Bioactivity of Chromatographic Fractions from Eucalyptus citriodora Leaf Against Some Bacterial Pathogens

Abstract

Considering the application of Eucalyptus citriodora in Folklore medicine in the treatment of Typhoid fever and respiratory tract infections, fractions were obtained from n-hexane extract by reflux extraction and chromatography techniques to determine its antibacterial activity and phytochemical properties. A total of 25.85g (5.17%) was obtained from 500gms of dry plant material while the phytochemical analysis result revealed the presence of 10 different bioactive constituents viz; alkaloids, flavonoids, saponins, cardiac glycosides, tannins, steroids, terpenes, resins, phenols and volatile oils with the absence of anthraquinones. The crude extract exhibited antibacterial activity against all the test organisms at 20mg/mL with mean inhibition zone (MZI) ranging from 15.00±0.57a mm to 20.66±0.33a mm, which were effective than the fractions. A total of 8 fractions namely ECO1, ECO2, ECO3, ECO4, ECO5, ECO6, ECO7 and ECO8 were obtained from the crude extract by column chromatography, 5 (ECO2, ECO4, ECO6, ECO7 and ECO8) were active at 40mg/mL against all the test organisms with MZI range of 8.00±0.00mm to 21.66±0.88mm while ECO2 and ECO4 exhibited intermediate activity with MZI range of 15.00±0.00mm 18.66±0.33mm and 9.33±0.33mm to 21.66±0.88mm respectively. The minimum inhibitory concentration (MIC) and corresponding minimum bactericidal concentration (MBC) of the crude extract and fractions were 7.5mg/mL & 120mg/mL and 3.25mg/mL & 120mg/mL respectively. Thirty nine (39) and fifteen (15) compounds were identified in ECO2 and ECO4 respectively by column chromatography with gamma.-Tocopherol (10.25%), Hemimellitene (8.64%), n-Decane (6.82%), 11-Octadecenoic acid, methyl ester (6.56%) & Decane, 2-methyl- (5.13%) and delta. (Sup9)-cis-Oleic acid (21.02%), Stigmasterol, 22,23-dihydro- (14.35%), 6.beta.Bicyclo[4.3.0]nonane, 5.beta.-iodomethyl-1.beta.- isopropenyl-4.alpha.,5.alpha.-dimethyl- (14.13%), n-Hexadecanoic acid (8.62%), Hydrofol Acid 150 (7.64%) and Ricinoleic acid methyl ester (7.61%) as the most abundant respectively. All the identified compounds have been reported to possessing antibacterial activity, therefore, based on the results obtained in this research study and considering the toxicity level of the plant extract with a safe dose (LD50) of 1369mg/kgbw, fractions from Eucalyptus citriodora can be used to develop drug for the treatment of infections caused by the test organisms. is a component in many commercial pesticides Fradin and Day, (2002). Their bioactivity is yet to be fully harnessed and therefore, the aim of this research study is to determine the antibacterial activity of column chromatography fractions from n-hexane extract of the leaf of Eucalyptus citriodora.