Ent-Labdane

Sideritis (Labiatae) have been a rich source of novel bi- and tetra-cyclic diterpenoids. Andalusol (10), which has been isolated from S. arborescens, was assigned the ent-labdane configuration. Its structure was deduced by a combination of spectroscopic measurements and an X-ray analysis of the degradation product (11). 

Waridel, P. et al., Identification of the polar constituents of Potamogeton species by HPLC-LTV with post-column derivatization, HPLC-MSn and HPLC-NMR, and isolation of a new ent-labdane diglycoside, Phytochemistry, 65, 2401, 2004. 

Briand A, Komprobst J-M, Al-Easa HS, Rizk AFM, Toupet L (1997) (-)-Paniculatol, a New ent-Labdane Bromoditerpene from Laurencia paniculata. Tetrahedron Lett 38 3399... 

Aquatic plant ent-labdane diterpenes from Potamogetonaceae TBA A,I,I,I,I (Cangiano et al., 2002)... 

Cangiano, T., Dellagreca, M., Fiorentino, A., Isidori, M., Monaco, P. and Zarrelli, A. (2002) Effect of ent-labdane diterpenes from Potamogetonaceae on Selenastrum capricornutum and other aquatic organisms, Journal of Chemical Ecology 28 (6), 1091-1102. 

The plants were air dried and extracted with solvents of increasing polarity. Chromatographic processing of the extracts led to the isolation of twenty ent-labdane diterpenes, identified on the basis of their spectroscopic properties and by chemical correlation. 

Unlike in the previously mentioned species, compounds 1 and 8 were very active on T. platyurus. The LC50 value of the first compound (0.84 pmol/L) was comparable with its IC50 value found for S. capricornutum (0.80 pmol/L). Compounds 3, 10, 13 and 13a were inactive at the tested concentrations, while ent-labdanes 2 and 12 showed high values of LC5o. 

The structure of the epoxy-dialdehyde (15), from Afromomum daniellii (Zingiberaceae), was established by correlation with c -12-norambreinolide. The hydroxy-acid (16), salvic acid from Eupatorium salvia,and the ring B seco-labdane jhanic acid (17) from Eupatorium jhanii are two further diterpenoids from these species of the Compositae. The structure of the latter rests on interpretation of the H and C n.m.r. data. Gutierrezia lucida (Compositae) contains the 13-epimeric acids (18) related to agathic acid together with the butenolide (19). Some esters of 6-hydroxylabdane-17-carboxylic acids were detected in G. mandonii. The investigation of Cistus species has continued. The ent-labdane acetyl-laurifolic acid (20) is a component of Cistus laurifolius ... 

Many new diterpenoids, occurring in 5. canariensis, harvested in Canary Islands, have been also isolated. Trachinodiol (152) and trachinol (150) showing the enf-trachilobane skeleton [20] were accompanied by epicandicandiol (7) and two known diterpenes the hydrocarbons ent-kaur-16-ene (1) and dehydroabietane (161). Moreover e/U-trachilobane (149), already known as a synthetic product, was found for the first time in nature. Later, the ketone tiganone (90) with a modified ent-labdane... 

The species S. gomerae, from Canary Islands, yielded five ent-labdanes [56] the four new em-manoyloxides, gomeraldehyde (95), 13-epi-gomeraldehyde (87), gomeric acid (96), 13-epi-gomeric acid (88) and the known e t-8a,15-dihydroxy-labd-13(14)-ene (109) this last product had been isolated previously by Jefferies and Payne [57] from an Australian Beyera species. 

Another species from Andalusia, S. hirsuta subsp. nivalis gave [83] many known derivatives siderol (34), linearol (18), sidol (17), leucanthol (24), 18-acetyl-leucanthol (26), foliol (16), ribenol (72), 6-deoxy-andalusol (100), and a new ent-labdane, ent-%a-hydroxylabda-13(16), 14-diene (98). 

The taxon S. arborescens subsp. paulii was collected in Andalusia and found to be rich in diterpenoids [90]. Some known ent-labdanes were found 6-deoxyandalusol (100), 6-deoxyandalusal (101), 6-... 

The Australian hop bush, Dodonaea viscosa—which is also distributed across parts of Oceania, Africa, Southern Asia and Central America—is a rich source of diterpenoids, some of which are pharmacologically active. Ent-labdanes such as hautriwaic add have been shown to produce spasmolytic effects on isolated guinea-pig ileum, involving interference with calcium influx into the smooth muscle cells (Mata et al. 1997). Current attention is focused on a new subtype of clerodane diterpenes to be isolated, known as methyl dodonates (Ortega et al. 2001). 

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