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CHEMISTRY 1000
Topics of Interest #8:
Mango Medicine?
Mango Pits Contain Antibacterial Tannins
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Mangoes are big business. Including all of the processed foods
containing mango (canned fruit, fruit purees, chutneys, etc.),
mangoes are the fruit with the fifth highest production in the
world.
Since many of the mangoes are skinned and pitted for use in the
processed foods, that generates a large amount of waste skin and
pits.
Christine Engels, a researcher at the University of Alberta, recently
published work demonstrating that a class of food preservatives
called tannins can be extracted from mango pits that would
otherwise just be dumped or burned.
C. Engels et al. Journal of Agricultural and Food Chemistry (2009) 57, 7712-7718.
Mango Pits Contain Antibacterial Tannins
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Tannins are a class of polyphenols that occur in many plants. (A
polyphenol is a benzene ring with more than one –OH attached.)
Polyphenols are very good at acting as Lewis bases toward metal
cations. Since coffee and tea contain significant amounts of
polyphenols (including kinds of tannins), drinking them when
eating foods rich in iron, zinc, etc. will inhibit uptake of those
minerals unless there is an acid (usually lemon juice) in the
tea/coffee:
3+
available for
body to absorb
not available for
body to absorb
C. Engels et al. Journal of Agricultural and Food Chemistry (2009) 57, 7712-7718.
Mango Pits Contain Antibacterial Tannins
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This is not to say that tannins (and other polyphenols) don’t have
good uses. Some of them can act as antioxidants.
Also, because of their ability to
bind to essential minerals, some
tannins can inhibit growth of
bacteria. In the research at the
University of Alberta, it was
clearly demonstrated that tannins
extracted from the mango pits
(sample
structure
at
right)
prevented growth of several
different species of bacteria
including Listeria monocytognes,
a species known to have caused
several food poisoning outbreaks.
C. Engels et al. Journal of Agricultural and Food Chemistry (2009) 57, 7712-7718.