Antiproliferative Effect of Synadenium grantii Hook f. stems (Euphorbiaceae) and a Rare Phorbol Diterpene Ester

Synadenium grantii is frequently used for the treatment of various diseases such as allergies, gastric disorders, and especially cancer. The aim of this study was to evaluate the possible antiproliferative potential of the methanol extract, fractions, and pure compounds from the stems of S grantii. Phytochemical analysis was carried out by conventional chromatographic techniques, and the antiproliferative activity was analyzed using the sulforhodamine B assay and an MTT-based assay. Nonpolar fraction and its subfractions from the stems of S grantii exhibited promising cytostatic effect against several human tumor cell lines (glioma, breast, kidney, and lung), with total grown inhibition values ranging from 0.37 to 2.9 μg/mL. One of the active principles of this plant was identified as a rare phorbol diterpene ester, denoted as 3,4,12,13-tetraacetylphorbol-20-phenylacetate. This compound demonstrated antiproliferative activity against glioma, kidney, lung, and triple-negative breast cancer cell lines. These results demonstrate that S grantii stems produce active principles with relevant antiproliferative potential.

Reniformin, a Unique Diterpene Ester from the Roots of Pelargonium reniforme

The natural occurrence of the first diterpene in the roots of Pelargonium reniforme (Geraniaceae) is demonstrated. The unique metabolite, reniformin, represents an ester in which a novel diterpene acid with an uncommon -CH2-CH2-bridging element is linked to 2-(4-hydroxyphenyl)ethansulfonic acid. The latter entity has also hitherto not been encountered as a component in natural products. The structure of reniformin was established on the basis of spectroscopic methods.