Structural analysis of pentacyclic triterpenes from the gum resin of Boswellia serrata by NMR spectroscopy

Abstract

3a-Acetyl-b-boswellic acid (1), 3a-acetyl-a-boswellic acid (2), 3a-acetyl-9,11-dehydro-b-boswellic acid (3), 3a-acetyl-9,11-dehydro-a-boswellic acid (4) and 3a-acetyl-11-keto-b-boswellic acid (5) were isolated from the gum resin of Boswellia serrata. 1D and 2D NMR (COSY45, HMQC, HMBC, ROESY) spectra at 500 MHz were used for shift assignments and structure verification. All boswellic acids investigated share the cis conformation at ring D/E and the 3a orientation of the acetyl ester group. Owing to high-order spectra, NMR could not determine the exact conformation of H-20/H-30 of the b-boswellic acids. 3a-Acetyl-b-boswellic acid methyl ester (1 ) was synthesized for experiments with a shift reagent, Eu(fod) 3 , that enhanced the resolution considerably. The oxygen atoms of the 3a-acetyl group form the apparent complex binding site for the shift reagent.

A Novel Semisynthetic Inhibitor of the FRB Domain of Mammalian Target of Rapamycin Blocks Proliferation and Triggers Apoptosis in Chemoresistant Prostate Cancer Cells

“…AKbBA was isolated from the oleogum resin of African frankincense (B. carterii) and purified to chemical homogeneity (.99.5% purity) by reversed-phase HPLC (Belsner et al, 2003;Büchele and Simmet, 2003). For the chemical characterization of the starting compound AKbBA, see the Supplemental Material.…”

Antiinflammatory and Antiatherogenic Effects of the NF-κB Inhibitor Acetyl-11-Keto-β-Boswellic Acid in LPS-Challenged ApoE −/− Mice

“…17 The compound was further characterized by mass spectrometry and 1-and 2-dimensional nuclear magnetic resonance spectroscopy. 17 For the application of AK␤BA in animals we developed a hydrophilic derivative by generating ␥-cyclodextrin complexes that allowed administration of the lipophilic compound in aqueous solutions in vivo. 16 …”

Acetyl-Boswellic Acids Inhibit Lipopolysaccharide-Mediated TNF-α Induction in Monocytes by Direct Interaction with IκB Kinases

“…A␣BA and AK␤BA were isolated from African frankincense, purified by reverse-phase HPLC to chemical homogeneity (i.e., Ͼ99% purity), and characterized by mass spectrometry and one-and two-dimensional nuclear magnetic resonance spectroscopy (14,15,18). The compounds were dissolved in DMSO, and controls contained equivalent amounts of solvent.…”

“…Such extracts, which are marketed in the United States, have already been used in small clinical pilot studies for the treatment of rheumatoid arthritis and inflammatory bowel diseases (10 -13). After purification to chemical homogeneity, we have previously characterized the structural configuration of acetyl-boswellic acids (ABAs) 3 belonging to the family of pentacyclic triterpenes (14,15); these compounds are believed toMonocytes and macrophages represent essential effector cells in both chronic inflammation and in the host defense against bacterial infection. Using LPS as a potent activator of human monocytes, we found that acetyl-␣-boswellic acid (A␣BA) and acetyl-11-keto-␤-boswellic acid (AK␤BA) inhibit NF-B signaling.…”