ASSESSMENT OF THE ANTIBACTERIAL AND ANTIOXIDANT PROPERTIES OF ANDROGRAPHIS PANICULATA (Nees) AND MORINDA LUCIDA (Beth)

Abstract

Plants have become alternative drug sources since microorganisms have developed resistance to many antimicrobial drugs in use. This research aimed at investigating the antibacterial properties of the methanol, n- hexane and aqueous extracts of the stem of Andrographis paniculata (Nees) and fruit of Morinda lucida (Beth) against some clinical and typed bacterial isolates especially the multiple antibiotic resistant bacteria. The phytochemical and antioxidant compositions of the extracts were investigated using standard methods. The antibacterial activities of the extracts were determined individually and in synergy against the antibiotic resistant bacterial isolates using agar diffusion method. The Minimum Inhibitory Concentration (MIC) of the extracts was evaluated and the therapeutic effect and biosafety of the most effective extract was determined using albino rats model. The glucose tolerance dose and mechanism of action of the most effective extract were determined using standard methods. The extract with the highest antibacterial activity was purified using column chromatography and fractions obtained were spotted on thin layer chromatographic plates. Fractions with same refractive factor values were bulked together and were further tested for their antibacterial activities on the antibiotic resistant bacteria. The bioactive components in the antibacterial potent fraction were determined using Gas Column Mass Spectrophotometer (GCMS) and Fourier Transform Infra- Red Spectroscopy (FTIR). Results showed that the prevalence of bacterial isolates resistant to antimicrobials are as follows: Ampicillin (100%), Augmentin (100%), Ceftriaxione (100%), Cefuroxime (100%), Ceftazidime (100%), Cloxacin (100%), Erythromycin (73%), Nitrofurantoin (69%), Gentamycin (68%), Ciprofloxacin (62%) and Ofloxacin (40%). The phytochemical analysis of the extracts showed the presence of saponin, flavonoid, terpenoid, phlobotannin and tannin, however, there was absence of tanin in the aqueous extract of A. paniculata. Saponin was found to be the most abundant in the methanol extract of A. paniculata while the aqueous extract had the least. For M. lucida extract, appreciable amount of saponin and tannin were recorded. The highest quantity of flavonoids, total phenol and ascorbic acid were obtained in the methanol extract of A. paniculata. All the isolates were susceptible to n- hexane and methanol extracts of A. paniculata with the zone of inhibition ranging from 10- 18 mm and 15- 28 mm respectively. Pseudomonas aeruginosa isolated from wound of diabetic patient was the most susceptible to the methanol extract of A. paniculata with zone of inhibition value 28 mm followed by S. typhi (26 mm) isolated from blood of diabetic patient. The synergistic activity against the test isolates showed considerably higher potency on the isolates compared to the individual activity of the extracts. The MIC of the extracts on the typed isolates ranged between 25 mg/ml and 50 mg/ml while for the clinical isolates, it ranged from 3.125 mg/ml to 50 mg/ml. Result of the acute toxicity showed no mortality or change in either the appearance or behavior of the model rats but there was increase in body weight. Macroscopic and microscopic studies of the internal organs revealed no pathological changes. Blood sugar level of the groups treated with A. paniculata (15 and 30 mg/kg) were significantly lower than glucose induced group. The mechanism of action showed leakage of both sodium and potassium ions from the cells of the bacteria. Antibacterial activities of the column fractions revealed that the fractions had higher inhibitory effects in comparism to the crude extracts. Result of the FTIR revealed the presence of various functional groups such as OH, carbonyl, alcohol, aromatic group etc. The bioactive components analysed by GCMS revealed various compound such as naphthalene, benzene, dodecanoic acid etc. Findings from this research revealed that the methanol extract of A. paniculata has numerous bioactive components which could be exploited in the treatment of bacterial infections especially those caused by antibiotic resistant ones.