Antispasmodic effects and structure-activity relationship of labdane diterpenoids from Marrubium globosum ssp. libanoticum - Rigano, D; Aviello, G; Bruno, M; Formisano, C; Rosselli, S; Capasso, R; Senatore, F; Izzo, A A; Borrelli, F (J Nat Prod, 2009)