Nimbin

CAS Number	5945-86-8 (live-verified; independent registry confirmation)
Molecular Formula / MW	C30H36O9 / 540.6 g/mol
Chemical Class	Tetranortriterpenoid (limonoid) — one of 400+ compounds isolated from neem
Botanical Source	Azadirachta indica (neem; nimba)
Plant Part(s)	Leaf, bark, seed (nimbin concentrates in seed oil)
Typical Standardisation	Nimbin by HPLC; 1% commercial grade. Azadirachtin is a separate limonoid marker
Claim Strength (Overview)	Emerging — the neem limonoid family carries a documented antifertility and spermicidal signal that governs use
Buy from Herbuno	Nimbin 1% Powder (Neem Extract) | Standardized Azadirachta indica → Azadirachtin 3% Powder (Neem Extract) | Standardized Azadirachta indica →

Name origin: Nimbin is named for nimba, the Sanskrit and Hindi name for the neem tree. It was among the first neem limonoids isolated — early chemical work reported nimbin, nimbidin, and nimbinin from the oil — and it is a tetranortriterpenoid, a structural class characteristic of the Meliaceae. More than 400 compounds have now been isolated from neem, which is why any single-marker specification for this plant conveys less than buyers assume. Traditional use: Neem is arguably the most extensively used medicinal tree in the Indian subcontinent, applied for skin disease, wounds, fever, dental care, and pest control, and treated in Ayurveda as a premier bitter and blood-purifying drug. Its insecticidal use is ancient and remains its largest commercial application globally. Safety context: This page leads with safety because neem carries a substantial and long-documented antifertility and spermicidal signal that any formulator must confront. Neem oil and leaf extracts have been shown to immobilise and kill human spermatozoa in vitro, neem oil has been used experimentally as an intravaginal contraceptive in animals and humans, and reversible male antifertility activity has been reported for neem leaf. This is not a theoretical concern derived from a single paper. Commercial source: Azadirachta indica extract standardized to nimbin; note that nimbin and azadirachtin are separate limonoid markers standardised independently.

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Evidence for Nimbin Applications

The reproductive-toxicity signal for neem is the governing fact for any ingestible application and must be reported plainly. In a study of male Wistar rats of proven fertility, a single 50-microlitre dose of neem oil administered into the lumen of the vas deferens on each side left every treated male infertile throughout an eight-month observation period, while controls impregnated their partners normally; the effect was a block of spermatogenesis without any change in testosterone production and without inflammatory or obstructive histological change (Upadhyay 1993). Eight months of total infertility from a single dose, explicitly framed by the authors as an alternative approach to vasectomy, is not a marginal finding. Claim strength: Moderate (adverse/antifertility).

The signal extends beyond sperm to oocyte quality, and to oral rather than merely local administration. Work examining neem leaf extract in mammals reported deterioration of oocyte quality by inducing ROS-mediated apoptosis (Chaube 2014). Separately, ethanol extract of neem stem bark given to male rats for ten weeks produced dose-dependent decreases in testis, epididymis and seminal vesicle weights, adversely affected sperm count, morphology and viability, and reduced serum testosterone and LH — with rats at the highest dose unable to impregnate females at all, though fertility returned about four weeks after treatment ceased. A compound with documented effects on both male and female gametes is not one to formulate casually into a general-population ingestible, and this page will not soften that. Claim strength: Moderate (adverse).

Nimbin itself sits within a very large limonoid family, and the attribution question is genuinely unresolved. The bioactive neem limonoids include azadirachtin, nimbidin, nimbin, nimbolide, and gedunin, among more than 400 isolated compounds, and the various pharmacological activities attributed to "neem" are distributed unevenly and often unclearly across them. Notably, the classic antifertility work implicated nimbidin (as sodium nimbidinate) and the volatile neem-oil fraction rather than nimbin specifically — a distinction worth preserving intellectually, though it offers no practical reassurance for a whole-extract product. Claim strength: Moderate (compositional).

Nimbin and azadirachtin are separate markers with separate specifications, and this is a commercially consequential distinction. Azadirachtin is the principal insecticidal limonoid and is the compound driving neem’s enormous agricultural market; nimbin is a distinct limonoid with a different (and less well characterised) pharmacological profile. A "nimbin 1%" extract and an "azadirachtin 3%" extract are different products for different applications, and a buyer specifying one should not accept the other. Claim strength: High (compositional fact).

The defensible commercial applications for neem-derived material are, in this index’s reading, agricultural (azadirachtin-driven biopesticide), topical/cosmetic (where the antifertility concern does not apply and the antimicrobial and anti-acne literature is more supportive), and oral care. The neem limonoids have documented anti-inflammatory, antimicrobial, antimalarial, and antiproliferative activity, and nimbolide and azadirachtin have shown antiproliferative and apoptotic effects in an animal model of oral oncogenesis. But these preclinical findings do not offset the reproductive signal for an ingested product. Claim strength: Emerging.

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Dosage & Formulator Specification

Herbuno carries Azadirachta indica extract standardized to 1% nimbin and to 3% and 1% azadirachtin, alongside neem leaf extract powder, organic neem leaf powder, dehydrated neem flower, and water-soluble extracts of neem leaf, bark, and seed. Buyers should note that nimbin and azadirachtin are independently standardised markers and are not interchangeable specifications.

Herbuno does not provide oral serving-size guidance for neem-standardized material, and the reason is the reproductive-toxicity signal documented above rather than an absence of tradition — neem has been consumed traditionally for centuries, but traditional use is not a safety dataset, and the modern experimental record on spermicidal and antifertility activity is substantial. For topical, cosmetic, oral-care, and agricultural applications — where the reproductive concern does not apply — use levels should be set against the assayed marker (nimbin or azadirachtin as appropriate) and against the intended functional endpoint.

Analytical verification should specify nimbin by HPLC separately from azadirachtin, since the two are independent markers and a supplier quoting one is telling the buyer nothing about the other. Plant part should be documented: the limonoid profile of leaf, bark, and seed differ substantially, and nimbin concentrates in seed oil. Azadirachtin is notably unstable to light, heat, and alkaline pH, so for azadirachtin-standardized material, stability data across the intended shelf life — not merely a release assay — is a reasonable requirement.

Neem’s safety profile is dominated by the reproductive signal detailed above: documented spermicidal activity against human spermatozoa, antifertility activity in male and female animal models, and reported deterioration of oocyte quality. Any ingestible neem product requires clear contraindication in pregnancy and in anyone of reproductive intent. A second, separate and serious caution: neem oil ingestion has been associated with severe toxicity in infants and young children, including encephalopathy and metabolic acidosis, and neem oil must not be administered to children. Neem leaf products may also lower blood glucose, warranting caution alongside antidiabetic medication.

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Frequently Asked Questions — Nimbin

Is neem safe to take orally?
The reproductive-toxicity signal is substantial and must be confronted. Neem leaf extract has been shown to immobilise and kill 100% of human spermatozoa within 20 seconds in vitro; neem oil has been used experimentally as a contraceptive; and neem leaf extract has been reported to deteriorate oocyte quality via ROS-mediated apoptosis. Ingestible neem requires clear contraindication in pregnancy and for anyone of reproductive intent.

Is nimbin the same as azadirachtin?
No. They are separate limonoids, standardised independently. Azadirachtin is the principal insecticidal compound driving neem's large agricultural market; nimbin is a distinct limonoid with a different and less well characterised profile. A "nimbin 1%" and an "azadirachtin 3%" extract are different products, and a buyer specifying one should not accept the other.

Which neem applications are defensible?
Topical and cosmetic use (where the reproductive concern does not apply and the antimicrobial and anti-acne literature is more supportive), oral care, and agricultural biopesticide use driven by azadirachtin. The preclinical anti-inflammatory and antiproliferative findings are real, but they do not offset the reproductive signal for an ingested product.

Is there a specific danger for children?
Yes, and it is serious. Neem oil ingestion has been associated with severe toxicity in infants and young children, including encephalopathy and metabolic acidosis. Neem oil must not be administered to children. This is a distinct concern from the reproductive signal.

Related compounds: Curcumin, Berberine, Andrographolide, Bitter Diterpenoids

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Claim-strength scale – High = multiple human RCTs; Moderate = limited trials or strong preclinical convergence; Emerging = early-stage lab or animal data.

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