Immunomodulating properties of the diterpene andalusol.

Andalusol [ent-13(16),14-labdadiene-6 alpha,8 alpha,18-triol], a labdane diterpene isolated from an anti-inflammatory extract of the medicinal plant Sideritis foetens Clem. was evaluated for immunomodulating properties. It exhibited a dose-dependent inhibitory effect on the hemolytic activity of the classical complement pathway and also inhibited lymphocyte proliferation induced by concanavalin A at non-cytotoxic concentrations (1-100 microM). No effect on the alternative pathway was observed. These results indicate that andalusol has immunosuppressive effects in vitro in addition to its anti-inflammatory activity.