New cytotoxic clerodane diterpenes from the leaves of Premna tomentosa

Cytotoxicity of naturally occurring phenolics and terpenoids from Kenyan flora towards human carcinoma cells

Background

Cancer constitutes a major hurdle worldwide and its treatment mainly relies on chemotherapy.

Objectives

The present study was designed to evaluate the cytotoxicity of eleven naturally occurring compounds including six phenolics amongst them were 4 chalcones and 2 flavanones as well as 5 terpenoids (3 clerodane and 2 trachylobane diterpenoids) against 6 human carcinoma cell lines and normal CRL2120 fibroblasts.

Materials and methods

The neutral red uptake (NR) assay was used to evaluate the cytotoxicity of the compounds, whilst caspase-Glo assay was used to detect caspase activation. Cell cycle and mitochondrial membrane potential (MMP) were all analyzed via flow cytometry meanwhile levels of reactive oxygen species (ROS) was measured by spectrophotometry.

Results

Chalcones: 2′,4′-dihydroxy-6′-methoxychalcone (1); 4′,6′-dihydroxy-2′,5′-dimethoxychalcone (2); 2′,4′,6′-trihydroxy-5′-methoxychalcone (3); 2′,6′-diacetate-4′-methoxychalcone (4), trachylobane diterpenoids: 2,6,19-trachylobanetriol; (ent-2α,6α)-form (10) and 2,18,19-trachylobanetriol; (ent-2α)-form (11) as well as doxorubicin displayed IC₅₀ values below 110 μM in the six tested cancer cell lines. The IC₅₀ values of the most active compounds were between 6.30 μM and 46.23 μM for compound 1 respectively towards breast adenocarcinoma MCF-7 cells and small lung cancer A549 cells and between 0.07 μM and 1.01 μM for doxorubicin respectively against SPC212 cells and A549 cells. Compounds 1 induced apoptosis in MCF-7 cells mediated by increasing ROS production and MMP loss.

Conclusion

Chalcones 1–3 are potential cytotoxic phytochemicals that deserve more investigations to develop novel anticancer drugs against human carcinoma.

Diterpenes and Their Derivatives as Potential Anticancer Agents

As therapeutic tools, diterpenes and their derivatives have gained much attention of the medicinal scientists nowadays. It is due to their pledging and important biological activities. This review congregates the anticancer diterpenes. For this, a search was made with selected keywords in PubMed, Science Direct, Web of Science, Scopus, The American Chemical Society and miscellaneous databases from January 2012 to January 2017 for the published articles. A total 28, 789 published articles were seen. Among them, 240 were included in this study. More than 250 important anticancer diterpenes and their derivatives were seen in the databases, acting in the different pathways. Some of them are already under clinical trials, while others are in the nonclinical and/or pre-clinical trials. In conclusion, diterpenes may be one of the lead molecules in the treatment of cancer. Copyright © 2017 John Wiley & Sons, Ltd.