Less known facts about Excipients: Tragacanth

This article is part of the “Less Known Facts About Excipients” series by Philippe Tschopp.

Tragacanth: A natural gelling and sustaining agent

Tragacanth is one of the oldest pharmaceutical excipients still recognized in modern pharmacopeias. Used for more than 2,000 years, it remains a remarkable example of how natural polymers continue to find applications in pharmaceutical formulations.

Unlike many plant-derived excipients obtained from seeds or fruits, tragacanth is a natural gum exuded from the stems and branches of shrubs belonging to the genus Astragalus. The gum is produced by the plant as a natural response to injury, forming a protective barrier that hardens upon exposure to air.¹–³

Today, tragacanth is valued for its exceptional viscosity, stability and emulsifying properties, particularly in semi-solid and liquid formulations.

How is pharmaceutical tragacanth produced?

The production process consists of several carefully controlled steps:

1. Tapping Small incisions are made in the stems or branches of mature Astragalus shrubs growing in arid and mountainous regions, primarily in Iran and parts of Turkey.
2. Natural Exudation The gum slowly exudes from the cuts and hardens naturally into ribbon-like or flake-like pieces over several days.
3. Harvesting The dried gum is collected by hand and sorted according to appearance, colour and purity.
4. Cleaning and Milling Pharmaceutical-grade tragacanth is cleaned, milled and tested to comply with pharmacopeial specifications before use.¹–⁵

What makes tragacanth unique?

Tragacanth is composed primarily of two naturally occurring polysaccharide fractions:

• Tragacanthin, a water-soluble polysaccharide.
• Bassorin, a water-insoluble polysaccharide that swells extensively in water.

Together, these two fractions produce one of the most stable natural hydrocolloids available.¹,⁶

Its most valuable pharmaceutical properties include:

• Extremely high viscosity at low concentrations
• Excellent suspension stability
• Strong emulsifying capacity
• High swelling ability
• Good film-forming properties
• Stability over a broad pH range

Unlike many other natural gums, tragacanth forms highly stable viscous dispersions that resist separation during storage.

Pharmaceutical applications

Pharmaceutical-grade tragacanth is used in:

• Oral suspensions
• Emulsions
• Topical gels
• Creams
• Ointments
• Tablet binders
• Lozenges
• Controlled-release formulations¹,²

Its primary functions include:

• Suspending agent
• Thickening agent
• Emulsifier
• Binder
• Stabilizer
• Gelling agent

Considerations for formulators

As a natural botanical product, tragacanth exhibits variability depending on the Astragalus species, geographical origin and harvesting conditions. Pharmaceutical manufacturers therefore apply rigorous quality control to ensure compliance with pharmacopeial requirements.

Although tragacanth has largely been replaced by synthetic polymers and microbial gums such as xanthan gum in many modern formulations, it remains valued where exceptional viscosity, natural origin or historical use are desired.¹–⁴

Major pharmaceutical manufacturers

Examples of established manufacturers and suppliers include:

• Arthur Branwell & Co. Ltd.
• Hawkins Watts Ltd.
• TIC Gums (Ingredion)
• Alfa Chemistry
• Merck (analytical and pharmaceutical grades)

Did you know?

More than 2,000 species of Astragalus exist, but only a relatively small number produce tragacanth gum of pharmaceutical quality.

Iran has traditionally been the world’s largest producer, supplying the majority of pharmaceutical-grade tragacanth for decades due to its ideal climate and the abundance of suitable Astragalus species.

By Philippe Tschopp
Philippe Tschopp writes about pharmaceutical excipients, formulation and oral drug delivery, with a focus on excipient functionality, practical formulation considerations and lesser-known material properties.

Source:

1. Rowe RC, Sheskey PJ, Quinn ME (Eds.). Handbook of Pharmaceutical Excipients. Pharmaceutical Press / American Pharmacists Association.
2. European Pharmacopoeia (Ph. Eur.). Monograph: Tragacanth.
3. United States Pharmacopeia–National Formulary (USP–NF). Monograph: Tragacanth.
4. FAO. Compendium of Food Additive Specifications – Tragacanth.
5. Arthur Branwell & Co. Ltd. Technical documentation for pharmaceutical tragacanth.
6. Whistler RL, BeMiller JN (Eds.). Industrial Gums: Polysaccharides and Their Derivatives. Chapter on Tragacanth.

Disclaimer

This article is based on publicly available information and industry sources at the time of writing and supported by AI. While every effort has been made to ensure accuracy, completeness, and fair representation, the author does not guarantee that all information is current, error-free, or reflective of the latest developments.

The content is provided for informational and educational purposes only and does not constitute technical, regulatory, or commercial advice. No liability is accepted for decisions made based on this material. Readers are encouraged to consult the original manufacturers and official sources to verify details before making professional or business decisions.

Read also the other article from the series “Less known facts about…” here:

• Pullulan – Less known facts about: Pullulan
• Carnauba Wax – Less known facts about: Carnauba Wax
• Gum Arabic – Less known facts about: Gum Arabic
• Calcium Carbonate – Less known facts about: Calcium Carbonate
• Magnesium Stearate – Less known facts about Excipients: Magnesium Stearate