ANTIBACTERIAL, PHYTOCHEMICAL AND ANTIOXIDANT CHARACTERISTICS OF SOME NIGERIAN MEDICINAL PLANTS

Abstract

The present study was designed to investigate the antibacterial, phytochemical and antioxidant effects of Sennahirsuta, Landolphia dulcis, Spathodea campanulata, Datura metel, Cnestis ferruginea, Cleome ciliata and Gliricidia sepium. The test pathogenic bacteria used wereSalmonella typhi, Shigella dysenteriae, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus, Streptococcus pyogenes, Campylobacter jejuni, Klebsiella pneumoniae, Escherichia coli and Enterococcus faecium.The crude aqueous, ethanol, methanol and petroleum ether extracts of the plants’ leaves, stem barks and roots were prepared and screened for antibacterial activity,minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against the test pathogenic bacteria species by agar well diffusion, tube dilution and pour plate methods. Grown colonies on the nutrient agar for MBC test were counted after incubation, to identify the extract concentrations that caused cells death. The qualitative and quantitative estimation of phytochemicals and antioxidants in the plants extracts was done using standard chemical methods. The invivo effects of the pathogens and the plants’ extracts were assessed by determining thebiochemical indices, haematological and histopathological parameters of the experimental mice’s liver, kidney and intestine. Among the plants,Landolphia dulcis extracts exhibited the highest antibacterial activity with inhibitory zones ranging from 10 to 41mm. This was followed by Spathodea campanulata whose leaf extracts displayed inhibitory haloes of 17 – 38mm and the smallest zone of inhibition was recorded forCleome ciliata where inhibitory zones ranging from 0-32 mm were observed. The leaf extracts of the plants showed higher inhibitory activity than the stem bark and root extracts. Among the solvents extract, the ethanol extract exhibited highest inhibitory potency on the test bacteria followed by aqueous, methanol and petroleum etherextracts.Staphylococcus aureus, Klebsiella pneumoniae, Campylobacter jejuni, Pseudomonas aeruginosa and Enterococcus faecium were the most inhibited while Streptococcus pyogenes, Shigella dysenteriae and Bacillus cereus were the least inhibited by the plants extracts among the testmicroorganisms. The MICand MBC of the extracts against the test pathogenic bacteria species were 12.5 – 400 mg/ml and 10 -500 mg/ml with Cleome ciliata extract showing the lowest MIC and MBC of 350 and 400 mg/ml respectively. The time killing kinetics of the plants crude extracts was within 24 - 48 hours. The reference antibiotics (streptomycin and methecilin) at concentration of 20mg/ml were not active against Escherichia coli, Salmonella typhi, Campylobacter jejuni and Klebsiella pneumoniae. The reference bacterial species (control) were less susceptible to the plants extracts (0 – 38 mm). The fraction extracts of the plants were higher in antibacterial activity (3 – 49 mm) than the crude extracts. Saponin, steroids, flavonoids, tannins, glycosides, alkaloids, phenol, terpenoids, anthraquinone and phlobatannins were present in the extracts. The quantitative phytochemicals estimated was higher (20.98 – 0.16 mg/ml) in L. dulcis, followed by S. hirsuta and was lowest (8.75 – 0.1 mg/ml) in C. ciliata.The amounts of in vitro antioxidants screened from the plants were higher in ethanol extracts, followed by aqueous and lowest in petroleum ether extracts. The red blood cells counts in the negative control (extracts treated mice after infection) group of the experimented mice were higher than those from positive control (paracetamol treated mice after infection).The loads of the white blood cells and haemoglobin concentrations were lower in the negative control than the positive control mice. The biochemical indices of the plants’ extracts in positive control mice revealedaspertate aminotransferase, alanine aminotransferase and alkaline phosphate values as 34.50±1.60, 43.20±4.01, 87.25±2.54. The bilirubin, urea, uric acid, creatinine and cholesterol values were 1.08±0.10, 18.15±1.50, 6.05±0.60, 1.38±0.30, 113.70±0.50 respectively. In the negative control mice lesser values of 67.47±4.02, 64.92±3.69 and 321.12±2.11 were respectively obtained for aspertate aminotransferase, alanine aminotransferase and alkaline phosphate. Bilirubin, urea, uric acid, creatinine and cholesterol values were 2.11±0.63, 23.40±0.16, 8.02±1.10, 1.96±0.09, 218.14±0.64 respectively. The concentrations of the total albumin and protein were higher (4.90±0.11, 7.15±0.45) in the negative control group of mice than the positive control animals (2.21±0.60, 5.18±0.60). After administering the plant extracts to the groups of mice induced with Salmonella typhi and paracetamol, lost heamatological and histopathological properties were recovered. Conclusively, the adverse physiological changes induced by the test pathogens in the mice as shown in theantioxidant,biochemical, histopathological and hematological profiles were improved by the extracts of L. dulcis, S. hirsuta, S. campanulata and C. ferrugineae in dose dependent pattern. Meanwhile, D. metel, C. ciliate and G. sepiumdid notexpress enough efficacies to improve the negative physiological effects examined in the mice. Though these three plants showed antibacterial potentials good enough for a reliable therapeutic agent on some of the test bacterial species, they did not possess toxins as evidenced by the biochemical analysis of the blood samples, hence they were not detrimental to the physiological status of the mice.