Eggplant

Eggplant (Solanum melongena) is an annual or short-lived herbaceous plant (in the tropics it may live several years), 40–150 cm tall (wild forms to 225 cm), growing as a bushy shrub whose stems and young leaves often bear small prickles. The leaves are large, alternate, ovate to elliptic, 10–20 cm long and 5–10 cm wide, with entire or roughly lobed margins, and the surface is covered in star-shaped hairs. The flowers are bisexual, borne singly or in small clusters in the leaf axils, with a fused wheel-shaped corolla of white to pale purple, 5 lobes (sometimes more because eggplant flowers are often fasciated), and 5 yellow stamens whose anthers form a tube around the style. The fruit is a fleshy berry, spherical, ovoid, elongated or flattened, less than 3 cm across in wild forms but much larger in cultivars (some up to 30 cm long), with glossy purple skin (some cultivars white, green, striped or red) and spongy cream-white flesh enclosing many small flat yellow-brown seeds. The stalk and calyx are often prickly in primitive cultivars.

According to Kew POWO, Solanum melongena is native to the W. Indian Ocean and tropical–subtropical Asia; its native countries include India, Sri Lanka, Bangladesh, Assam, Myanmar, Thailand, Laos, Vietnam, southern China (South-Central and Southeast), Hainan, the East and West Himalaya, Pakistan, Malaysia, Borneo, Java, Sulawesi, the Philippines, together with Madagascar, Mauritius and Réunion. The species was first described by Linnaeus in 1753. Eggplant was domesticated in Asia from the wild ancestor Solanum insanum; analysis of more than 3,400 worldwide accessions and population-genetic work indicate at least two independent domestication centres — Southeast Asia and the Indian subcontinent — with limited gene exchange between them. Sanskrit and Chinese agricultural literature mention cultivated eggplant about 2,000 years ago; it was known in Iran by the 6th–7th century, spread to the Maghreb in the 8th–9th century and to Ethiopia by the 14th century, and later to Europe and the Americas. Today eggplant is grown throughout the tropics and subtropics and in temperate regions (under glass); in 2023 world production reached about 61 million tonnes, with China and India together accounting for some 85%. In Vietnam, eggplant is widely grown in the lowlands and midlands, mainly in the summer–autumn crop.

Chemically, the edible part of the fruit is about 90–92% water; its dry matter is mainly carbohydrate, fibre (abundant in the peel) and a little protein, together with vitamins and minerals such as vitamin K, vitamin B6, folate, potassium, magnesium and manganese. The main phenolic compound of eggplant is chlorogenic acid — the major polyphenol of the flesh and regarded as antioxidant and lipid-lowering. The purple peel is characterised by delphinidin-based anthocyanins: nasunin [delphinidin 3-(p-coumaroylrutinoside)-5-glucoside], first isolated by Kuroda and Wada in 1933 and structurally identified by Watanabe et al. (1966), is the main anthocyanin of 'Japanese-type' eggplants, whereas delphinidin 3-rutinoside (D3R) predominates in 'non-Japanese' types. Azuma et al. (2008) analysed the peels of 123 eggplant and related accessions, additionally identifying delphinidin 3-glucoside and petunidin 3-(p-coumaroylrutinoside)-5-glucoside. The fruit also contains flavonols (quercetin, myricetin glycosides), glycoalkaloids (solasonine, solamargine), saponins and a small amount of solanine. Genetic studies (the SmelAAT gene, 2021) and metabolome–transcriptome analyses (2022, 2025) have identified genes and transcription factors (SmMYB32, SmMYB67) that regulate anthocyanin biosynthesis.

Eggplant is an important fruit vegetable in Asian and Mediterranean cuisines: the fruit is grilled, fried, stir-fried, stewed, curried, made into cà bung, stuffed, or mashed into baba ganoush; its spongy flesh soaks up oil and flavour, giving rich dishes. In Vietnam, grilled eggplant with shrimp paste, eggplant in fish sauce, stir-fries and the dish cà bung are very popular. In research, nasunin (Noda et al., 2000) was shown to be a potent scavenger of the superoxide anion radical and to protect brain-membrane lipids, and it also acts as an iron chelator. The peel anthocyanins show strong antioxidant activity (Azuma et al., 2008; Lattuada et al., 2015 — comparing nasunin and D3R). Eggplant chlorogenic acid has been studied for lipid-lowering and antioxidant effects (review by Plazas et al., 2016). In 2021, a variant of the SmelAAT gene was identified as the main determinant of peel anthocyanin composition (D3R versus nasunin); metabolome–transcriptome studies (2022; 2025) clarified the regulatory network of peel colour and identified MYB transcription factors such as SmMYB32 and SmMYB67. Eggplant is also regarded as a functional food because of its high phenolic content and ranks among the top ten vegetables for oxygen-radical scavenging capacity (Cao et al., 1996).

As food, ripe eggplant is wholesome but must be cooked: the fruit contains glycoalkaloids (solasonine, solamargine) and a little solanine, which can cause digestive upset if eaten raw in large amounts; do not eat unripe fruit, over-mature fruit, or the leaves and stems, which have higher glycoalkaloid levels. Eggplant belongs to the nightshade family with tomato, potato and pepper. Because its spongy flesh absorbs oil, fried dishes can be high in calories, and people with kidney disease should note its oxalate content. On conservation, on the IUCN Red List Solanum melongena has not been evaluated (NE) and is not listed in the CITES appendices; it is an important crop grown worldwide and therefore not threatened. However, its wild relatives — especially the ancestor Solanum insanum and the spiny eggplant species — are valuable gene sources for disease resistance, drought tolerance and fruit quality; many genebanks (IPGRI; India ~3,000 accessions; China ~1,000; the Vavilov Institute >1,000; the European EGGNET network) conserve these genetic resources.