Antibacterial, antifungal and phytochemical analysis of crude extracts from the leaves of Ludwigia abyssinica A. Rich. and Ludwigia decurrens Walter

Abstract

Ludwigia abyssinica and Ludwigia decurrens are two plant species of the genus Ludwigiaused traditionally for the treatment of various skin, gastrointestinal, wound and bone joint disorders in Nigeria. The antibacterial and antifungal properties of extracts from the leaves of both plants against clinically important species of bacteria and fungi were examined. The two plant species produced activities with absolute similarity. The n-butanol extract was the most potent with maximum zone of inhibition (32.0 mm) followed by the ethyl acetate extract (12.0 to 31.0 mm) amongst other extracts (aqueous, dichloromethane and n-hexane). The n-butanol extract exhibited broad spectrum activity against all test bacteria and fungi and compared favourably with standard reference drugs – ampicillin, streptomycin and amphotericin B. The minimum inhibitory concentrations (MIC) exhibited by both n-butanol and ethyl acetate extracts against test bacteria species ranged between 0.625 to 5.0 mg ml-1 and 1.25 to 5.0 mg ml-1, respectively. The killing rate of the minimum bactericidal concentration (MBC) of n-butanol extract of L. abyssinica on Escherichia coliwas about 99.3% in 120 min while it was about 98.2% for Staphylococcus aureus. The phytochemical screening of crude extracts from the leaves of L. abyssinica and L. decurrens revealed the presence of only alkaloids and tannins. This study establishes the effective ethnomedicinal use of these plants in the treatment of various infectious diseases. There is high potential for the exploitation of the plants for development of new, novel antimicrobial agents.     Key words: Ludwigia abyssinica, Ludwigia decurrens, Onagraceae, antibacterial, antifungal, phytochemical constituent.