Structure, Absolute Configuration, Antiproliferative and Phytotoxic Activities of Icetexane and Abietane Diterpenoids from Salvia carranzae and Chemotaxonomic Implications.

From the aerial parts of Salvia carranzae Zamudio and Bedolla, three new icetexane-type diterpenoids were isolated. Their structures were established through spectroscopic methods and named the following: salvicarranzanolide ( 1 ), 19-deoxo-salvicarranzanolide ( 2 ) and 19-deoxo-20-deoxy-salvicarranzanolide ( 3 ). In addition, the known icetexane-type diterpenoids, 6,7,11,14-tetrahydro-7-oxo-icetexone ( 4 ), iso -icetexone ( 5 ), 19-deoxo- iso -icetexone ( 6 ), icetexone ( 7 ), 19-deoxo-icetexone ( 8 ) and 7α-acetoxy-6,7-dihydroicetexone ( 9 ), were also isolated, along with the abietanes sessein ( 10 ) and ferruginol ( 11 ). α-Tocopherol was also identified. Compounds 5 , 6 and 8 were tested for their antiproliferative activity using the sulforhodamine B assay on six cancer and one normal human cell lines. Diterpenoids 5 and 6 showed noteworthy antiproliferative activity, exhibiting an IC 50 (μM) = 0.43 ± 0.01 and 1.34 ± 0.04, respectively, for U251 (glioblastoma), an IC 50 (μM) = 0.45 ± 0.01 and 1.29 ± 0.06 for K5621 (myelogenous leukemia), 0.84 ± 0.07 and 1.03 ± 0.10 for HCT-15 (colon cancer), and 0.73 ± 0.06 and 0.95 ± 0.09 for SKLU-1 (lung adenocarcinoma) cell lines. On the other hand, the phytotoxicity of compounds 5 - 7 and 9 - 10 was evaluated on seed germination and root growth in some weeds such as Medicago sativa , Panicum miliaceum , Amaranthus hypochondriacus and Trifolium pratense as models. While compounds 5 and 10 exhibited a moderate inhibitory effect on the root growth of A. hypochondriacus and T. pratense at 100 ppm, the diterpenoids 6 , 7 and 9 were ineffective in all the plant models. Taxonomic positions based on the chemical profiles found are also discussed.