Phytochemical Screening and Antibacterial Activity of Stem Bark Extract of Maesa Lanceolate and Isolated Compounds

Maesa lanceolate locally known as “Kowwaada” in Hadiya, and “Yekalaha zaf” in Amharic is one of the species in Primulaceae family whose aerial and axial parts have been in wide use for the treatment of a variety of diseases in different parts of the world. Its stem bark in association with leaves or alone is employed for medicinal value among the Hadiya community of Southern Ethiopia. The stem bark of Maesa lanceolata was collected, chopped into pieces, air-dried, ground and extracted successively with dichloromethane (DCM) and methanol (MeOH) to afford 0.8% DCM and 12.26% methanol crude extracts, respectively. The methanol crude extract, which showed clear TLC profile and yield, was subjected to silica gel column chromatography in n-hexane to ethyl acetate solvent system with increasing polarity and two compounds, namely, 2, 5-dihydroxy-3-methyl-6- (nonadec-14-enyl)-1, 4-benzoquinone and isopropyl oleate were isolated. The methanol extract as well as the isolated compounds were investigated for their in vitro antibacterial activities against two gram-negative bacterial strains (P. aeruginosa (ATCC27853), E. coli (ATCC25922), and two gram-positive bacterial strains (S. pyogen (ATCC19615), S. aureus (ATCC25923) using ampicillin as a positive control. The results showed that the methanol crude extract and isolated compounds were all active against the tested bacterial strain but 2,5-dihydroxy-3-methyl-6-(nonadec-14-enyl)-1 4- 1,4-benzoquinone was the most active among them. The later exhibited 8mm, 8.5mm, 8 mm, and 9 mm zones of inhibitions at concentrations of 350 µg/ml and 9.5mm, 10mm, 9mm, and 11mm at (400 µg/ml) against E. coli, S. aureus, P. aeruginosa and S. pyogen, respectively. The results further indicated the increase in the inhibition zone with concentration. This study supports the traditional medicinal uses of Maesa lanceolata for the treatment of infectious diseases.