Cativic acid-caffeic acid hybrid exerts cytotoxic effects and induces apoptotic death in human neuroblastoma cells.

The development of hybrids from natural products is a promising strategy for drug discovery. In cancer therapy, there is a need to discover novel agents that can induce apoptosis in cancer cells. To contribute to this field of interest, we investigated the effect of a synthetic hybrid from cativic acid and caffeic acid (5) on viability, proliferation, and apoptosis in human neuroblastoma cells (IMR-32). Three hybrids were prepared via Mitsunobu esterification from 17-hydroxycativic acid (1) and natural phenols. Cell viability was analyzed by MTT assay. SYTOX green and LDH leakage were used to determine the cytotoxic effect. Caspase-3 activity, cell cycle phases, and proliferation were analyzed in order to characterize the biological effects of hybrid 5. The mitogen-activated protein kinase (MAPK) status was evaluated for elucidating the potential mechanisms involved in hybrid 5 effect. Hybrid 5 reduced the viability of IMR-32 cells in a time- and concentration-dependent manner (IC50 = 18.0 ± 1.3 µM) as a result of its antiproliferative effect through changes in the cell cycle distribution and induction of apoptosis associated with activation of caspase-3. Exposure to 5 triggered ERK1/2 activation and nuclear translocation. Hybrid 5 also promoted an increase in nuclear localization of the transcription factor c-Jun. Inhibition of ERK1/2 and JNK potentiated 5-induced inhibition of IMR-32 viability. Hybrid 5 displays cell growth inhibition by promoting cell cycle arrest and apoptosis, through ERK1/2 and JNK participation.

A New Depigmenting-Antifungal Methylated Grindelane from Grindelia chiloensis.

The new methylated grindelane diterpenoid, 7ß-hydroxy-8(17)-dehydrogrindelic acid (1b), together with the known 7α-hydroxy-8(17)-dehydrogrindelic acid (2a), 6-oxogrindelic acid (3a), 4ß-hydroxy-6-oxo-19-norgrindelic (4a), 19-hydroxygrindelic acid (5a), 18-hydroxygrindelic acid (6a), 4α-carboxygrindelic acid (7a), 17-hydroxygrindelic acid (8a), 6α-hydroxygrindelic acid (9a), 8,17-bisnor-8-oxagrindelic acid (10a), 7α,8α-epoxygrindelic acid (11a), and strictanonic acid (12a) as methyl esters were obtained from an Argentine collection of Grindelia chiloensis (Cornel.) Cabrera. Their structures and relative configurations were established on the basis of spectroscopic analysis. CHCl3 extract from the aerial parts and their pure compounds were evaluated for their antifungal and depigmenting effects. Methyl ester derivative of 10a (10b) exhibited a remarkable mycelial growth inhibition against Botritis cinerea with an IC50 of 13.5 µg ml-1 . While the new grindelane 1b exerted a clear color reduction of the yellow-orange pigment developed by Fusarium oxysporum against UV-induced damage.

Synthesis and cholinesterase inhibition of cativic acid derivatives.

Alzheimer's disease (AD) is a neurodegenerative disorder associated with memory impairment and cognitive deficit. Most of the drugs currently available for the treatment of AD are acetylcholinesterase (AChE) inhibitors. In a preliminary study, significant AChE inhibition was observed for the ethanolic extract of Grindelia ventanensis (IC50=0.79 mg/mL). This result prompted us to isolate the active constituent, a normal labdane diterpenoid identified as 17-hydroxycativic acid (1), through a bioassay guided fractionation. Taking into account that 1 showed moderate inhibition of AChE (IC50=21.1 µM), selectivity over butyrylcholinesterase (BChE) (IC50=171.1 µM) and that it was easily obtained from the plant extract in a very good yield (0.15% w/w), we decided to prepare semisynthetic derivatives of this natural diterpenoid through simple structural modifications. A set of twenty new cativic acid derivatives (3-6) was prepared from 1 through transformations on the carboxylic group at C-15, introducing a C2-C6 linker and a tertiary amine group. They were tested for their inhibitory activity against AChE and BChE and some structure-activity relationships were outlined. The most active derivative was compound 3c, with an IC50 value of 3.2 µM for AChE. Enzyme kinetic studies and docking modeling revealed that this inhibitor targeted both the catalytic active site and the peripheral anionic site of this enzyme. Furthermore, 3c showed significant inhibition of AChE activity in SH-SY5Y human neuroblastoma cells, and was non-cytotoxic.

Inhibition of NO production by Grindelia argentina and isolation of three new cytotoxic saponins.

A bioassay-guided phytochemical analysis of the ethanolic extract of Grindelia argentina Deble & Oliveira-Deble (Asteraceae) allowed the isolation of a known flavone, hispidulin, and three new oleanane-type saponins, 3-O-ß-D-xylopyranosyl-(1→3)-ß-D-glucopyranosyl-2ß,3ß,16α,23-tetrahydroxyolean-12-en-28-oic acid 28-O-ß-D-xylopyranosyl-(1→2)-ß-D-apiofuranosyl-(1→3)-ß-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl ester (2), 3-O-ß-D-glucopyranosyl-2ß,3ß,23-trihydroxyolean-12-en-28-oic acid 28-O-ß-D-xylopyranosyl-(1→2)-ß-D-apiofuranosyl-(1→3)-ß-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl ester, (3) and 3-O-ß-D-xylopyranosyl-(1→3)-ß-D-glucopyranosyl-2ß,3ß,23-trihydroxyolean-12-en-28-oic acid 28-O-ß-D-xylopyranosyl-(1→2)-ß-D-apiofuranosyl-(1→3)-ß-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl ester (4), named grindeliosides A-C, respectively. Their structures were determined by extensive 1D- and 2D-NMR experiments along with mass spectrometry and chemical evidence. The isolated compounds were evaluated for their inhibitory activities against LPS/IFN-γ-induced NO production in RAW 264.7 macrophages and for their cytotoxic activities against the human leukemic cell line CCRF-CEM and MRC-5 lung fibroblasts. Hispidulin markedly reduced LPS/IFN-γ-induced NO production (IC50 51.4 µM), while grindeliosides A-C were found to be cytotoxic, with grindelioside C being the most active against both CCRF-CEM (IC50 4.2±0.1 µM) and MRC-5 (IC50 4.5±0.1 µM) cell lines.

Manoyl oxide diterpenoids from Grindelia scorzonerifolia.

Two new norditerpenoids, 4beta-hydroxy-19-normanoyl oxide (1) and 4alpha-hydroxy-18-normanoyl oxide (2), the new 18-O-alpha-l-arabinopyranosylmanoyl oxide (3a), and the known diterpenoids jhanol (4) and 18-hydroxy-13-epi-manoyl oxide (5) were isolated, together with other common plant constituents from an Argentine collection of Grindelia scorzonerifolia. The structures of the new compounds were established by extensive 1D and 2D NMR techniques and chemical transformations. Structural features of compounds 2 and 4 were verified by X-ray crystallographic analyses. The insecticidal effect of compound 3a was evaluated against the polyphagous pest Spodoptera frugiperda. Pupal and adult malformations leading to death occurred when 3a was incorporated in a larval diet at a concentration of 100 ppm.