Abstract
Traditional remedies have a long-standing history in Cameroon and continue to provide useful and applicable tools for treating ailments. Here, the anticancer, antimicrobial and antioxidant activities of ten antioxidant-rich Cameroonian medicinal plants and of some of their isolated compounds are evaluated.The plant extracts were prepared by maceration in organic solvents. Fractionation of plant extract was performed by column chromatography and the structures of isolated compounds (emodin, 3-geranyloxyemodin, 2-geranylemodin) were confirmed spectroscopically. The antioxidant activity (AOA) was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) bleaching method, the trolox equivalent antioxidant capacity (TEAC), and the hemoglobin ascorbate peroxidase activity inhibition (HAPX) assays. The anticancer activity was evaluated against A431 squamous epidermal carcinoma, WM35 melanoma, A2780 ovary carcinoma and cisplatin-resistant A2780cis cells, using a direct colorimetric assay. The total phenolic content in the extracts was determined spectrophotometrically by the Folin–Ciocalteu method. Rumex abyssinicus showed the best AOA among the three assays employed. The AOA of emodin was significantly higher than that of 3-geranyloxyemodin and 2-geranylemodin for both TEAC and HAPX methods. The lowest IC50 values (i.e., highest cytotoxicity) were found for the extracts of Vismia laurentii, Psorospermum febrifugum, Pentadesma butyracea and Ficus asperifolia. The Ficus asperifolia and Psorospermum febrifugum extracts are selective against A2780cis ovary cells, a cell line which is resistant to the standard anticancer drug cisplatin. Emodin is more toxic compared to the whole extract, 3-geranyloxyemodin and 2-geranylemodin. Its selectivity against the platinum-resistant A2780cis cell line is highest. All of the extracts display antimicrobial activity, in some cases comparable to that of gentamycin.
Highlights
Many rural people in Cameroon still rely on plant-derived preparations for primary health care needs
The highest total phenol content was recorded with the MeOH extracts of Ficus asperifolia (GAE: 31.96 mg/mL) and Pentadesma butyracea (GAE: 30.43 mg/mL) while the hexane extract of Hibiscus asper (GAE: 1.57 mg/mL) contained the lowest amount of total phenols
For the DPPH method, the lowest area values corresponding to the most antioxidant substances were found for the extracts from Tectona grandis, Rumex abyssinicus, Pentadesma butyracea, Vismia laurentii, Dichrostachys glomerata and Rumex bequaertii while the highest area values were those of Hibiscus asper and Psorospermum febrifugum (Figure 3)
Summary
Many rural people in Cameroon still rely on plant-derived preparations for primary health care needs. We report the results of studies designed to evaluate the anticancer, antibacterial and antioxidant activities of selected Cameroonian medicinal plants, with previously demonstrated pharmacological activities. These plants were selected on the basis of recorded ethnobotanical knowledge, evidence for their continued wide usage and local availability. The Hibiscus asper plant extract is an effective neuroprotective, with antioxidant and antiapoptotic activities [1,2]. The Tectona grandis leaf extract was proven to be bioactive [3], due to the presence of two quinones: naphthotectone and anthratectone; it has antibacterial activity [4] and good antiradical properties [5]. A new compound: 5-hydroxylapachol [6], was isolated from the T. grandis root, and reported to be biologically active
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