Poor antimicrobial activity on seven cuban plants

Abstract

Background: Plant Kingdom still constitutes a source for antimicrobials, screening
bioassays of plants extracts is one of the first steps in the search of new antimicrobial
compounds. Cuba has a rich flora with a high degree of endemism that practically has
not been investigated. Method: Twelve acetone extracts (1mg/ml) of seven Cuban
plants (four endemic), were tested by agar disc diffusion method against selected strains
of bacteria and fungi: Escherichia coli (three strains), Staphylococcus aureus and Candida
albicans. Results: In general null or poor antimicrobial effect was observed, except in
Caesalpinia bahamensis subs bahamensis heartwood, that showed activity of interest against
bacteria even at 0,5mg/ml; while modest antibacterial effects was found in endemics:
Hypericum styphelioides (leave, stem), H. limosum (leave, stem), Vaccinium leonis (leave)
and V. ramonii (leave, stem); Agdestis clematidea show lowest effect. S. aureus was the
most sensitive bacteria (six species and 11 extracts) and only a negligible activity was
found against C. albicans in four extract of four species. Discussion: Morphology of
Gram positive bacteria, in contrast to Gram negative that have a more resistant outer
membrane, seem to be the cause of S. aureus sensitiveness. Starting from these results,
further current antimicrobial research approach related virulence factors mechanisms
interference can be carried out in these plants. Conclusions: In this experimental
conditions, except in one specie, null or poor antimicrobial effect was found in tested
plants, studies on these plants have to be continues, since in other conditions maybe
could be found some bacteriostatic or bactericide activity