Ethnopharmacological relevance: Acanthosicyos naudininus, Gomphocarpus fruticosus, and Cryptolepis decidua are, according to the knowledge of traditional healers, used in Namibia to treat inflammatory disorders such as pain, fever and skin rashes.Aim of the study: The present study was conducted to evaluate the immunomodulatory effects and the possible underlying mechanisms of action of the plant extracts on peripheral blood mononuclear cells (PBMCs) such as T-lymphocytes. Materials and methods: Methanolic and EtOAc extracts of A. naudinianus, G. fruticosus and C. decidua were analysed for their immunomodulatory potential. PBMCs were isolated from the blood of healthy donors and incubated with the plant extracts at concentrations 100, 30, 10, 3, 1 and 0.3 μg/mL. Effects on proliferation and viability of activated human lymphocytes were assessed in comparison to ciclosporin A by flow cytometry using carboxyfluorescein succinimidyl ester (CFSE) and WST-1 assay. Flow cytometry by annexin V/propidium iodide (PI) staining was performed to investigate the necrotic/apoptotic effect of the plant extracts on mitogen-activated human lymphocytes. In addition, analysis of the influence of plant extracts on the regulatory mechanisms of T-lymphocytes was performed using activation marker and cytokine production assays. An HPLC-PDA-ELSD-ESIMS profile was recorded for each of the extracts. Results: T-lymphocyte proliferation was inhibited in a dose-dependent manner by the extracts of A. naudinianus, G. fruticosus, and C. decidua in concentrations not causing apoptosis or necrosis. This effect was mediated by inhibition of lymphocyte activation, specifically the suppression of CD25 and CD69 surface receptor expression. Moreover, the extracts suppressed effector functions, as indicated by reduced production of IFN-γ and IL-2. Based on the HPLC profile, possible responsible compound classes could be identified for the extracts of A. naudinianus (cucurbitacins) and C. decidua (indole alkaloids), but not for G. fruticosus. Conclusions: The data show that the extracts of A. naudinianus, G. fruticosus and C. decidua have in vitro immunomodulatory activity and they interfere with the function of immunocompetent cells, suggesting an antiinflammatory mode-of-action. The present chemical determination and pattern recognition results explain the therapeutic potency. However, further studies to investigate the therapeutic potential of the plants in inflammatory disorders should be done.

Background: Plants have consistently proven to be a reliable and yet not fully explored source of medicines. In light of this, there is a constant demand for new treatment regimens for cancer. Namibia has a rich diversity of plant species of over 4300 with 17 % of them being endemic to Namibia. Plants growing in Namibia's diverse climatic zones produce many secondary metabolites as part of adaptation to their environment. This article focused on the screening of such phytochemicals and their cytotoxic and anticancer properties in vitro. Two Namibian plants Diospyros chamaethamnus and Guibourtia coleosperma were randomly selected for this purpose. Materials and Methods: The plants were screened for the presence of coumarins, alkaloids, flavonoids, anthraquinones, steroids and terpenoids using thin layer chromatography. Anticancer screening was performed on a panel of three cancer cell lines, while cytotoxicity was determined using a human fibroblast cell line, both using the SRB method. Results: Alkaloids, anthraquinones, flavonoids and steroids were detected in both organic and aqueous extracts of the two plants. The organic plant extracts had a greater anti-proliferative effect on the cancer cell lines than the aqueous extracts; the D. chamaethamnus organic root extract was the most potent with an IC50 of 16.08, 29.12 and 24.67 µg/mL against TK10, UACC62 and MCF7 cells, respectively. Furthermore, cytotoxicity analysis revealed the non-toxic nature of the extracts, except for the organic root extract of D. chamaethamnus that showed significant cytotoxicity (IC50 13.03 µg/mL). Conclusion: D. chamaethamnus is a potential candidate for the development of a plant based cancer treatment. The study showed the value of random screening in drug discovery from plants for pharmacological activity that is unrelated to their ethnomedicinal uses.