Phytochemical investigation of the anti-foodborne pathogens and antioxidant constituents of two combretum species leaf extracts
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Date
2025
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Department of Chemistry, Faculty of Science, Obafemi Awolowo University, Ile-Ife.
Abstract
This study obtained the crude and solvent fractions of the leave extracts of C. platypterum and C. zenkeri and determined the yield and percentage yield of each extract,screened the anti-biofilm, anti-spores and anti-oxidant potentials of the plant extracts, isolated bioactive compounds from the active fractions of the plant
extracts,characterized the isolated compounds using nuclear magnetic resonance spectroscopic techniques 1D and 2D; and evaluated the anti-biofilm, anti-spores of the most active compound and anti-oxidant potentials of each compound. These were with a view to establishing the constituents of the selected two
Combretum species that are responsible for the anti-foodborne pathogens and antioxidant activities of the plants’ extracts.
The leaves of Combretum platypterum and Combretum zenkeri were collected, identified, air dried, and powdered at room temperature. Powdered leaves (1.2 kg) each were extracted with 20 L of 80% v/v methanol/water. The crude extract obtained was partitioned using n-hexane, dichloromethane, ethyl acetate, and n-butanol in succession. The anti-bacterial and anti-oxidant activities screening of the extracts were carried out and the most active fraction was selected for fractionation. Isolated compounds were characterized using Nuclear Magnetic Resonance spectroscopy. The minimum inhibitory concentration (MIC), anti-biofilm and anti-spores activities of the most active isolated compound were evaluated against Bacillus cereus, Klebsiella pneumoniae, and Staphylococcus aureus. The anti-oxidant and anti cholinesterase activities of the extracts and isolated compounds were assessed.Combretum platypterum produced a lower extract yield (0.93%) compared to
Combretum zenkeri (3.54%). The ethyl acetate fractions from both plants demonstrated the strongest anti-bacterial and antioxidant activities. The isolated bioactive compounds were characterized as kaempferol-3-O-glucoside (1), kaempferol-3-O-rutinoside (2) and 4hydroxybenzoic acid (3) from the Combretum platypterum, while catechin (4) and hydroxybenzoic acid were isolated from Combretum zenkeri. Antimicrobial sensitivity screening against Staphylococcus aureus, Bacillus cereus, and Klebsiella pneumoniae indicated resistance to kaempferol-3-O-rutinoside, kaempferol-3-O-glucoside and catechin and susceptibility to 4-hydroxybenzoic acid at 6 mg/mL. The MIC and MBC of 4-hydroxybenzoic acid were 1.5 and 3.0 mg/mL, respectively. At the MIC of 1.5 mg/mL, 4-hydroxybenzoic acid exhibited anti-biofilm activity of 93.03% (Staphylococcus aureus), 92.14% (Bacillus cereus), and 93.68% (Klebsiella pneumoniae). None of the compounds exhibited anti-spore activity. All the isolated compounds demonstrated significantly higher nitric oxide inhibition activity than the ascorbic acid standard (P ≤ 0.05); compounds 1-3 are not significantly different from the standard eserine in anti-cholinesterase activity. The 4-hydroxybenzoic acid isolated from the two plants recorded 727.45 AAE mg/g in the ferric reducing antioxidant power and 717.12 AAE mg/g in the total antioxidant capacity assay. The study concluded that 4-hydroxybenzoic acid is responsible for the plants' activity against foodborne pathogens and exhibited strong anti-biofilm properties. Additionally, every isolated compound demonstrated antioxidant activity in every model tested.
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Olusiji, O. A.(2025),Phytochemical investigation of the anti-foodborne pathogens and antioxidant constituents of two combretum species leaf extracts, Department of Chemistry, Faculty of Science.