Abstract:
Large proportions of the world’s population use traditional medicinal plants to treat various
diseases. Brucea antidysenterica and Tagetes minuta are one of the most common medicinal
plants used to treat infectious diseases in Ethiopia. This study was aimed to analyze major
classes of secondary metabolites and evaluate the antimicrobial properties of crude leaf extracts
from Brucea antidysenterica and Tagetes minuta against Staphylococcus aureus, Escherichia
coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus niger. Distilled water, ethanol
and hexane were used for extraction. To determine total phenolic contents, total alkaloids and
total terpenoids, standard procedures were used. Antimicrobial activities and minimum
inhibitory concentration of the extracts were determined using disc diffusion and broth dilution
method, respectively. Ciprofloxacin and distilled water were used as positive control and
negative control, respectively. From the result, total terpenoids from hexane extract of Tagetes
minuta was found 40.43±0.40 mg/g which is significantly different from the values of other
extracts (P < 0.05). Likewise, total alkaloids of ethanol extract from Brucea antidysenterica was
found 27.71±0.10 mg/g which was significantly different from values of other extracts. Except for
100mg/mL of Brucea antidysenterica, all the extracts showed antimicrobial activities. The zone
of inhibition of ethanol extract from Brucea antidysenterica against Staphylococcus aureus was
11.33±0.58 mm with minimum inhibitory concentration of 12.50±0.17 mg/mL. Except for the
200 mg/mL of ethanol extract, Candida albicans was not inhibited by other extract types of
Brucea antidysenterica. Similarly, ethanol extract from Tagetes minuta inhibited the growth of
Staphylococcus aureus with a zone of inhibition of 16.33±0.58 mm and minimum inhibitory
concentration of 8.33±3.61 mg/mL. Zone of inhibition of positive control against Staphylococcus
aureus was 22.33±0.58 mm. In general, the plants studied produce secondary metabolites in
different quantities and their extracts have the medicinal potential for treating bacterial and
fungal infections
