Anti-inflammatory norhopanes from the root bark of Fagaropsis angolensis (Engl.) H.M.Gardner

Abstract

Two new norhopane derivatives namely 3β,6β,22-trihydroxy-7β,11α-di[(4-hydroxybenzoyl)oxy]-21αH-24- norhopa-4(23)-ene (1) and 3β,6β,22-trihydroxy-7β-[(4-hydroxybenzoyl)oxy]-21αH-24-norhopa-4(23)-ene (2) together with two previously reported compounds, including a norhopane, 3β,6β,11α-trihydroxy-7β-[(4-hydroxybenzoyl) oxy]-24-norhopa-4(23),17(21)-diene (3) and a norneohopane, (21αH)-24-norneohopa-4(23), 22(29)-diene-3β,6β,7β-triol 7-caffeate (4) were isolated from the root bark of Fagaropsis angolensis. Elucidation of their structures was achieved by spectroscopic (NMR, IR and UV) and spectrometric (HRESIMS) data and by comparison of these data with those of related compounds in the literature. Compounds 1–4 were evaluated for their anti-inflammatory activity by measuring the levels of cytokines, IL-1β, IL-2, GM-CSF and TNF-α in lipopolysaccharide (LPS) stimulated peripheral blood mononuclear cells (PBMC). All tested compounds decreased secretion of IL-1β and TNF-α. Compounds 2 and 4 caused significant decrease of the production of IL-2, GM-CSF and TNF-α compared to the reference drug, ibuprofen. These findings showed that the root barks of F. angolensis are rich source of norhopane derivatives and further provide a scientific rationale of using this plant in Kenyan folk medicine to relieve pain.