Description and Constituents

Boswellia serrata is a moderate to large branching tree found in India, Northern Africa, and the Middle East. Strips of bark are peeled away, yielding a gummy oleo-resin which contains oils, terpenoids, and gum. Up to 16 percent of the resin is essential oil, the majority being alpha thujene and p-cymene. Four pentacyclic triterpene acids are also present, with ß-Boswellic acid being the major constituent. Extracts of this gummy exudate have been traditionally used in the Ayurvedic system of medicine as an anti-arthritic. These gum resins are also known as guggals. S. Nityanand et al showed the guggal of Commiphora mukul to be an effective hypolipidemic agent, but it does not have the anti-inflammatory action of the gum resin of Boswellia serrata.

Mechanism of Action

Animal studies performed in India showed ingestion of a defatted alcoholic extract of Boswellia decreased polymorphonuclear leukocyte infiltration and migration, decreased primary antibody synthesis,^1,2 and caused almost total inhibition of the classical complement pathway.³ In an in vitro study of the effects of ß-Boswellic acid on the complement system, the extract demonstrated a marked inhibitory effect on both the classical and alternate complement systems.⁴ An investigation of Boswellia's analgesic and psychopharmacologic effects noted that it "was found to exhibit marked sedative and analgesic effects" in these animals.⁵

In vitro testing revealed Boswellia specifically, and in a dose-dependent manner, blocks the synthesis of pro-inflammatory 5-lipoxygenase products, including 5-hydroxyeicosatetraenoic acid (5-HETE) and leukotriene B4 (LTB4),⁶ which cause bronchoconstriction, chemotaxis, and increased vascular permeability.⁷ Other anti-inflammatory plant constituents, such as quercetin, also block this enzyme, but they do so in a more general fashion, as an antioxidant; whereas, Boswellia seems to be a specific inhibitor of 5-lipoxygenase.^8,9 Boswellia has also been observed to inhibit human leukocyte elastase (HLE), which may be involved in the pathogenesis of emphysema. HLE also stimulates mucus secretion and thus may play a role in cystic fibrosis, chronic bronchitis, and acute respiratory distress syndrome.^10,11

It is known that non-steroidal anti-inflammatory drugs can cause a disruption of glycosaminoglycan synthesis which can accelerate the articular damage in arthritic conditions.^12-15 A recent in vivo study examined Boswellia extract and ketoprofen for their effects on glycosaminoglycan metabolism. Boswellia significantly reduced the degradation of glycosaminoglycans compared to controls, whereas ketoprofen caused a reduction in total tissue glycosaminoglycan content.¹⁶

Clinical Studies

Human clinical studies are woefully lacking for this substance, and need to be conducted to better elucidate its effects in humans, as well as to determine optimal dosing. Animal and in vitro studies suggest it is useful for many inflammatory and bronchoconstrictive conditions.

Leukotrienes are suggested to play a role in the inflammatory process of ulcerative colitis. Boswellia extract (350 mg three times daily) was compared to sulfasalazine (1 g three times daily) in ulcerative colitis patients. Patients on the Boswellia extract showed similar improvements as patients on sulfasalazine, although 82 percent of Boswellia patients went into remission, compared with 75 percent on sulfasalazine.¹⁷

Toxicity

Toxicity studies of Boswellia in rats and primates showed no pathological changes in hematological, biochemical, or histological parameters at doses of up to 1000 mg/kg. The LD50 was established at >2 g/kg.

References

1. Sharma ML, Khajuria A, Kaul A, et al. Effects of salai guggal extract of Boswellia serrata on cellular and humoral immune responses and leukocyte migration. Agents and Actions 1988;24(1-2):161-164.

2. Sharma ML, Bani S, Singh GB, et al. Anti-arthritic activity of boswellic acid in bovine serum albumin-induced arthritis. In J Immunopharmac 1989;6:647-652.

3. H. Wagner. Search for new plant constituents with potential antiphlogistic and antiallergic activity. Planta Medica 1989;55:235-241.

4. Knaus U, Wagner H. Effects of boswellic acid of Boswellia serrata and other triterpenic acids on the complement system. Phytomedicine 1996;3:77-81.

5. Menon MK, Karr A. Analgesic and psychopharmacological effects of the gum resin of Boswellia serrata. Planta Medica 1971;4:332-341.

6. Ammon HP, Mack T, Singh GB, Safayhi H. Inhibition of leukotriene B4 formation in rat peritoneal neutrophils by an ethanolic extract of the gum resin exudate of Boswellia serrata. Planta Medica 1991;57:203-207.

7. Robertson RP. Arachidonic acid metabolites relevant to medicine. In: Braunwald E, Isselbacher KJ, Petersdorf RG, et al, eds. Harrison's Principles of Internal Medicine. 11th ed. New York. McGraw-Hill;1987:375.

8. Safayhi H, Mack T, Sabieral J, et al. Boswellic acids: novel, specific nonredox inhibitors of 5-lipoxygenase. J Pharmac Exp Ther 1992;261:1143-1146.

9. Ammon HPT. Salai guggal ­ Boswellia serrata: from a herbal medicine to a specific inhibitor of leukotriene biosynthesis. Phytomedicine 1996;3:67-70.

10. Rall B, Ammon HPT, Safayhi H. Boswellic acids and protease activities. Phytomedicine 1996;3:75-76.

11. Safayhi H, Rall B, Sailer ER, Ammon HPT. Inhibition by Boswellc acids of human leukocyte elastase. J Pharmacol Exp Ther 1997;281:460-463.

12. Lee KH, Spencer MR. Studies on mechanism of action of salicylates V: Effect of salicylic acid on enzymes involved in mucopolysaccharide synthesis. J Pharmacol Sci 1969;58:464-468.

13. Palmowski MJ, Brandt KD. Effect of salicylate on proteoglycan metabolism in normal canine articular cartilage in vitro. Arthritis Rheum 1979;22:746-754.

14. Dekel S, Falconer J, Francis MJO. The effect of anti-inflammatory drugs on glycosaminoglycan sulphation in pig cartilage. Prostaglandins Med 1980;4:133-140.

15. Brandt KD, Palmoski MJ. Effect of salicylates and other non-steroidal anti-inflammatory drugs on articular cartilage. Am J Med 1984;77:65-69.

16. Reddy GK, Chandraksan G, Dhar SC. Studies on the metabolism of glycosaminoglycans under the influence of new herbal anti-inflammatory agents. Biochem Pharm 1989;38:3527-3534.

17. Gupta I, Parihar A, Malhotra P, et al. Effects of Boswellia serrata gum resin in patients with ulcerative colitis. Eur J Med Res 1997;2:37-43.