Immunomodulatory activity of a lupane triterpenoid ester isolated from the eastern Nigeria mistletoe, Loranthus micranthus (Linn)

Abstract

Objective To provide further evidence for the ethnomedicinal use of the Eastern Nigeria mistletoe, Loranthus micranthus (L. micranthus), as an immunostimulant. Methods Solvent fractions from the crude extract of the mistletoe plant was obtained and screened by the cell mediated delayed type hypersensitivity reaction (DTHR) model in mice. Then the immunomodulatory potentials of a major lupane triterpenoid ester isolated from an active hexane fraction of the Eastern Nigeria mistletoe was investigated. Three lupeol-based triterpenoid esters: 7β 15α-dihydroxyl-lup-20(29)-ene-3β-palmitate (I), 7β, 15α-dihydroxyl-lup-20(29)-ene-3β-stearate (II) and 7β, 15α-dihydroxyl-lup-20(29)-ene-3β-decadecanoate (III) were isolated from the plant leaves epiphyting on a local kola nut tree and were characterized. Compound 1 was subjected to cell proliferation studies using C57Bl/6 splenocytes at three dose levels (5, 25 and 100 μg/mL) in presence of controls. Furthermore, the effect of this compound on IL-8 receptor expression was evaluated at three doses (1, 5 and 10 μg/mL) using the real time polymerase chain reaction assay. Results This triterpenoid ester produced some enhancement of the splenocytes at the tested doses but at doses higher than 5 μg/mL caused inhibition of the IL-8 receptor expression. Conclusions The present findings support the ethnomedicinal use of the Eastern Nigeria Mistletoe in the management of diseases affecting the immune system. The triterpenoid(s) have some immunomodulatory abilities on splenocytes and IL-8 receptors and may partly account for the overall immunomodulatory activity of this plant.