The present invention refers to tricyclic diterpenes and their derivatives of the formulae (I) and (II), wherein R1 is hydrogen or C1-6-alkyl; R2 is hydroxy, C3-5-acyloxy, hydroxymethyl, 1,3-dihydroxypropyl or C1-6-alkyl; R3 and R4 independently from each other are hydrogen, hydroxy, hydroxymethyl, C1-5-acyloxy or C1-6-alkoxy; R5 is C1-6-alkyl, hydroxymethyl carboxy or methoxycarbonyl; R9 is hydrogen, hydroxymethyl, methoxy, oxo or C1-5-acyloxy; R10 is hydrogen, or R5 and R9 taken together are —CH2—O— or —O—CH2—; or R5 and R10 taken together are —CO—O—, —O—CO—, —CH2—O— or —O—CH2—; R6 is hydrogen, or R5 and R6 together to form a bond; R7 and R8 independently from each other are C1-6-alkyl, carboxy, x-hydroxy-Cx-alkyl (with x being an integer from 1 to 6), or C1-6-alkoxycarbonyl with the proviso that at least one of R7 and R8 is C1-6-alkyl; R11 and R12 are both hydrogen or R11 and R12 together are oxo, with the further proviso for formula (I) that if R2 is hydroxy R1 is C1-6-alkyl, for use as medicaments for the treatment of a disorder connected to impaired neurotransmission, as well as to dietary and pharmaceutical compositions and their uses.