Nimbidin

Other Names

Bitter principle of neem oilC-seco meliacin (nimbidin-class)Nimbidic acidNimbidininNimbindinPrimary bitter principle of Azadirachta indicaSulphur-containing bitter amorphous principle of neem

Synopsis

Nimbidin: A Comprehensive Reference Article

1. Identity: Botanical Source, Chemical Names, and Forms

1.1 Botanical Source

Nimbidin is a naturally occurring bitter principle derived from Azadirachta indica A. Juss, the neem tree. Azadirachta indica, a member of the Meliaceae family, is commonly known as neem, and its different parts contain numerous types of ingredients including limonoids such as nimbin, nimbidin, and nimbinin with diverse pharmacological activities. The tree is native to India and is also cultivated in Nepal, Pakistan, Bangladesh, and Sri Lanka. Neem is a fast-growing tree that can reach a height of 15–20 m, and it is evergreen.

1.2 Chemical Identity and Classification

Nimbidin is a mixture of tetranortriterpenes and is the major active principle of the seed oil of Azadirachta indica A. Juss (Meliaceae). Nimbidin is the primary component of the bitter principles obtained when neem seeds are extracted with alcohol, and it occurs in sizable quantities — about 2 percent of the kernel. Nimbidin and its related neem compounds belong to a general class of natural products called triterpenes; more specifically, limonoids.

Nimbidin and its epimer nimbidinin are compounds of the same molecular weight but structurally different, making them difficult to isolate and identify using conventional methods. The CAS registry number for nimbidin is 1407-80-3. As a tetranortriterpene (limonoid), nimbidin shares structural kinship with other neem limonoids such as nimbin, nimbolide, azadirachtin, and gedunin, all of which are characterized by a highly oxygenated triterpenoid skeleton with the loss of four carbon atoms (hence "tetranor") relative to their triterpene precursors.

1.3 Distribution Across Plant Parts

The trunk bark of neem contains nimbn (0.04%), nimbinin (0.001%), nimbidin (0.4%), nimbosterol (0.03%), essential oil (0.02%), tannins (6.0%), the bitter principle margosine, and 6-desacetyl nimbinene. The leaves also contain a variety of active ingredients including sodium nimbinate, gedunin, salannin, quercetin, nimbin, nimbidin, and nimbidol. Nimbidin is also concentrated in the seed oil, where it was first identified and chemically characterized.

1.4 Historical Isolation and Characterization

Chemical investigations of neem were undertaken by Indian pharmaceutical chemists as early as 1919, but real chemical research originated in 1942 with the isolation of three active constituents: nimbin, nimbidin, and nimbinene. Nimbin was first isolated in 1942 by Salimuzzaman Siddiqui and his collaborators from the seeds of the neem tree through extraction of neem oil using solvent partitioning techniques, yielding a crystalline bitter principle; this marked the initial chemical fractionation of neem's bioactive components, with nimbin identified as one of three key compounds alongside nimbinin and nimbidin. Early characterization efforts in the 1940s and 1950s classified nimbin as a tetranortriterpenoid limonoid based on preliminary chemical analyses, including solubility tests and degradation studies that revealed its highly oxygenated triterpenoid skeleton, and these investigations laid the groundwork for understanding its relation to other meliaceous compounds.

1.5 Preparation and Common Forms

A tetranortriterpene alcohol has been isolated from the nimbidin fraction of the methanol extract of neem oil, illustrating that the nimbidin fraction itself is a complex mixture rather than a single pure molecule. In research settings, nimbidin is typically extracted from neem seed oil or bark using alcoholic (methanol or ethanol) solvents, then further purified by column chromatography. In traditional and commercial contexts, nimbidin is present in whole neem seed oil, standardized neem bark extracts, dried neem leaf powders and capsules, neem leaf decoctions, and neem-based toothpastes and mouth rinses. Isolated or highly purified nimbidin is primarily encountered in laboratory and preclinical research rather than as a standalone commercial supplement.

2. Traditional and Historical Use

2.1 Ayurveda

Since antiquity, neem has been renowned for healing. The earliest Sanskrit medical writings refer to the benefits of its fruits, seeds, oil, leaves, roots, and bark, each of which has long been used in the Indian Ayurveda and Unani systems of medicine. Over thousands of years, millions of Asians have used neem medicinally. It has been widely utilized in Ayurveda, Unani, and Homeopathic treatments and has gained significant attention in modern medicine.

In Ayurveda, neem is classed as tikta (bitter) and kashaya (astringent), cooling in nature, and is grouped with the Kapha- and Pitta-settling herbs. The Bhavaprakasha Nighantu places Nimba in the Guduchyadi Varga and describes it as Kushtaghna (for the skin), Kandughna (for itching), and Krimighna (against micro-organisms). Traditionally, neem leaves, flowers, seeds, fruits, roots, twigs, and bark have been used to treat fever, infection, skin conditions, and dental problems.

Practitioners of the Indian Ayurveda medicine system have been preparing neem in oral doses for malarial patients for centuries. Neem's antimalarial activity was reported in Ayurveda books as far back as 2000 B.C. (by Charaka) and 1500 B.C. (by Sushruta). Neem preparations are reportedly efficacious against a variety of skin diseases, septic sores, and infected burns. The leaves, applied in the form of poultices or decoctions, are also recommended for boils, ulcers, and eczema. The oil is used for skin diseases such as scrofula, indolent ulcers, and ringworm.

Classical Ayurvedic texts referenced neem extensively across its primary medicinal preparations. References to Azadirachta indica appear as early as 1000 BCE in the Charaka Samhita, where it is praised for its bitter rasa and cooling virya. Sushruta Samhita elaborates on neem's blood-purifying properties, recommending leaf decoctions for skin eruptions and wound care. Vagbhata's Astanga Hridaya mentions "Nimba swarasa" in formulations targeting kapha-pitta imbalance. While classical recipes used fresh juice or decoctions, medieval dravyaguna treatises gradually shifted toward more stable powdered and churn forms, reflecting both convenience and improved shelf-life.

2.2 Unani and Other Traditions

Neem, called "Arista" in Sanskrit meaning "reliever of sickness," often referred to as "the bitter gem," is one of the most celebrated plants in the Indian Traditional Healthcare system for its diverse medicinal properties. In places where the tree has been introduced in recent times, such as tropical America and Africa, it has also established a reputation as a useful cure for various ailments. The bitter constituent nimbidin, as part of the crude seed oil, has thus been encountered across multiple healing traditions wherever the neem tree has been cultivated or naturalized.

2.3 Traditional Preparations Containing Nimbidin

The most nimbidin-rich traditional preparations include:

Neem seed oil (Margosa oil): The primary source of nimbidin. Pressed or extracted from the kernel of neem seeds; historically administered for skin conditions, as a topical antiseptic, and — controversially — as an oral remedy in small doses for specific conditions.
Neem bark decoction: The trunk bark contains 0.4% nimbidin, making bark decoctions a significant traditional source of the compound. Such decoctions were used for fever, gastrointestinal ailments, and wound healing.
Neem leaf preparations: Leaf poultices, decoctions, and fresh-leaf pastes were the most common forms used for fevers, skin infections, and as a general antiseptic.
Sodium nimbidinate: A semi-synthetic salt form of nimbidin's cognate acid, investigated as a more soluble form for pharmacological study and with historically noted diuretic properties.

3. Key Constituents, Chemical Context, and Mechanisms of Action

3.1 Nimbidin in the Context of Neem's Phytochemistry

Neem contains a high concentration of antioxidants and other valuable active substances including azadirachtin, salannin, nimbidin, nimbolinin, nimbidol, nimbin, and quercetin, which are extracted from various plant parts. Other compounds that have biological activity include a number of salannin, nimbin, nimbinin, nimbidin, 6-desacetylnimbin, phenolic compounds, carotenoids, steroids, ketones, and others.

Neem's potent antibacterial, antifungal, and antiviral properties are due to its diverse array of phytochemicals, which include limonoids (azadirachtin, nimbin, nimbidin), flavonoids (quercetin, kaempferol), tannins, and triterpenoids. Nimbidin is distinguished from other neem limonoids by being the most abundant bitter principle in alcoholic extracts of the seed kernel, and it is the compound most closely associated with the anti-inflammatory, antiarthritic, and antiulcer activities of the seed oil fraction.

3.2 Anti-Inflammatory and Antiarthritic Mechanisms

The anti-inflammatory mechanism of nimbidin has been elucidated at multiple levels through preclinical research. Nimbidin is the major active principle of the seed oil of Azadirachta indica possessing potent anti-inflammatory and antiarthritic activities; the compound significantly inhibited some of the functions of macrophages and neutrophils relevant to the inflammatory response following both in vivo and in vitro exposure.

Oral administration of 5–25 mg/kg nimbidin to rats for 3 consecutive days significantly inhibited the migration of macrophages to their peritoneal cavities in response to inflammatory stimuli and also inhibited phagocytosis and phorbol-12-myristate-13-acetate (PMA)-stimulated respiratory burst in these cells; in vitro exposure of rat peritoneal macrophages to nimbidin also inhibited phagocytosis and PMA-stimulated respiratory burst.

Nimbidin also inhibited nitric oxide (NO) and prostaglandin E2 (PGE2) production in lipopolysaccharide (LPS)-stimulated macrophages. Probing the mechanism of NO inhibition revealed that nimbidin ameliorated the induction of inducible NO synthase (iNOS) without any inhibition in its catalytic activity. In addition, nimbidin also attenuated degranulation in neutrophils assessed in terms of release of beta-glucuronidase, myeloperoxidase, and lysozyme.

3.3 Antiulcer Mechanisms

The ulcer-healing properties of nimbidin from neem seeds are attributed to the stearic and palmitic acid components. Anti-ulcer effects are believed to be via inhibition of the proton pump, H⁺-K⁺-ATPase, to control secretion of hydrochloric acid and gastric mucus depletion, and to prevent oxidative mucosal damage. A significant antiulcer effect was observed with nimbidin in preventing acetylsalicylic acid-, indomethacin-, stress-, or serotonin-induced gastric lesions as well as histamine- or cysteamine-induced duodenal ulcers; nimbidin can also suppress basal as well as histamine- and carbachol-stimulated gastric acid output and may act as an antihistamine by blocking H2 receptors, thereby helping as an antiulcer agent.

3.4 Antimicrobial Mechanisms

The antimicrobial compounds in neem, including nimbidin, act by several mechanisms including disrupting microbial cell membranes, inhibiting vital metabolic enzymes, preventing biofilm formation, and inducing oxidative stress in pathogens. In vitro, nimbidin can completely inhibit the growth of Mycobacterium tuberculosis and was also found to be bactericidal.

3.5 Autonomic and Central Nervous System Effects

Nimbidin, the major bitter principle from oil of seeds of Azadirachta indica, was investigated for various pharmacological actions in a number of animal models. On the central nervous system it exhibited a moderate sedative effect; it did not show any significant cardiovascular effects in experimental animals. Autonomic pharmacological studies (in vitro) revealed pronounced anticholinergic, antihistaminic (H1-receptor), anti-5HT, and antinicotinic activities; however, in vivo tests did not show any anticholinergic or antihistaminic activity. Nimbidin possessed moderate diuretic activity and was found to be devoid of local anaesthetic and antiandrogenic effects in rodents.

4. Scientific Evidence by Area of Use

4.1 Anti-Inflammatory and Antiarthritic Activity

Evidence level: Preclinical (animal models); no controlled human clinical trials for isolated nimbidin.

Nimbidin, a compound isolated from the oil of seeds of Azadirachta indica, was screened in comparison with two standard anti-inflammatory agents — phenylbutazone (a non-steroidal agent) and prednisolone (a steroid) — against various experimental models of inflammation. It was found to significantly reduce acute paw oedema in rats induced by phlogistic agents, carrageenin and kaolin, and the test drug significantly suppressed the formalin-induced arthritis of the ankle joint and the fluid exudation in croton oil-induced granuloma in rats. This landmark 1981 study by Pillai and Santhakumari (Planta Medica, 43:59–63) remains a foundational reference for nimbidin's anti-inflammatory and antiarthritic properties.

The mechanistic work published in 2004 by Kaur, Sarwar Alam, and Athar in Phytotherapy Research (18:419–424) extended these findings at the cellular level: the study revealed that nimbidin significantly inhibited some of the functions of macrophages and neutrophils relevant to the inflammatory response following both in vivo and in vitro exposure. All anti-inflammatory evidence for isolated nimbidin is, however, derived from animal and in vitro models. No randomized controlled trials (RCTs) in human subjects with isolated nimbidin have been reported in the peer-reviewed literature.

4.2 Antiulcer and Gastroprotective Activity

Evidence level: Preclinical (animal models); limited clinical data for neem bark extract overall; no human RCTs for isolated nimbidin.

Azadirachta indica is known to have potent gastroprotective and antiulcer effects; reviews deal with the pharmacological and biochemical studies carried out regarding the antiulcer activities of neem extracts and their mechanism of action, including the inhibition of acid secretion; a comparison with ranitidine and omeprazole in some animal models has been included and clinical studies, where available, have also been incorporated along with a safety evaluation; neem bark extract has the potential for the development of novel medicines for the therapeutic control of gastric hyperacidity and ulcer.

Seminal animal model work by Pillai, Seshadri, and Santhakumari (Indian Journal of Medical Research, 1978, 68:169–175) demonstrated anti-gastric ulcer activity of nimbidin, followed by a 1984 Planta Medica study (50:143–146) examining effects on both acute and chronic gastro-duodenal ulcer models in experimental animals. These studies collectively showed that nimbidin could reduce ulcer index scores in multiple pharmacologically induced ulcer models in rats.

4.3 Antibacterial Activity

Evidence level: In vitro; limited in vivo animal data; no clinical trials for isolated nimbidin.

In vitro, nimbidin can completely inhibit the growth of Mycobacterium tuberculosis and was also found to be bactericidal. Broader antibacterial activity against various pathogens has been attributed to the limonoid-rich fractions of neem of which nimbidin is a component, though the specific contribution of isolated nimbidin versus other limonoids in complex extracts is difficult to disentangle from the available literature. All antibacterial evidence for nimbidin itself is from in vitro studies.

4.4 Antifungal Activity

Evidence level: In vitro; no clinical trials for isolated nimbidin.

Nimbidin demonstrated antifungal activity by inhibiting the growth of Tinea rubrum. Additional in vitro antifungal effects have been observed for neem-derived fractions enriched in nimbidin. No clinical antifungal trials for isolated nimbidin exist in the peer-reviewed literature.

4.5 Spermicidal Activity

Evidence level: Early human and animal data; further clinical development needed.

The spermicidal activity of nimbidin and nimbin was reported in rats and humans as early as 1959. Sharma and Saxena (Indian Journal of Medical Research, 47:322–324, 1959) published on the spermicidal action of sodium nimbinate, a salt related to nimbidin. Subsequent research developed the NIM-76 preparation — a neem oil fraction enriched in nimbidin and related compounds — as an intravaginal contraceptive. Efficacy of NIM-76, a spermicidal fraction from neem oil, was investigated for its antimicrobial action against certain bacteria, fungi, and poliovirus as compared to whole neem oil; the NIM-76 preparation showed stronger antimicrobial activity than whole neem oil; it inhibited growth of various pathogens including Escherichia coli and Klebsiella pneumoniae; NIM-76 also exhibited antifungal activity against Candida albicans and antiviral activity against poliovirus replication in Vero cell lines; it also protected mice from systemic candidiasis; this shows that NIM-76 has a potent broad-spectrum antimicrobial activity. This combined spermicidal and antimicrobial profile of nimbidin-containing neem oil fractions has been examined as a basis for potential contraceptive applications, though broad clinical development of isolated nimbidin as a spermicide has not been published as of the available literature.

4.6 Hypoglycemic Activity

Evidence level: Preclinical; one randomized clinical trial for neem leaf extract (not isolated nimbidin).

Oral administration of nimbidin demonstrated a significant hypoglycemic effect in fasting rabbits. Pillai and Santhakumari reported hypoglycemic activity of Melia azadirachta (neem) in the Indian Journal of Medical Research (74:931–933, 1981). At the clinical level, a double-blind, randomized, placebo-controlled study examined the effects of an aqueous extract of Azadirachta indica leaves and twigs in subjects with Type 2 diabetes mellitus. Twelve-week treatment with neem, at all dosages studied, significantly decreased postprandial blood sugar (PPBS) levels compared to placebo; some pre-clinical studies support this finding; however, no RCTs have been found in the literature for evaluating the antidiabetic effects of neem leaf extract specifically for isolated nimbidin. Many in vitro and in vivo studies have reported hypoglycemic activity of neem extracts made with different solvents. The hypoglycemic evidence for isolated nimbidin specifically remains preclinical.

4.7 Antipyretic Activity

Evidence level: Preclinical animal data.

Antipyretic activity has been reported and confirmed in nimbidin. David and Mediscope (1969) demonstrated that neem oil and nimbidin suppressed the secondary rise in temperature in animal models. These findings are supported by the broader observation that nimbidin and nimbin are key anti-inflammatory and antipyretic agents, and they contribute to anti-ulcer, analgesic, and antifungal activities. No human clinical trials specifically examining isolated nimbidin's antipyretic effects have been published.

4.8 Diuretic Activity

Evidence level: Early animal data; one early study in dogs.

Diuretic activity was also reported for sodium nimbidinate in dogs. The study by Bhide, Mehta, and Lewis (1958) in the Indian Journal of Pharmacology documented this diuretic action. No modern clinical trials have revisited this effect in humans.

4.9 Immunomodulatory Activity

Evidence level: Preclinical and mechanistic; no human RCTs for isolated nimbidin.

The immunomodulatory, antiviral, anti-ulcer, antioxidant, anti-inflammatory, antihyperglycemic, antifungal, and anti-carcinogenic properties of neem and its components are well known. The immunomodulatory effects attributed to nimbidin center on its capacity to suppress key functions of professional immune cells (macrophages and neutrophils) at the inflammatory interface, as described above under mechanisms of action. These are all preclinical findings.

4.10 Anticancer Activity

Evidence level: Preliminary in vitro and animal data for neem limonoids broadly; limited specific evidence for isolated nimbidin.

Neem exerts antitumor effects through modulation of several cellular processes; the anticancerous bioactive compounds from neem oil include several steroids and triterpenoids like nimbin, nimbinin, and others; azadirachtin and a range of limonoids stimulate cancer cell death via multiple mechanisms including the intrinsic pathway of apoptosis. While nimbidin is listed among the triterpenoid compounds in neem with potential relevance to antitumor activity, the most extensively studied neem limonoids for anticancer effects are nimbolide and azadirachtin. Specific human or animal studies attributing anticancer activity to isolated nimbidin are limited in the available literature.

5. Body Systems and Health Areas Associated with Nimbidin

Based on the peer-reviewed evidence reviewed above, nimbidin has been investigated in relation to the following body systems:

Gastrointestinal system: Antiulcer and gastroprotective effects; inhibition of gastric acid secretion and H2-receptor blockade; cytoprotection against chemically induced gastric and duodenal ulcers.
Immune system: Suppression of macrophage migration and phagocytosis; inhibition of neutrophil degranulation; reduction of iNOS expression and PGE2 production.
Musculoskeletal system: Anti-inflammatory activity in acute and chronic arthritis models; reduction of inflammatory oedema and granuloma formation.
Metabolic/Endocrine system: Hypoglycemic effects observed in animal models; relevance to blood glucose regulation.
Reproductive system: Spermicidal activity in both animal and early human studies.
Urinary system: Moderate diuretic effects (primarily as sodium nimbidinate, in dogs).
Integumentary/Dermatological system: As part of neem preparations, used for skin infections, ringworm, and eczema in traditional medicine.
Central nervous system: Moderate sedative effects in animal models.
Antimicrobial axis (multi-systemic): Activity against bacteria (M. tuberculosis), fungi (Tinea rubrum, Candida albicans), and viruses (poliovirus) in vitro.

6. Dosage Forms and Doses Reported in Studies

The following dosages are reported directly from the peer-reviewed literature and are presented solely as documentation of what was studied, not as recommendations.

Anti-inflammatory / macrophage suppression studies (oral, rats): Oral administration of 5–25 mg/kg nimbidin to rats for 3 consecutive days significantly inhibited the migration of macrophages to their peritoneal cavities in response to inflammatory stimuli.
Neem leaf extract clinical study (oral, humans, Type 2 diabetes): Twelve-week treatment with neem, at all dosages studied, significantly decreased postprandial blood sugar levels compared to placebo. This study used aqueous leaf extract standardized to specific doses; the dosing used 125 mg and 500 mg of neem leaf extract as reported in the original trial design.
In vitro cell-based studies: Nimbidin has been applied at varied concentrations to isolated macrophage and neutrophil preparations; specific in vitro concentrations were reported in the Kaur et al. (2004) Phytotherapy Research paper.
Gastroprotective animal studies: Nimbidin was administered to rat models of gastric ulceration, as reported by Pillai and Santhakumari (Planta Medica, 1984, 50:143–146), though specific mg/kg dose values from this study are not available in the abstracts reviewed.
Diuretic studies (dogs): Sodium nimbidinate was studied as reported by Bhide, Mehta, and Lewis (Indian Journal of Pharmacology, 1958), as a sodium salt form for improved solubility, with specific doses administered intravenously in dog models.

Standardized nimbidin-specific dosage guidelines have not been established by any major regulatory or monograph body (WHO, EMA, USP, or Pharmacopoeia). No therapeutic dose for isolated nimbidin in humans has been formally defined.

7. Safety Considerations and Known Interactions

7.1 Toxicity of Neem Oil and Nimbidin-Containing Preparations

Several cases of hepatotoxicity, neurodeficit, and renal tubular acidosis associated with margosa (neem seed oil) poisoning have been reported; the toxic effect of margosa oil has been attributed to the bitter constituents of this oil including nimbin, nimbidin, nimbinin, and nimbidol. Nimbidin, along with related bitter neem limonoids, is thus directly implicated in toxicological case reports involving neem oil ingestion.

Sinniah and Baskaran (1981) summarized 13 — including 2 fatal — poisoning cases due to neem seed (margosa) oil, a traditional remedy in India and Malaysia; 5 to 10 mL of the oil given orally to children against minor ailments caused vomiting, drowsiness, tachypnea with acidotic respiration, and polymorphonuclear leukocytosis, and encephalopathy developed within hours of ingestion.

Neem oil appears quite toxic by ingestion and can cause metabolic acidosis, seizures, kidney failure, encephalopathy, and severe brain swelling in infants and young children.

Oral adverse effects (from rare case reports) include vomiting, drowsiness, diarrhea, vision loss, toxicity to the nervous system, poisoning, seizures, and brain damage from swallowing neem oil.

7.2 Reproductive and Fertility Effects

For all neem preparations, reversible reproductive toxicity was evident in both male and female mammals upon subacute or chronic exposure; in female rats, neem oil disturbs the estrus cycle, resulting in higher abortive rates and reduced fertility. Neem oil is not recommended for use by pregnant women, women who are trying to conceive or are breastfeeding, and those under the age of 18. Given the established spermicidal properties of nimbidin-containing neem fractions, these reproductive safety concerns are directly relevant.

7.3 Hepatotoxic and Nephrotoxic Risk

Acute tubular necrosis is a major finding in neem oil toxicity, along with intravascular hemolysis, hepatic damage, and hypersensitivity reactions. The attribution of these effects partly to nimbidin-containing bitter fractions means that high or prolonged oral doses of nimbidin-rich preparations carry documented hepatotoxic and nephrotoxic risk.

7.4 Dose-Dependent Nature of Risk

The non-aqueous extracts of neem are perhaps the most toxic neem-based products, with an estimated safe dose of 0.002 and 12.5 µg/kg body weight per day; the unprocessed materials like seed oil and the aqueous extracts are less toxic. This gradient of toxicity is relevant because nimbidin is concentrated most heavily in alcoholic extracts and in the crude seed oil.

7.5 Pediatric Safety

Systemic ingestion of neem oil in the range of 5–30 mL in infants and 60 mL in adults has been established to cause neem poisoning resulting in neurological and psychotic symptoms. The particular vulnerability of infants and young children to neem oil (and by inference to nimbidin-rich fractions) is well-established in clinical case literature.

7.6 Potential Drug Interactions

No pharmacokinetic drug-drug interaction studies have been published for isolated nimbidin in humans. Based on its documented mechanisms — inhibition of iNOS, suppression of PGE2 and NO production, H2-receptor-blocking effects, and potential hypoglycemic activity — clinically relevant interactions can be anticipated but have not been formally characterized. The hypoglycemic effect of neem extracts, in which nimbidin is a contributing principle, suggests potential additive effects when combined with antidiabetic medications. Azadirachtin, nimbidiol, gedunin, and azadiradione have all shown anti-hyperglycemic activity, but toxicity is of concern with these bioactives.

7.7 Gastrointestinal Adverse Effects

One patient in each of the 125 mg and 500 mg neem extract groups in one clinical study reported mild gastrointestinal disturbances, which subsided with symptomatic treatment; none of the subjects discontinued the study due to adverse events; no incidence of hypoglycemia was reported by any of the subjects. At clinically studied doses of aqueous leaf extract, gastrointestinal tolerability appeared acceptable in this study, though the population was small.

8. Summary of Evidence Strength

The following represents an honest characterization of the evidence base for nimbidin:

Anti-inflammatory and antiarthritic effects: Well-established in animal models and in vitro; mechanisms are mechanistically defined (macrophage/neutrophil suppression, iNOS/PGE2 inhibition). No human RCTs for isolated nimbidin.
Antiulcer and gastroprotective effects: Solid preclinical data across multiple ulcer models in animals; mechanistic data support H⁺/K⁺-ATPase inhibition and H2-receptor blockade. No human RCTs for isolated nimbidin.
Antibacterial and antifungal effects: Demonstrated in vitro; no controlled clinical data for isolated nimbidin.
Spermicidal effects: Reported in early human and animal studies (since the 1950s); nimbidin-containing neem fractions (NIM-76) also investigated for combined contraceptive/antimicrobial use.
Hypoglycemic effects: Animal and in vitro data for isolated nimbidin; one RCT of neem leaf extract (not isolated nimbidin) showed significant PPBS reduction over 12 weeks.
Antipyretic, diuretic, CNS sedative effects: Preclinical animal data; no modern human clinical trials.
Safety: Nimbidin-containing bitter fractions of neem are associated with documented human toxicity cases at higher doses, particularly in children; hepatotoxic, nephrotoxic, neurological, and reproductive risks are supported by case reports and animal studies.

Overall: The scientific evidence for nimbidin's pharmacological activities is predominantly preclinical (animal models and in vitro studies). The extensive traditional use of neem across millennia and the mechanistic depth of preclinical research make nimbidin a compound of genuine pharmacological interest, but the near-complete absence of well-designed human clinical trials specifically for isolated nimbidin means that its therapeutic applications in humans remain unproven. Clinical research on neem extracts (not isolated nimbidin) provides limited but supportive evidence for some effects, particularly blood glucose regulation. The risk-benefit profile of orally ingested nimbidin-rich preparations in humans has not been systematically assessed in modern clinical contexts.

References

Health Conditions

Health conditions that Nimbidin may help support.

Parasite CleanseTraditional
Nimbidin is a key bioactive triterpenoid from neem (Azadirachta indica) used in traditional Ayurvedic and Indian medicine as an antiparasitic agent against helminths and protozoa. A US patent specifically names nimbidin among neem isolates employed as antiparasitic agents in India.

Body Systems

Body systems that Nimbidin may help support.

No body systems available.