Antistaphylococcal Activity of Crude Extracts from Monodora myristica (Annonaceae) and Dacryodes edulis (Burseraceae)

Abstract

Staphylococcal infections are a major health problem worldwide due to bacterial resistance to antibiotics. Medicinal plants contain bioactive compounds that possess anti-staphylococcal properties and could be used as an alternative to conventional medicines. Monodora myristica and Dacryodes edulis are significant medicinal plants used traditionally in Cameroon to treat microbial infections, including Staphylococcus aureus-causing diseases. This study aims to evaluate the in vitro antibacterial activity of extracts from Monodora myristica and Dacryodes edulis against Staphylococcus aureus NR-46003 and Staphylococcus aureus HM-468. The plant extracts were obtained by successive maceration of the seeds and envelope of M. myristica, and from D. edulis leaves using solvents of increasing polarity (hexane, dichloromethane, ethyl acetate, methanol and water). A total of twenty (20) extracts were obtained and evaluated for their inhibitory effects on S. aureus NR-46003 and S. aureus HM-468 using the microdilution method. The mode of action of the bioactive extracts was explored through their effects on bacterial mortality kinetics. As a result, the yields of extraction ranged from 1.04 to 11.69%. From the 20 extracts tested, the methanol extract of D. edulis bark (MeOHDeEc extract) was the most active extract (MICs : 62.5 and 125 µg/mL on S. aureus NR-46003 and S. aureus HM-468, respectively), followed by the methanol extract of D. edulis leaves (MeOHDeF ; MIC : 125 µg/mL on S. aureus HM-468). The time-kill kinetics of MeOHDeEc showed a concentration-dependent bactericidal effect after 2 h and 4 h of incubation with S. aureus HM-468 at 4MIC and 2MIC, respectively. These results suggest that Monodora myristica and Dacryodes edulis extracts possess anti-staphylococcal activity and could be used as starting points for the discovery of drugs against Staphylococcus aureus infections.