Effects of fructus Ligustri Lucidi extracts on concanavalin A-stimulated proliferation of isolated murine splenocytes

Fructus Ligustri Lucidi (FLL), the fruit of Ligustrum lucidum Ait., was fractionated into petroleum ether (FLL-Pe), chloroform (FLL-Ch), butanol (FLL-Bu) and aqueous (FLL-Aq) fractions. The effects of FLL fractions and oleanolic acid (OLA), an active ingredient of FLL, on concanavalin A (Con A)-stimulated proliferation of murine splenocytes were examined under both in vitro and ex vivo conditions. In vitro administration of FLL-Pe could produce an immunostimulatory effect, as evidenced by the significant enhancement of the Con A-stimulated mitogenic response of splenocytes in culture. While FLL-Ch and OLA did not produce any detectable effect on the mitogenic response, FLL-Bu and FLL-Aq inhibited the in vitro ConA-stimulated splenocyte proliferation. In ex vivo experiments, pretreatment with FLL-Pe, FLL-Ch or OLA was found to enhance the extent of Con A-stimulated splenocyte proliferation to a varying degree as assessed under in vitro conditions, with FLL-Pe being more potent. The ensemble of results indicates that both FLL-Pe and FLL-Ch were able to produce immunostimulatory action under ex vivo assay conditions, but only FLL-Pe produced a similar effect under in vitro conditions. The immunostimulatory action produced by FLL-Pe could not be fully explained by the presence of OLA.