Abstract:
Vernonia leaf scientifically known as Vernonia amygdalina, of Asteraceae family is one of
the traditional medicinal plants used found in Africa and Asia. Thus, the objective of the
study was to investigate major secondary compounds from, roots, leaves and flowers
extracts of Vernonia amygdalina and their antibacterial activities in vitro. The experiment
was designed in a complete random design arranged as 2*3*2*3 multi-factor factorial.
That is 2 test pathogens by -3 extract sources obtained in 2 solvents (ethanol and water) at
3 concentration levels a factorial design in three replications. Data was analysed using
computer software SPSS, version 20. The phytochemical composition of ethanol and water
extracts from Vernonia amygdalina leaf, root and flower showed the presence of
flavonoids, saponins, tannins, alkaloids, terpenoids in all analysed plant parts. In this
study, Steroids and phlobatannins were not detected in all plant parts. As indicated in the
results, the leaves of V. amygdalina produced the highest yield of flavonoids in both
extracts. The quantity of alkaloids, flavonoids, phenol and saponins were highest in leaves
than root and flower. The study also indicated ethanol crude extracts contain more
bioactive compounds than water extracts. The highest concentration of the ethanolic
extract (200mg/ml) presented the strongest antibacterial activity with maximum zone of
inhibition (16.0±0.9mm) for leaf ethanol extract against Staphylococcus aureus. The
Vernonia amygdalina leaf, root and flower was observed that, ethanolic extract from leaf
presented strongest antibacterial activity with minimum inhibitory concentration
(62.5mg/ml) and corresponding minimum bactericidal concentration (125mg/ml) against
Staphylococcus aureus. This indicates Staphylococcus aureus (gram positive) more
susceptible than Escherichia coli (gram negative) in both minimum inhibitory
concentration and zone of inhibition. In water extracts (flower and root) there is no
minimum inhibitory concentration and minimum bactericidal concentration against both
Escherichia coli and Staphylococcus aureus. Further studies are needed to isolate and
separate the bioactive compounds responsible for, antibacterial activities using advanced
tools and scientific techniques
