Scientific Name(s): Sterculia urens Roxb.
Common Name(s): Bassora tragacanth, Indian chestnut, Indian tragacanth, Kadaya, Kadira, Karaya, Katila, Kullo, Mucara, Sterculia
The majority of commercial karaya gum is obtained from S. urens, a soft-wood tree that grows to approximately 10 m. The small, yellow flowers bloom from February to March, and the tree bears a star-shaped fruit.1, 2
The plant is native to India and Pakistan, where it is found on the dry, rocky hills and plateaus and is cultivated for karaya production.3 All parts of the tree exude a soft gum when injured. Karaya gum is produced by charring or scarring the tree trunk and removing a piece of bark or by drilling holes into the trunk. The gum seeps from the scars and is collected, washed, dried, and then graded. A mature tree may yield 1 to 5 kg of gum per season.1, 3, 4
Karaya gum has been used commercially for approximately 100 years. Its use became widespread during the early 20th century, when it was used as an adulterant or as an alternative to tragacanth gum.3 However, experience indicated that karaya possessed certain physiochemical properties that made it more useful than tragacanth and less expensive. Traditionally, India has been the largest producer and exporter of karaya gum.3 The gum has been used in a variety of products, including cosmetics and lotions, and as a bulking agent.5 The fruit of the related Sterculia villosa has been used traditionally as an antidiabetic agent in India.6
Karaya gum is a complex, partially acetylated polysaccharide obtained as a calcium and magnesium salt. The polysaccharide component of karaya has a high molecular weight and is composed of galacturonic acid, beta-D-galactose, glucuronic acid, L-rhamnose, and other residues.1, 2
The quality of karaya gum depends on the thoroughness of impurity removal. Food-grade gum is usually a white to pinkish-gray powder with a slight vinegar odor from acetic acid released during storage.1 Pharmaceutical grades of karaya may be almost clear or translucent.2
Karaya gum is the least soluble of commercial plant exudates, but it absorbs water rapidly and swells to form viscous colloidal solutions even at low concentrations (1%).1 The swelling reaction of karaya gum is dependent upon the presence of acetyl groups in its structure. Deacetylation through alkali treatment results in a water soluble gum. When used in higher concentrations in water (up to 4%), karaya forms gels or pastes. Unlike other gums, karaya swells in 60% alcohol but remains insoluble in other organic solvents. Karaya may absorb up to 100 times its weight in water.1
The astringent bark, containing alpha cellulose, botulin, and tannin, has also been investigated.2, 7 Sesquiterpenoids possessing antiproliferative properties have been identified in the bark of the related Madagascan species Sterculia tavia.8
In addition, seeds of the karaya plant contain carbohydrates and lignoceric, linoleic, myrstic, oleic, palmitic, and stearic acids.7 Cerebroside chemicals, with antioxidant properties, and polysaccharides have been identified in the related species Sterculia lychnophora, that is used in traditional Chinese medicine,9, 10 whereas lectins have been identified in Serissa foetida seeds.11
Uses and Pharmacology
There are no clinical data regarding the use of extracts of Sterculia species for anti-inflammatory effects.
No clinical data exist regarding the use of karaya extracts for the management of dyslipidemia. Earlier preliminary studies suggested that gums may normalize blood sugar and plasma lipid levels.15
There are no recent animal data regarding the use of karaya gum as a laxative. Studies were conducted in dogs in the 1930s.16
Karaya gum particles absorb water and swell to 60 to 100 times their original volume, making it useful as a bulk laxative.1, 3, 17 Excessive doses as a laxative may cause diarrhea and, with inadequate water consumption, may result in bowel obstruction.18 Recent clinical data is lacking.
Karaya gum has also been used as an adhesive for dental fixtures. A protective coating of karaya gum applied to dentures has been shown to reduce bacterial adhesion by 98%.19
The gum has been used in ostomy care, as a base for transdermal delivery of medicines,20, 21 and as a carrier for poorly soluble medicines.22, 23 Similarly, the gum has been tested as a biosorbent of toxic heavy metal ions.24
Antiproliferative properties of the bark of the related Madagascan S. tavia plant have been described,8 whereas antioxidant properties have been identified in the related plant S. lychnophora, used in traditional Chinese medicine.9 Antimicrobial activity against human pathogens was demonstrated by lectins extracted from the seeds of S. foetida.11
No specific dosage of karaya gum preparations has been determined by clinical studies. Studies conducted in the 1980s used doses of 10 g/day.16
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented. Use with antiperistalsis agents (eg, loperamide) is unadvisable.1
A report published in 1989 found that widespread use of karaya gum throughout the United States and Europe was not associated with any clinically important adverse experiences.25 Aside from allergy,16 case reports of adverse reactions with the use of karaya gum are limited; however, excessive doses as a laxative may cause diarrhea and, with inadequate water consumption, may result in bowel obstruction.18
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