Date Published: March 20, 2018
Author(s): Abere Habtamu, Yadessa Melaku.
Vernonia amygdalina is traditionally used in Ethiopia to treat various diseases. This prompted us to isolate bioactive compounds from the flowers of this plant. The CHCl3 extract after silica gel column chromatography has led to the isolation of two compounds identified as tricosane (1) and vernolide (2), while the acetone extract furnished isorhamnetin (3) and luteolin (4). The acetone extract and isorhamnetin significantly scavenged the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical by 91.6 and 94%, respectively. It was also shown that the acetone extract and isorhamnetin inhibited lipid peroxidation by 74 and 80%, respectively. The extracts and isolated compounds were also evaluated for their antibacterial activity with the CHCl3 extract and vernolide showing strong activity against S. aureus with an inhibition zone of 21 and 19 mm, respectively. On the other hand, the acetone extract and isorhamnetin were active against all bacterial pathogens tested. The work presented herein has demonstrated that vernolide and isorhamnetin had antibacterial activity. The antioxidant activity displayed by the flowers of V. amygdalina is accounted to the presence of isorhamnetin. Therefore, the biological activities displayed by the extracts and isolated compounds from this plant corroborate the traditional uses of this plant by the local people against various diseases.
Vernonia amygdalina Del. is a soft woody shrub or tree belonging to the family Asteraceae and genus Vernonia . The plant is predominantly found in Africa. It is a perennial plant characterized by its bitter sap from the leaf which has been widely explored for its medicinal use. This plant grows to 10 m tall with petiole leaf of about 6 mm in diameter and elliptic in shape . In the Ethiopian highland, V. amygdalina has been classified by the farmer as a multipurpose fodder tree with high biomass yield, easy propagation, high adaptability, and high compatibility with other crops which do not compete with them for soil nutrients or moisture but instead help to improve the soil fertility and growth of perennial crops . V. amygdalina, locally called ebicha in Afan Oromo and Grawa in Amharic (Ethiopia), is quite commonly used in Ethiopia in the preparation of local beer and also as fumigant. It is also used as fire wood .
Four compounds were isolated and characterized from the flower extracts of V. amygdalina (Figure 2).
In conclusion, the work presented herein has demonstrated that the acetone extract and vernolide had strong antibacterial activity compared to chloramphenicol. The antioxidant activities displayed by the acetone extract and isorhamnetin were significant compared with ascorbic acid indicating the potential of the flowers of this species as natural antioxidants. Therefore, biological activities displayed by the flower extracts and constituents of the flowers of V. amygdalina corroborate the traditional uses of this plant against various ailments including bacteria.