Browsing by Author "Busulwa, George"

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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; Busulwa, George; Opio, Boniface; Heydenreich, Mathias; Omara, Timothy
    Objective: 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. Methods: 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. Results: 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. Conclusion: 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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    Phytochemical investigation of Alstonia Boonei for Antimicrobial activities
    (Kyambogo University [unpublished work], 2023-07) Busulwa, George
    Alstonia boonei was investigated with the aim of identifying bioactive compounds present in its leaves. The plant was chosen because it is one of the most widely used plants in traditional herbalimedicine. The leaves of Alstonia boonei were collected from Nakawuka village, Wakiso District, Central Uganda, in November 2017. Extraction of the crude was done by soaking the dry powdered leaves in a mixture of dichloromethane and methanol (1:1, iv/v) followed by preliminary phytochemical screening. Isolation and purification of compounds was carried out using Column Chromatography over silica gel and the extent of separation was monitored using Thin Layer Chromatography(TLC). Bioactivity of ithe crude extract, as well as one isolated compound, was determined against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella typhi Preliminary phytochemical analysis revealed the presence of tannins, flavonoids, saponins, terpenoids, cardiac glycosides and alkaloids. The isolated compounds were identified with the help of a combination of both 1D and 2D NMR spectroscopic techniques. Two compounds were isolated and identified; viz: an amide derivative, trans fagaramide (1) and a triterpene, lupeol i(2). Compound 1 is hereby reported for the first time from the genus Alstonia. The crude extract exhibited strong antibacterial activity against E. coli in the disc diffusion assay with a diameter zone of inhibition of 20 mm and moderately active against P. aeruginosa and S. aureus (diameter zone of inhibition of 10 and 9 mm, respectively), but it was inactive against S. typhi. Trans-fagaramide showed moderate antibacterial activities in the disc diffusion assay with zones of inhibition (diameter) of 13, 12, 10 and 10 imm against S. typhi, P. aeruginosa, S. aureus and E. coli, respectively. The minimum inhibitory concentration of trans-fagaramide was 125 mg/mL against P. Aeruginosa and 250 mg/mL against the rest of the test bacterial strains. The results in this study justify the use of Alstonia boonei in the management of infectious diseases by traditional healers.