Browsing by Author "Gumula, Ivan"

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    Antibacterial Properties of Phytochemicals Isolated from Leaves of Alstonia boonei and Aerial Parts of Ipomoea cairica
    (Natural Product Communications, 2024-09-26) Gumula, Ivan; Kyarimpa, Christine; Nanyonga, Sarah Kiwanuka; Kwesiga, George; Heydenreich, Mathias; Omara, Timothy
    The leaves of Alstonia boonei and aerial parts of Ipomoea cairica are used for treatment of microbial infections among other ailments in African traditional medicine. The aim of this study was to investigate the antimicrobial phytochemicals in A. boonei leaves and Ipomoea cairica aerial parts to validate their traditional use in Ugandan herbal medicine. The plant materials were separately extracted using a dichloromethane/methanol (1:1) solvent system and subjected to repeated chromatographic separation to isolate pure compounds. The chemical structures of the isolated compounds were determined through 1H NMR, 13C NMR and 2D NMR (COSY, HSQC and HMBC). The antibacterial activity of the extracts and pure compounds were assessed using the agar well diffusion method. Chromatographic fractionation of the extracts yielded trans-fagaramide and a pentacyclic lupane-type triterpenoid, lupeol, from A. boonei, and friedelin from I. cairica. Trans-fagaramide was identified for the first time in the Alstonia genus while friedelin was identified for the first time in I. cairica. The isolated compounds demonstrated antibacterial activity, with trans-fagaramide showing a minimum inhibitory concentration (MIC) of 125 μg/mL against Pseudomonas aeruginosa and 250 μg/mL against Staphylococcus aureus, Salmonella typhi and Escherichia coli. Friedelin exhibited a MIC of 125 μg/mL against Escherichia coli and 250 μg/mL against Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella typhi. The antibacterial activities observed in this study support the traditional use of A. boonei and I. cairica by indigenous communities in Uganda for treating microbial infections.
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    Antimicrobial potency of extracts from selected medicinal plants towards Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa
    (Kabale University Interdisciplinary Research Journal, 2023-10-16) Buyinza, Daniel; Gumula, Ivan; Akampuira, Denis; Ninsiima, Herbert
    Antibiotic resistance has become a very big threat to the existing first line antibiotics. Some of the infectious pathogens are becoming multidrug resistant including Mycobacterium tuberculosis. This has necessitated social, scientific and financial interventions from key players. The strain this puts on the fragile health care systems of developing nations is frustrating. Scientific interventions have involved campaigns for improved hygiene, use of combination therapies and revived search for new drugs with different modes of action. It is on this basis that this research was conducted as phase I into the search for antibiotic agents from nature. This was done by screening several plant extracts to identify bioactive extracts that can be developed into drugs or purified for better active single molecules in the second phase. Extracts were obtained by cold percolation of pulverized samples of different dried plant parts using different mono-solvents. Agar diffusion and froth floatation were used to measure the potency of the extracts. Many of the screened extracts had good to moderate activities. Five of the plant species; Zanthoxylum chalybeum and gilletii, Diospyros abyssinica, Prunus africana, Peptadeniastrum africana and Blighia unijugata showed very promising activities (1.9 to 9.4 mg/mL) against Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. The other species had moderate activity (10.6 to 47.5 mg/mL). The species (Albizzia coriaria, Maytenus senegalense and Kigellia africana) that inspired this research from literature only demonstrated moderate activity against all the tested organisms, probably due to antagonistic effect of the active compounds within the extracts. In conclusion, Z. chalybeum and gilletii, D. abyssinica, P. africana, Peptadeniastrum. africana and B. unijugata have a very strong potential for drug development and are recommended for use in the management of infections caused by the tested microbes and purification to isolate the individual active compounds for better formulation, standardization and drug acceptability.
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    Flemingins G−O, Cytotoxic and Antioxidant Constituents of the Leaves of Flemingia grahamiana
    (Journal of Natural Products, 2014-09-16) Gumula, Ivan; Alao, John Patrick; Ndiege, Isaiah Omolo; Yenesew, Abiy; Erdélyi, Máté
    The known flemingins A–C (1–3) and nine new chalcones, named flemingins G–O (4–12), along with deoxyhomoflemingin (13) and emodin (14) were isolated from a leaf extract of Flemingia grahamiana. The isolated chalcones were found to have a geranyl substituent modified into a chromene ring possessing a residual chain, as shown by spectroscopic methods. The leaf extract showed an IC50 value of 5.9 μg/mL in a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The chalcones flemingins A, B, C, G, and H were active in the DPPH radical scavenging assay (ED50 4.4–8.9 μM), while flemingins A and C showed cytotoxicity against MCF-7 human breast cancer cells (IC50 8.9 and 7.6 μM, respectively).
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    Legacy and emerging organic pollutants in indoor and outdoor environments in Africa: Contamination levels, health risks, and analytical techniques
    (Emerging Contaminants, 2025-01-02) Muhwezi, Godfrey; Kyarimpa, Christine; Gumula, Ivan; Nagawa, Christine Betty; Odongo, Silver; Kato, Charles Drago; Ssebugere, Patrick
    The World Health Organisation reported that over 20 % of the global disease burden and deaths are caused by environmental factors such as air and dust pollution. Legacy organic pollutants (LOPs) and emerging organic pollutants (EOPs) are among the biggest contributors to this burden. Herein we reviewed literature published for the period 2000–2023 on selected LOPs and EOPs in indoor dust and outdoor air in Africa to understand the occurrence, associated human health risks and common analytical techniques used to identify and quantify these contaminants. The findings revealed generally lower contamination levels for most pollutants than that in most regions outside Africa except for PCBs in outdoor air and OCPs in indoor settled dust. Apart from a few studies for polychlorinated biphenyls (PCBs), most studies reported hazard index (HI) values less than 1 for outdoor air and indoor dust exposure, which suggested negligible non-carcinogenic risks in children and adults. Gas Chromatography and mass spectrometry were the most frequently used analytical techniques for both air and dust probably due to their sensitivity and selectivity in detecting chemical traces at the pg m−3 and ng g−1 levels. Although the current contamination levels are generally low, their synergistic and cumulative effects may in the long run affect the environment and human health. There is also a paucity of data on most contaminants, especially for PCNs, and PFASs in both outdoor air and dust. Coordinated efforts are needed to limit the trade, importation, and disposal of products containing LOPs and EOPs in Africa.
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    Medicinal Plants Used in the Management of Sexual Dysfunction, Infertility and Improving Virility in the East African Community: A Systematic Review
    (Evidence‐Based Complementary and Alternative Medicine,, 2023-08-12) Kyarimpa, Christine; Nagawa, Christine Betty; Omara, Timothy; Ssebugere, Patrick; Lugasi, Solomon Omwoma; Gumula, Ivan
    Sexual disorders such as erectile dysfunction (ED), sterility, and sexual inappetence represent some of the complex reproductive challenges that require addressing the underlying causes. The aim of this paper was to systematically synthesize literature on the ethnobotany, phytochemistry, bioactivities, and safety of plants used as remedies for managing sexual dysfunction and infertility, and improving fertility and virility in the EAC. Through an extensive review conducted in multidisciplinary electronic databases, 171 plant species were identified to have been reported for the management of sexual inappetence (i.e., used as aphrodisiacs, 39.4%), ED (35.9%), infertility (18.7%), and increasing fertility (6.0%). The most used plants are Mondia whitei, Acalypha villicaulis, Combretum illairii, Erythrina abyssinica, Pappea capensis, Rhus vulgaris, and Warburgia ugandensis while roots (44.9%), leaves (21.8%), stem and root barks (16.7%) of shrubs (35%), trees (31%), herbs (26%), and climbers (8%) are the preferred organs for making decoctions (69%). The research strides to date indicate that Citropsis articulata, Cola acuminata, Ekebergia capensis, Plumbago zeylanica, Tarenna graveolens, Urtica massaica, and Zingiber officinale have been assessed for their bioactivity. The majority (71.4%) of the plants either increased testosterone levels and mounting frequency or elicited prosexual stimulatory effects in male rats. More studies investigating the relevant pharmacological activities (aphrodisiac, fertility, and phosphodiesterase-5 inhibitory activities), safety aspects, responsible compounds, and clinical studies are warranted to establish the pharmacological potential of the unstudied species and elucidate the mechanism of action of the bioactive compounds.
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    Rotenoids, Flavonoids, and Chalcones from the Root Bark of Millettia usaramensis
    (Journal of Natural Products, 2015-12-14) Deyou, Tsegaye; Gumula, Ivan; Mumo, Michael; Yenesew, Abiy
    Five new compounds, 4-O-geranylisoliquiritigenin (1), 12-dihydrousararotenoid B (2), 12-dihydrousararotenoid C (3), 4′-O-geranyl-7-hydroxyflavanone (4), and 4′-O-geranyl-7-hydroxydihydroflavanol (5), along with 12 known natural products (6–17) were isolated from the CH2Cl2/MeOH (1:1) extract of the root bark of Millettia usaramensis ssp. usaramensis by chromatographic separation. The purified metabolites were identified by NMR spectroscopic and mass spectrometric analyses, whereas their absolute configurations were established on the basis of chiroptical data and in some cases also by X-ray crystallography. The crude extract was moderately active (IC50 = 11.63 μg/mL) against the ER-negative MDB-MB-231 human breast cancer cell line, and accordingly compounds 6, 8, 9, 10, 12, and 16 also showed moderate to low cytotoxic activities (IC50 25.7–207.2 μM). The new natural product 1 exhibited antiplasmodial activity with IC50 values of 3.7 and 5.3 μM against the chloroquine-sensitive 3D7 and the chloroquine-resistant Dd2 Plasmodium falciparum strains, respectively, and was also cytotoxic to the HEK293 cell line.