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 IC50 (μM) = 0.43 ± 0.01 and 1.34 ± 0.04, respectively, for U251 (glioblastoma), an IC50 (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.
Keywords: Salvia carranzae; abietane diterpenoids; antiproliferative activity; icetexane diterpenoids; phytotoxicity.