Antimicrobial Activity Of Khat (Catha Edulis) On Selected Pathogenic Bacteria

Abstract

Infectious diseases are the critical problems of the world as a result of the emergence of different antimicrobial resistant microorganisms. Medicinal plants play great roles in the treatment of various infectious diseases. Catha edulis, of the Celastraceae family, is a natural stimulant found as a flowering evergreen tree and is widespread in Africa and southern parts of Arabia. Therefore, the aim of the study was to detect the presence of the main secondary compounds classes from leaf and stem extracts of C. edulis and evaluate their antimicrobial activity in vitro. The experiment was designed in a complete random design arranged as 4*2*2*3 multi-factor factorial. That is 4 test pathogens by -2 extract sources obtained in 2 solvents at 3 concentration levels a factorial design in three replications. Data were analyzed using SPSS version 21 computer software. The phytochemical composition of methanol and water extracts from leaves and stems of Catha edulis revealed the presence of flavonoids, alkaloids, tannins and terpenoids in all analyzed plant parts from water and methanol extracts. Saponins are also present in all plant parts except stem water extract. Steroid was also present in all plant parts of methanolic extracts; but not seen at all in stem water extracts. It has been found that the antibacterial activity of Catha edulis depends on the type of solvent used for extraction and the concentration of the extract, as well as types of microorganisms. Zones of inhibition produced by methanolic extracts in table 3 ranged from 6.6±0.5mm to 12.3±0.2mm against E. coli, 7mm to 13mm against S. typhi, and 10.3±0.6mm to 16.3±0.6mm against S. aureus and also 10mm to 15.8±0.5mm against S. pyogen. While, zone of inhibition produced by water extract ranges from 4.3±0.5 mm to 10.8±0.3mm against E. coli and 5mm to 12mm against S. typhi and 8mm to 14.2±0.2mm against S. aureus and also 8.3±7mm to 14mm against S. pyogen. It was observed that the leaf and stem of Catha edulis showed the strongest antibacterial activity with MIC (6.25mg/ml, the lowest value) and corresponding MBC (25mg/ml) against S. aureus and S. pyogen and the methanolic extract from the leaf also showed MIC (25), MBC (100) against E. coli and S. typhi. This indicates that S. pyogen and S. aureus (gram+ve) are more sensitive than E. coli and S. typhi (gram-ve) in terms of both MIC and zone of inhibition. In water extracts, the MIC and MBC of E. coli and S. typhi are 50mg/mL and 200mg/mL, respectively. But the MIC (25mg/ml) and MBC (100mg/ml) against S. aureus and S. pyogen in water extracts