Antimicrobial and antioxidant flavonoids from the leaves of Oncoba spinosa Forssk. (Salicaceae)

Abstract

BackgroundNaturally occurring flavonoids have been reported to possess various pharmacological properties. The aim of this study was to evaluate the antimicrobial and antioxidant activities of the MeOH extract and flavonoids from the leaves of Oncoba spinosa, a plant used for the treatment of syphilis, wounds and sexual impotence.MethodsThe plant extract was prepared by maceration in methanol and sequentially fractionated by column chromatography. The structures of isolated compounds were elucidated on the basis of spectral studies and comparison with published data. The MeOH extract and its isolated compounds were evaluated for their antibacterial and antifungal activities by broth microdilution method. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) and trolox equivalent antioxidant capacity (TEAC) assays were used to detect the antioxidant activity. The samples were tested spectrophotometrically for their hemolytic properties against human red blood cells.ResultsThe fractionation of the MeOH extract afforded five known flavonoids including kaempferol (1), quercetin (2), apigenin-7-O-β-D-glucuronopyranoside (3), quercetin 3-O-β-D-galactopyranoside (4) and quercetin 3-O-α-L-rhamnopyranosyl (1 → 6) β-D-glucopyranoside (5). The MeOH extract displayed weak to moderate antimicrobial activities (MIC = 256–2048 μg/ml). Quercetin 3-O-α-L-rhamnopyranosyl (1 → 6) β-D-glucopyranoside (5) and quercetin (2) were respectively the most active compounds against bacteria (MIC = 8–64 μg/ml) and fungi (MIC = 64 – 128 μg/ml). These tested samples also showed high radical-scavenging activities (EC50 = 5.08 – 70.56 μg/ml) and gallic acid equivalent antioxidant capacities (TEAC = 53.76 – 89.86 μg/ml) when compared with vitamin C (EC50 = 4.72 μg/ml). The MeOH extract and compounds 2–5 were non-toxic to human red blood cells indicating their high selectivity to be used as antimicrobial and antioxidant drugs.ConclusionThe MeOH extract of O. spinosa as well as compounds 2 – 5 could be a potential source of natural antimicrobial and antioxidant products.

Complex secondary metabolites from <i>Ludwigia leptocarpa</i> with potent antibacterial and antioxidant activities

“…The antioxidant capacity of the tested extracts may be due to the hydrogendonating ability of phenols and flavonoids present in those extracts. Similarly, previous studies have reported that phenolic compounds contribute significantly to the antioxidant activity of medicinal plants (39,48). The compounds that had the most potent DPPH…”

“…All of the compounds that were found to be active in the present study are members of the triterpenoid, flavonoid, and phenolic acid groups. Although triterpenoid, flavonoid, and phenolic acid compounds have been reported to possess antibacterial activity (39,44), no study has reported the activity of compounds 3 and 6-10 on the types of MDR pathogenic bacterial strains used in the present study.…”

“…However, a MeOH extract had the highest MIC, 512 μg/mL, for V. cholerae SG24(1) while a MeOH extract had the highest MBC, 512 μg/mL, for V. cholerae SG24(1), V. cholerae CO6, and V. cholerae PC2. A lower MBC or MIC (≤ 4) means that a minimum amount of the plant extract or isolated compound was needed to kill the bacterial species while a higher value means that a comparatively higher concentration of the extract or compound was needed to control of the microorganism (39).…”

Anticancer and antibacterial secondary metabolites from the endophytic fungus Penicillium sp. CAM64 against multi-drug resistant Gram-negative bacteria

“…The results of MIC and MBC showed that the MIC values obtained were four times equal to or lesser than the MBCs on the corresponding (sensitive) bacteria, suggesting the bactericidal effects of the concerned samples. 27,28,29 This is interesting in view of the perspective of developing new antibacterial drugs from endophytic fungus. The present study showed antibacterial activity of penialidin A-C (1-3), citromycetin (4), p-hydroxyphenylglyoxalaldoxime (5) and brefelfin A (6) from Penicillium sp.…”

Antibacterial activity of seneciolactone isolated from <i>Senecio scandens</i> against some common gastrointestinal tract disease causing bacterial pathogens

“…Many plant derived compounds including phenols, quinones, terpenoids, flavones have been reported to possess antibacterial activity. (Djouossi et al, 2015;Cabral et al, 2015). …”