In Vitro Antibacterial Activity of Vernonia amygdalina and Croton macrostachyus Leaf Extracts against Selected Human Pathogenic Bacteria

Genet Zelalem
Debre Markos University, Department of Biology, Debre Markos, Ethiopia

Tilahun Alelign
Department of Biomedical Sciences, School of Medicine, Debre Berhan University, Ethiopia

Asmamaw Habtamu
Debre Markos University, Department of Biology, Debre Markos, Ethiopia

Abstract

Humans have used plants to cure various disorders throughout their history. Vernonia amygdalina and Croton macrostachyus are among the commonly used medicinal plants in various parts of Ethiopia.  This study evaluated the antibacterial potential of two plants against some standard bacteria. Plants materials were collected from natural vegetation, air-dried under shade, ground into powder, and soaked in separate Erlenmeyer flasks. The extract mixture was shaken by rota-evaporator for 3 days. The extracts were screened for phytochemicals.  Methanolic leaf extracts of V. amygdalina revealed bacterial zone of inhibition (19.5 ± 1.5 mm) at 200 mg/mL against Staphylococcus aureus.  Similarly, C. macrostachyus revealed inhibition (18.0 ± 0.0 mm) at 200 mg/mL on S. aureus. On the contrary, the lowest inhibition zone was obtained from the extract of C. macrostachyus on S.typhi at 25 mg/mL. Metanolic extract of  C. macrostachyus revealed significantly higher inhibitions against S. aureus than K. pneumoniae , S.  typhi  and  E. coli  (p < 0.05). Extract of V. amygdalina showed the lowest minimum inhibitory and bactericidal concentration at 6.25 and 12.5 mg/mL against S. aureus respectively. The findings indicate that extracts of V. amygdalina and C. macrostachyus possess potential antibacterial activities against selected human pathogenic bacteria.

Keywords: Croton macrostachyus; Minimum inhibitory concentration; Phytochemical screening; Vernonia amygdalina; Inhibition zone.