Catjang cowpea

Catjang Cowpea (Vigna unguiculata subsp. cylindrica): A Comprehensive Reference

1. Identity, Nomenclature, and Botanical Classification

1.1 Scientific and Common Names

Catjang (Vigna unguiculata subsp. cylindrica) is a subspecies of cowpea. Cowpea belongs to the kingdom Plantae, order Fabales, family Fabaceae, subfamily Faboideae, tribe Phaseoleae, genus Vigna. The species was originally described by Carl Linnaeus in 1753 as Dolichos unguiculatus in Species Plantarum, and later transferred to the genus Vigna by Wilhelm Walpers in 1843 in Repertorium Botanices Systematicae.

The NCBI taxonomy recognizes the full accepted name Vigna unguiculata subsp. cylindrica (L.) Verdc., 1970, with the historical basionym Phaseolus cylindricus L., 1759, and lists catjang cowpea as its GenBank common name.

Botanical synonyms include Dolichos biflorus, Dolichos catjang, Dolichos monachalis, Dolichos sinensis, Dolichos sphaerospermus, Dolichos unguiculatus, Vigna catjang, Vigna cylindrica, Vigna sesquipedalis, and Vigna sinensis.

Common names include cowpea, black-eyed pea, field pea, China-bean, southern pea, Jerusalem pea, black-eyed bean, marble pea, China pea, yard-long bean, asparagus bean, Catjang cowpea, and Bombay cowpea; in Japan it is known as "Sasage."

The name "catjang" derives from the Indonesian and Malay word kacang, a generic word for beans and nuts.

1.2 Subspecies Classification and Taxonomic Notes

A high level of morphological diversity is found within the species, with large variations in the size, shape, and structure of the plant. Four subspecies are recognized, three of which are cultivated.

Some authors do not consider the three cultivated subspecies as distinct and group them under one subspecies V. unguiculata subsp. unguiculata, differentiating them by the intraspecific category/cultigroup. The subspecies unguiculata, cylindrica, and sesquipedalis have been renamed by Maréchal and colleagues as cultigroups Unguiculata, Biflora, and Sesquipedalis, respectively. The Biflora cultigroup is commonly called catjang bean and is used as dry seeds and fodder.

Catjang bean is considered to have developed in India from cowpea (cultigroup Unguiculata), which originated in West Africa. Catjang is widely cultivated in India, China, Kampuchea, Japan, Korea, Laos, Vietnam, Africa, and America.

1.3 Botanical Description and Natural Source

The catjang plant is native to Africa, and is an erect, densely branched, shrubby perennial of Old World tropics. It now grows in other warm regions as well.

The catjang cowpea is a member of the Fabaceae family, characterized by its climbing or bushy growth habit. It features trifoliate leaves, white or purple flowers, and cylindrical pods that contain the edible beans.

Its tolerance for sandy soil and low rainfall have made it an important crop in the semiarid regions across Africa and Asia.

1.4 Common Forms and Preparations

The primary use of catjang cowpeas is as a food source. The beans are rich in protein, fiber, vitamins, and minerals. They can be eaten fresh, dried, or processed into various products, including flour and snacks.

In Africa, the dry seed is commonly ground and consumed in several traditional dishes, such as porridge, bread, and as a food for weaning children, or processed into fritters. Young leaves and immature pods are also used as vegetables in tropical countries.

In the United States, catjang is grown primarily as fodder, but elsewhere is used as a food crop. In addition to human consumption, cowpeas are used as fodder for livestock, improving animal nutrition and health.

2. Historical and Traditional Use

2.1 Origins and Archaeological Record

Cowpea was originally domesticated in sub-Saharan Africa but is now cultivated on every continent except Antarctica. Utilizing archaeological, textual, and genetic resources, the spread of cultivated cowpea has been reconstructed. Cowpea was domesticated in Africa, likely in both West and East Africa, before 2500 BCE, and by 400 BCE was long established in all the modern major production regions of the Old World, including sub-Saharan Africa, the Mediterranean Basin, India, and Southeast Asia.

The earliest archaeological evidence of domesticated cowpea dates to 3410 ± 60 BP in Central Ghana. From examining the remains of charred cowpeas from rock shelters in Central Ghana, researchers have illuminated the subsistence strategies of the Kintampo people of the second millennium BCE. Perhaps driven southwards from the Sahel by aridification, the Kintampo operated as both foragers and farmers, cultivating selected plants of the West African tropics, notably cowpea, pearl millet, and oil palm.

Vigna unguiculata is indigenous to sub-Saharan Africa, with domestication believed to have occurred in West Africa around 6,000 years ago. It is thought to have been introduced to southern Africa during the Bantu migrations 1,500 to 2,000 years ago.

The crop was subsequently taken to the Americas along with the slave trade.

2.2 Traditional Dietary Use

Use as a nutritious component in the human diet constitutes the primary traditional use of cowpea seeds worldwide. Cowpea seeds are an important nutritional food for populations living in tropical climates. For example, every Nigerian eats cowpeas and per capita consumption is roughly 25–30 kg per year. In Brazil, per capita consumption is 20 kg per year.

Young leaves and immature pods are eaten as a vegetable, and the haulms are used as livestock fodder. Usually, women make the cowpea harvest, sale, and processing (couscous, thiakry, cake, coffee, etc.) in Senegal.

Cowpea is often referred to as the "poor man's meat" as it is a significant source of protein, minerals, and vitamins for the rural poor who have limited access to protein from animal sources such as meat and fish.

2.3 Traditional Medicinal Use

Traditionally, different potentials of cowpea have been reported for the management of various conditions including schistosomiasis, stubborn boils, common cold, tooth ailments, swelling, infections, epilepsy, chest pain, constipation, dysmenorrhea, tachycardia, and painful menstruation. It is also used as a diuretic, anthelmintic, and antidote for snakebites.

Various parts of the cowpea are used medicinally. The leaves and seeds are applied to skin infections as a poultice; the leaves are chewed to relieve toothache, and powdered carbonized seeds are applied to insect stings. The roots are used as treatment for epilepsy, chest pain, constipation, and as an antidote to snakebites.

In folklore, cowpea is used in sacrifices by the Hausa and Yoruba tribes to drive away evil and to pacify the spirits of sickly children.

In Ayurveda, cowpeas are identified as Rajamasha and are esteemed for their nourishing and strengthening properties. Unlike many legumes, they do not aggravate Kapha dosha, which is beneficial for individuals with Kapha-dominant constitutions. Cowpeas are mildly diuretic, support healthy urinary function, and aid in maintaining proper gastrointestinal balance.

Cowpeas, including catjang, have been cultivated for over 3,000 years, particularly in West Africa, where they remain a staple food. They spread to India, Southeast Asia, and the Americas through trade and colonial agriculture. While not commonly featured in classical herbal pharmacopoeias, catjang was used in African and South Asian folk medicine as a strengthening food, given to the sick, elderly, or pregnant women to build strength and vitality. It was also considered cooling and grounding, sometimes used to manage digestive issues, heat conditions, or mild edema.

It is a useful plant that helps a large number of people in tropical and subtropical nations, especially in Africa including Nigeria, Burkina Faso, Kenya, Niger, Uganda, Tanzania, Ghana, Senegal, and Togo, and in Asia including India, Pakistan, Sri Lanka, Burma, Bangladesh, Thailand, China, Malaysia, and Nepal, for the improvement and betterment of health and fulfillment of nutritional needs.

3. Key Constituents and Active Compounds

3.1 Macronutrient Composition

Cowpea grain contains, on average, 23–25% protein and 50–67% carbohydrate. As in the case of most legumes, the amino acid profile of cowpea complements cereal grains. The presence of significant amounts of protein, calories, and some water-soluble vitamins makes cowpea a promising food ingredient.

Cowpea is a nutritious food source, rich in protein, digestible and nondigestible carbohydrates, and potassium, with very low lipids and sodium content. Cowpeas also contain a number of essential amino acids and polyphenols with antioxidant activity.

Catjang is low in saturated fat and is a good source of dietary fiber, protein, iron, phosphorus, zinc, copper, and manganese, and a very good source of folate and magnesium.

The protein content across studied varieties ranges from 25.38% to 27.56%, ash content between 3.47% and 6.84%, crude fiber between 5.81% and 15.08%, and carbohydrate content from 45.64% to 57.12%.

Cowpea is renowned for its high protein content (23–29%) and rich nutritional value, providing essential amino acids, vitamins, minerals, and lipids, making it a vital food source for millions.

3.2 Phytochemical Compounds

A number of compounds have been isolated from V. unguiculata, including flavonoids, steroids, alkaloids, phenolic compounds, saponins, fatty acids, tannins, carbohydrates, vitamins, amino acids, carotenoids, and fibers from various parts of the plant.

Crude methanolic extracts of cowpea subjected to HPLC-MS analysis resulted in the identification of flavonols such as quercetin and kaempferol, phenolic acids such as p-coumaric acid, protocatechuic acid, and gallic acid.

The phytochemicals identified from leaves mainly belong to the family of phenolic acids, flavonoids, terpenoids, and alkaloids.

Phenolic profiling of cowpea leaf cultivars found glycosides of gentisic acid, p-coumaric acid, ferulic acid, and quercetin.

Seed coat extracts showed higher contents of phenolics (291.0 ± 4.6 mg GAE/g) and flavonoids (83.5 ± 1.1 mg CE/g) and a stronger radical scavenging capacity (50.4 ± 0.7 µmol TE/g) than those obtained from the leaves (22.0 ± 0.5 mg GAE/g, 13.7 ± 0.5 mg CE/g, and 19.7 ± 0.6 µmol TE/g, respectively).

The total polyphenol content of different cowpea varieties varied widely, from 692.03 ± 9.58 to 63.14 ± 4.45 mg GAE/100 g of seeds dry weight. The pigmented seeds of cowpea varieties possess higher total phenolic and total flavonoid content, ferric reduction ability, and anti-lipid peroxidation activities than the colorless ones.

Studies of cowpea leaf cultivars demonstrated that gentisic acid 5-O-glucoside, quercetin 3-(2G-xylosylrutinoside), and quercetin 3-glucosyl-(1→2)-galactoside are among the predominant identified phenolic compounds.

Carotenoids are also present; lutein (124.6 mg/100 g) and all-trans-beta-carotene (92.6 mg/100 g) were among the highest levels detected across cultivars studied.

Catechin 7-O-β-D-glucopyranoside has been identified in cowpea and demonstrated free radical scavenging activity and protection of human B lymphoma BJAB cells under hydrogen peroxide-mediated oxidative stress in laboratory studies.

3.3 Proposed Mechanisms of Action

Among the mechanisms proposed in the prevention of chronic diseases, the most established are attributed to the presence of compounds such as soluble and insoluble dietary fiber, phytochemicals, and proteins and peptides in cowpea.

Cowpea cultivars demonstrated the highest gene expression levels of regulation of the glucose transporter GLUT4 in C2C12 skeletal muscle cells, similar to insulin, in laboratory studies. A positive correlation was found between the phenolic components and the inhibitory effect on antidiabetic enzymes and FRAP activity.

These compounds exhibit widespread pharmacological potentials both in vitro and in vivo, including anthelmintic, antibacterial, antinociceptive, thrombolytic, antidiabetic, hypocholesterolemic and antiatherogenic effects, antimicrobial, anti-sickling, antioxidant, anti-COVID activity, anticancer, and neurobehavioral activities.

4. Scientific Evidence by Area of Use

4.1 Glycemic Response and Antidiabetic Effects

Human/Clinical Evidence: A human study determined the glycemic index (GI) and glycemic load (GL) of processed brown cowpea (Vigna unguiculata). The whole seeds were dehulled, ground into a paste, and either steamed ("moin-moin") or fried ("Akara"). Forty healthy volunteers participated; the test groups consumed processed cowpea while 50 g glucose was administered to the control group. Blood glucose response was assessed at 0, 30, 60, 120, and 180 minutes. GI values for boiled beans, moin-moin, and fried beans were 46.63 ± 9.0, 50.98 ± 5.74, and 53.42 ± 9.50, respectively. The GI and GL values for the test foods did not differ significantly.

In another human study, cowpea (brown and white/black varieties) had GI values of 29 ± 9 and 30 ± 11, respectively, and the legumes elicited a low postprandial rise in blood glucose.

A more recent study in eutrophic adults (n = 11) compared iron-biofortified and conventional cowpeas. Participants consumed each cowpea and a glucose control, with postprandial glucose and appetite responses obtained over 120 minutes. All cowpeas had a lower incremental area under the glycemic curve than glucose. In appetite responses, one variety (Pajeú) had the lowest "hunger sensation" and higher "satiety sensation."

In Vitro and Preclinical Evidence: High inhibition (>50%) of α-glucosidase and α-amylase activities was shown by cowpea leaf extracts at concentrations of 50 and 25 mg/mL in two cultivars tested.

Strength of Evidence: The glycemic response evidence in humans is moderate in quantity but limited in study size and scope. All human GI studies involved small numbers of healthy subjects, and clinical trials in diabetic populations are extremely limited. The preclinical enzyme-inhibition data is in vitro only. This plant has been studied extensively for antidiabetic activities; however, detailed preclinical studies are required to further assess and confirm molecular mechanisms and to find lead compounds. After that, clinical studies are required for the evaluation of impact in humans. Findings from network pharmacology and in vitro analyses underscore V. unguiculata as a promising source for anti-diabetic agents, supporting further clinical trials for type 2 diabetes management.

4.2 Antioxidant Activity

In Vitro Evidence: Studies suggest that cowpea cultivars from Burkina Faso are rich in phenolic compounds and have significant antioxidant and anti-lipid peroxidation activities. Consumption of cowpea, particularly of colored seed varieties, may be beneficial for chronic human disease prevention.

One study reported that the highest total phenolic and flavonoid content was recorded for cowpea from the Afuze site at 34.18 ± 0.07 μg/mg and 27.10 ± 0.02 μg/mg. Another site demonstrated the highest ABTS, hydroxyl radical scavenging activity, and ferric reducing power with 0.89 ± 0.01 μg/mg, 0.89 ± 0.04 μg/mg, and 0.80 ± 0.12 μg/mg, respectively.

Strength of Evidence: Antioxidant evidence is predominantly in vitro. No adequately powered human clinical trials specifically assessing catjang cowpea's antioxidant capacity as an intervention have been identified in the literature reviewed. The in vitro data are consistent across multiple independent laboratories and cultivar studies, but extrapolation to human benefit requires further research.

4.3 Anti-Inflammatory Effects

In Vitro and Combined Evidence: In one study using RAW 264.7 cells stimulated with lipopolysaccharide (LPS) at 1 µM/L and treated with digested cowpea beans (1 mg/mL), total antioxidant capacity, nitric oxide, superoxide dismutase (SOD), TNF-α, IL-10, and NF-κB were analyzed.

Reported bioactivities of cowpea-derived compounds include antioxidant, antidiabetic, anticancer, antimicrobial, analgesic, thrombolytic, hepatoprotective, and anti-aging effects.

Strength of Evidence: Studies on the anti-inflammatory properties of cowpea have produced conflicting results. Evidence in this area is currently limited to cell-based and animal models; human clinical data are lacking.

4.4 Antimicrobial and Anthelmintic Effects

Compounds from V. unguiculata exhibit anthelmintic and antibacterial effects among their documented pharmacological potentials in both in vitro and in vivo studies.

The plant's vermicidal action has been noted in traditional contexts for helping to eliminate intestinal parasites.

Strength of Evidence: Antimicrobial and anthelmintic effects are supported by in vitro and some animal-model data. Human clinical evidence is absent in the current peer-reviewed literature.

4.5 Cardiovascular and Hypolipidemic Effects

Cowpea seeds exhibit beneficial health effects related to their antioxidant, hypoglycemic, hypolipidemic, and antihypertensive properties.

Cowpea has gained attention from consumers and researchers worldwide due to health-beneficial properties including anti-hyperlipidemic and anti-hypertensive properties, though these remain largely at preclinical or in vitro stages.

Strength of Evidence: Cardiovascular and lipid-modulating evidence is predominantly animal-model and in vitro. No robust human randomized controlled trials on catjang cowpea specifically for cardiovascular endpoints were identified in the sources reviewed.

4.6 Prebiotic and Digestive Effects

Cowpea leaves, seeds, and pods contain substantial macronutrients (carbohydrates, proteins, fats), micronutrients (vitamins and minerals), anti-nutrients (trypsin inhibitors, phytates, tannins), and diverse bioactive phytochemicals. Mineral levels are generally highest in leaves, followed by seeds and pods. Thermal processing markedly reduces anti-nutritional factors but also causes variable nutrient losses.

The high content of dietary fiber, including resistant starch, provides a basis for prebiotic effects on gut microbiota, though direct human clinical trial data specifically in catjang cowpea are not established in the reviewed sources.

4.7 Anticancer Effects

Compounds from V. unguiculata exhibit anticancer activity in in vitro and in vivo studies.

Strength of Evidence: Studies on the anti-cancer properties of cowpea remain at early research stages. There are no human clinical trials on cowpea as an anticancer intervention in the sources reviewed. All anticancer evidence is preclinical.

5. Body Systems and Health Areas of Association

• Metabolic / Endocrine: Multiple human GI studies indicate low glycemic index across processing methods; in vitro inhibition of α-amylase and α-glucosidase; modulation of GLUT4 expression in muscle cells in laboratory models.
• Cardiovascular: Preclinical evidence of hypolipidemic, antihypertensive, and antiatherogenic properties; no human cardiovascular trials identified.
• Gastrointestinal: Traditional use for digestive conditions; high fiber content; prebiotic potential from resistant starch; traditional anthelmintic use.
• Immune / Inflammatory: In vitro anti-inflammatory activity via modulation of TNF-α, IL-10, and NF-κB; conflicting published findings.
• Musculoskeletal and Protein Nutrition: High-quality plant protein source complementing cereal amino acid profiles; used for protein-energy malnutrition programs.
• Hematological: Anti-sickling activity reported in preclinical studies; seed iron content with relevance to iron-deficiency anemia.
• Dermatological (Traditional): Leaf and seed poultices applied to skin infections; powdered carbonized seeds applied to insect stings.
• Neurological (Traditional): Root preparations used traditionally for epilepsy.

6. Nutritional and Supplement Forms; Dosages Reported in Studies

6.1 Forms Used

Catjang cowpea beans are rich in protein, fiber, vitamins, and minerals. They can be eaten fresh, dried, or processed into various products, including flour and snacks. Scientific studies have employed whole cooked seeds, dehulled and ground pastes (steamed or fried), seed coat extracts, methanolic and aqueous leaf extracts, and seed oil extracts, depending on the research question.

For phytochemical extraction studies, leaves were boiled at 100°C for 30 min to simulate traditional cooking procedures and compared to raw leaves. The best laboratory extraction condition was found to be EtOH/H₂O 1:2 v/v, drug-to-solvent ratio 1:47 w/v, and 3 extraction cycles. Phytochemicals identified mainly belong to the family of phenolic acids, flavonoids, terpenoids, and alkaloids. Boiled leaves revealed a significant loss of most phytochemicals and a net decrease of antioxidant activity compared to raw ones.

6.2 Dosages in Studies

In the human GI studies, proximate analyses were done to determine the quantity of food containing 50 g available carbohydrate, which was the dose administered to forty healthy volunteers.

In the 2025 human crossover glycemic study, eutrophic adults (n = 11) consumed each cowpea variety in the amount equivalent to the reference food, with postprandial glucose and appetite responses measured over 120 minutes.

In in vitro antidiabetic enzyme inhibition assays, cowpea leaf extracts were tested at concentrations of 50 mg/mL and 25 mg/mL, with high inhibition (>50%) of both α-glucosidase and α-amylase demonstrated at these concentrations.

In the in vitro anti-inflammatory cell study, digested cowpea beans were used at a concentration of 1 mg/mL in RAW 264.7 cell cultures.

No standardized pharmaceutical dosage forms or formally established clinical dose ranges for catjang cowpea as a dietary supplement have been identified in the sources reviewed. All dosages in the literature pertain to food consumption studies.

7. Safety Considerations

7.1 Anti-Nutritional Factors

Anti-nutrients found in cowpea seeds include phytates, hemagglutinating activity (lectins), tannins, phenolic compounds, oxalate, trypsin inhibitors, cyanogenic glycosides, and alpha-galactosides. One of the major challenges associated with cowpea as a legume is the presence of anti-nutritional factors such as trypsin inhibitors, protease inhibitors, phytic acid, saponins, tannins, polyphenols, and lectins.

The presence of anti-nutritional factors including phytates, alpha-galactosides such as raffinose and stachyose, and tannins reduce significantly the micronutrient bioavailability and also create problems of digestive acceptability. Specifically, phytate levels can reach 1,230 mg/g dry matter, significantly binding minerals like iron and zinc.

In ten cultivated varieties of dry Vigna unguiculata, trypsin inhibitor activity ranged from 19.6 to 28.2 TUI mg⁻¹ protein, hemagglutinating activity from 33.5 to 98.9 HU mg⁻¹ protein, phytic acid from 280 to 331 mg per 100 g, and tannic acid from 0.42 to 0.78 g per 100 g dry weight.

7.2 Effect of Processing on Anti-Nutritional Factors

Pressure cooking and boiling resulted in significant (p ≤ 0.05) destruction of anti-nutrients like phytates, tannins, and trypsin inhibitors. In vitro protein digestibility was highest (93.9%) with 3-minute pressure cooking, followed by 15-minute boiling (91.0%).

Germination can reduce phytate levels by 48.8% to 81.8% in cowpea seeds. Germination also decreases tannin content by 33% to 72%, enhancing overall nutritional value.

The content of anti-nutritional factors in cowpea does not pose any significant problems as these can be removed or inactivated during food processing procedures.

7.3 Flatulence and Digestive Tolerance

Alpha-galactosides such as raffinose and stachyose, present in cowpea, create problems of gastrointestinal acceptability, which are well-recognized issues shared with other legumes. These oligosaccharides are not digested in the small intestine and are fermented by colonic bacteria, producing gas.

7.4 Amino Acid Profile Limitations

The amino acid profiles of cowpea meals almost cover human dietary requirements based on FAO/WHO/UNU-suggested profiles, but are deficient in sulphur amino acids. This makes cowpea a nutritionally incomplete protein source when consumed as a sole protein food, underscoring the traditional practice of combining it with cereal grains.

7.5 Root Toxicity

The roots of cowpea are reportedly very poisonous. This is a consistent finding across traditional use documentation and represents a significant safety consideration: while seeds, leaves, and pods are used as food and medicine, root preparations described in traditional medicine contexts carry inherent toxicological risk and should not be used without expert guidance.

7.6 Nutritional Interactions

Phytate levels in cowpea, reaching up to 1,230 mg/g dry matter, significantly bind minerals like iron and zinc, meaning that in populations relying on cowpea as a primary iron and zinc source, bioavailability of these minerals may be substantially reduced unless appropriate processing methods are employed.

Thermal processing markedly reduces anti-nutritional factors but also causes variable nutrient losses, including documented losses of ascorbic acid and beta-carotene during boiling.

7.7 Overall Evidence Gap

It is concluded that V. unguiculata possesses strong pharmacological, nutritious, and phytochemical potential; therefore, it is strongly recommended for additional comprehensive investigations in order to determine its clinical utility. As of the current literature, there are no published formal adverse event profiles or drug interaction studies specific to catjang cowpea as a dietary supplement distinct from its role as a whole food. The safety record of cowpea as a food is ancient and extensive; its safety as an isolated extract or concentrated supplement form has not been systematically evaluated in clinical trials.

References

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