Cola nut

Cola Nut (Cola nitida / Cola acuminata): A Comprehensive Reference

1. Identity, Taxonomy, and Botanical Description

Botanical Names and Classification

The kola nut is the seed of certain species of plant of the genus Cola, placed formerly in the cocoa family Sterculiaceae, and now usually subsumed in the mallow family Malvaceae (as subfamily Sterculioideae). About 5 centimetres (2 in) across, the kola nut is a nut of evergreen trees of the genus Cola, primarily of the species Cola acuminata and Cola nitida. The substance is referred to interchangeably as "cola nut," "kola nut," "guru nut," or "bissy nut" in trade and ethnobotanical literature. Scientific names include Cola acuminata and Cola nitida; common names include abata cola, bissy nut, cola, cola nut, and guru nut.

Cola belongs to the family Malvaceae and contains 125 Cola plants. Among the Cola species, Cola acuminata and Cola nitida are the most studied for their pharmacological effects. The two principal commercial species differ slightly in seed structure: there are two common species, namely Cola acuminata, which is multicotyledonous, and Cola nitida, which is dicotyledonous. Cola nitida has two subspecies, alba and rubra (white and red respectively).

Morphology and Growing Conditions

Cola acuminata is an evergreen tree of the family Malvaceae, native to tropical Africa, while Cola nitida belongs to the family Sterculiaceae. They are native to the rainforests of tropical West Africa. The trees grow to about 20–25 m tall, with long, ovoid, leathery-textured leaves, pointed at both ends. The flowers are yellow with purple spots, giving rise to star-shaped fruits. About a dozen round or square seeds develop in a white seed-shell inside the fruit pod.

The nut has a sweet and rose-like aroma; and when eaten, the first taste is bitter, but it sweetens with chewing. Cola nitida is also cultivated in regions such as Brazil and India.

Common Forms and Preparations

The seeds contain caffeine and are chewed as a stimulant, or can be boiled to extract the cola used in the manufacture of soft drinks. Traditionally, cola nut is consumed in various forms, including raw chewing, pulverized powder, or liquid extract, and is known for its stimulant effects due to its caffeine content. In herbal medicine, the nut is usually soaked in alcohol to make tinctures. It may be taken as tea although bitter, and the powder can be taken as a capsule. Kola nut extract is also used in the food industry as a flavoring ingredient.

2. Historical and Traditional Use

Origins and African Cultural Significance

Human use of the kola nut, like the coffee berry and tea leaf, appears to have ancient origins. Kola nuts are an important part of the traditional spiritual practice, culture, and religion in West Africa, particularly Ghana, Niger, Nigeria, Sierra Leone, Democratic Republic of Congo, and Liberia.

In West Africa, the kola nut is known as ọjị in Igbo, obi in Yoruba, goro in Hausa, and bese among the Akan people of Ghana. The kola nut tradition varies across Africa: among the Igbo, the breaking of kola (ịwa ọjị) follows strict protocols, with the eldest male typically leading the ceremony with specific prayers and rituals. The Yoruba call them obi and incorporate them into elaborate divination practices and deity offerings.

The nut was a major trade commodity in intra-African trade, being imported from the Ashanti region of Ghana by large caravans heading to further inland markets such as Kano and Bornu where their primary consumers were aristocrats and scholars. Kola nuts once functioned as currency in pre-colonial West Africa and marked wealth and social status.

Kola nut is traditionally seen as a sacred nut which is used as a link to communicate with the gods (spirit beings), and was chosen by the elders as the king of all seeds. Throughout history, kola nuts have been planted on graves as part of various rituals.

Medicinal and Practical Uses in Traditional Contexts

Kola nuts are commonly chewed in West and Northern Africa for their stimulant properties and to aid digestion and suppress cough. In traditional medicine, kola nut and bitter kola are dried, ground, and mixed with honey to make a traditional cough mixture. The bitter and astringent flavor of kola nut is used as a digestive aid before meals to stimulate gastric juice and bile production.

Laborers in many countries also chew kola nuts in efforts to fight fatigue and hunger, while Brazilians and people of the West Indies use the nut as a remedy for hangovers, intoxication, and diarrhea. In folk medicine, it has been valued as an aphrodisiac and a remedy for morning sickness, migraines, and indigestion, as well as for topical applications on wounds and inflammation.

Traditionally, this genus has been popular for the treatment of jaundice, diarrhea, fever, toothache, wound healing, asthma, leprosy, vaginal and urinary complaints, skin diseases, piles, gastrointestinal disorders, smallpox, hepatitis, tumor, HIV, ulcers, and ringworm.

Spread and Diaspora

The spread of the kola nut across North Africa seems to be connected to the spread of Islam across West Africa during the 17th century, as trading across the Mediterranean became established. Kola nuts were used to improve the taste of poor-quality drinking water on ships sailing to the Americas, including those used in the transatlantic slave trade. Enslaved African people in the Caribbean planted some of the transported nuts around their dwellings, drawing on their heritage to establish local folk medicine and traditions.

In the 1880s, a pharmacist in Georgia, John Pemberton, took caffeine extracted from kola nuts and cocaine-containing extracts from coca leaves and mixed them with sugar, other flavorings, and carbonated water to invent Coca-Cola, the first widely popular cola soft drink. Kola nuts were used as an ingredient within Coca-Cola and Pepsi-Cola in 1886 and 1893 respectively. Although the exact details of its cola recipe remain confidential, as of 2016 the Coca-Cola formula no longer contained actual kola nut extract.

3. Key Constituents and Active Compounds

Methylxanthine Alkaloids

Cola contains phytochemicals such as alkaloids, caffeine, theobromine, theophylline, quinic acid, chlorogenic acid, purine, (−)-epicatechin, (+)-catechin, sterols, anthraquinones, flavonoid glycosides, cardenolides, tannins, rostratanic acid, bauerenol, lupeol, acotatarone A, lignoceric acid, betulinic acid, friedelanone, friedelan, stigmasterol, and nonanedioic acid, among others.

The dominant bioactive compounds are the methylxanthine alkaloids. The three varieties of kola nuts contain appreciable levels of (+)-catechin (27–37 g/kg), caffeine (18–24 g/kg), (−)-epicatechin (20–21 g/kg), procyanidin B1 [epicatechin-(4β→8)-catechin] (15–19 g/kg), and procyanidin B2 [epicatechin-(4β→8)-epicatechin] (7–10 g/kg). Earlier analyses reported caffeine content ranging from 2–3.5% and theobromine from 1.0–2.5% of dry weight.

It is considered that there are unstable complexes which occur in fresh kola nuts, consisting of kolanins, tannins, and caffeine glycosides. These complexes oxidize and hydrolyze to form "kola red" and free caffeine under the influence of enzymes when the nuts are drying out. If these enzymes are inactivated prior to drying the seeds, for instance with heat treatment, this process will not occur and the dried seeds will retain their physiological actions.

Polyphenols and Flavonoids

Phytochemical profiling of C. nitida showed several secondary metabolites. The nuts revealed the presence of various chemical compounds, including catechin, caffeine, epicatechin, procyanidin B1, procyanidin B2, polyphenols, alkaloids, tannins, saponins, bromelain, cardenolides, proanthocyanidins, triterpenes, glycosides, flavonoids, anthraquinones, and steroids.

Antioxidant capacity of the extracts and purified metabolites was assessed by two HPLC-based and two colorimetric in vitro assays. Extracts of all varieties exhibited antioxidant capacity with IC₅₀ values in the range 1.70–2.83 and 2.74–4.08 mg/mL in the hypoxanthine/xanthine oxidase and 2-deoxyguanosine HPLC-based assays, respectively.

Utilization of HPLC-based assays designed to reflect in situ generation of free radicals (e.g., HO·), as opposed to general assays (DPPH, FRAP) in common use which do not, indicate that of the major secondary plant metabolites present in kola nut extracts, caffeine is potentially the more effective cancer chemopreventive metabolite in terms of its antioxidant capacity.

Other Constituents

The exact composition of Cola nitida has been shown to include xanthine alkaloids (caffeine, theophylline, theobromine), tannin, betaine, and kolanine. The bitter taste is due to the presence of tannin and betaine, while the reddish stain extracted is due to the kolatine and kolanine content. Key chemical constituents of kola nut include caffeine, theobromine, tannins and phenolics, including d-catechin, l-epicatechin, and kolanin. It also contains phlobaphens, proteins, and starch.

4. Mechanisms of Action

Adenosine Receptor Antagonism

The primary mechanisms of pharmacological action of cola nut are attributed to its methylxanthine content, principally caffeine. Caffeine's primary mechanism of action involves its effects on adenosine receptors in the brain. Being both fat- and water-soluble, caffeine easily crosses the blood-brain barrier and antagonizes all four adenosine receptor subtypes (A1, A2a, A2b, and A3). The antagonism of the A2a receptor is particularly responsible for caffeine's wakefulness effects.

Direct antagonism of receptor A1 in cardiac muscles results in positive inotropic effects. Likewise, adenosine receptor antagonism stimulates the release of catecholamines, contributing to the systemic stimulatory effects of caffeine and further stimulating cardiac inotropy and chronotropy.

Phosphodiesterase Inhibition

The main action mechanism of caffeine and theobromine consists of blocking adenosine receptors and inhibiting phosphodiesterases. Methylxanthines inhibit phosphodiesterase (PDE) enzymes, which normally break down cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Inhibition of PDE raises intracellular cAMP levels, thereby amplifying adrenergic signaling and smooth-muscle relaxation.

Differential Effects of Caffeine vs. Theobromine

Both theobromine and caffeine block adenosine receptors (primarily A1 and A2a subtypes) in the brain and body. Adenosine normally promotes relaxation and drowsiness; by blocking its receptors, methylxanthines increase alertness and neuronal firing. However, theobromine is considered a weaker adenosine receptor antagonist than caffeine, which likely contributes to its milder stimulant effect on the CNS.

Methylxanthines have the ability to relax smooth muscle, stimulate the CNS, and produce diuresis. Theophylline is the most potent of the methylxanthines for relaxing bronchial muscles, making it effective as an asthma treatment.

Gastric Acid Secretion

Both cola species contain xanthines — the same type of alkaloids found in tea and coffee. Common among these xanthine derivatives are caffeine, theophylline, and theobromine. These xanthines are known to stimulate gastric acid secretion.

Flavonoid-Mediated Activities

Tannins are reported not only to promote tissue regeneration in case of superficial burn injury but also to have antibacterial, antiviral, antifungal, and antioxidant effects. The presence of flavonoids in the extracts indicates their potentiality to reduce in vitro cholesterol and to induce an antifungal activity. Flavonoids are known to inhibit α-amylase activity which regulates the amount of glucose in the blood; therefore the extracts of C. nitida can be used as an antidiabetic.

5. Scientific Evidence by Area of Use

5.1 CNS Stimulation and Fatigue Reduction

Clinical trials are lacking to support use; however, CNS stimulation is evident, likely due to the caffeine content. The CNS stimulant effects of one nut have been reported to be equal to or greater than the effects of the caffeine content of two large cups of coffee.

The stimulant action is mechanistically well understood and pharmacologically attributable to caffeine. Caffeine is classified as a central nervous system (CNS) stimulant and an organic molecule called methylxanthine. It has three notable mechanisms of action on the CNS that produce a psychostimulant effect. However, direct clinical trials using whole kola nut as an intervention in human fatigue outcomes remain absent from the peer-reviewed literature. Most supporting evidence is extrapolated from extensive caffeine pharmacology data rather than from kola nut-specific clinical studies.

Evidence strength: Mechanistically plausible and extrapolated from robust caffeine science, but kola nut-specific human clinical trials are lacking.

5.2 Antioxidant Activity

Varieties of kola nuts (Cola nitida alba, Cola nitida rubra A. Chev, and Cola acuminata Schott & Endl.), a group of popular Nigerian and West African stimulants, were analyzed for their content of secondary plant metabolites. In vitro assays demonstrated meaningful antioxidant capacity, though these findings have not been translated into controlled human clinical trials for specific health outcomes.

Extracts of the kola nut were effective against pathogens at 50, 100, and 200 mg/mL concentrations in laboratory conditions. Antioxidant activities showed that ethanol extract was the most effective in scavenging nitric oxide and ferric reducing power compared to chloroform and water extracts.

Antioxidant activity of nuts such as kola nuts (Cola acuminata; Cola nitida), coconut (Cocos nucifera), bitter kola (Garcinia cola), African walnut (Plukenetia conophora), and cashew nut (Anacardium occidentale) ranged from 13.0 to 53.21 µmol Trolox Equivalent/100 g dry weight, while the total phenolic content ranged from 204.95 to 1955.14 mg Gallic acid Equivalent/100 g of dry sample.

Evidence strength: Preliminary; confined to in vitro assays and comparative laboratory measurements. No controlled human trials exist.

5.3 Antimicrobial Activity

The in vitro antimicrobial evaluation of ethanol extracts of four species of Cola was done using human-isolated strains of Staphylococcus aureus, Staphylococcus albus, Bacillus subtilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger as test organisms. The assays were carried out by agar well diffusion; erythromycin and ketoconazole served as the control drugs. The leaf ethanol extracts of the plants were found to be more effective against the tested fungi than the bacteria at high concentrations. None of the extracts was active against Staphylococcus aureus.

Secondary metabolites in Cola species are responsible for various pharmacological activities such as antioxidant, antibacterial, antifungal, antimalarial, anti-inflammatory, antidiabetic, antidiarrheal, antiviral, anticancer, antimycobacterial, and antiatherosclerotic and hypolipidaemic activities. These findings derive from laboratory-based (in vitro) investigations using cell cultures and isolated microbial strains.

Evidence strength: Preliminary; in vitro only. No human clinical trials have assessed antimicrobial benefit from kola nut consumption.

5.4 Anti-inflammatory and Analgesic Activity

There is paucity of studies on anti-inflammatory, nociception, and mechanisms of Cola nitida in rodents. One study investigated the anti-inflammatory and anti-nociceptive activities of methanol extract of Cola nitida. The findings from this animal study showed that the methanol extract produced anti-inflammatory and pain-reducing effects in rodent models, but the research was conducted in experimental animals rather than human subjects.

Evidence strength: Animal (rodent) models only. No human clinical data available.

5.5 Gastric Acid Secretion and Digestive Effects

A study published in the Scandinavian Journal of Gastroenterology directly examined the effects of both cola species on gastric physiology. Researchers found that both cola species significantly induced gastric acid secretion. The authors noted that this corroborates clinical advice to peptic ulcer patients not to eat cola nuts. This is among the few human-relevant physiological studies involving actual kola nut preparations rather than isolated caffeine.

Evidence strength: Weak; a single study in a specialized gastroenterology supplement volume. Results are plausible given the known action of xanthines on gastric secretion, but independent replication is lacking.

5.6 Diuretic Activity

Animal research has examined cola nut's diuretic potential. A study referenced in the literature found that methanolic extract of Cola nitida elicits dose-dependent diuretic, natriuretic, and kaliuretic activities without causing electrolyte impairment, hepatotoxicity, and nephrotoxicity in rats. This is consistent with the known diuretic effect of caffeine and theophylline acting on renal tubular adenosine receptors.

Evidence strength: Animal study only. No human clinical data verify a clinically meaningful diuretic effect from kola nut supplementation specifically.

5.7 Anticancer Research

Based on enhanced fractionation studies, an expanded chemical profile of kola nut seeds has been obtained, and selected phytochemicals may serve as promising candidates for anticancer drug development. Further experimental validation is warranted to translate these insights into therapeutic applications.

Caffeine, theobromine, tannins, flavonoids, and phenolic compounds found in Cola acuminata contribute to its antioxidant, anti-inflammatory, anti-microbial, anti-glucose, neuroprotective, and cancer-fighting activities in laboratory models.

Evidence strength: Extremely preliminary; in silico (computational) and in vitro only. No human clinical trials have investigated kola nut as an anticancer agent.

5.8 Theobromine and Cognitive Function

Considering animal studies, it can be asserted that acute exposition to theobromine has a reduced and delayed nootropic effect with respect to caffeine, whereas both animal and human studies suggested a potential neuroprotective action of long-term assumption of theobromine through a reduction of Aβ amyloid pathology. Whereas the effects of caffeine are extensively researched, the same is not the case for theobromine; research summarizing evidence on the effect of theobromine on cognitive functions concludes that the conceivable action of theobromine alone and associated with caffeine or other constituents on cognitive modulation is yet underexplored and future studies are needed.

Evidence strength: Preliminary; most evidence pertains to theobromine as a component of cocoa, not as a component of kola nut specifically.

6. Body Systems and Health Areas

Based on available phytochemical and pharmacological research, cola nut and its constituent compounds have been studied or are associated with effects on the following body systems:

• Central nervous system: The nut is a nervous system stimulant and is chewed in many West African countries, in both private and social settings. CNS stimulation is mediated primarily by caffeine's adenosine receptor antagonism.
• Cardiovascular system: Possible cardiovascular disorders such as hypertension and arrhythmia are associated with excessive use. Caffeine's direct antagonism of cardiac A1 adenosine receptors can produce positive inotropic and chronotropic effects.
• Gastrointestinal system: Cola nut stimulates gastric acid secretion, and has traditionally been used as a digestive aid. However, this same property raises concerns for individuals with peptic ulcer disease.
• Respiratory system: Kolanuts are often used to treat whooping cough and asthma in traditional African medicine, consistent with the bronchodilatory effects of theophylline.
• Renal system: Cola nut extracts show diuretic, natriuretic, and kaliuretic activity in animal models.
• Immune and microbial defense: In vitro antibacterial and antifungal activity has been demonstrated against select pathogens.
• Metabolic / antidiabetic: Flavonoids present may inhibit α-amylase activity, and cola nut has been used in traditional medicine as a stimulant, to improve memory and focus, as an aphrodisiac, to treat respiratory diseases, and to control gastrointestinal issues; in addition to its diuretic properties, Cola acuminata has been used in wound healing and ulcer care.

7. Dosage Forms and Reported Dosages

Clinical studies are lacking to provide dosing guidance. In the absence of controlled clinical trials establishing effective therapeutic doses, reported figures derive from traditional practice and herbal reference sources.

The recommended therapeutic dosages in herbal reference sources vary, with guidelines suggesting 2 to 6 grams of whole nut or equivalent amounts of extracts.

Regarding caffeine content specifically, cola nut contains caffeine, but only the amount of added caffeine must be stated on product labels. Caffeine found in ingredients that naturally contain caffeine, such as cola nut, does not need to be provided, which can make it difficult to determine the total amount of caffeine in a given product.

Dosage forms encountered in commerce and traditional practice include:

• Whole raw seed (chewed): The most traditional form. One nut chewed directly provides the full spectrum of constituents including bound caffeine glycosides.
• Tincture / liquid extract: Prepared by soaking in ethanol.
• Powder / capsule: Dried, powdered seed material encapsulated for supplement use.
• Decoction (tea): An aqueous preparation; bitter in taste.
• Standardized extract: Industrial preparations standardized to caffeine content for use in food and beverage flavoring.

8. Safety Considerations and Drug Interactions

Regulatory Status

Kola nut has US Food and Drug Administration (FDA) generally recognized as safe (GRAS) status; however, information regarding safety and efficacy in pregnancy and lactation is lacking.

Adverse Effects

Possible adverse effects include insomnia, cardiovascular disorders such as hypertension and arrhythmia, nervous restlessness, or gastric and duodenal ulcers. No studies are available on the safety of cola seeds for use in children and adolescents under 18 years of age; use is not recommended in this population.

The caffeine in cola nut might make anxiety disorders worse. Cola nut contains caffeine which might slow blood clotting, raising concerns in individuals with bleeding disorders.

Caffeine from cola nut can cause sleep disturbances, irritability, and increased bowel activity in breast-fed infants.

Cardiac Stress Testing

The caffeine in cola nut might block the effects of adenosine (Adenocard). Adenosine (Adenocard) is often used by doctors to perform a test on the heart called a cardiac stress test. Consuming cola nut or other caffeine-containing products should be stopped at least 24 hours before a cardiac stress test.

Drug–Herb Interactions

The interactions of cola nut with drugs are primarily driven by its caffeine content. Key documented interactions include:

• Ephedrine and sympathomimetics: Stimulant drugs speed up the nervous system. The caffeine in cola nut and ephedrine are both stimulant drugs; taking cola nut along with ephedrine might cause too much stimulation and sometimes serious side effects and heart problems.
• Quinolone antibiotics: Some antibiotics can decrease how quickly the body breaks down caffeine, and taking these drugs along with caffeine might increase the risk of side effects including jitteriness, headache, increased heart rate, and others.
• Oral contraceptives and estrogens: Birth control pills can decrease how quickly the body breaks down caffeine, which might increase the risk for side effects such as jitteriness, headache, and fast heartbeat.
• Carbamazepine: Caffeine might lower the effects of carbamazepine; taking cola nut with carbamazepine might increase the risk of seizures in some people.
• Lithium: Caffeine withdrawal (after regular cola nut consumption) has been documented to increase lithium blood levels in the clinical literature.
• Fluconazole and grapefruit: Both fluconazole and grapefruit increase levels of kolanut by decreasing caffeine metabolism.
• Psychoanaleptic drugs: Enhanced stimulant effect occurs when cola nut is combined with psychoanaleptic drugs.

Oral Health and Cancer Risk

Epidemiological data from sub-Saharan Africa raise concerns about chronic kola nut chewing as a potential risk factor in oral and oropharyngeal cancer. Kola nut is a stimulant used both socially and ceremonially in many forested regions of sub-Saharan Africa. A study from Nigeria observed that four of five patients with oropharyngeal/oral cavity squamous cell carcinoma reported using kola nut. Identified risk factors among reviewed Nigerian case series included kola nuts, tobacco, farming, viral infections, alcohol, and smoking. In a report from Maiduguri, tobacco smoking, tobacco chewing, and chewing of kola nuts were associated with carcinoma of the oral cavity. Kola nuts (Cola acuminata) have been reported to promote palatal mucosa keratinization in cigarette smokers and are considered a co-carcinogen.

Importantly, these epidemiological associations come from case series and observational reports, not controlled prospective cohort studies, and many individuals in these populations simultaneously used tobacco and alcohol, making it impossible to isolate kola nut as an independent carcinogen from the existing evidence.

Pregnancy

Information regarding the safety of kola nut specifically during pregnancy and lactation is lacking according to current authoritative drug monographs. Animal research has examined the potential for intrauterine exposure to affect neonatal neurodevelopment, but as a significant number of studies have reported the beneficial effect of kola nuts, it remains undiscovered whether this plant product exhibits positive or negative gestational effects on pups' hippocampi after birth when consumed by pregnant mothers. Given the caffeine content, general caffeine-in-pregnancy guidance from obstetric authorities is applicable.

9. Summary of Evidence Quality

The overall body of clinical evidence for cola nut as a therapeutic or health-promoting supplement is limited. Scientific research on health benefits remains limited, predominantly relying on anecdotal evidence. The pharmacological activity of its constituent caffeine is extensively validated in human clinical research, and CNS stimulant effects are therefore reliably extrapolated. However, kola nut-specific controlled human clinical trials — addressing dose, efficacy, or safety for any particular indication — are substantially absent from the peer-reviewed literature. Most pharmacological findings for anti-inflammatory, antimicrobial, antidiabetic, and antioxidant properties derive from in vitro cell studies and animal experiments, neither of which is sufficient to establish clinical efficacy in humans.

The most scientifically grounded uses of cola nut remain those attributable to its caffeine pharmacology: transient CNS stimulation, alertness, reduced perception of fatigue, and mild diuresis. All other potential therapeutic applications require confirmation by adequately powered, randomized human clinical trials before any evidence-based claims can be made.

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