Neem

Azadirachta indica

MeliaceaeIndian subcontinent (India, Pakistan, Bangladesh, Sri Lanka, Nepal, Myanmar); widely naturalized in tropical Africa, Middle East, Australia, and Central America

Description

overall appearance

Medium to large evergreen tree reaching 15–20 m in height with a spreading, rounded crown 10–20 m in diameter; trunk 30–80 cm in diameter; heavy shade producer. One of the most important medicinal trees in Asia and Africa, described in Sanskrit texts as 'Sarva Roga Nivarini' (the universal healer).

roots

Deep taproot system enabling drought survival; roots extend far below the water table; bark is light brown to gray, fibrous and bitter; medicinally active

stem

Stout trunk with thick, rough, deeply furrowed, grayish-brown bark; exudes bitter aromatic gum; wood is hard, heavy, and rot-resistant

leaves

Pinnately compound, alternate, 20–40 cm long with 8–18 pairs of leaflets; leaflets lanceolate, 3–8 cm long and 1–3 cm wide; serrate (toothed) margins; slightly asymmetric at base; dark shiny green; extremely bitter taste due to limonoids

flowers

Small, white, 5-petaled, highly fragrant flowers 5–6 mm across in axillary panicles 10–20 cm long; produced in profusion; honey bee source

fruits/seeds

Olive-like drupe 1–2 cm long and 1 cm in diameter; fleshy yellow-green pulp around hard seed; 1 seed per fruit; seed kernel yields neem oil (30–50% oil content)

Active Compounds

Tetranortriterpenoid limonoids: azadirachtin A and B (primary bioactive/insecticidal), nimbin, nimbinin, nimbidinin, nimbolideTerpenoids: gedunin, nimbolide (anticancer), epoxyazadiradioneTetranortriterpenoids: salannin, melandriolSulphurous compounds: nimbicidinPolyphenols: quercetin, kaempferol, gallic acid, catechin, epicatechinFatty acids in seed oil: oleic acid (50–60%), palmitic acid, stearic acidAlkaloids: nimbidin, margosineSterols: β-sitosterol, stigmasterol, campesterol

Traditional Uses

Ayurveda: Nimba — broad anti-infective, antiparasitic, and anti-inflammatory; one of the most widely used plants in classical Ayurvedic texts
Oral hygiene: neem twigs (datun) used as natural toothbrush across South Asia and Africa; antimicrobial against Streptococcus mutans and periodontal pathogens
Ayurvedic treatment for skin diseases including eczema, psoriasis, ringworm, and scabies
Traditional malaria treatment in sub-Saharan Africa and India; leaf decoction for fever reduction
Agricultural pesticide: azadirachtin is widely used as natural insecticide; traditional use of neem leaves to protect stored grain
Contraceptive: seed oil used vaginally as spermicide in Indian folk medicine; research confirms significant spermicidal activity
Ayurvedic blood purifier and liver tonic for chronic fevers, skin conditions, and detoxification
Traditional wound and ulcer treatment: neem leaf poultice applied to boils, abscesses, and non-healing wounds

Modern Applications

Antibacterial: leaf and bark extracts active against MRSA, E. coli, Salmonella, H. pylori; nimbolide particularly potent
Antifungal: neem oil effective against Candida albicans, Aspergillus, and dermatophytes in clinical and in vitro studies
Antidiabetic: nimbolide and gedunin inhibit α-glucosidase; leaf extract reduces blood glucose 30% in alloxan-diabetic rats
Anticancer: nimbolide induces apoptosis and inhibits proliferation in multiple cancer cell lines (breast, colon, prostate) via Akt/mTOR and Nrf2 pathways
Anti-inflammatory: nimbidin inhibits COX-2 and 5-LOX; comparable to hydrocortisone in carrageenan edema model
Oral health: RCTs confirm neem mouthwash equivalent to 0.2% chlorhexidine for reducing plaque and gingivitis scores
Spermicide/contraceptive: 100% spermicidal activity at 1 mg/mL neem oil in vitro; Phase II trial showed vaginal suppository effective at preventing pregnancy in women
Immunomodulation: polysaccharides stimulate macrophage and T-cell activity; potential adjuvant in malaria and cancer therapy

⚠️ Safety Information

Contraindications

Pregnancy: uterine-stimulating and abortifacient activity; strictly contraindicated in all trimesters
Infants and young children: neem oil ingestion linked to Reye-like syndrome with hepatotoxicity and encephalopathy; do not use internally in children
Autoimmune conditions: immunostimulant activity may exacerbate autoimmune diseases (lupus, MS, RA)
Organ transplant patients: immunostimulation may precipitate rejection; contraindicated with immunosuppressants

Side Effects

Hepatotoxicity with high-dose or prolonged internal use of neem oil; case reports of liver failure in children
Nausea, vomiting, and gastric irritation with oral leaf/bark preparations
Contact dermatitis with topical neem oil in sensitive individuals
Sperm motility reduction with long-term oral leaf consumption in men (reversible)

Drug Interactions

Immunosuppressants (cyclosporine, azathioprine, corticosteroids): immunostimulant activity may reduce efficacy
Antidiabetics (insulin, metformin): additive hypoglycemic risk; monitor blood glucose
Lithium: neem diuretic effects may increase lithium renal clearance; monitor lithium levels
Hepatotoxic drugs (isoniazid, acetaminophen, methotrexate): additive hepatotoxicity risk