Bwalya, AG; (2015) Evaluation of the in vitro biological activities and phytochemical profiling of eight Ficus species collected in Zambia. Doctoral thesis , UCL (University College London).

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Abstract

Infectious diseases are responsible for an overwhelming number of deaths and morbidity worldwide. In tropical regions of the world, in particular, developing countries like Zambia, poor health is prevalent and diseases such as malaria, meningitis, pneumonia, tuberculosis and gastrointestinal infections strongly persist. Folkloric medicines are still actively used against some of these infections as primary care before seeking conventional treatment at hospitals. Members of the genus Ficus (Moraceae) are traditionally used in Zambia against many diseases caused by bacterial, fungal and protozoal infections. Thus according to the plant parts used traditionally for herbal preparations, aerial and root parts of eight Ficus species namely; F. ingens, F. lutea, F. natalensis, F. ovata, F. sansibarica subsp. macrosperma, F. sycomorus subsp. gnaphalocarpa, F. sycomorus subsp. sycomorus and F. wakefieldii were collected from different parts of Zambia. The main aim of this thesis was to evaluate the medicinal potential of members of the genus Ficus. This was achieved by three objectives, which involved the phytochemical profiling of the crude extracts and subextracts of the Ficus for their constituents using chromatographic methods such as thin layer chromatography (TLC), proton Nuclear Magnetic Resonance (1H NMR) and high performance liquid chromatography (HPLC). Secondly, the extracts were screened for various biological activities after which they were evaluated against recombinant FAS-II elongation enzymes, FabG, FabI and FabZ as potential targets in liver stage malaria parasites. In this case, finely ground dried plant material was extracted with methanol (MeOH) to yield the crude methanol extracts (CR-MeOH) which, were further partitioned to provide a coarse separation of the crude extracts according to polarity. The three subextracts obtained included n-hexane, chloroform (CHCl3) and aqueous methanol (aq-MeOH). The obtained extracts and subextracts were screened for biological activities such as: antifungal and antibacterial activities using the broth dilution and agar disc diffusion assays, antitubercular activity using the MTT assay, antischistosomal activity using the microscopic in vitro assay. In addition, antiprotozoal activitites which included antileshmanial activity using an assay against amastigotes of L. donovani strain MHOM/ET/67/L82, trypanocidal activity against T. cruzi and T. brucei rhodesiense STIB 900 strain, and antiplasmodial activity by modified [3H]-hypoxanthine incorporation assay, using the chloroquine/pyrimethamine resistant K1 strain were performed. Cytotoxity activity was also performed using rat skeletal myoblasts L6-cells. The chemical profiling was done by TLC, NMR and RP-HPLC. Meanwhile the chemical compound isolation for F. sansibarica was attempted by different chromatographic techniques and characterization by spectroscopic methods. The phytochemical profiling revealed the presence of closely related polyphenolic compounds to which some of the biological activities were attributed to. For instance, the antibacterial and the FAS-II enzyme inhibition activities were mostly retained in the aq-MeOH subextracts, which were composed of very polar metabolites including flavonoids. Antiplasmodial activity was observed mostly in the less polar metabolites which were retained in the hexane and CHCl3 subextracts of the stem barks. This pattern was similar with antitrypanosomal and antileishmanial activities, though with lesser sensitivity. The same subextracts including those of the root barks showed the most activity against M. tuberculosis with MIC values of 256 and 128 μg/ml, and against Schistosoma, for both larval and adult worms. The extracts did not exert any antifungal activity by the agar disc diffusion method we used. Detailed phytochemical investigation of the leaves of F. sansibarica was performed, and led to the isolation of two compounds; epicatechin and apigenin-6-C-glucoside from the chloroform and aq. MeOH subextracts respectively. The predominant constituent of the CR-MeOH extract of F. sansibarica was identified as having a molecular weight of 432 g/mol by LC-MS analysis which could be set as an identification chemical marker for F. sansibarica. The results highlight the potential that Ficus species could have as a valuable source for potent compounds which can be identified as scaffolds for the development of novel liver stage antimalarial drugs. Our results support previous research on the antimicrobial activity of Ficus species and they also provide an in vitro scientific basis supporting the use of Ficus species in traditional herbal preparations against some bacterial and parasitic infections.

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