Sacred lotus

Sacred lotus is a perennial aquatic herb whose rhizome (lotus root) creeps through mud; petioles 1–2 m long raise peltate leaves above the water. The large bisexual flower, 15–30 cm across, is thermogenic and warms to 30–36 °C to attract beetle pollinators; each flower opens over 3–4 consecutive mornings before fading. Seeds have a very hard coat and deep embryo dormancy, retaining viability for centuries — a Chinese specimen germinated after more than 1,000 years.

According to Kew POWO, Nelumbo nucifera has a very wide native range: from Ukraine and northern Iran across the Caucasus, the Russian Far East, China, Japan, Korea, the Indian subcontinent, Southeast Asia and New Guinea to northern and north-eastern Australia. It has been introduced and cultivated in the Americas, Africa and many Pacific islands. The family Nelumbonaceae contains a single genus, Nelumbo, with just two species: N. nucifera (Asia–Oceania) and N. lutea (the Americas), separated only geographically, not reproductively.

Lotus accumulates benzylisoquinoline alkaloids (BIAs) in almost all tissues; at least 59–61 BIAs have been identified, falling into three groups: 1-benzylisoquinolines, aporphines and bisbenzylisoquinolines. The leaves are rich in aporphines such as nuciferine and roemerine, whereas the seed embryo (plumule) concentrates bis-BIAs including liensinine, isoliensinine, neferine and nelumboferine. Notably, most lotus BIAs are R-conformers, in contrast to the S-conformers typical of Ranunculales. Besides alkaloids, lotus contains flavonoids (quercetin, kaempferol, rutin), phenolic acids, tannins and polysaccharides; its genome was published in 2013.

In East Asian medicine, lotus leaf clears heat, the plumule calms the mind and lowers blood pressure, and the seed tonifies spleen and kidney; lotus root, stems and seeds are staple foods. Modern research focuses on the alkaloids: nuciferine shows anti-obesity, lipid-lowering and hypoglycaemic effects; neferine is anti-arrhythmic, anti-hypertensive and anticancer and inhibits Ca2+-dependent membrane fusion by SARS-CoV-2; liensinine and isoliensinine suppress cancer cells by inducing apoptosis. A 2023 review notes that lotus alkaloids have low bioavailability that can be improved with nanoliposomes or microcapsules.

The plumule and leaf carry potent alkaloids, so standardised preparations are advisable and overuse should be avoided; caution is warranted in pregnancy, in cardiac patients on medication and in young children. The species is not fully assessed — Kew records the IUCN status as Data Deficient (DD), while some regional assessments (India) list it as Least Concern (LC). The main risks are loss of wetlands and pond pollution, plus erosion of native landraces through hybridisation; widespread cultivation and long-lived seeds mean the species is not at high extinction risk.