Guaranine

Guaranine: A Comprehensive Encyclopedic Reference

1. Identity and Nomenclature

Guaranine is the historical and colloquial term for the primary alkaloid constituent isolated from the seeds of the Amazonian plant Paullinia cupana. The term was coined in the nineteenth century to describe the stimulant principle of guarana seeds but has since been unambiguously established as chemically identical to caffeine (1,3,7-trimethylxanthine). Seeds cultivated from the plant yield guaranine, which has the same chemical composition as caffeine. Because of this identity, modern pharmacological and botanical literature uses the terms "guaranine" and "caffeine" interchangeably when referring to the principal alkaloid of guarana, while the broader term "guarana" refers to the whole seed material or extract, which contains numerous additional biologically active compounds.

Guarana is an extract of roasted and pulverized seeds of the plant Paullinia cupana, which is indigenous to the Amazon Basin, and its major active components are caffeine and other xanthine alkaloids such as theophylline and theobromine. The plant's full taxonomic designation is Paullinia cupana H.B.K., variety sorbilis, belonging to the family Sapindaceae (soapberry family). The commercially cultivated variety most widely used is Paullinia cupana Kunth var. sorbilis (Mart.) Ducke.

Several vernacular and regional names are used for the plant and its products. Guarana is also called guaraná-da-amazônia, guaranaina, guaranauva, uarana, or narana — a species native to the Amazon region known for its stimulant and medicinal properties and used for centuries by indigenous communities.

Natural Source and Botanical Description

Guarana is a rainforest vine, scientifically known as Paullinia cupana, whose seeds contain stimulants theobromine and theophylline, and have four times more caffeine than any other plant. The plant is native to the Amazon Basin and is cultivated as a source of guarana and caffeine in South America. The seeds contain a high concentration of caffeine (2% to 8%), far higher than in coffee beans (1% to 3%). Guarana is primarily produced in the Brazilian states of Amazonas and Bahia, and approximately 70% of the production is used by the industry of soft and energy drinks. The other 30% becomes guarana powder for direct consumption in capsules or dilution in water, or it serves as a raw material for the pharmaceutical and cosmetics industries.

Common Forms and Preparations

A syrup extract is obtained from the seeds and used in soft drinks, or the seeds can be roasted and ground into powder. Guarana (Paullinia cupana), also known as Brazilian cocoa, has emerged as a key ingredient in various products, including powder, capsules, cosmetics, sweetened carbonated drinks, syrups, and energy shots used in the improvement of training performance, cognitive function, and weight control. Standardized dry extracts — such as the purified extract designated "PC-18" used in several clinical trials — represent a pharmaceutical-grade preparation used specifically in research and supplement contexts.

2. Traditional and Historical Use

The story begins with guaraná as the pre-Columbian cultivar of the Sateré-Mawé people in the Lower Amazon region, where it figured centrally in the Indigenous nation's origin stories, dietary regimes, and communal ceremonies. Guaraná had a rich cultural history long before European naturalists explored South America and even before the Portuguese arrived in Brazil in 1500.

The first report about the use of guarana as a beverage in European literature occurred in 1669 when, during the Jesuit expedition to the Amazon, the missionary João Felipe Bettendorf observed that the Sateré-Mawé Indians consumed a stimulating beverage that had diuretic properties and therapeutic effects against headache, fever, and cramps. Domestication occurred because the properties of the drink made with guarana caught the interest of settlers in the region, who went on to explore commercial production of the plant.

A few decades later, in A Journey to Brazil (1869), French naturalist Louis Agassiz defined it as one of the "great staples" of the Amazonian settlements and described how Indigenous peoples consumed their seeds.

Traditional Preparations

Traditional preparation methods were established over centuries by Amazonian peoples. Guarana seeds are ground into a fine powder and mixed with water to create a paste that is then shaped into balls and roasted. The resulting balls are then grated and mixed with water to create a beverage known as "guarana tea" or "guaranázinho." As soon as the kernels are completely dry, they are roasted in a fire and then ground like cocoa. Then the guarana powder is mixed with freshwater and served as a kind of coffee, sweetened with honey.

Traditional Medicinal Uses

Guarana has been used as a stimulant and tonic to treat fatigue, decrease hunger and thirst, and for headaches and dysmenorrhea. Its other chemical properties are used by Indigenous Peoples to treat a host of conditions, from migraine to dysentery to arteriosclerosis. Guarana has also been indicated as a diuretic, calming aphrodisiac, and tonic. Guarana has been used for centuries as an effective tonic, heart tonic, to thin the blood, and for mental acuity and to benefit long-term memory. Guarana was used in the Amazon area particularly during fasting periods because this remedy is said to have a hunger-dampening effect.

3. Key Constituents and Active Compounds

Guarana has a chemical composition characterized by alkaloids known as methylxanthines, which include caffeine, theophylline, and theobromine, as well as terpenes, flavonoids, and amides. The seeds are also rich in other xanthine alkaloids such as theophylline and theobromine, as well as catechins, epicatechins, and procyanidins.

Other phytochemicals identified in guarana include adenine, catechutannic acid, choline, d-catechin, guanine, guaranine, hypoxanthine, mucilage, saponin, tannins, theobromine, theophylline, timbonin, and xanthine.

Catechin, epicatechin, and epicatechin gallate are the phenolic constituents of guarana and have been associated with several health benefits, including anti-proliferative, antitumoral, and cytoprotective activities.

Caffeine (Guaranine) Content

Pure guarana composition can contain up to 5.3% of caffeine, although typical caffeine sources such as espresso coffee contain about 0.21% and dark chocolate about 0.08% of caffeine, respectively. It is possible to obtain 40–80 mg of caffeine per gram of guarana extract.

The Tannin Matrix and Putative Slow-Release Effect

Tannins are thought to contribute to the slower release of caffeine, as they bind to it. Tannins also have antioxidant properties. The short-term medicinal effects of guaraná are commonly thought to result from a high content of caffeine and associated alkaloids, as well as from considerable amounts of tannin. Future research may well show that various saponins also play an important part in the drug's pharmacology, particularly with regard to its long-term influence as a general tonic and prophylactic. It must be noted that the "slow-release" hypothesis regarding tannin-caffeine binding is mechanistically plausible but has not been rigorously confirmed in pharmacokinetic studies in humans.

4. Mechanisms of Action

Primary Mechanism: Adenosine Receptor Antagonism

Of the known biochemical actions of caffeine, only inhibition of adenosine receptors occurs at concentrations achieved during normal human consumption of the drug. Under normal physiological conditions, adenosine is present in sufficient concentrations to activate A1 and A2a receptors. Via actions on A1 receptors, adenosine decreases neuronal firing and the release of neurotransmitters. Caffeine is believed to act by antagonizing (blocking) receptors for the inhibitory neurotransmitter adenosine, thereby producing a stimulant effect on brain activity.

Caffeine action is thought to be mediated via several mechanisms: the antagonism of adenosine receptors, the inhibition of phosphodiesterase, the release of calcium from intracellular stores, and antagonism of benzodiazepine receptors. The ability of caffeine to inhibit adenosine receptors appears to be highly important in its effects on behavior and cognitive function.

Chronic caffeine does alter the density not only of adenosine receptors, but also of adrenergic, cholinergic, GABAergic, and serotonergic receptors. Behavioral responses to agents acting through dopaminergic and cholinergic pathways are altered.

Theophylline Mechanisms

Theophylline, also known as 1,3-dimethylxanthine, is a drug that inhibits phosphodiesterase and blocks adenosine receptors. It is used to treat chronic obstructive pulmonary disease (COPD) and asthma. Its pharmacology is similar to other methylxanthine drugs such as theobromine and caffeine.

Additional Stimulant Activity Beyond Caffeine

The mix of other natural chemicals contained in guarana seeds is thought to heighten the stimulant effects of guarana over caffeine alone. A 2015 study published in PLOS ONE used a planarian invertebrate locomotor model to investigate this question. By observing changes in planarian motility with exposure to guarana, caffeine, and glucose, the researchers determined that guarana seeds contain an additional stimulant over caffeine alone, and that glucose can support these tonic effects. While the caffeine in guarana likely works by established methylxanthine mechanisms, other constituents possibly function using different pathways. In addition to caffeine, guarana seeds are known to harbor a number of other possible stimulants such as catechins, tannins, and other alkaloids such as theophylline. These findings are from a non-mammalian model and do not establish equivalent effects in humans.

Antioxidant Mechanisms

Studies have shown that guarana has antioxidant and anti-inflammatory effects that reduce oxidative stress levels in other pathological processes. The chemical composition of guarana, which in addition to a relatively high concentration and bioavailability of methylxanthines, also contains flavonoids (e.g., catechins, epicatechins) and pro-anthocyanidins, which may have other potential positive impacts on human health.

5. Scientific Evidence by Area of Use

5.1 Cognitive Performance and Mental Alertness

Overview: The plant extract guarana is known for its caffeine content and other bioactive ingredients, which purportedly may improve cognitive performance. Recent reviews have examined the effects of chronic supplementation of guarana in clinical populations; however, the acute effects of guarana on cognitive tasks, while of interest, have produced mixed results.

Systematic review and meta-analysis (2023): Whether acute guarana ingestion improves human cognitive performance was assessed by performing a systematic review coupled with a meta-analysis. Eight placebo-controlled studies were identified and met the inclusion criteria providing data on 328 participants. The dose of guarana (37.5 to 500 mg) with reported caffeine content (4.3 to 100 mg) varied. The effect sizes for guarana averaged across a variety of cognitive measures and outcome variables were less than trivial (Hedge's g = 0.076, p = 0.14). The meta-analysis therefore did not find statistically significant support for an acute cognitive-performance benefit of guarana as a whole extract.

Individual positive clinical trial evidence: An earlier double-blind, placebo-controlled, multi-dose trial (Haskell et al., 2007, Journal of Psychopharmacology) found that guaraná improved secondary memory performance and increased alert and content mood ratings. The two lower doses produced more positive cognitive effects than the higher doses. This research supports previous findings of cognitive improvements following 75 mg guaraná and provides the first exploration of different dose effects of guaraná in humans.

Another study found that a single dose of 37.5 mg and 75 mg guarana increased the secondary memory accuracy of activities in the Cognitive Drug Research (CDR) Computerized Assessment Battery among healthy young adults. Participants who took 75 mg of guarana displayed improved scores in secondary memory activities at 150 minutes after ingestion compared to placebo.

Unresolved question of caffeine attribution: An important question researchers have raised is "whether such performance changes are linked to the caffeine content or other bioavailable substances in guarana," suggesting that "future studies might investigate this further through matched-dose comparison trials between caffeine and guarana."

Evidence strength: Mixed and preliminary. The 2023 systematic review and meta-analysis found no statistically significant aggregate effect from acute guarana ingestion on cognitive performance across eight placebo-controlled studies with 328 participants. Individual smaller trials have observed positive effects, particularly on secondary memory, at doses of 37.5–75 mg. Whether these effects are attributable solely to caffeine or to other constituents remains an open research question. Evidence is insufficient to support definitive clinical recommendations.

5.2 Cancer-Related Fatigue

This is the area with the most concentrated clinical trial activity for guarana. Evaluation in patients with cancer has been performed related to the symptoms of fatigue, hot flashes, sleep-wake disturbances, and depression.

Key clinical trial dosages: Researchers evaluated the effect of guarana on chemotherapy-related fatigue and reported favorable outcomes with doses of 37.5 mg to 75 mg orally twice daily.

Small studies in cancer patients suggest guarana may help reduce chemotherapy-related fatigue, stabilize weight, and increase appetite. However, it did not reduce fatigue post-radiation or in patients with head and neck cancers, and some symptoms worsened compared with a placebo.

ASCO/SIO Guideline position: In 2018, the American Society of Clinical Oncology (ASCO) endorsed the Society for Integrative Oncology's (SIO) evidence-based guideline for the use of integrative therapies after breast cancer treatment, stating that guarana should not be recommended for improving fatigue during treatment (Grade D).

Meta-analytic conclusion: A meta-analysis also concluded that guarana was not superior to placebo for cancer-related fatigue and that evidence was of low quality.

Evidence strength: Weak to insufficient. Multiple small randomized controlled trials have produced inconsistent findings. The aggregate evidence from meta-analysis does not support superiority over placebo, and the 2018 ASCO/SIO guideline assigned a Grade D recommendation against its use for cancer treatment-related fatigue.

5.3 Metabolic Health: Obesity, Cardiovascular Risk, and Diabetes

Epidemiological data: Epidemiologic data suggest protective effects against metabolic disorders in elderly populations. Previous experimental investigations have suggested that guaraná consumption is associated with a lower prevalence of cardiovascular metabolic diseases and has positive effects on lipid metabolism, mainly related to low density lipoprotein (LDL) levels.

LDL oxidation (in vitro and in vivo): Guarana exhibits strong antioxidant and cardioprotective effects, as evidenced by in vitro and in vivo studies demonstrating its ability to reduce LDL cholesterol oxidation, a critical factor in the development of cardiovascular disease. A study using blood samples from 42 healthy elderly subjects who habitually ingested guarana found changes in markers related to LDL oxidation resistance, though the evidence base for human outcomes remains limited.

Antidiabetic potential: In terms of metabolic health, guarana extracts have been shown to inhibit key carbohydrate-hydrolyzing enzymes, including α-amylase and α-glucosidase, suggesting potential for managing type 2 diabetes. These findings are primarily from in vitro and in silico studies and have not been replicated in robust human clinical trials.

Evidence strength: Preliminary (largely epidemiological and in vitro). No large-scale, adequately powered human randomized controlled trials have established guarana as an evidence-based intervention for obesity, dyslipidemia, or type 2 diabetes.

5.4 Antioxidant Activity

Researchers assessed the effects of guarana consumption on plasma catechins, erythrocyte antioxidant enzyme activity (superoxide dismutase, catalase, and glutathione peroxidase) and biomarkers of oxidative stress in healthy overweight subjects. These authors showed that daily intake of guarana had both acute and cumulative effects on GPx (glutathione peroxidase) and catalase, which are phase II antioxidant enzymes that reduce peroxides to water molecules. However, antioxidant status markers such as reducing ex vivo LDL-c oxidation and hydrogen peroxide-induced DNA damage in lymphocytes improved only transiently. The authors believe that the daily dose of guarana was probably not enough to keep the fasting plasma catechin concentration above a threshold level required to exert sustained effects.

Evidence strength: Preliminary. In vitro antioxidant activity is well-established. Human evidence of clinically meaningful antioxidant protection from guarana supplementation is limited, inconsistent, and requires further investigation.

5.5 Antimicrobial Activity

Several phenolic compounds (e.g., catechins and proanthocyanidins) have been recognized as potential antimicrobial agents with bacteriostatic or bactericidal actions. One study tested guarana seed extracts against three food-borne fungi — Aspergillus niger, Trichoderma viride, and Penicillium cyclopium — and three pathogenic bacteria — Escherichia coli, Pseudomonas fluorescens, and Bacillus cereus.

Evidence strength: In vitro only. No human clinical studies have evaluated guarana as an antimicrobial agent. Findings are restricted to laboratory models.

5.6 Physical Performance and Anti-Fatigue

Exercise undertaken in a fasted state can lead to higher post-exercise mental fatigue. The administration of a vitamin and mineral complex with guaraná has been shown to attenuate mental fatigue and improve performance during cognitively demanding tasks. However, this finding was from a multi-ingredient formula and not guarana alone. Caffeine administered via guaraná may have different influences than when administered in isolation if the other constituents of this compound (some of which may have psychoactive properties, such as saponins and tannins) act synergistically with the caffeine.

A randomized double-blind crossover trial (PubMed PMID 36146946) investigated the effects of guarana supplementation on cognitive performance before and after a bout of maximal intensity cycling and compared this to an equivalent caffeine dose. Twenty-five participants completed the randomized double-blind crossover trial performing cognitive tests with one of three supplements: guarana (125 mg/kg), caffeine (5 mg/kg), or placebo (65 mg/kg protein powder).

Evidence strength: Very limited. There has been very limited research investigating the effect of guaraná only, consumed prior to exercise, in human subjects.

6. Body Systems Associated with Guaranine/Guarana

The methylxanthines caffeine, theobromine, and theophylline are secondary metabolites derived from the nitrogenous base purine that have health effects on the body, including the central nervous system, cardiovascular, gastrointestinal, respiratory, and renal systems. Specifically:

• Central Nervous System: Stimulant and alerting effects via adenosine receptor antagonism; potential effects on mood and secondary memory.
• Cardiovascular System: Caffeine's effects include skeletal muscle, CNS, and cardiac stimulation, diuresis, increased blood pressure, and inhibition of platelet aggregation. Studies have suggested that guaraná exhibits a cardioprotective effect by inhibiting platelet aggregation.
• Renal System: The primary mechanism of methylxanthines includes antagonism of adenosine receptors (A1, A2a, A2b, A3), and diuresis with increased sodium excretion results from inhibition of the A1 adenosine receptors, which inhibit proximal tubule sodium reabsorption.
• Gastrointestinal System: Caffeine in guarana acts as a natural laxative and can stimulate gastric acid secretion.
• Metabolic/Endocrine System: Potential inhibition of carbohydrate-hydrolyzing enzymes; effects on lipid oxidation and energy expenditure attributed largely to its methylxanthine content.

7. Dosage Forms and Dosages Reported in Studies

The following dosages are drawn directly from peer-reviewed clinical studies and systematic reviews:

• Doses ranging from 75 mg to 1,000 mg daily were administered in limited clinical trials evaluating stimulant effects.
• The dose of guarana used in placebo-controlled cognitive trials ranged from 37.5 to 500 mg, with reported caffeine content of 4.3 to 100 mg.
• In the Del Giglio et al. (2013) cancer fatigue trial, patients received 37.5 mg of Paullinia cupana extract (PC-18), twice a day, 12 hours apart, for 21 days.
• In one randomized double-blind crossover exercise trial, participants received guarana at 125 mg/kg, caffeine at 5 mg/kg, or placebo (65 mg/kg protein powder).
• Research supports cognitive improvements following 75 mg guaraná, with this representing the most commonly studied lower dose in behavioral studies.

Guarana is available in capsules, tablets, powder, liquid extracts, and as an ingredient in energy drinks and soft drinks. Guarana powder is used for direct consumption in capsules or dilution in water, or serves as a raw material for the pharmaceutical and cosmetics industries.

8. Safety Considerations and Drug Interactions

General Safety Profile

In conventional doses, guarana has few side effects and has not been linked to episodes of liver injury or jaundice. The mechanism by which guarana might cause liver injury is unknown. Guarana is found in many multi-ingredient dietary supplements and energy drinks, and it is sometimes one of many ingredients in products implicated in causing liver injury. The contribution of guarana to these cases is, however, not particularly likely.

Common side effects include a fast heartbeat, an increased need to urinate, nervousness, irritability, an upset stomach, and trouble sleeping.

Cardiovascular Effects

Guarana contains caffeine, which may increase the risk for certain heart effects. It may raise heart rate or blood pressure or cause an abnormal heart rhythm (arrhythmia). Higher doses of caffeine are more likely to cause heart effects. Reported adverse events in case reports include vomiting, agitation, tachycardia, and hypertension in pediatric cases with abuse or misuse of guarana-containing supplements, and tachycardia in two women consuming guarana-containing supplement or energy drinks.

Cumulative Caffeine Load

Many products that contain guarana also contain other sources of caffeine, and caffeine is found in many common foods and drinks. It is important to keep track of all caffeine sources to ensure excessive amounts are not consumed. Guarana dry extracts are very often significantly enriched with caffeine. However, guarana seeds naturally contain more than just caffeine. A caffeine-enriched guarana dry extract will not display the traditional action typically associated with guarana.

Drug Interactions

CYP1A2 enzyme interactions: Caffeine is metabolized via the CYP1A2 enzyme, and medicines that inhibit this pathway — such as ciprofloxacin — may increase caffeine levels and the risk of adverse effects.

Anticoagulants: There is a theoretical concern regarding interactions with anticoagulants such as warfarin, though the clinical evidence is limited.

Monoamine oxidase inhibitors (MAOIs): Guarana contains caffeine. Caffeine can stimulate the body. Some medications used for depression can also stimulate the body. Taking guarana with these medications used for depression might cause serious side effects including fast heartbeat, high blood pressure, nervousness, and others. Some of these medications used for depression include phenelzine (Nardil) and tranylcypromine (Parnate).

Amiodarone (preclinical evidence): A significant reduction in the peak plasma concentration (73.2%) and in the extent of systemic exposure (57.8%) to amiodarone was found in rats simultaneously treated with Paullinia cupana and amiodarone. This finding is from a rat model and has not been confirmed in human pharmacokinetic studies, but suggests that caution may be warranted when guarana is co-administered with narrow therapeutic index drugs.

Additive stimulant effects: The caffeine in guarana might speed up the nervous system. Taking guarana along with stimulant drugs might cause serious problems including increased heart rate and high blood pressure.

Pregnancy and Pediatrics

Individuals who are pregnant or breastfeeding are advised to avoid guarana-containing products due to the high caffeine content.

Long-Term Safety

Long-term safety data for guarana supplementation in humans is sparse. An extensive review of the chemical composition of guarana, its pharmacology, biologic effects in vitro and in animal models, efficacy in human studies of mental health, depression, dyslipidemia, diabetes, obesity and cancer, and its safety and tolerability found no mention of ALT elevations during therapy or hepatotoxicity.

Product Quality Concerns

Out of 58 samples analyzed during one quality-control campaign, 36 samples were identified as being significantly enriched with caffeine, representing 62%. This means a substantial proportion of commercial guarana products may consist largely or entirely of added caffeine rather than authentic whole-seed extract, making dose-standardization challenging for consumers and researchers.

References

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• Haskell et al. "A double-blind, placebo-controlled, multi-dose evaluation of the acute behavioural effects of guaraná in humans." Journal of Psychopharmacology, 2007 – PubMed
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