metabolized into other aromatic acids. Both parent compound and its metabolites (caffeic acid, ferulic acid, isoferulic acid) are considered to contribute to pharmacological activity. Upon oral ingestion, a significant portion of CGA remains in the colon and becomes metabolized and absorbed into circulation. Therefore, the observed pharmacological effects are likely to result from CGA and its bioactive metabolites, which further impedes the mechanistic interpretation of the data.
4. Mechanisms of Action
Anti-inflammatory Pathways
CGA can thwart inflammatory constituents at multiple levels such as curtailing NF-κB pathways to neutralize primitive inflammatory factors, hindering inflammatory propagation, and alleviating inflammation-related tissue injury. It executes its anti-inflammatory function by moderating the synthesis and secretion of inflammatory mediators, namely TNF-α, IL-1β, IL-6, IL-8, NO, and PGE2. Concurrently, it modulates key signaling pathways and associated factors, including NF-κB, MAPK, Nrf2, and others, bestowing protection upon cells and tissues against afflictions such as cardio-cerebrovascular diseases and diabetes mellitus.
Antioxidant Pathways
CGA raises pivotal antioxidants by activating the Nrf2 pathway, thus scavenging excessive cellular free radicals. Research indicates that chlorogenic acid facilitates the liberation of Nrf2 from its binding partner Keap1, culminating in Nrf2 activation and concomitant upregulation of HO-1 and NQO-1.
Metabolic Regulation (AMPK Pathway)
CGA elevates AMPK pathways for the maintenance and restoration of metabolic homeostasis of glucose and lipids. More specifically, CGA can potentially (A) target NF-κB, MAPKs, and JAK pathways to mitigate inflammation; (B) activate Nrf2-dependent and independent pathways to execute antioxidation function; (C) regulate lipid metabolism through increasing lipolysis and fatty acid oxidation and suppressing synthesis of cholesterol and fatty acids; (D) modulate glucose metabolism through increasing glycolysis and suppressing glucose uptake and glucose synthesis; and (E) exhibit neuromodulation through targeting multiple neuroreceptors and ion channels.
Neuroprotective Mechanisms
Chlorogenic acid exhibits significant neuroprotective effects; it is capable of crossing the blood-brain barrier, scavenging free radicals within the brain, and inhibiting the aggregation and oxidation of β-amyloid (Aβ). Additionally, CGA shows functions of neuromodulation by targeting neuroreceptors and ion channels.
Cardioprotective Mechanisms
Chlorogenic acid manifests a robust protective effect against doxorubicin-mediated cardiotoxicity in rats; this cardioprotection appears to be hinged on chlorogenic acid's ability to suppress apoptotic marker caspase-3 expression and tyrosine, whilst enhancing Nrf2 and HO-1 expression in the cardiac milieu.
Bioavailability and Gut Microbiota Metabolism
The majority of CGA escapes absorption in the small intestine and reaches the colon, where the resident microbiota transforms it into several metabolites. The absorption of chlorogenic acid from instant coffee occurred in both the small and large intestines, with absorption occurring primarily in the large intestine. Microbial metabolites accounted for 57.4% (mol/mol) of the chlorogenic acid intake. Such a high abundance of microbial metabolites shows that the bioavailability of chlorogenic acid depends largely on its metabolism by the gut microflora. Their potential importance in explaining the biological effects of dietary polyphenols is emphasized. Metabolism results in phenolic conjugates in the blood and urine, but varying depending on the acyl-quinic acid, and subject to significant interperson variability. The balance between hydrogenation and complete β-oxidation of the cinnamic acids, both by liver and gut microbiota, determines the profile of metabolites.
5. Scientific Evidence by Area of Use
5.1 Blood Glucose Regulation and Diabetes
Human randomized controlled trials (RCTs) report that chlorogenic acid supplementation can significantly reduce postprandial blood glucose and glycated hemoglobin (HbA1c) levels and improve insulin sensitivity.
In a cohort of 15 patients with impaired glucose tolerance (IGT), CGA (400 mg three times per day for 3 months) decreased fasting serum glucose, insulinogenic index, body weight, body mass index, waist circumference, triglycerides, total cholesterol, LDL-c, and very low-density lipoprotein levels, with an upregulated Matsuda index. This RCT (ClinicalTrials.gov NCT02621060) was a randomized, double-blind, placebo-controlled clinical trial carried out in 30 patients with a diagnosis of impaired glucose tolerance in accordance with American Diabetes Association criteria. The patients received 400 mg capsules of chlorogenic acid or placebo, three times daily one-half hour before meals for 90 days.
In a randomized, double-blind, placebo-controlled crossover study to evaluate acute response, a one-time intake of green tea catechins together with coffee CGA significantly increased GLP-1 and decreased blood sugar levels and GIP secretion in healthy subjects compared with the placebo group after consumption of a 75 g glucose load. This data was echoed by a related study showing that a three-week intake of green tea catechins + CGA-enriched beverages exhibited similar beneficial effects in postprandial glycemic control and diabetic prevention.
Based on data from population intervention studies, daily oral doses of CGA at 13.5 mg to 1,200 mg can reduce fasting blood glucose, improve glucose tolerance, enable weight loss or prevent weight gain, and improve blood pressure in hypertensive patients. Daily intake of 200 mg or more may reduce fasting blood glucose, with a dose-effect relationship in the range 13.5–500 mg/d. A specific proposed level of CGA to improve fasting blood glucose could be ≥200 mg/d.
Evidence strength: Preliminary to moderate. Human RCT evidence exists but studies are generally small, short in duration, and often test CGA within multi-ingredient formulations, making it difficult to isolate the specific contribution of CGA. Larger, longer trials are needed.
5.2 Blood Pressure
A systematic review and meta-analysis of published RCTs assessed the effect of CGA on blood pressure. Meta-analysis revealed a statistically significant reduction in systolic blood pressure in favor of CGA (mean difference: −4.31 mm Hg; 95% CI: −5.60 to −3.01; I2=65%; P<0.00001). Meta-analysis also showed a significant reduction in diastolic blood pressure favoring CGA (MD: −3.68 mm Hg; 95% CI: −3.91 to −3.45; I2=97%; P<0.00001). All studies reported no adverse events.
Evidence strength: Moderate, based on pooled RCT data. Statistically significant reductions were observed in both systolic and diastolic blood pressure, though the high heterogeneity (I2=97% for DBP) in the meta-analysis warrants cautious interpretation. Chlorogenic acid is under preliminary research for its possible biological effects, such as regulation of blood pressure, although there is insufficient evidence for its effectiveness per Wikipedia's summary of the regulatory situation.
5.3 Body Weight and Obesity
Epidemiological evidence supports that chlorogenic acid can slightly reduce body weight and body fat percentage while improving flow-mediated dilation. The primary vehicle tested in clinical trials is green coffee bean extract (GCBE). Supplemental green bean coffee extract (GBCE) with caffeine has been shown to prevent weight gain. There are different dosages of GBCE that contain chlorogenic acid (CGA), and the data for their effectiveness in preventing weight gain at 500 mg/day is currently out of date. A 2023 systematic review and meta-analysis sought to better understand the effects of GBCE containing CGA on body weight.
One study found that supplementation with chlorogenic acid-rich green coffee extract improved glycemic parameters and adiposity scores. Similar results have been obtained in a study where CGA-rich green coffee bean extract (CGB70®) was investigated in 105 patients with BMI >25 kg/m2.
Evidence strength: Weak to preliminary. Most positive findings come from small trials using multi-ingredient green coffee extracts (which also contain caffeine), making it impossible to attribute effects solely to CGA. Animal data are more robust. Further well-controlled human trials isolating CGA are needed.
5.4 Lipid Metabolism and Dyslipidemia
In a randomized, double-blind controlled trial, participants (n=65) were given an 8-week cooked ham enriched with a pool of antioxidants (including 22.5 mg CGA/100 g cooked ham) or a placebo. Subjects with intervention showed significantly lower levels of ox-LDL, malondialdehyde (MDA), total cholesterol, high-sensitive C-reactive protein, and IL-6. Numerous short-to medium-term randomized controlled trials (RCTs) have confirmed that chlorogenic acid supplementation significantly lowers blood pressure and improves fasting blood glucose, HOMA-IR index, and blood lipid profiles.
Evidence strength: Preliminary to moderate for lipid improvements. Most evidence is derived from RCTs that combine CGA with other bioactives. Standalone CGA lipid trials in humans are limited.
5.5 Liver Protection (Hepatoprotection)
A narrative review summarized available information on the therapeutic effect of CGA in metabolic dysfunction-associated steatotic liver disease (MASLD). While some clinical trials have employed nutritional supplements containing CGA and other compounds for the treatment of MASLD, it is strongly recommended that future trials focus on the use of CGAs alone or in combination with other compounds as hepatoprotective agents. The specific target cell and key molecule targeted by CGAs remain unknown, requiring further in-depth investigation. A seminal study posited that chlorogenic acid mitigated acetaminophen-induced inflammatory perturbations in liver tissues.
Evidence strength: Mostly preclinical (in vitro and animal). Human clinical trial data on CGA for liver disease specifically are limited and often involve multi-compound formulations.
5.6 Neuroprotection and Neurodegenerative Disease
Currently, relevant research is primarily in the preclinical and clinical trial stages, and chlorogenic acid is regarded as a potential dietary supplement for the prevention and delay of Alzheimer's disease and Parkinson's disease progression. Although the literature regarding the neuroprotective and anticancer properties of chlorogenic acid is extensive in cellular and animal models — with mechanisms involving NF-κB inhibition, Nrf2 activation, and mitochondrial-dependent apoptotic pathways well-established — the clinical evidence in these areas remains limited.
Evidence strength: Preclinical only. No robust human clinical trials in neurodegeneration have been completed. Mechanistic data from animal and cell studies are promising but insufficient to support therapeutic claims in humans.
5.7 Antioxidant and Anti-inflammatory Activity
CGA is considered one of the most important dietary phenolic compounds, exhibiting a wide range of biological activities, such as antioxidant, anti-inflammatory, anticancer, antibacterial, hepatoprotective, cardioprotective and neuroprotective effects, and modulation of lipid and glucose metabolism. The antioxidant mechanisms are well characterized at the molecular level. However, the translation of these antioxidant effects into measurable clinical outcomes in dedicated human trials remains an active area of research.
Evidence strength: Strong mechanistic and in vitro evidence; moderate indirect clinical evidence through metabolic syndrome trials; standalone antioxidant clinical endpoint trials in humans are limited.
5.8 Antimicrobial Activity
CGA has antioxidant, anti-inflammatory, antibacterial, antiviral, hypoglycemic, lipid-lowering, anticardiovascular, antimutagenic, anticancer, immune regulation, and other biological functions. However, the specific mechanism of action is unclear. Several in vitro and animal studies suggest that extracts from CGA-rich plants possess anti-inflammatory, antioxidant, and antimicrobial properties. Studies have demonstrated that honeysuckle extracts can inhibit the growth of certain bacteria and viruses, supporting traditional use for infections.
Evidence strength: Primarily in vitro. Human clinical antimicrobial trials for isolated CGA are lacking.
6. Body Systems and Health Areas Associated with Chlorogenic Acid
- Metabolic system: Glucose homeostasis, insulin sensitivity, lipid balance, weight regulation, metabolic syndrome components.
- Cardiovascular system: Blood pressure reduction, flow-mediated dilation, reduction in ox-LDL, cardioprotection.
- Hepatic system: Liver protection, modulation of hepatic fatty acid metabolism, potential benefit in MASLD/NAFLD.
- Nervous system: Neuroprotection, potential relevance to Alzheimer's and Parkinson's disease, neuromodulation via receptor and ion channel targeting.
- Immune and inflammatory system: Suppression of NF-κB–driven cytokine production, modulation of macrophage activation.
- Gastrointestinal system: Modulation of gut microbiota, prebiotic-like effects on colonic bacterial communities.
- Renal system: CGA can inhibit oxidative stress and inflammatory responses in renal tissues, reduce proteinuria, and delay the progression of renal fibrosis (based on preclinical data).
7. Dosage Forms and Reported Dosages
CGA is available in the following forms:
- Green coffee bean extract (GCBE/GBCE): Standardized powders and capsules, the most common commercial preparation.
- Isolated CGA: High-purity CGA in capsule form, used in some clinical research settings.
- Multi-ingredient nutraceuticals: CGA combined with other polyphenols, plant extracts, or vitamins.
- Dietary intake: Through regular consumption of coffee, tea, and polyphenol-rich fruits and vegetables.
Dosages reported in human intervention studies:
- The estimated dietary intake of CGA is 5 to 1,000 mg/d. Based on data from population intervention studies, daily oral doses of CGA at 13.5 mg to 1,200 mg can reduce fasting blood glucose, improve glucose tolerance, enable weight loss or prevent weight gain, and improve blood pressure in hypertensive patients.
- In one RCT, 400 mg capsules of chlorogenic acid were administered three times daily, one-half hour before meals, for 90 days.
- For the meta-analysis examining the impact of GBCE containing CGA on body weight, 500 mg/day was the dose examined with a random-effects model.
- Research indicates that a single 200 mL cup of coffee contains approximately 50–150 mg of CGAs. Frequent coffee consumers may ingest 0.5–1.0 g per day.
- Daily intake of 200 mg or more may reduce fasting blood glucose, with a dose-effect relationship in the range 13.5–500 mg/d. A specific proposed level of CGA to improve fasting blood glucose could be ≥200 mg/d.
8. Safety, Tolerability, and Drug Interactions
General Safety Profile
Toxicological, pharmacokinetic, and clinical data from animal and human studies indicated no significant evidence of toxic or adverse effects following acute oral exposure. The current state of knowledge suggests that long-term exposure to chlorogenic and isochlorogenic acids by daily consumption does not appear to pose a risk to human health when observed at doses within the normal range of dietary exposure.
CGA exhibits a good safety profile, which has not shown any obvious adverse effect and toxicity to normal cells or tissues, and is well-tolerated by humans.
Regulatory Status
Due to a lack of data, EFSA has not yet derived any health-based guidance values such as tolerable or acceptable daily intake levels (TDI/ADI) for both 5-caffeoylquinic acid and 3,5-dicaffeoylquinic acid. Thus, there are currently no specific regulations in place in the EU or other regions worldwide. Chlorogenic acid has not been approved as a prescription drug or as a food additive recognized as safe for use in foods or beverages.
Potential for Hepatotoxicity at High Doses
Conversely, excessive levels of CGA, upon oxidation, may induce significant hepatotoxicity. This concern is based on preclinical findings at supraphysiological concentrations and has not been robustly confirmed in human dietary or supplementation contexts. Acute systemic toxicity has been observed in animal models following high-dose intravenous injection (≥250 mg/kg), with rapid mortality suggesting potential acute effects on systems beyond the hepatocellular pathway.
Drug Interactions
Chlorogenic acid has been found to counteract the effects of metformin, a pharmaceutical drug used to manage elevated blood sugar levels. This interaction is only observed at high levels of chlorogenic acid, which is unlikely to occur in humans and thus may not have a significant impact. So far, no other adverse effects for 5-CQA and/or 3,5-DCQA have been documented.
Due to its potential blood pressure-lowering effect, chlorogenic acid may cause blood pressure to drop too low in people already taking medication with this effect.
Allergy
Allergy to green coffee bean extract, the natural source of chlorogenic acid, has been reported. Symptoms were primarily asthma attacks. However, coffee compounds other than chlorogenic acid appear to be responsible for this effect.
Caffeine Content of Green Coffee Extracts
Because green coffee bean extract contains caffeine, it may cause some of caffeine's unwanted effects. This is a formulation-specific consideration rather than a property of chlorogenic acid itself.
Evidence Limitations — Overall Assessment
There is not enough evidence to determine whether chlorogenic acid is safe or effective for human health, and its use in high doses, such as excessive consumption of green coffee, may have adverse effects. Further studies for defining its specific targeting molecules, improving its bioavailability, and validating its clinical efficacy are required to corroborate the therapeutic effects of CGA. The inherent low bioavailability of chlorogenic acid poses challenges in practical deployments.
References
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