Preparation of iminium pigments from the naturally occurring chromophore betalamic acid obtained via

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Beta Vulgaris
Preparation of iminium pigments from the
naturally occurring chromophore betalamic acid
obtained via in situ hydrolysis of betanin
isolated from Beta vulgaris. Carolyn U. T. Nguyen
and Paul I. Higgs. Department of Chemistry, The
University of Tennessee at Martin,
Betalamic acid
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Plant Pigments Four Classes
Betalains

• chromoalkaloids
• conjugates of the chromophore betalamic acid and
  an amine.
• Betacyanins from L-DOPA derivative (glycosylated)
• betaxanthins from L-amino acids.
• Vacuoles highly water soluble,
• stable in acidic conditions
• but hydrolyze in basic conditions

Betacyanins
Betaxanthins
Betalamic acid
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Biochemical Construction of Betalains
?spontaneous (non-enzymatic) condensation of an
amino acid with betalamic acid (2 steps form
tyrosine via L-DOPA)
Betacyanins
Betaxanthins
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UV-Vis of Betalains
Betaxanthins
Betacyanins
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Tailored Semisynthetic Colorants
Betaxanthins
Betacyanins
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Why?
Natural Pigments gt Natural coloring agents food,
pharmaceuticals ?increasing consumer critique of
synthetic dyes FDC Red 2 Amaranth cake mixes,
fruit-flavoured fillings, jelly crystals can
provoke asthma, eczema and hyperactivity it
caused birth defects and fetal deaths in some
animal tests, possibly also cancer banned in the
USA, Russia, Austria and Norway and other
countries FDC Red 40 Allura, sweets, drinks
and condiments, medications and cosmetics,
synthetic introduced in the early eighties to
replace amaranth which was considered not safe
allura red has also been connected with cancer
in mice banned in Denmark, Belgium, France,
Germany, Switzerland, Sweden, Austria and Norway
Allura
Amaranth
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Extraction of Betacyanins
1. Red beet (homogenized or juiced) macerated
with acidified water (TFA pH 5-6) 2. Filtered,
Separated by Ion Exchange Chromatography with
Amberlite XAD-16. Elution with water (TFA pH 5-6)
followed by methanol gave fractions containing
the vivid red-violet betacyanins
Crude
Betanin
Fractionated betaxanthins and betacyanins
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Betalains Literature

• Very small scale, very dilute solution, UV
  amounts products not isolated
• Kept in solution, used as is without isolation

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Improved In Situ Generation of Betalamic Acid
?Concentrated betanin solution, excess
NH4OH(aq) 10-15 mins by UV hydrolysis completed
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Condensation of Amines with Betalamic Acid
Benzylamine
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Condensation of Amines with Betalamic Acid
Benzylamine
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Condensation of Amines with Betalamic Acid
Methylamine
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Condensation of Amines with Betalamic Acid
tert-Butylamine
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Condensation of Amines with Betalamic Acid
?Current Three new betalamic iminium adducts
prepared ?benzylamine, methylamine,
tert-butylamine ? variation in ?max gt different
colors ? NMR ?Foreseeable Future ?keep
adding structurally different amines to betalamic
acid ? use amines with a chromophore ? use
amines that extend betalamic acid chromophore
gt effect on ?max gt different colors
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FUTURE Condensation of Amines with Betalamic Acid
Secondary Amines?
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Acknowledgements
UTM College of Engineering and Natural Sciences
(CENS) undergraduate research grant UTM College
of Engineering and Natural Sciences (CENS)
Instrument grant purchase of UV-Vis
(Thermoscientific evolution 300)