Black pepper

Black pepper is an evergreen woody vine 6–10 m long in cultivation, trailing or climbing support trees by adventitious roots at the nodes. The leaves are simple, alternate, ovate to cordate, 5–10 cm long and 3–6 cm wide, leathery and glossy, with 5–7 main veins radiating from the base and a short petiole. The inflorescence is a slender spike 5–15 cm long borne opposite a leaf, carrying very many minute, perianth-less, mostly bisexual flowers. The fruit is a spherical drupe 3–5 mm across, densely set along the spike, turning from green to yellow to red at maturity, each holding one seed. The vine flowers after 1–2 years and the fruit ripens about 6–9 months after pollination. The chromosome number is 2n = 52.

According to Kew POWO the native range of Piper nigrum is recorded as Sri Lanka, while Kew's Species Profile gives the Malabar coast (Kerala, India) as the place where it grows wild; recent genetic and archaeological work suggests a centre of origin in the Western Ghats–Sri Lanka region. From there pepper spread along spice trade routes to Southeast Asia (Indonesia, Malaysia, Vietnam) and later to tropical Africa and the Americas. Today it is grown throughout the tropical belt. In 2022 world pepper production was about 812,000 tonnes; Vietnam led with about 272,000 tonnes (over 30%), followed by Brazil (~128,000 t), Indonesia (~82,000 t) and India (~64,000 t). Vietnam is the largest exporter, concentrated in Dak Lak, Gia Lai, Dak Nong, Ba Ria–Vung Tau, Dong Nai and Binh Phuoc.

The signature active of black pepper is piperine, a piperamide alkaloid responsible for its pungency, making up 2–7% of dry weight (depending on cultivar and ripeness); other piperamides include piperanine, piperettine and piperlongumine. The essential oil (1–2.5%) is dominated by the sesquiterpene β-caryophyllene together with the monoterpenes limonene, sabinene, α- and β-pinene, which give the sharp aroma. Dried peppercorns contain about 10–12% protein, 4% lipid, 60–65% carbohydrate (roughly 25% of it fibre) and 12% water; they are rich in manganese, vitamin K and iron, and also contain flavonoids, phenolic acids and amino acids. Piperine's most notable biological property is inhibition of the drug-metabolising enzyme CYP3A4 and of the intestinal and hepatic transporter P-glycoprotein, thereby raising the bioavailability of many other compounds — an action known as the 'bioenhancer' effect.

Black pepper is a universal spice: ground black pepper seasons almost every dish, white pepper is used where colour matters and brined green pepper serves premium cuisine; the oil flavours foods, perfumes and cosmetics; and piperine is extracted as an absorption-enhancing excipient in supplements and medicines. The classic study of its bioavailability role is that of Shoba et al. (Planta Medica, 1998): added piperine raised the bioavailability of curcumin by about 154% in rats and up to about 2,000% in humans. Srinivasan (Critical Reviews in Food Science and Nutrition, 2007) and Meghwal & Goswami (2013) reviewed piperine's antioxidant, antimicrobial, anti-inflammatory, digestive and lipid-modulating actions. Clinical work also shows piperine increases plasma levels of some drugs (e.g. phenytoin, rifampicin), and piperamides are studied as insecticides, antiparasitics and potential anticancer agents.

On safety, black pepper and piperine at food doses are considered safe; however, because piperine enhances absorption it can cause drug interactions — increasing or prolonging the effects of medicines metabolised by CYP3A4 and others — so people on medication should be cautious. Whole peppercorns rarely cause allergy, but pepper dust irritates the nasal mucosa, and high doses may cause stomach warmth, heartburn and digestive irritation. On conservation, the IUCN has not evaluated the species (Not Evaluated) and Piper nigrum is not listed in the CITES appendices; nevertheless wild populations in the Western Ghats (India) and Sri Lanka are contracting as land is converted. The main cultivation risks are quick and slow wilt (foot rot caused by Phytophthora capsici and P. tropicalis), anthracnose (Colletotrichum), root-knot and burrowing nematodes (Meloidogyne, Radopholus similis), mealybugs and the pollu beetle (Longitarsus nigripennis), and the 'pepper yellows/mosaic' disorder. Conservation priorities are to safeguard wild genetic diversity and cultivated cultivars in genebanks such as the Indian Institute of Spices Research (IISR) and national pepper research centres.