In vitro activities and mechanisms of action of anti-cancer molecules from African medicinal plants: a systematic review

Abstract

Cancer is one of the leading causes of death worldwide. In recent years, African countries have been faced with a rapid increase in morbidity and mortality due to this pathology. Management is often complicated by the high treatment costs, side effects and the increasing occurrence of resistance to treatments. The identification of new active ingredients extracted from endemic medicinal plants is definitively an interesting approach for the implementation of new therapeutic strategies: their extraction is often lower cost; their identification is based on an ethnobotanical history and a tradipratic approach; their use by low-income populations is simpler; this can help in the development of new synthetic molecules that are more active, more effective and with fewer side effects. The objective of this review is to document the molecules derived from African medicinal plants whose in vitro anti-cancer activities and the mechanisms of molecular actions have been identified. From the scientific databases Science Direct, PubMed and Google Scholar, we searched for publications on compounds isolated from African medicinal plants and having activity on cancer cells in culture. The data were analyzed in particular with regard to the cytotoxicity of the compounds and their mode of action. A total of 90 compounds of these African medicinal plants were selected. They come from nine chemical groups: alkaloids, flavonoids, polyphenols, quinones, saponins, steroids, terpenoids, xanthones and organic sulfides. These compounds have been associated with several cellular effects: i) Cytotoxicity, including caspase activation, alteration of mitochondrial membrane potential, and/or induction of reactive oxygen species (ROS); ii) Anti-angiogenesis; iii) Anti-metastatic properties. This review points out that the cited African plants are rich in active ingredients with anticancer properties. It also stresses that screening of these anti-tumor active ingredients should be continued at the continental scale. Altogether, this work provides a rational basis for the selection of phytochemical compounds for use in clinical trials.

Keywords: Africa; cancer; molecular mechanisms; phytochemicals; plants.

Figure 1

Summary of the main mechanisms of resistance of cancer cells to chemotherapy.

Figure 2

PRISMA diagram for the systematic analysis of research on cancer molecules in African plants 2005-2022.

Figure 3

Phytochemical groups of bioactive molecules.

Figure 4

Number of anti-cancer molecules isolated from African medicinal plants. A. By country; B. By region.

Figure 5

Sites of action of the bioactive molecules from African medicinal plants as anticancer agents. A. Therapeutic approaches of bioactive molecules from African medicinal plants targeting apoptosis pathways in cancer cells. Anticancer molecules from African medicinal plants are able to induce cancer cell apoptosis via: The apoptotic extrinsic pathways activation (site 1); activation of caspases 8, -9, -7 and -3 and PARP cleavage (site 2-3-4); apoptotic intrinsic pathways activation by loss of the potential of the mitochondrial membrane (MMP), ROS increase, Bcl2/Bcl-xl anti-apoptotic proteins inhibition, p53 activity and cytochrome c release, (site 5-6-7); inhibition of IKK/NF-κB activity (site 8) and preventing the transcription of anti-apoptotic regulators (site 9). B. Therapeutic approaches of bioactive molecules from African medicinal plants targeting cell cycle in cancer cells. Anticancer molecules from African medicinal plants act mainly on cell cycle to inhibit the proliferation of cancer cells at G0/G1 (site 1), G1 (site 2), G1/S (site 3), S (site 4) and G2/M (site 5).