A novel sesquiterpene acid and an alkaloid from leaves of the Eastern Nigeria mistletoe, Loranthus micranthus with potent immunostimulatory activity on C57BL6 mice splenocytes and CD69 molecule.

Context: The Eastern Nigeria mistletoe, Loranthus micranthus Linn. (Loranthaceae), is used in the treatment of several diseases including immune-modifying diseases and thus there is a need to identify the immunoactive constituents.

Objective: This research isolated and characterized the immunoactive constituents in the Eastern Nigeria mistletoe.

Materials And Methods: Bioassay-guided fractionation was employed in the isolation and purification of the constituents. The characterized compounds were screened for immunostimulatory activities on isolated C57BL/6 mice splenocytes and early activation marker, CD69 at concentrations of 10, 25, and 100 μg/mL using flow cytometry techniques and compared to lipopolysaccharide (LPS; 10 μg/mL) and concanavalin A (ConA; 2 μg/mL) as standards.

Results: Two compounds, a novel sesquiterpene, 2, 3-dimethoxy-benzo [a, b] cyclopentenyl-3′,3′,5′-trimethyl pyran-4-carboxylic acid, and a known alkaloid, lupinine were isolated and characterized. The compounds (25 μg/mL) showed statistically significantly (p < 0.05) stimulatory activity on the splenocytes with values of 56.34 ± 0.26% and 69.84 ± 0.19%, respectively, compared to 7.58 ± 0.42% recorded for the unstimulated control. Similarly, the CD69 expression assay showed immunostimulation with statistically significant values (p < 0.05) of 2.31 ± 0.07% and 2.71 ± 0.03%, respectively, compared to 1.69 ± 0.05% recorded for the nonstimulated control.

Discussion: These data suggest that the isolated compounds possess immunomodifying abilities. In addition, the activation of the CD69 molecule is possibly one of its mechanisms of action.

Conclusion: These compounds may be responsible in part, for the immunostimulatory activities already established for the Eastern Nigeria mistletoes.