WHO Monographs on Selected Medicinal Plants

The World Health Organization (WHO) publishes monographs that provide a scientific assessment of the quality, safety and efficacy of medicinal plants. These documents are intended to support the development of national pharmacopoeias, guide regulatory decisions and promote the rational use of traditional medicines. Below is an overview of several key WHO monographs, the plants they cover and the major conclusions drawn by the WHO expert committees.

Why WHO Monographs Matter

Traditional herbal medicines are used by billions of people worldwide. However, variability in botanical identification, harvesting practices, processing methods and dosage forms can lead to inconsistencies in therapeutic outcomes and safety concerns. WHO monographs address these gaps by:

• Providing a standard botanical description and nomenclature.
• Defining accepted quality specifications (e.g., moisture, ash, microbial limits).
• Summarising pharmacological and clinical evidence.
• Highlighting known toxicities, contraindications and drugherb interactions.
• Recommending dosing ranges and administration routes.

Selected Plant Monographs

1. Curcuma longa (Turmeric)

Botanical name: Curcuma longa L., family Zingiberaceae.

The WHO monograph on turmeric focuses on the rhizome, which contains curcuminoids (curcumin, demethoxycurcumin, bisdemethoxycurcumin). Key points include:

• Quality standards: Minimum curcuminoid content of 3% (w/w) for powdered material, maximum heavymetal limits (lead <10ppm, mercury <1ppm).
• Pharmacology: Antiinflammatory, antioxidant and mild analgesic activities demonstrated in animal models.
• Clinical evidence: Controlled trials suggest modest benefit for osteoarthritis pain when used at 500mg of standardized extract twice daily.
• Safety: Generally well tolerated; occasional gastrointestinal upset at high doses. Caution in patients on anticoagulants because of potential plateletaggregation inhibition.

2. Echinacea purpurea (Purple Coneflower)

Botanical name: Echinacea purpurea (L.) Moench, family Asteraceae.

The monograph evaluates both the aerial parts and root extracts. Highlights include:

• Quality parameters: Minimum alkylamide content 0.3% (w/w) for dried herb, limits for microbial contamination (total aerobic count <10CFU/g).
• Pharmacology: Immunomodulatory actions attributed to polysaccharides and caffeicacid derivatives, with invitro enhancement of phagocytosis.
• Clinical data: Metaanalysis of randomized trials indicates a reduction in the incidence of commoncold symptoms when taken prophylactically (dose 300mg of standardized extract daily).
• Safety considerations: Rare cases of allergic reactions, especially in individuals with ragweed allergy. Not recommended for autoimmune disease patients without physician guidance.

3. Ginkgo biloba (Ginkgo)

Botanical name: Ginkgo biloba L., family Ginkgoaceae.

The WHO monograph concentrates on leaf extracts, the part most commonly used for cognitive enhancement.

• Standardisation: Minimum 24% flavonoid glycosides and 6% terpene lactones (ginkgolides A, B, C and bilobalide) for dried extract.
• Evidence of efficacy: Systematic reviews show modest improvement in episodic memory in older adults at 120mg/day.
• Safety profile: Generally safe, but may increase bleeding risk; contraindicated with warfarin or other anticoagulants.
• Adverse effects: Headache, gastrointestinal discomfort, rare cases of allergic skin reactions.

4. Peppermint (Mentha piperita)

Botanical name: Mentha piperita L., family Lamiaceae.

The monograph deals with the essential oil and dried leaf, both used for gastrointestinal complaints.

• Quality markers: Menthol 40% (w/w) in oil; total volatile oil content 2% in dried herb.
• Therapeutic use: Effective in relieving symptoms of irritable bowel syndrome (IBS) especially abdominal pain and bloating when given as entericcoated capsules (0.2mL oil per capsule, 3capsules/day).
• Safety: Generally safe for adults; avoid in children <12years and in patients with severe GERD due to risk of reflux.

5. Andrographis paniculata (Kalmegh)

Botanical name: Andrographis paniculata (Burm.f.) Nees, family Acanthaceae.

This monograph focuses on the aerial parts, standardized to andrographolide content.

• Standardisation: Minimum 10% andrographolide (w/w) for dried herb.
• Clinical data: Randomized trials support its use for acute uncomplicated upperrespiratory infections, with a typical dose of 300mg of standardized extract three times daily.
• Safety: Well tolerated; occasional bitter taste and mild gastrointestinal upset. Contraindicated in pregnancy because of potential uterotonic effects.

How to Use WHO Monographs

Regulators, manufacturers and healthcare practitioners can apply the monographs in several ways:

1. Product development: Use the quality specifications as a basis for Good Agricultural and Collection Practices (GACP) and Good Manufacturing Practices (GMP).
2. Label claims: Align therapeutic indications with the evidence summaries to avoid overstated health claims.
3. Pharmacovigilance: Monitor the adverseevent data highlighted in the safety sections.
4. Education: Incorporate monograph content into curricula for pharmacists, physicians and traditionalmedicine practitioners.

Accessing the Full Monographs

All WHO monographs are freely available on the WHO website. The documents are provided in PDF format and can be downloaded without registration. For the most uptodate information, users should check the revision date listed at the beginning of each monograph.

Future Directions

The WHO continues to expand its library of monographs, with current priorities including:

• Plants used in emerging traditional systems (e.g., African traditional medicine, Indigenous Australian remedies).
• Standardisation of multiherb formulations, which present additional challenges for quality control.
• Incorporation of latest clinical trial data, especially largescale, doubleblind studies.

By providing a transparent, evidencebased framework, WHO monographs help bridge the gap between traditional knowledge and modern regulatory science, ultimately safeguarding public health while respecting cultural heritage.

Reference: World Health Organization. WHO Monographs on Selected Medicinal Plants. Geneva: WHO; latest editions 20222024.