Portuguese propolis disturbs glycolytic metabolism of human
colorectal cancer in vitro
Background
Propolis is a resin collected by bees from plant buds and
exudates, which is further processed through the activity of bee enzymes.
Propolis has been shown to possess many biological and pharmacological
properties, such as antimicrobial, antioxidant, immunostimulant and antitumor
activities. Due to this bioactivity profile, this resin can become an
alternative, economic and safe source of natural bioactive compounds.
Antitumor action has been reported in vitro and in vivo for
propolis extracts or its isolated compounds; however, Portuguese propolis has
been little explored. The aim of this work was to evaluate the in vitro
antitumor activity of Portuguese propolis on the human colon carcinoma cell
line HCT-15, assessing the effect of different fractions (hexane, chloroform
and ethanol residual) of a propolis ethanol extract on cell viability,
proliferation, metabolism and death.
Methods
Propolis from Angra do Heroismo (Azores) was extracted with
ethanol and sequentially fractionated in solvents with increasing polarity,
n-hexane and chloroform. To assess cell viability, cell proliferation and cell
death, Sulforhodamine B, BrDU incorporation assay and Anexin V/Propidium iodide
were used, respectively. Glycolytic metabolism was estimated using specific
kits.
Results
All propolis samples exhibited a cytotoxic effect against
tumor cells, in a dose- and time-dependent way. Chloroform fraction, the most
enriched in phenolic compounds, appears to be the most active, both in terms of
inhibition of viability and cell death. Data also show that this cytotoxicity
involves disturbance in tumor cell glycolytic metabolism, seen by a decrease in
glucose consumption and lactate production.
Conclusion
Our results show that Portuguese propolis from Angra do
Heroismo (Azores) can be a potential therapeutic agent against human colorectal
cancer.
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