Antibacterial Properties of Propolis

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Journal of the Royal Society of Medicine Volume 83 March 1990 159

Antibacterial properties of propolis (bee glue)

JMGrangeMScMD RWDaveyMFHom DepartmentofMicrobiology,NationalHeart&

Lung Institute, Dovehouse Street, London SW3 6LY

Keywords: propolis; honey; flavonoid; antibacterial agent

Summary
Propolis (bee glue) was found to have antibacterial
activity against a range of commonly encountered
cocci and Gram-positive rods, including the human
tubercle bacillus, but only limited activity against
Gram-negative bacilli. These findings confirm previous
reports of antimicrobial properties of this material,
possibly attributable to its high flavonoid content.

Introduction
Thetherapeutic potential ofhoneyhasrecentlybeen
reviewed by Zumla and Lulat 1. Other bee products,
royal jelly and propolis, have also been widely used
in 'folklore medicine' for centuries. Propolis is a hard,
resinous material derived by bees from plant juices
and used to seal openings in the hives. It contains
pollen, resins and waxes and large amounts of
flavonoidswhich arebenzo-y-pyrone derivatives found
in allphotosynthesizingcells.Flavonoidshavemany
biological effects inanimal systemsbuthave received
relatively little attention from pharmacologists2.

Weare currently undertaking a screening study of
a large number ofplants andplant-derived materials
in a search for possible new antimicrobial agents,
particularly for use against methicillin resistant
Staphylococcus aureus (MRSA). In this paper we
report our findings with propolis and review the
literature, mostly from Eastern Europe, on the
antimicrobial and other properties ofthis substance
and of its therapeutic applications.

Materials and methods
An ethanolic extract of propolis was obtained from
Boiron et Cie, Lyon, France. Onevaporation, 1 ml of
this extract yielded 60mgofsolid resinous material.

Twenty-one bacterial strainswere receivedfrom the
BacteriologyDepartment oftheBrompton Hospital
and from the Public Health Laboratory, Dulwich:
Staphylococcus aureus6 strains(includingthe Oxford
reference strain and 3 MRSAs), Staph. epidermis 2
strains, Enterococcus spp. 2 strains, Branhamella
catarrhalis 1 strain, Corynebacterium sp. 1 strain,
Bacillus cereus 2 strains, Pseudomonas aeruginosa
3 strains, Escherichia coli 2 strains, Klebsiella
pneumoniae.1strainandMycobacteriumtuberculosis
1 strain (the H37Rv reference strain).

Screeningwasperformedbymakinga 1: 20 dilution
ofthe ethanolic extract ofpropolis inblood-agarbase
(Difco): 1mlofpropoliswasaddedto19mlofmolten
mediumat450C, mixed andpoured into a petri dish.
After cooling and drying, the plates were inoculated
withbacterialsuspensions(approx. 1mgwetweight
in 1 ml of nutrient broth) with a Denley applicator.
Control studies showed that themethod ofpreparation
allowed most of the ethanol to evaporate and that

residual amounts, if any, did not inhibit bacterial
growth. The minimal bactericidal concentrations
(MBC)ofpropoliswereestimatedbymakingdoubling
dilutionsfrom 1: 20 in nutrientbrothand inoculating
each tube with one drop of a bacterial suspension
(approx. 1mgwetweightin10mlofnutrientbroth).
After 14 h, loopfuls ofmediumwere takenfromeach
tube and streaked on propolis-free agar medium to
check for bacterial growth.

TheMBCofpropolisforMycobacterium tuberculosis
wasdeterminedbyremoving all ethanol (towhichthe
tuberclebacillus isverysensitive)byevaporationand
resuspending the residue in Middlebrook-Dubos 7H9
broth containing 0.05% Tween 80. This was used to
make doubling dilutions from 1: 20 in Middlebrook-
Dubos 7H11 agar slopeswhichwere inoculated with
onedropofa 1mg/mlsuspensionofthestrain.The
slopes were observed for bacterial growth for up to
one month.

Results
Inscreeningstudiesatadilutionof1:20 (ie3mgof
solid material per ml) in nutrient agar, the preparation
of propolis completely inhibited the growth of
Staphylococcus aureus (including the...
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