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- Propolis
- Biological Properties
- Therapeutic Actions
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Date:
03-31-2017 | HC# 091641-565
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Re: Review Discusses Biological Properties and Therapeutic Actions of Propolis
Sforcin JM. Biological properties and
therapeutic applications of propolis. Phytother
Res. June 2016;30(6):894-905.
Propolis is a substance made by bees from
plant exudates, bee enzymes, wax, and pollen and used to smooth interior hive
walls, repair holes in the honeycomb, and protect hives from contamination. It
has been used historically for its antiseptic and wound-healing properties and
to treat colds and ulcers. It has a rich history and was used in ancient Egypt
in embalming and as a local anesthetic as recently as the Boer War (1899-1902
CE) to help heal wounds and bolster tissue regeneration. While not describing
the extent or methodology of his literature search, the author reports on known
research on the composition and therapeutic use of propolis.
The chemical composition and biological
properties of propolis have been extensively studied, although reports in
languages other than English have had little distribution. In general, propolis
has about 30% wax, 50% resins, 10% essential and aromatic oils, and 5% pollen
and other substances. There are significant differences in content of
polyphenols, flavonoids, and other bioactive components in samples from
different areas. Geography also affects propolis composition, depending on the
plant species bees use to collect needed resins.
Propolis has been reported as originating
from balsam poplar (Populus balsamifera,
Salicaceae), willow (Salix spp.,
Salicaceae), silver birch (Betula pendula
syn. B. verrucosa, Betulaceae), alder
(Alnus glutinosa, Betulaceae), pine (Pinus spp., Pinaceae), citron-scent gum
(Corymbia citriodora syn. Eucalyptus citriodora, Myrtaceae), Brazilian
pine (Araucaria angustifolia,
Araucariaceae), and different palm (Arecaceae) trees; Baccharis spp. (Asteraceae); Clusia
spp. (Clusiaceae); and Brazilian bugi
(Dalbergia ecastaphyllum, Fabaceae). Yearly
and seasonal variation, even by the same bee colonies from the same sources,
may also influence propolis composition. Fresh and aged propolis also differ,
but samples frozen for 15 years showed no changes in composition.
Choice of solvent affects the composition of
propolis extracts. Ethanol is most commonly used and most of propolis' active
compounds are soluble in propylene glycol and ethanol. Few are water soluble,
but even water extracts show some bactericidal, fungicidal, and wound-healing
effects. Some poorly soluble compounds are more soluble in hot water. One study
compared traditional maceration, ultrasound, and microwave-assisted extraction,
with both of the latter providing higher yields in less time and with less
effort. Ultrasound extraction was the most efficient, considering yield, time,
and selectivity. Research to date has identified over 300 compounds in propolis,
all of which are dependent on local flora and plant sources used. Difference in
composition can influence differences in its therapeutic activity. Because of
this variability, medical use and standardization has been difficult.
Propolis does not seem to cause serious
adverse effects in mice or human studies and does not appear to be genotoxic. Allergy
and contact dermatitis have been reported, with beekeepers often affected.
In various models, propolis protected renal
tissue against toxins and free radicals, protected the liver from fibrosis, and
protected the testis from doxorubicin-induced toxicity. Of its benefits,
propolis' antimicrobial effects have been the most studied, including
antibacterial, antiviral, antifungal, and antiprotozoal effects. It is more
efficient against Gram-positive rather than -negative organisms. In addition to
acting directly against microorganisms, it may stimulate the immune system to
action.
Antitumor effects of propolis and some compounds
found in propolis have been investigated in vitro and in vivo, with mechanisms
of action including induction of apoptosis, cell-cycle arrest, inhibition of
matrix metalloproteinases, inhibition of angiogenesis, and prevention of
metastasis and cell invasion. Propolis has been found to modulate nonspecific
immunity and to have anti-inflammatory effects, strengthening its potential as
an anticancer agent. Immunomodulatory effects include increased antibody production,
suggesting the adjuvant potential of propolis with vaccines. Propolis stimulates
formation of connective tissue fibroblasts, supporting its traditional use to
treat wounds and suggestive of its potential in treating burns. Propolis is used
in many cosmetic products to reduce visible signs of aging. Potential
mechanisms of action involve cellular receptors, intracellular pathways,
transcription factors, second messengers, microRNAs, and other targets.
Complete characterization of propolis will be
difficult if not impossible and any attempts at standardization complex. Clinical
trials are lacking in part because distinct samples cannot be compared and used
for the same purpose due to its variability. This has been a barrier to its recognition
as a therapeutic agent by conventional medicine. Poor aqueous solubility and consequent
minimal systemic bioavailability also have limited its therapeutic use. New
technology, such as nanoparticle-based delivery systems and propolis-containing
biocellulose membranes, may potentially resolve this issue. Propolis'
therapeutic effects have been most used in dentistry, where propolis
mouthwashes, chewing gums, and gels have been found to prevent caries and act
against gingivitis, chronic periodontitis, and denture stomatitis.
Much research remains to be done on this
intriguing natural product.
—Mariann
Garner-Wizard
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