- ItemOpen AccessStructure-based in silico identification of novel anticancer natural compounds for enhanced breast cancer chemotherapy(Kamuzu University of Health Sciences, 2022-01-01) Bvunzawabaya, Jonathan TatendaBreast cancer remains a serious public health concern all over the world with heavier burdens on developing countries. In Sub-Saharan Africa, the mortality rate for breast cancer is currently on the rise because of late diagnosis and poor treatment. Currently available chemotherapeutic drugs for breast cancer are associated with severe side effects and are now facing multi-drug resistance. Therefore, identifying new anti-cancer drugs by using structural information of potential drug targets such as the gamma secretase will enhance the fight against breast cancer. The objective of this study was to identify and characterize drug-like natural anti-breast cancer compounds from selected African natural products databases using structure-based virtual screening and chemoinformatic approaches. Exactly11304 compounds from four databases (Afrodb, NANPDB, Afrocancer, and ConmedNP) were curated and filtered to remove structural alerts and compounds that violate drug-like rules according to Lipinski and Veber, using KNIME analytics. The resulting druglikeNP dataset (437 compounds) had its, chemical space, scaffold diversity, and complexity analyzed using scaled Shannon entropy and cyclic system retrieval curves (CSR). The 437 compounds were docked into the binding site of gamma-secretase enzyme and the pharmacokinetic properties of the hit compounds were profiled using the pkCSM server. 60% of the compounds in the druglikeNP dataset contained lead-like physicochemical properties and occupied the same space as FDA-approved drugs. The scaffold diversity of druglikeNP was observed to be higher than that of FDA drugs based on Shannon entropy and CSR. Docking studies identified 12 compounds as potential inhibitors of the gamma-secretase enzyme (with binding energies ranging between -7.6 and -8.8 KCal/mol). In silico ADMET predictions revealed a majority of the 12 hit compounds have good pharmacokinetic and toxicity profiles. In this study drug-like natural compounds of African origin with potential inhibitory properties against a validated breast cancer target; gamma secretase enzymes were computationally identified. This work could be valuable to the ongoing efforts to discovery novel drugs for enhanced breast chemotherapy.
- ItemOpen AccessThe antimicrobial activities of selected local medicinal herbs against Streptococcus pneumoniae(Kamuzu University of Health Sciences, 2021-07-01) Salifu Mindress, ChifundoStreptococcus pneumoniae (S. pnuemoniae) is a major cause of invasive pneumococcal infections. Current treatment involves antibiotic therapy and vaccination. The emergence of antibiotic resistance and vaccine serotype replacement negatively affects the control of pneumococcal infections, necessitating the need for other treatment alternatives. We investigated the antimicrobial activity of local herbs against pneumococcal serotypes 1 and 6A. Dry powdered leaves/stem material (50 g) from 6 plants; Annona senegalensis (A. senegalensis), Bidens pilosa (B. pilosa), Dichrostachys cinerea (D. cinerea), Erythrina abyssinica (E. abyssinica), Lippia javanica (L. javanica) and Trichodesma zeylenicum (T. zeylenicum)) were extracted using 200 mL of distilled water or methanol. Disc diffusion method was employed for antimicrobial activity testing. The minimum inhibitory concentrations (MIC’s) and minimum bactericidal concentrations (MBC’s) were determined using agar dilution method. Column chromatography was employed for fractionation of crude extracts. Penicillin and DMSO (1 % in DPBS) were used as positive and negative control, respectively. Water extraction yielded 5.1 % (10.2 g/200 g) of the crude extract material versus 12.1 % (24.3 g/200 g) from methanol. The Bp (1.0 mg/mL) and Ea (1.0 mg/mL) water extracts showed highest activity against serotype 1 (zone of inhibition (ZI) ~9.0 mm each), while Bp and Dc (ZI ~11.0 mm) exhibited the highest activity against serotype 6A. The methanol extracts of B. pilosa (1.0 mg/mL) and D. cinerea (1.0 mg/mL), showed the highest activity against serotype 1 (ZI ~15.6 ± 0.57, MIC<100 𝜇g/mL, MBC ~ 2 mg/mL and ZI ~13.6 ± 0.57 mm, 100 ≤ MIC <512 𝜇g/mL, MBC ~ 4 mg/mL respectively) and serotype 6A (ZI ~24.3 ± 0.00 mm, MIC <100 𝜇g/mL, MBC ~2 mg/mL and ZI ~15 ± 0.00 mm, 100 ≤ MIC<512 𝜇g/mL, MBC ~ 4 mg/mL respectively). The ZI for both serotypes 1 and 6A were 0.00 mm for DMSO (1 %) and 25 ± 0.00 mm for penicillin (25 μg). Column fractionation vi was conducted on methanol extracts of B. pilosa and D. cinerea. Of the 9 fractions from B. pilosa, only one fraction showed activity against serotypes 1 and 6A (ZI ~10 mm). Of 11 fractions from D. cinerea, only one showed activity against pneumococcal serotypes 1 (ZI ~8 mm) and 6A (ZI ~7 mm). Phytochemical analysis of methanol extracts showed higher content of total polyphenols, flavonoids, 2, 2-Diphenyl-1-Picrylhydrazyl (DDPH), Ferric Reducing Antioxidant Power (FRAP) and total alkaloids compared to water extracts. The Brine Shrimp’s lethality analysis for highly active plant (Bp and Dc) showed no and mild toxicity respectively. We recommend further exploration of these two plants as potential antimicrobials against pneumococcal infections.
- ItemOpen AccessPhytochemical, antioxidant activity and toxicity evaluation of medicinal plants commonly used for asthma management in Malawi(Kamuzu University of Health Sciences, 2021-12-01) Mwambyale, TuntufyeAsthma is a chronic disease characterized by recurrent attacks of breathlessness and wheezing, which vary in severity and frequency from person to person. There is minimal scientific research on the efficacy, doses, toxicity and safety of herbal remedies used in the management of asthma in many countries including Malawi. Therefore, this study determined the brief chemical composition and toxicity and/or safety of herbal extracts from the medicinal plants that are commonly used to manage asthma in Malawi. This was achieved through qualitative and quantitative assessment of flavonoids and phenolics, screening for antioxidant activity using 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) assay and Ferric reducing antioxidant power assay (FRAP) as well as validated in vitro and in vivo acute toxicity test on Wistar rats of ethanolic herbal extracts of Erythrina abbysinica Lam. ex DC., Paederia bojeriana (A.Rich. ex DC.) Drake and Trichodesma zeylanicum (Burm.f.) R. Br. The results showed that Trichodesma zeylanicum (Burm.f.) R. Br, Paederia bojeriana (A.Rich. ex DC.) Drake and Erythrina abbysinica (Lam. ex DC) contained flavonoids and phenols. Highest total flavonoid content was found in E. abyssinica (Lam. ex DC.), (806.12±0.01 QE/mg). Highest total phenolic content was also found in E. abyssinica (Lam. ex DC.) (98.48±0.08 mg GAE/g). Antioxidant activity using DPPH % inhibition was highest in E. abyssinica (Lam. ex DC.) (86.59%) while FRAP results were highest in T. zeylanicum (Burm.f.) R. Br (21.85mg TAEC/g). In vitro toxicity showed that ethanolic root extract of P. bojeriana (A.Rich. ex DC.) Drake had the lowest LC50 values (LC50 = 11.09μg/ml) however, in vivo toxicity studies showed LC50 of 2000mg/kg in all extracts. This study has revealed that the ethanolic extracts of all extracts are rich in phytochemicals and antioxidant activities that are indicative of asthmatic activity in human beings according to the literature. The study has also shown that the plants are toxic in vitro but non-toxic in vitro.
- ItemOpen AccessInvestigation of antimycobacterial and antiviral activities of extracts and compounds isolated from Malawian medicinal plants(Kamuzu University of Health Sciences, 2020-11-01) Ngonda, Frank Billy BestonInfectious diseases accounts for approximately one-half of all the deaths that occurs in tropical countries including Malawi. Some of these infectious diseases are caused by microorganism such as mycobacteria and viruses. However, the threat of antimicrobial resistance is growing at an alarming rate and the situation has been aggravated in these developing countries due to so many factors including presence of multidrug resistants’ strains and over prescriptions. Therefore, the purpose of present study was to investigate the phytochemical constitutes and compounds isolated from Aeschynomene nyassana, Euphorbia whyteana, Euphorbia cooperi, Flueggea. virosa, Phyllanthus amarus, Ericae milanjiana and Rhus acuminatissima medicinal plants, determine their antimicrobial activities and cytotoxic properties. Ethnobotanical survey was conducted and several methods were used to identify and confirm the selections of plants understudy. Search engine on several online databases (Google Scholar, PubMed, MEDLINE, Scopus, Cochrane Library, and Science Direct) were used to identify medicinal plants with antiviral and antimycobacterial activities. The plants found were then matched with published and unpublished ethnobotanical survey data and database on the Flora of Malawi, Chewa Medical Botany by Brian Morris, Useful Plants of Nyasaland by Jessie Williamson and other sources. Seven plants, were identified for this research and these were extracted twice with solvents such as methanol, ethyl acetated and dichloromethane. Part of the methanol/water extracts obtained were subjected to alkaloid extraction scheme while the other part was subjected to column chromatograph. 1,3,6 – tri(3,4,5-trihydroxyphenyl) acetyl ester - β-Dglucopyranose, 1,2,3,4,6 – penta(3,4,5-trihydroxyphenyl) acetyl ester - β-D- glucopyranose, 1,2,3,6 – tetra(3,4,5-trihydroxyphenyl) acetyl ester - β-D- glucopyranose, 2,3,6 – tri(3,4,5- trihydroxyphenyl) acetyl ester - β-D- glucopyranose, compounds were obtained from Hexane: Ethyl acetate 50%; 80%; 90% and Ethyl acetate: Methanol 5% and the compounds were identified from the NMR spectra while Betulinic acid was obtained as a white amorphous powder, soluble in methanol, having been eluted with methylene chloride: methanol 9:1 from the silica gel column. The NMR spectral data was compared in reference literature and showed to be very similar to those of Betulinic acid compound. Benzoxylanthaquinone was identified by direct comparison of the spectroscopic data with those published literatures. The compound, Cyclanoline, greyish in colour was obtained from alkaloid extraction scheme and identified by direct comparison of the spectroscopic data with those published literatures. Mass spectra(ESIMS) were obtained with a Thermo-Finningan LCD DECA mass spectrometer and HRESIMS spectra were measured with a FTHRMS-Orbitrap (Thermo-Finnigan) mass spectrometer. The compound E5 m/z 695.33, yellowish in colour was obtained from alkaloid extraction scheme and identified by direct comparison of the spectroscopic data with those published literatures. Mass spectra(ESI-MS) were obtained with a Thermo-Finningan LCD DECA mass spectrometer and HRESIMS spectra were measured with a FTHRMS-Orbitrap (Thermo- Finnigan) mass spectrometer. The resultant crude extracts, fractions and compounds were used in the phytochemical screening and antimicrobial analysis. The phytochemical analysis involved spectrophotometric screening for pro/antioxidant properties of the crude extracts, fractions and compounds using HPTLC, DPPH, FRAP, Reducing power, Crocin bleaching assay, Cupric reducing antioxidant capacity and Nitric oxide radical scavenging activities. Cell viability and cytotoxicity studies were conducted using the Trypan blue dye exclusion, (3-(4,5- Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MTT and Mammalian macrophage cytotoxicity assays while heavy metals analysing was performed using atomic absorption spectrometry. The antimycobacterial activities of crude extracts, fractions and compounds were assessed using microplate alamar blue assay. Compounds obtained were further assessed for drug susceptibility against resistant Mycobacterium tuberculosis using the BACTEC™ MGIT 320 system. The results of the review study identified 50 different families of medicinal plants comprising 90 plants species that are frequently used by traditional healers to treat various diseases in Malawi such as sexually transmitted infections, diarrhoea/dysentery, skin infections/rash, respiratory infection, cold/cough, fever, tuberculosis and herpes zoster. Furthermore, these medicinal plants also demonstrated some anti-viral and antimycobacterial activities. The compounds/compound groups identified in this study were categorized into eight distinct groups of flavonoids, alkaloids, saponins, phenolics, lignins, xanthones, proteins and peptide. In phytochemical analysis, results of crude extracts, fractions and compounds showed moderate DPPH scavenging activity, a dose dependent decrease in NO scavenging activity except for R. acuminatissinia while A. nyassana revealed reducing power ability that was significantly greater than standard Ascorbic acid. In HPTLC analysis, DPPH active spots showed pale-yellow coloured spots for the 4 plants understudy while the phenolic active blue colour spots were observed to be more visible on R. acuminatissinia and E. milanjiana. In PBMC viability analysis, the lymphocytes treated with Rhus acuminatissima and Ericae milanjiana had the lowest cell percent viability. The plants understudy also demonstrated a decrease in percent viability with increased time for all the plants extracts except for E. milanjiana and A. nyassana which showed some stimulative effects. A. nyassana and Euphorbia whyteana demonstrated relatively high cytotoxicity as compared to E. milanjiana, R. acuminatissima and standard drug, Doxorubicin. In heavy metal analysis, all the plants understudy displayed the least levels of toxic metals concentration in the order of Cadmium˂Chromium˂Lead. In the antimycobacterial analysis, F. virosa and E. milanjiana crude extracts displayed Minimum Inhibitory Concentration of 128 ug/ml and 512 ug/ml respectively while A. nyassana ANX fraction showed MIC of 256 ug/ml for M. smegmatis. E. cooperi, E. milanjiana and E. whyteana crude extracts displayed MIC value of 512 ug/ml while E. whyteana W1 fraction had MIC value of 252 ug/ml for M. ulcerans. The selectivity index (SI) values of plants understudy ranged from <0.082 – 2.20 and considerably good SI were observed in F. virosa, E. whyteana crude extracts and E. whyteana W1 fraction at 2.20, 0.625 viii and 0.985 respectively. In synergistic antimycobacterial analysis, the synergistic drug action showed Betulinic acid (EM8), 1,2,3,6 – tetra(3,4,5-trihydroxyphenyl) acetyl ester - β-Dglucopyranose (FV8) and Cyclanoline (C5) exhibited synergistic antimycobacterial activity at a final concentration of 18 ug/ml. The good synergistic results (susceptibility) were observed in combined EM8+INH and FV8+INH while a moderate synergistic result was observed in C5+INH indicating an additive effect of the combination. However, antagonistic activity (resistance) was observed in combined EM9+ETH and E1+ETH. Therefore, it can be concluded from the results that all the plants understudy showed considerable antimycobacterial activities against M. tuberculosis, M. ulcerans and M. smegmatis. The compounds obtained from the plants understudy also demonstrated synergistic properties with the first-line tuberculosis drugs, rifampicin; isoniazid ethambutol and streptomycin. Consequently, this study recommends that further studies to be undertaken in order to determine the mechanism of action of the novel compounds in order to unravel its exact potential to inhibit several pathogenic microbes especially resistant M. tuberculosis and M. ulcerans and also to evaluate whether its true pharmacological activities exist. Currently, an all-oral and less toxic treatment regimen of Buruli ulcer is been sought after and encouraged by WHO.