Boswellia serrata extract with low 3O-acetyl-11-keto-β-boswellic acid-content causes efficient lipid mediator class...

Extracts of the gum resin from Boswellia (B.) serrata Roxb. (Burseraceae), termed frankincense, are popular natural remedies for treatment of inflammatory disorders, and clinical trials confirm the anti-inflammatory efficacy, especially in osteoarthritis. The pentacyclic triterpenes boswellic acids are exclusive to frankincense, where 3-O-acetyl-11-keto-β-boswellic (AKBA) is considered as the main active principle. AKBA allosterically modulates lipoxygenases (LOX) in lipid mediator (LM) biosynthesis. This LOX modulation leads to suppression of pro-inflammatory leukotrienes while increasing formation of specialized pro-resolving mediators (SPM), a process called LM class switch that promotes inflammation resolution.

Here, we studied the role of AKBA in frankincense preparations for LM class-switching in human M1/M2 macrophage phenotypes by comparing the B. serrata extracts Boswellin® Super (BSR) and BoswelliaSan® (BOS), which contain 30 % and 3 % AKBA, respectively.

Concentration-response studies revealed only 2-fold increased effectiveness of BSR (30 % AKBA content) versus BOS (3 % AKBA content) for evoking 15-LOX product/SPM formation, and at doses corresponding to 10 µM AKBA each, BOS was much more efficient than BSR. This implies a limited role of AKBA and indicates additional active principles in BOS, supported by the finding that BOS corresponding to only 6 µM AKBA strongly exceeded the effects of 10 µM AKBA. Addition of BOS to AKBA-stimulated cells concentration-dependently increased 15-LOX product formation. Finally, exogenous omega-3 substrate supply synergizes with BOS in analogy to AKBA by marked elevation of SPM/15-LOX product levels.

B. serrata extracts promote a beneficial LM class switch in human macrophages, which might not be primarily attributed to AKBA, but to additional compounds.