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Cancer stands as second most common cause of disease-related deaths in humans. Resistance of cancer to chemotherapy remains challenging to both scientists and physicians. Medicinal plants are known to contribute significantly to a large population of Africa, which is to a very large extent linked to folkloric claims which is part of their livelihood. In this review paper, the potential of naturally occurring anti-cancer agents from African flora has been explored, with suggested modes of action, where such data is available. Literature search revealed plant-derived compounds from African flora showing anti-cancer and/or cytotoxic activities, which have been tested in vitro and in vivo. This corresponds to 400 compounds (from mildly active to very active) covering various compound classes. However, in this part II, we only discussed the three major compound classes which are: flavonoids, alkaloids and terpenoids.

A new altersolanol derivative, 4-dehydroxyaltersolanol A (9), along with two known sesquiterpenoids, (S)-7'-hydroxyabscisic acid (7) and (S)-abscisic acid (8) were obtained from the endophytic fungus, Nigrospora oryzae, isolated from leaves of Combretum dolichopetalum. The host plant yielded six known compounds including ellagic acid (1), 3, 3', 4-tri-O-methylellagic acid (2), arjunolic acid (3), 4'-dihydrophaseic acid (4), echinulin (5) and arestrictin B (6). Close structural similarities with regard to compounds 4, 7 and 8 were observed between the metabolites from the host plant and those of the endophytic fungus. Furthermore compounds 5 and 6 are related to alkaloids isolated from N. oryzae previously thus stressing the notion that some of the isolated plant metabolites may actually be of fungal origin. The structures of the isolated compounds were established by spectroscopic methods including 1D, 2D NMR, MS, and by comparison with the literature. 4-Dehydroxyaltersolanol A (9) and 3, 3', 4-tri-O-methylellagic acid (2) showed cytotoxicity against L5178Y mouse lymphoma cells with IC50 values of 9.4 and 29.0 μM, respectively., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Cancer is known to be the second most common disease-related cause of death among humans. In drug discovery programs anti-cancer chemotherapy remains quite challenging due to issues related to resistance. Plants used in traditional medicine are known to contribute significantly within a large proportion of the African population. A survey of the literature has led to the identification of ~400 compounds from African medicinal plants, which have shown anti-cancer, anti-proliferation, anti-tumor and/or cytotoxic activities, tested by in vitro and in vivo assays (from mildly active to very active), mainly alkaloids, terpenoids, flavonoids, coumarins, phenolics, polyacetylates, xanthones, quinones, steroids and lignans. The first part of this review series focuses on xanthones, quinones, steroids, coumarins, phenolics and other compound classes, while part II is focused on alkaloids, terpenoids, flavonoids.

Naturally occurring anticancer compounds represent about half of the chemotherapeutic drugs which have been put in the market against cancer until date. Computer-based or in silico virtual screening methods are often used in lead/hit discovery protocols. In this study, the "drug-likeness" of ~400 compounds from African medicinal plants that have shown in vitro and/or in vivo anticancer, cytotoxic, and antiproliferative activities has been explored. To verify potential binding to anticancer drug targets, the interactions between the compounds and 14 selected targets have been analyzed by in silico modeling. Docking and binding affinity calculations were carried out, in comparison with known anticancer agents comprising ~1,500 published naturally occurring plant-based compounds from around the world. The results reveal that African medicinal plants could represent a good starting point for the discovery of anticancer drugs. The small data set generated (named AfroCancer) has been made available for research groups working on virtual screening.

Context: The Eastern Nigeria mistletoe, Loranthus micranthus Linn. (Loranthaceae), is used in the treatment of several diseases including immune-modifying diseases and thus there is a need to identify the immunoactive constituents., Objective: This research isolated and characterized the immunoactive constituents in the Eastern Nigeria mistletoe., Materials and Methods: Bioassay-guided fractionation was employed in the isolation and purification of the constituents. The characterized compounds were screened for immunostimulatory activities on isolated C57BL/6 mice splenocytes and early activation marker, CD69 at concentrations of 10, 25, and 100 μg/mL using flow cytometry techniques and compared to lipopolysaccharide (LPS; 10 μg/mL) and concanavalin A (ConA; 2 μg/mL) as standards., Results: Two compounds, a novel sesquiterpene, 2, 3-dimethoxy-benzo [a, b] cyclopentenyl-3′,3′,5′-trimethyl pyran-4-carboxylic acid, and a known alkaloid, lupinine were isolated and characterized. The compounds (25 μg/mL) showed statistically significantly (p < 0.05) stimulatory activity on the splenocytes with values of 56.34 ± 0.26% and 69.84 ± 0.19%, respectively, compared to 7.58 ± 0.42% recorded for the unstimulated control. Similarly, the CD69 expression assay showed immunostimulation with statistically significant values (p < 0.05) of 2.31 ± 0.07% and 2.71 ± 0.03%, respectively, compared to 1.69 ± 0.05% recorded for the nonstimulated control., Discussion: These data suggest that the isolated compounds possess immunomodifying abilities. In addition, the activation of the CD69 molecule is possibly one of its mechanisms of action., Conclusion: These compounds may be responsible in part, for the immunostimulatory activities already established for the Eastern Nigeria mistletoes.