Nymphaea nouchali

Nymphaea nouchali (Blue Water Lily): A Comprehensive Reference

1. Identity, Nomenclature, and Botanical Description

Accepted scientific name: Nymphaea nouchali Burm. f. (family Nymphaeaceae). The plant was formerly referred to by the synonym Nymphaea stellata Willd., and these two names appear interchangeably throughout the pharmacological literature. The leaves and shoots of N. stellata (Blue water lily) and N. nouchali (Red water lily) have been treated as different species in some chemical-composition studies, reflecting an ongoing taxonomic debate; however, the predominant consensus in pharmacognostic and phytochemical reviews treats them as synonymous.

Nymphaea nouchali (syn. Nymphaea stellata Willd.) belongs to the family Nymphaeaceae and is a species of perennial aquatic flowering plant with huge round floating leaves and rhizomes. Nymphaea nouchali is a day-blooming non-viviparous plant with submerged roots and stems. It originates from southern and eastern regions of Asia and is the national blossom of both Sri Lanka and Bangladesh. The plant is locally known as "Shapla" in Bangladesh and "Suryeon" in Korea, and grows abundantly in mixed populations in almost all shallow natural bodies of water.

Common names vary considerably by region and language. In English it is known as the Blue water lily, Manel flower, and Blue star water lily; in Tamil as Alli, Ambal, Vellambal, and Nilotpalam; in Telugu as Allitamara, Kaluvapoovu, and Neelattamara; in Marathi as Kamoda and Neel Kamal; and in Hindi as Neel Kamal and Kumudinee. In Ayurveda it is described as Nilotpala. Despite being called the Indian blue lotus, it is a water lily, not a lotus.

Parts used medicinally and as food: Like all waterlilies, its tubers and rhizomes can be used as food items, usually boiled or roasted. Its tender leaves and flower peduncles are also valued as food. The dried plant is collected from ponds, tanks, and marshes during the dry season and used in India as animal forage. The fruit is globose, containing round flask-shaped seeds. The seeds are used as stomachic and restorative and are also prescribed as diet for diabetes in the Ayurvedic system of medicine.

Common preparation forms in research settings include hydroalcoholic, methanolic, ethanolic, aqueous, chloroform, and ethyl acetate extracts of the flower, leaf, seed, stem, rhizome, and tuber. One 2021 study investigated N. nouchali petal extracts for potential application as natural food additives, assessing toxicity via in vitro model systems and formulating a herbal beverage from petal extract combined with green tea.

2. Traditional and Historical Use

Nymphaea nouchali (syn. Nymphaea stellata) is an important and well-known medicinal plant widely used in the Ayurveda and Siddha systems of medicines for the treatment of diabetes, inflammation, liver disorders, urinary disorders, menorrhagia, blenorrhagia, and menstruation problems, as well as being employed as an aphrodisiac and as a bitter tonic.

In traditional systems of medicine, it is used for the treatment of Prameha (urogenital disorders including diabetes), Shopha (inflammation), Yakrit Vikara (liver diseases), Mutrakricha (urinary difficulties), and Pradararoga (menstrual disorders), and as a vajikarana (aphrodisiac/reproductive tonic) drug and rasayana (rejuvenating agent).

Known in Ayurvedic texts (Nighantu) as Kumud, the herb is described as useful in Rakta (blood) and Pitta (metabolic fire) doshas and is well-known in Ayurveda for its many medicinal properties. Due to its bitter taste (Tikta Rasa), it is widely used in pitta disorders and helps in reducing fever, acting as a cooling agent for the body. This bitter taste quality is held to be helpful in all rakta and pittaja ailments in addition to possessing the guna of agnivardhana (digestive fire enhancement).

The seeds specifically are used as stomachic and restorative and are prescribed as part of the dietary regimen for diabetes in the Ayurvedic system.

Traditional practice of Ayurveda in ancient India dates back to at least the first millennium BC, placing the use of this plant within one of the world's oldest continually practised medical traditions. The plant also holds cultural significance: in Indian culture, this traditional plant has a number of ceremonial uses in addition to its medicinal applications.

3. Phytochemistry: Key Constituents and Active Compounds

Sterols, saponins, alkaloids, flavonoids, and polyphenols have been detected in different solvent extracts of the complete plant. The chemical profile varies by plant part.

3.1 Sterols

Nymphayol (25,26-dinorcholest-5-en-3β-ol), a new sterol, has been isolated from the successive chloroform extract of the flower. Its structure was determined on the basis of X-ray crystallography and spectral data. This compound is considered the principal bioactive lead compound of the plant and has been the subject of multiple dedicated pharmacological studies.

A new steroid was isolated from the methanolic fraction of the ethanol extract of seeds of Nymphaea stellata and was characterized as 24-methyl-cholesta-5-ene-3-ol-(23,24,29)-cyclopropane, designated as nymphasterol. Its structure was elucidated by UV, IR, 1D and 2D NMR, and mass spectroscopy.

3.2 Flavonoids and Phenolic Compounds

Astragalin, corilagin, gallic acid, gallic acid methyl ester, isokaempferide, kaempferol, quercetin-3-methyl ether, quercetin, 2,3,4,6-tetra-O-galloyl dextroglucose, and 3-O-methylquercetin-3'-O-beta dextroxylopyranoside have been identified in the flowers.

The presence of gallic acid, catechin, epicatechin, epigallocatechin, epicatechin gallate, caffeic acid, quercetin, and apigenin in the N. nouchali flower (NNF) was confirmed by HPLC. A separate study of the leaf fraction found that HPLC analysis revealed the presence of gallic acid, catechin, epigallocatechin, epicatechin gallate, caffeic acid, luteolin, and kaempferol as the key polyphenolic composition.

Quercetin, patuletin, kaempferol, myricetin, and isorhamnetin, along with their conjugates, were the most abundant flavonols identified in Nymphaea organs by UHPLC/PDA/ESI-QTOF-MS analysis.

In the flower, quercetin, gallic acid, ellagitannin, methyl gallate, 3-methylkaempferol, kaempferol-3-O-glucoside, flavonol, and isorhamnetin were identified.

3.3 Alkaloids

Coclaurine, a phenolic basic alkaloid, is found in the aerial parts of N. stellata. Coclaurine has been reported to exhibit anticonvulsant, anticancer, HIV inhibitory, hypoglycemic, and antioxidant effects.

3.4 Seed Composition

Protein, pentosan, mucilage, and tannins are reported in the seeds. Glycosides, phenols, tannins, flavonoids, saponins, and alkaloids are also reported in the seeds. Phytochemical analysis of the hydroalcoholic seed extract revealed the presence of phenols, flavones, tannins, protein, reducing sugars, glycosides, saponins, alkaloids, and steroids.

3.5 Nutritional Constituents

N. nouchali has been shown to be a nutritious food that contains a high level of polyphenols, flavonoids, amino acids, sugars, fatty acids, alkaloids, protein, and sterols. Seeds are reported to contain proteins, polyphenols, cellulose, and pectin.

4. Pharmacology and Mechanisms of Action

4.1 Antidiabetic / Antihyperglycemic Activity

Mechanism — Nymphayol and β-cell regeneration: Nymphayol (25,26-dinorcholest-5-en-3β-ol), a new sterol isolated from the bioactive successive chloroform flower extract, has been reported for its antidiabetic activity at 20 mg/kg body weight in streptozotocin-induced diabetic rats. Oral administration of nymphayol for 45 days significantly restored plasma glucose levels and increased plasma insulin levels to near normal in STZ-diabetic rats. Light microscopy and immunocytochemical staining of nymphayol-treated diabetic pancreas revealed an increased number of insulin-positive β-cells. The mode of action of nymphayol may be due to the reversal of the damaged endocrine tissue, thereby stimulating the secretion of insulin in β-cells, as revealed by insulin assay.

The protection of pancreatic β-cells is enhanced due to the antioxidant defense mechanism of nymphayol against reactive oxygen species produced in hyperglycemic conditions.

Mechanism — PPARγ activation and insulin sensitization: One in vitro mechanistic study on N. nouchali seed extract — described as the first of its kind — demonstrated that the extract promotes adipogenesis and enhances glucose uptake as evidenced by GLUT-4 expression mediated by PPARγ activation, thereby improving insulin sensitivity. This study provides evidence that the extract has an antidiabetic effect by activating the PPARγ gene in adipocytes. Increased mRNA of PPARγ (and GLUT4) by Nymphaea nouchali seed extract in 3T3-L1 adipocytes as the possible mechanism of its anti-hyperglycemic effect was reported (Parimala et al., 2015).

Mechanism — enzyme inhibition: The methanolic extract of seeds and tuber inhibited pancreatic lipase and intestinal α-glucosidase. These characteristics could minimize the occurrence of diet-related postprandial hyperlipidemia and hyperglycemia, demonstrating that the tuber and seeds can be utilized as an essential nutritional complement to counter diet-induced hyperglycemia and hyperlipidemia.

Rhizome evidence: Aqueous methanolic extract of N. nouchali rhizomes was investigated for antihyperglycemic activity. Numerous antidiabetic and antioxidant compounds were discovered by metabolomics screening. Boiled rhizome powder showed strong antihyperglycemic action in rats against sugar-induced postprandial hyperglycemia.

Seed extract in STZ-induced rats: The antihyperglycemic activity of a hydroalcohol extract of N. nouchali seeds (NN) was investigated in streptozotocin (STZ, 50 mg/kg i.p.)-induced diabetic male Sprague-Dawley rats. NN extract was administered orally at doses of 100 and 200 mg/kg body weight for 21 days; metformin was used as the reference drug at 250 mg/kg. Oral administration of NN extract showed significant restoration of blood glucose level to normal.

Evidence strength: All antidiabetic evidence is preclinical — from in vitro cell models and in vivo animal models (rats and mice). No human clinical trials have been reported.

4.2 Antioxidant Activity and DNA Protection

N. nouchali flower extract had a very potent capacity to scavenge numerous free radicals. The extract was also able to prevent DNA damage and quench cellular reactive oxygen species (ROS) generation induced by tert-butyl hydroperoxide (t-BHP) with no signs of toxicity. The extract augmented the expression of both primary and phase II detoxifying enzymes. This is accomplished by phosphorylation of MAP kinase (p38 kinase and ERK) followed by enhancing the nuclear translocation of Nrf2, attenuating cellular ROS generation and conferring protection from cell death.

The leaf extract (NNLE) was found to combat oxidative stress by enhancing the transcription and translation of both primary antioxidant enzymes and phase-II detoxifying enzymes, especially heme-oxygenase-1 (HO-1).

The activities of the hydroalcoholic seed extract against DPPH, nitric oxide, and lipid peroxidation were concentration-dependent, with IC₅₀ values of 42.82, 23.58, and 54.65 µg/mL respectively. The total antioxidant capacity was high, with 577.73 mg vitamin E/g of extract, and a moderately high vitamin C equivalent content of 197.22 mg/g.

Alkaloids and tannins displayed antibacterial activities, while phenolic compounds and flavonoids showed potent antioxidant capabilities.

Evidence strength: Antioxidant evidence is primarily in vitro (cell-based and cell-free assays) and limited in vivo animal data. No human clinical trials are available.

4.3 Hepatoprotective Activity

Flowers of Nymphaea stellata (syn. N. nouchali) have been reported to have hepatoprotective activity against CCl₄-induced hepatic damage. The hepatoprotective activity exerted by the extract could be due to cell membrane stabilization, hepatic cell regeneration, and activation of antioxidative enzymes such as glutathione reductase, glutathione peroxidase, and superoxide dismutase.

The whole plant is used for the treatment of liver disorders in Ayurveda.

Evidence strength: Hepatoprotective evidence is based on animal models (carbon tetrachloride-induced hepatotoxicity in rodents) and in vitro studies. No human clinical evidence is available.

4.4 Anti-inflammatory and Analgesic / Antinociceptive Activity

The methanolic extract of Nymphaea nouchali flowers (MNNF) was evaluated for anti-inflammatory activity using a carrageenan-induced hind paw edema model, while hot plate, writhing, and formalin tests were carried out for analgesic activity. The findings of the study suggested that Nymphaea nouchali has strong analgesic, anti-inflammatory, and antioxidant effects, confirming the traditional use of this plant for inflammatory pain alleviation.

In one study, the antinociceptive, immunomodulatory, and antipyretic activities of nymphayol were investigated in Wistar rats and mice. Antinociceptive effect was evaluated by acetic acid-induced writhing, formalin-induced paw licking, and hot-plate tests. Nymphayol produced significant (p<0.05) antinociceptive activity in acetic acid-induced writhing response and in the late phase of the formalin-induced paw licking response.

Another study evaluated the antinociceptive and neuropharmacological activities of methanol extract of N. nouchali flower (MENN). The antinociceptive activity was assessed by heat-induced (tail immersion test) and chemical-induced pain models (acetic acid-induced writhing), and the effect on the CNS was studied using the hole cross test and open field test. MENN showed strong, significant, and dose-dependent antinociceptive activity in both models at all experimental doses (200 mg/kg and 400 mg/kg). The extract at the lower dose inhibited 59.97% and at the higher dose produced a maximum of 64.75% inhibition of writhing, which the authors compared favorably to the reference drug diclofenac.

Evidence strength: Anti-inflammatory and antinociceptive evidence is exclusively preclinical (in vitro and animal models). No human clinical trials are available.

4.5 Gastroprotective / Antiulcer Activity

The goal of one research study was to assess the anti-ulcerogenic activity of nymphayol (NYM), isolated from Nymphaea stellata, against an ethanol-induced ulcer model in rats. Administration of ethanol elevated ulcer index (UI) along with increases in lipid peroxidation and myeloperoxidase (MPO), and significant decreases in gastric mucus, catalase, superoxide dismutase, glutathione, glutathione peroxidase, and prostaglandin E2. Animals pretreated with NYM at 45 mg/kg showed considerable increases in antioxidants, gastric mucus, and PGE2 levels, and significant decreases in UI, lipid peroxidation, and MPO levels.

Pretreatment with indomethacin, SC560, rofecoxib, and L-NAME considerably prevented the ulcer protective activity of NYM (45 mg/kg), indicating the involvement of both cyclooxygenase (COX) and nitric oxide synthase (NOS) in NYM-mediated gastroprotection against ethanol-induced ulcer.

Compared to the ethanol-induced ulcer group, NYM pretreatment increased Bcl-2, an anti-apoptotic marker, and decreased pro-apoptotic markers including caspase-8, caspase-9, and caspase-3.

Evidence strength: Gastroprotective evidence is animal-based only. No human clinical data exist.

4.6 Antimicrobial Activity

Antibacterial potency of methanol, acetone, ethyl acetate, and petroleum spirit extracts of N. nouchali flower was tested against four human pathogenic bacteria (Bacillus subtilis, Escherichia coli, Klebsiella pneumoniae, and Sarcina lutea) and one plant pathogenic bacterium (Xanthomonas campestris) by disc diffusion assay. Methanol extract possessed better antibacterial activity against B. subtilis and S. lutea than the commercial antibiotic nalidixic acid.

In a study of the hydroalcoholic seed extract, the zone of inhibition was extremely great for P. aeruginosa (25 mm), S. aureus (20 mm), and C. albicans (19 mm). The MIC value was 0.03 mg/mL for bacteria (K. pneumoniae, S. dysenteriae, and E. coli) and 0.31 mg/mL for fungi (C. albicans and T. mentagrophytes).

Nymphaea nouchali petal extract (NPE) also harbors strong antimicrobial activity against food pathogens, with negligible toxicity recorded in different model systems. NPE proved to be a promising source of nutraceuticals with no toxicological consequences.

Evidence strength: Antimicrobial data are entirely in vitro. No clinical trials for infectious disease indications have been reported.

4.7 Immunomodulatory and Antipyretic Activity

Pre-treatment with nymphayol (50 mg/kg, oral) evoked a significant increase in neutrophil adhesion to nylon fibers. The augmentation of humoral immune response to sheep red blood cells by nymphayol (50 mg/kg) was evidenced by an increase in antibody titers in rats.

Immunomodulatory activity was assessed by neutrophil adhesion test, humoral response to sheep red blood cells, delayed-type hypersensitivity, phagocytic activity, and cyclophosphamide-induced myelosuppression. Antipyretic activity was evaluated by yeast-induced hyperthermia in rats.

Evidence strength: Immunomodulatory and antipyretic evidence is preclinical (animal models). No human clinical evidence exists.

4.8 Anticancer / Antiproliferative Activity

One study investigated bioactive phytochemicals and antioxidant activities of Nymphaea nouchali and explored its anticancer pathways by a network pharmacology approach. Using HPLC-DAD, bioactive phytochemicals were quantified in the methanolic extract of the tuber. Anticancer-associated pathways were analyzed and hub genes in the protein-protein interaction network of predicted genes were identified.

Ethanolic extracts of rhizome peel and inner core were more effective against the MCF-7 (breast cancer) cell line than methanol and acetone extracts, with IC₅₀ values of 208.20 µg/mL and 136.16 µg/mL for peel and inner core ethanol extracts, respectively. N. nouchali rhizome was suggested as a potential candidate for developing novel anticancer phytoformulations.

A novel Ca²⁺-dependent lectin has been identified from N. nouchali tuber and exhibits potential antiproliferative activity.

Initial investigations suggested possible anticancer effects on some cell lines; nevertheless, further study is required.

Evidence strength: Anticancer evidence is entirely preliminary, consisting of in vitro cell-line experiments and computational (network pharmacology / in silico) analyses. No animal tumor models or clinical studies have been reported for this indication.

5. Body Systems and Health Areas of Association

Scientific investigation has revealed that N. nouchali exhibits a vast range of pharmacological actions, namely antihyperglycemic, antioxidant, antimicrobial, analgesic, anti-inflammatory, antipyretic, antitumor, hepatoprotective, antiulcer, anthelmintic, antinociceptive, and immunomodulatory activities. Based on the available literature, the following body systems are associated with its use:

• Endocrine / Metabolic system: Antidiabetic, antihyperglycemic, and antihyperlipidemic actions investigated across multiple plant parts.
• Hepatic system: Hepatoprotective properties studied against chemical-induced liver damage in animal models.
• Gastrointestinal system: Antiulcer activity of isolated nymphayol; seeds traditionally used as stomachic.
• Immune system: Immunomodulatory effects of nymphayol in preclinical models.
• Musculoskeletal / Nociceptive system: Anti-inflammatory and analgesic properties studied in rodent pain and edema models.
• Reproductive system: Traditional use as an aphrodisiac (vajikarana) and for menstrual disorders (menorrhagia, blenorrhagia).
• Urinary system: Traditional use for urinary tract disorders.
• Cellular / Oxidative stress: DNA-protective and antioxidant activity via Nrf2/HO-1/MAPK signaling pathways.
• Antimicrobial: Activity against a range of bacterial and fungal pathogens demonstrated in vitro.

6. Dosage Forms and Dosages Reported in Studies

All dosages cited below are from preclinical (animal and in vitro) studies only. No standardized human dosages have been established in the peer-reviewed literature.

• Nymphayol (isolated sterol), oral, rat: 20 mg/kg body weight in streptozotocin-induced diabetic rats, administered for 45 days, for antidiabetic activity.
• Nymphayol, oral, rat: 50 mg/kg body weight for immunomodulatory (neutrophil adhesion) activity.
• Nymphayol (NYM), oral, rat: 45 mg/kg body weight for gastroprotective (antiulcer) activity in an ethanol-induced ulcer model.
• N. nouchali seed hydroalcohol extract, oral, rat: 100 and 200 mg/kg body weight for 21 days in STZ-induced diabetic rats; metformin was used as reference at 250 mg/kg.
• Methanol extract of N. nouchali flower (MENN), oral: 200 mg/kg and 400 mg/kg in antinociceptive studies (acetic acid-induced writhing and tail immersion test).
• Nymphayol, acute toxicity study, rat: Doses of 10, 20, 40, 80, 160, and 320 mg/kg body weight were administered orally in 0.5% carboxymethyl cellulose for 7 days to determine acute toxicity.

7. Safety Considerations

7.1 In Vitro and Preclinical Toxicology

In a cell-based study using RAW 264.7 macrophages, N. nouchali flower extract was able to prevent DNA damage and quench cellular ROS generation with no signs of toxicity. Similarly, the leaf extract prevented DNA damage and quenched t-BHP-induced ROS generation without showing toxicity in the same cell model.

Nymphaea nouchali petal extract exhibited strong antimicrobial activity against food pathogens with negligible toxicity recorded in different model systems, and the authors concluded that NPE is a promising source of nutraceuticals with no toxicological consequences in the systems tested.

7.2 Acute Toxicity Studies

In an acute toxicity study of nymphayol in Wistar rats, different doses (10, 20, 40, 80, 160, and 320 mg/kg body weight) were administered orally in 0.5% carboxymethyl cellulose for 7 days. Behavioral changes observed included abnormal locomotion, respiratory distress, uncoordinated muscle movements, weight loss, and mortality.

Subchronic toxicity studies in animals show some dose-dependent changes in biochemical parameters, but generally no severe organ damage.

7.3 Absence of Human Safety Data

Safety data for consumption of Nymphaea nouchali are limited, primarily derived from historical use, small animal studies, and case reports. Although traditional medicinal usage supports its therapeutic benefits, further preclinical and clinical investigations are necessary to validate its efficacy and safety for pharmaceutical uses.

7.4 Taxonomic Overlap with N. nouchali var. caerulea

A variety of N. nouchali — var. caerulea (the Egyptian blue lily / blue lotus) — has received separate attention regarding psychoactive alkaloid content. Despite containing alkaloids such as nuciferine and apomorphine, which can influence dopamine pathways and produce mild sedative or euphoric effects in animal models, authentic samples of Nymphaea nouchali var. caerulea often show very low or absent levels of key psychoactive alkaloids. Case series for that variety have reported acute toxicity from ingestion or inhalation including altered mental status, hallucinations, seizures, and transient electrolyte imbalances such as hypokalemia and metabolic acidosis, though renal function remained normal in reported cases. These reports pertain specifically to the caerulea variety and are distinct from the mainstream pharmacological literature on N. nouchali used in Ayurveda and Siddha.

7.5 Overall Evidence Gap

Taking into account the magnitude of its traditional uses, the studies conducted are still negligible. The large body of traditional use has not yet been matched by a proportionate number of rigorously conducted scientific studies. No randomized controlled trials, systematic reviews of clinical data, or pharmacokinetic studies in humans have been published as of the available literature, and no regulatory health body (such as the WHO, EMA, or NCCIH) has issued a formal monograph or safety/efficacy assessment for Nymphaea nouchali as a dietary supplement.

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