Bioassay‑guided Isolation, Identification, and Evaluation of Anti‑inflammatory Activity of β‑Boswellic Alcohol and 3‑O‑Acetyl‑11‑hydroxy‑β‑Boswellic Acid from the Leaves of Boswellia serrata

Abstract

Objectives: The goal of this research plan was the isolation and purification of most active compounds from the leaves of BS via bioassay‑guided fractionation based on anti‑inflammatory activity.Materials and Methods: The silica gel column chromatographic techniques with different solvent systems were used for the separation of the constituents of the ethyl acetate‑soluble fraction of BS leaves. The structures of the isolated compounds were assigned based on various spectroscopic analysis (high‑resolution mass spectrometry, 1H NMR, and 13C NMR) and comparison with literature data. The anti‑inflammatory activity of all crude extracts, subfractions of ethyl acetate extract, and two isolated new compounds were evaluated in cell‑free (cyclooxygenase and 5‑lipoxygenase) and cell‑based assays (nitrite and tumor necrosis factor‑alpha) in RAW264.7.Results: Bioassay‑guided fractionation of the extracts of the leaves of BS afforded two ursane‑type triterpenoids (compound 5, β‑boswellic alcohol, and compound 6, 3‑O‑acetyl‑11‑hydroxy‑β‑boswellic acid) and other ten known triterpene acids. Compound 5 and 6 exhibited strong anti‑inflammatory activity with an IC50 value of a range 26.5–34.2 µM and 18.3–21.1 µM, respectively, in cell‑free and cell‑based assays.Conclusion: This is the first report on isolation and identification of β‑boswellic alcohol and 3‑O‑acetyl‑11‑hydroxy‑β‑boswellic acid from the leaves of BS, which showed strong anti‑inflammatory activity and holds great promise for the treatment of numerous inflammatory diseases.

Keywords: Acetyl‑11‑hydroxy‑β‑boswellic acid; anti‑inflammatory; Boswellia serrata; LC‑ESI‑MS; NMR; β‑boswellic alcohol