Browsing by Author "Beukes, Denzil"

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    Antibacterial Activities of Selected Green Seaweeds from West African Coast
    (EC Pharmacology and Toxicology ECronicon Open Access, 2020) Agbaje-Daniels, Folashade; Adeleye, Adeyemi; Bola, Adeniyi; Francis, Seku; Beukes, Denzil; Nwankwo, Duke
    The continually increasing antibiotic resistance amongst microorganisms had steered up an increased intensity in the search for new drugs. The marine environment had been reported to be a great source of novel compounds with diverse biological activities and this had engendered the attention of researcher globally, but the West African Coast despite being blessed with a variety of Macro-algae remain untapped. This study was, therefore, embarked upon to investigate the antibacterial activities of selected green algal species from the West African coast. Crude extracts of Ulva fasciata, Ulva lactuca, Chladophora vagabunda, Caulepa taxifolia, Chaetomorpha antennina and Chaetomorpha linum were obtained by maceration using Dichloromethane/methanol (DCM/MeOH), chloroform/methanol (CHL/MeOH) 90% (v/v), Ethanol and Diethyl ether as solvents. Extracts were screened against some bacterial pathogens including Gram-positive bacteria- clinical strain (Sa I), S. aureus laboratory strain (Sa II), S. aureus ATCC 25922 (Sa III), Bacillus subtilis (Bs), Streptococcus pneumonia (Sp), Streptococcus faecalis (Sf) and Mycobacterium aurum (Ma). Gram-negative test bacteria were Escherichia coli clinical (Ec I) and Escherichia coli laboratory strain (Ec II), Escherichia coli NCTC 10418 (Ec III), E. coli ATCC 25923 (Ec IV), Proteus vulgaris (Pv), Proteus mirabilis (Pm), Pseudomonas aeruginosa (Pa) Pseudomonas putida (Pp), Salmonella typhi clinical strain (St I), Salmonella typhi NCTC 8385 (St II), Serratia macerans (Sm) and Klebsiella pneumonia (Kp). Crude extracts were obtained using Antibacterial screening was carried out by disc diffusion method. The result analysis was done by mean ± SD. The result showed that all the screened algae had antibacterial activity against at least one of the test organisms. Four (57%) of the seven algal species tested demonstrated inhibitory activities against the Gram-positive test bacteria while all the seven species tested showed inhibitory activities against the Gram-negative test bacteria. Highest inhibitory zone against Gram-negative bacterial species was observed in dichloromethane/methanol extract of Caulepa taxifolia (DCCT) against E. coli measuring 14.67 mm while the highest activity against Gram-positive bacterial strain was observed in diethyl acetate extract of Chaetomorpha antennina (DECA) against S. aureus (SaII) with an inhibitory zone of 17.67 mm. Extracts of Chaetomorpha antennina showed the highest inhibitory activities in this study. The result of this study showed that extracts from species of green macro-algae from the West African Coast possess antibacterial compounds that can serve as lead drug candidates in the quest for new antibacterial therapy if well explored.
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    Discovery of anti-mycobacterial natural products from South African marine algae
    (University of the Western Cape, 2019) Mukaddam, Zaahirah; Beukes, Denzil
    Tuberculosis is a communicable disease which affects millions of people around the world. Although the case reports are declining, the eradication rate of this disease is far too slow. Natural products have played a key role in the treatment of the disease. However, tuberculosis is developing resistance to current first-line therapy. In this study, a prefractionated marine algal library was developed in order to identify and prioritise samples for isolation of their active metabolites which exhibit anti-tuberculosis activity. Based on the results of the library screening and chemical profiling, two seaweeds were selected for further investigation, Laurencia glomerata and Plocamium cornutum. The extraction and fractionation of Laurencia glomerata and Plocamium cornutum resulted in the isolation of three chamigrane seqsuiterpenes (prepacifenol epoxide, johnstonol and one newly proposed structure) and two monoterpenes (cartilagineal and 1,5,6-trichloro-2-(dichloromethyl)-6-methylocta-1,3,7-triene) respectively. The structures of these compounds were elucidated by 1 and 2D NMR data and were confirmed by literature comparisons. Although some of the initial library factions screened showed rather good activity against Mycobacterium tuberculosis, the selected seaweed fractions showed greater activity against M. aurum. The isolated monoterpenes showed moderate cytotoxicity against the cancer cell line MCF-12a and the sesquiterpenes however were more selective for MCF-7. The monoterpenes showed both activity and potential selectivity towards Mycobacterium tuberculosis.
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    Isolation and Bioassay evaluation of Angiotensin Converting Enzyme inhibitory compounds of Centella asiatica
    (University of the Western Cape, 2019) Ichoku, Emmanuel; Obikeze, Kenechukwu; Beukes, Denzil
    Hypertension is by far the most common risk factor for cardiovascular disease (CVD), which has been identified as the leading cause of death worldwide and a major economic burden in developing countries. Over the years, there has been an increased interest in isolating and identifying bioactive compounds from medicinal plant, with the aim of finding alternative sources of therapy to some of the problematic synthetic drugs and to validate the therapeutic use of some traditional plants. The renin angiotensin aldosterone system is a key regulator of blood pressure, on which ACE (Angiotensin Converting Enzyme) inhibitors act and have been at the forefront of therapeutic strategy for treatment and management of hypertension and CVD. But despite the success of ACEI’s, their long term use has been associated with side- effects coupled with its contraindication in pregnancy. The plant of interest, Centella asiatica is a widely known medicinal plant, used in treatment of a variety of conditions including hypertension. There is currently no scientific evidence validating its claimed use in hypertension. This study therefore, investigated the ACE inhibitory effects of Centella asiatica. Crude methanol, ethanol and aqueous extracts of Centella asiatica were assayed for ACE inhibition activity. Methanol and ethanol crude extract(s) was subjected to a bioassay guided fractionation process to isolate and identify the active compounds. A fluorescence based ACE assay was utilized at various stages of the process including HPLC purification stage to screen the fractions and compounds for ACE inhibition activity.
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    Phytochemical and biological studies of Helichrysum cymosum
    (University of the Western Cape, 2020) Jadalla, Baraa Mohamed Ibrahim Soliman; Beukes, Denzil
    Diabetes mellitus (DM) is well known as a group of systemic metabolic disorders with a considerable mortality rate around the world. Hyperglycemia is the main consequence of DM, which results from the shortage in insulin production or degradation of produced insulin. Other internal and external factors including obesity, oxidative stress, and sedentary lifestyle have been also suggested as the causes of DM. Among the well-known existing types of DM, type 1 and 2 are the most common. Treatment of type 1 necessitates insulin injection, while type II can be controlled by physical exercises, diet control in addition to different synthetic antidiabetic drugs. However, their effectiveness is restricted because of the high cost and unfriendly side effects. There is a significant need for producing alternative and more bioactive antidiabetic drugs from natural sources. Natural products are a well-known source for the discovery of new scaffold for drugs discovery, and South Africa is one of the most important megaflora with a high percentage of endemism. South Africa is home to about 245 species of Helichrysum species, which are generally rich sources of secondary metabolites, especially flavonoids, which give them a great value for global acceptability and wide application in the pharmaceutical fields as antibacterial, anti-inflammatory, antioxidant, and antidiabetic agents. The phytochemical investigation of the methanolic extract of H. cymosum resulted in the isolation and identification of seven pure compounds (1-7). Structural characterization of these isolated compounds was conducted using 1D NMR, in comparison with reported spectroscopic data. The in vitro bio-evaluation of H. cymosum against alpha-glucosidase shown that 5 exhibited the highest alpha-glucosidase inhibitory activity with IC50 value of 13 μM, followed by 7 and 3 with IC50 values of 18.16 μM and 44.4 μM respectively. Additionally, strong total antioxidant capacities were displayed by 6 and 2 as ORAC (122.86 ± 0.7 and 91.70 ± 0.4 μM TE/mL) respectively as well as 5 and 7 as FRAP (1006.34 ± 1.7; 977.79 ± 0.8) μM AAE/g. This is the first scientific report to be carried out on alpha-glucosidase inhibitory activities and antioxidant capacities of H. cymosum constituents. The findings suggest that these compounds might become prominent natural candidates to inhibit alpha-glucosidase as well as oxidative stress related to diabetes with the prospect to be employed in the formulation of diabetes drugs upon further biological studies.
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    Tandem lc-ms identification of antitubercular compounds in zones of growth inhibition produced by South African filamentous actinobacteria
    (MDPI, 2023) Watson, Daniel J.; Wiesner, Lubbe; Beukes, Denzil
    Novel antitubercular compounds are urgently needed to combat drug-resistant Mycobacterium tuberculosis (Mtb). Filamentous actinobacteria have historically been an excellent source of antitubercular drugs. Despite this, drug discovery from these microorganisms has fallen out of favour due to the continual rediscovery of known compounds. To increase the chance of discovering novel antibiotics, biodiverse and rare strains should be prioritised. Subsequently, active samples need to be dereplicated as early as possible to focus efforts on truly novel compounds. In this study, 42 South African filamentous actinobacteria were screened for antimycobacterial activity using the agar overlay method against the Mtb indicator Mycolicibacterium aurum under six different nutrient growth conditions. Known compounds were subsequently identified through extraction and high-resolution mass spectrometric analysis of the zones of growth inhibition produced by active strains. This allowed the dereplication of 15 hits from six strains that were found to be producing puromycin, actinomycin D and valinomycin.