Abstract:
An acetone extract of Loxostylis alata was separated into six fractions based on polarity by a solventsolvent
fractionation procedure and the different fractions were screened for antimicrobial and
antioxidant activities. The number of antimicrobial compounds in the carbon tetrachloride (CCl4),
chloroform (CC), aqueous methanol (AM) and butanol (BT) fractions were determined by bioautography.
Each fraction was loaded onto thin layer chromatography (TLC) plates and eluted using two different
mobile solvent systems, namely chloroform/ethyl acetate/formic acid (5:4:1): (CEF) and ethyl
acetate/methanol/water (40:5.4:5) (EMW). Relative front (Rf) values of active compounds against
bacteria ranged from 0.4 - 0.9 in CEF and EMW solvent system. Similarly, the Rf values of compounds
active against fungi were in the range of 0.7 - 0.9. Hexane, carbon tetrachloride, chloroform, aqueous
methanol and butanol fractions showed areas of inhibition against bacterial organisms, while only
hexane and carbon tetrachloride fractions depicted areas of fungal growth inhibition on their
chromatograms. The CCl4 extract was active against six out of the nine microbial strains used and was
particularly active against Staphylococcus aureus, Enterococcus faecalis, Aspergillus fumigatus,
Candida albicans, Cryptococcus neoformans and Microsporum canis with minimum inhibitory
concentration (MIC) of 0.04, 0.04, 0.1, 0.1, 0.06 and 0.03 mg/ml, respectively. M. canis was the most
sensitive organism with the lowest average MIC of 0.16 mg/ml. Qualitative antioxidation using
diphenylpicryl- hydrazyl (DPPH) and qualitative assay using both 2,2'-azinobis-3-ethylbenzothiazoline-6-
sulfonate (ABTS) and DPPH radicals revealed the presence of three antioxidant compounds in the AM
and BT fractions, while the water fraction had only one antioxidant compound. However, the
concentration of the antioxidant compounds was more in the AM and BT fractions as revealed by their
pronounced colour intensity on the TLC plates. The water fraction had more free radical scavenging
effect against DPPH with EC50 value of 0.62 ± 0.03 μg/ml. The lower the EC50 value of an extract, the
more effective its antioxidant activity. In a similar manner, TEAC value of water fraction was 2.97, which
further indicates superior free radical scavenging effect of the fraction against ABTS radical. The
greatest reduction of reactive oxygen species (ROS) production induced by diclofenac was also
achieved by the water fraction which on overall shows that the water fraction contains more
antioxidants. The presence of antimicrobial and antioxidant activities in the fractions of L. alata
suggests that this plant may be a source of pharmacologically active substances with beneficial actions
towards disease control and treatment in animals and humans.
