Antimicrobial potential of herbal creams based on extracts from Combretum zeyheri

Abstract

Microbial resistance has become a problem in the treatment of infectious diseases and the use of plant phytochemicals has been a valuable potential source of lead compounds that can be used for sustaining human health. One of the plants commonly used in African ethno-medicine is Combretum zeyheri from the Combretaceae family. This plant has been traditionally reported to treat many infections caused by microbes. The aim of this study was to determine the antimicrobial potential of phytochemicals from the leaf extracts of C. zeyheri against P. aeruginosa, S. aureus, C. tropicalis and C. glutamicum and formulation of a topical antimicrobial cream. Leaf extracts were prepared using polar and non-polar solvents. The antimicrobial activity of the extracts against the test microorganisms was determined in vitro using the broth micro-dilution method. C. tropicalis was most susceptible to ethanol, ethyl-acetate and hexane extracts with MICs at 25 µg/ml, 12.5 µg/ml and 25 µg/ml respectively. The ethyl- acetate extract had an MFC value of 12.5 µg/ml for C. tropicalis. S. aureus was also susceptible to ethanol, ethyl- acetate and hexane extracts with MICs at 125 µg/ml, 16 µg/ml and 32 µg/ml respectively. C. glutamicum was susceptible to ethanol, ethyl- acetate extracts with MICs at 125 µg/ml, 125 µg/ml and 500 µg/ml. The hexane extract had an MBC value of 500 µg/ml. There was no significant activity against P. aeruginosa from the crude extracts. Cream formulations were carried out with the three potent extracts at concentrations ranging from 0, 0.2, 0.5, 1 and 2% for each extract. Five formulations were subjected to evaluation for physicochemical parameters and stability testing. All formulations had almost constant pH, homogeneous, non-greasy and were easily removed after the application. All formulations were stable and safe in respect to skin irritation. Therefore, phytochemicals from C. zeyheri may be a useful template for providing leads for the development of new plant drug based antimicrobial agents.