The invention features a method for inhibiting or reducing the deleterious effects of tobacco smoking including increased incidence of cancers, cardiovascular diseases, various lung disorders and the oxidative effects. The method includes the incorporation of an effective amount of a compound or a standardized plant extract that is that comprises an inhibitor of NF-.kappa.B into tobacco or a tobacco product. In particular, it relates to useful NF-.kappa.B inhibitor diterpenes and compositions containing them for incorporation into tobacco or a tobacco product.