Antimicrobial potential of Gliricidia sepium flowers and Melipona beecheii honey

Leydi Fonte Carballo
Estación Experimental de Pastos y Forrajes Indio Hatuey, Central España Republicana 44280, Matanzas, Cuba

ABSTRACT
The objective of this thesis consisted in characterizing the biological material of Gliricidia sepium and determining the in vitro antimicrobial activity of different extracts of the flower and the honey obtained from the nectar of this species produced by Melipona beecheii. For such purpose a morphological characterization was made of the Gliricidia sepium trees, as well as the bromatological composition, the proportion of sugars in the flowers, the physical-chemical and sensorial characteristics of the honey produced by Melipona beecheii. In addition, the secondary metabolites involved in the antimicrobial response of the different flower extracts and the minimum inhibitory concentration (MIC) were identified. The antimicrobial activity of the extracts and the honey was evaluated against Staphylococcus aureus, Escherichia coli, Pseudomona aeruginosa and Candida albicans. To determine the existence of differences among the treatments, depending on the diameter of the inhibition halo, the non-parametric Kruskal Wallis test was used as the variance and normality homogeneity assumptions were not fulfilled, using the software InfoStat Free version. The results indicated that for the method of perforations in agar, in three of the four evaluated microorganisms, the honey in the 100 % dilution was the one with the highest inhibitory effect; being Staphylococcus aureus the most susceptible bacteria to honey in this group, showing inhibition halos of 28,0 mm in the 25 % dilution. Nevertheless, in the disc-dish-culture method, the honey at 100 % was effective only against Candida albicans, while Escherichia coli and Staphylococcus aureus showed susceptibility to the fresh ethanolic extract in this same dilution. It is concluded that in the two evaluated methods, S. aureus was the bacteria that showed the biggest inhibition halos, and was the most sensitive within the group to honey (in the first method) as well as to the fresh ethanolic extract, and that these results obtained confirm the high nutritional value of the M. beecheii honey for its therapeutic effects. It is recommended to extend the best results to in vivo bioassays with animals and to enlarge the spectrum of extracts to be tested and particularly propolis for their antibiotic properties in animals.