Mung bean

The mung bean (Vigna radiata (L.) R. Wilczek) is an annual herb, erect when cultivated (about 50 cm) or twining, generally 15–125 cm tall. The stem is round, finely hairy and branched. The leaves are ternate (three leaflets) and stipulate; the leaflets are ovate to rhombic, often three-lobed and hairy on both surfaces, the blade 6–12 cm long and 5–10 cm broad. The flowers are papilionaceous (pea-like), yellow-green, borne in racemes in the leaf axils. The fruit is a slender, slightly curved, hairy cylindrical pod about 5–10 cm long, containing 8–15 seeds. The seeds are small, about 2–4 mm across, with a shiny green coat, yellow cotyledons and a white hilum; the chromosome number is 2n = 22. The roots bear nodules with nitrogen-fixing bacteria (Bradyrhizobium), so mung bean leaves nitrogen in the soil for the following crop.

According to Kew POWO, the native range of the species Vigna radiata runs from the Arabian Peninsula and Taiwan to tropical Asia and northern–eastern Australia; it is a scrambling plant of the seasonally dry tropics. The cultivated variety (Vigna radiata var. radiata) is native from the Indian subcontinent to Myanmar, while the wild var. sublobata is regarded as its direct progenitor. Mung bean was domesticated in the Indian subcontinent several thousand years ago and then spread across South, East and Southeast Asia; the English word 'mung' comes from the Hindi 'mūng'. Today India is the largest producer, followed by China, Myanmar and Indonesia; the crop is also grown in Africa, the Americas and Oceania. In Vietnam, mung bean is familiar in the lowlands and midlands, grown mainly in the summer–autumn and winter seasons and harvestable after 60–90 days.

Chemically, mung bean stands out for its flavonoids, whose two main compounds are vitexin (apigenin 8-C-glucoside) and isovitexin (apigenin 6-C-glucoside); according to Hou et al. (2019), in the seed coat these make up about 95.6% and 96.8% of the respective flavonoids. There are also catechin, phenolic acids (gallic, caffeic, ferulic and p-coumaric acid) and other flavonoids. The seed is rich in protein (about 24% of dry weight, high in lysine) and, on hydrolysis, yields peptides with antioxidant and angiotensin-converting-enzyme (ACE) inhibitory activity — the basis of its antihypertensive effect. Other components include starch and carbohydrate (about 63%), dietary fibre (about 16%), polysaccharides and resistant starch, saponins and phytosterols; micronutrients include folate (B9), manganese, magnesium, phosphorus, iron, potassium and vitamin B1. Raw seeds also contain anti-nutritional factors such as trypsin inhibitor, phytate, tannins and lectins, which are reduced by cooking or by sprouting; sprouting also increases vitamin C, gamma-aminobutyric acid (GABA) and free amino acids.

Mung bean is widely used in cooking: in Vietnam the seeds are cooked in sweet soups, in sticky rice, as the filling of mung-bean cakes and in bánh khọt, and are ground for vermicelli and mung-bean starch; bean sprouts (germinated seeds) are a vitamin C-rich vegetable used in stir-fries and salads. In traditional medicine mung bean is considered cooling and is used to clear heat, detoxify, promote urination and aid digestion. In research, the review by Hou et al. (2019) records that mung bean ameliorates hyperglycaemia, hyperlipidaemia and hypertension and has potential to prevent cancer and inhibit melanogenesis; the critical review by Ganesan and Xu (2018) systematises its phytochemical profile and health-promoting effects; Lv et al. (2025) used untargeted metabolomics to identify vitexin, isovitexin and catechin as key hypoglycaemic compounds; and Desta et al. (2024) analysed flavonoids and antioxidant activity in 136 mung-bean accessions, showing large genetic variation in bioactive content.

As food, mung bean is safe once cooked. Raw seeds contain trypsin inhibitor, lectins (phytohaemagglutinin) and phytate, so eating them raw or undercooked can cause bloating, poor digestion and reduced mineral absorption; they should therefore be thoroughly cooked. Fresh bean sprouts are a microbiologically sensitive food: warm, moist sprouting conditions favour Salmonella and E. coli, so they must be kept refrigerated, washed and cooked, especially for pregnant women, young children, the elderly and immunocompromised people. Mung bean contains moderate levels of purines, so people with severe gout should eat it in moderation. On conservation, the species Vigna radiata has no global IUCN Red List assessment (NE) and is not listed in the CITES appendices; it is a common crop and is not threatened. Nevertheless the wild var. sublobata and local landraces are valuable gene sources for drought tolerance, disease resistance and seed quality, and should be maintained in genebanks (such as ICRISAT and WorldVeg) and on-farm, together with the wild relatives of the genus Vigna.