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Introduction
During the month of May, in the valleys of the northwestern Pacificcoastal regions of the United States, a small plant, bearing the botanicalname L imnanthes alba , begins to bloom with such an abundance ofdelicate, beautiful white flowers that there appears to be a natural foamon the meadow.
Meadowfoam is the common name for this plant.
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Nomenclature and Chemical Structure
Chemical Name (primary antioxidant):1,3-di(3-methoxybenzyl) thiourea (3MBTU)
NHNH
S
O
CH3
O
CH3
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Industrial Crops and Products 16 (2002) 43 – 57
1,3-di(3-Methoxybenzyl) thiourea and related
lipid antioxidants _Thomas P. Abbott a, *, Alan Wohlman b , Terry Isbell a ,
Frank A. Momany a ,Charles Cantrell a , Donald V. Garlotta a ,
David Weisleder a
a Agricultur al Research Se rvic e, Uni ted States Department of
Agricultur e, National Center for Agricultural Uti li zation Researc h,
1815 North Un iversity Stree t, Peori a, I L 61604, USA
b The Fanning Corporatio n, 2450 W. Hubbard S t., Chicag o, I L60612, USA
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Chemical and Physical Data
Molecular Formula = C17 H20 N2 O2 S
Formula Weight = 316.419
Composition = C(64.53%) H(6.37%) N(8.85%)
O(10.11%) S(10.13%)Molar Refractivity = 92.75 ± 0.3 cm3
Molar Volume = 270.0 ± 3.0 cm3
Index of Refraction = 1.602 ± 0.02
Surface Tension = 48.1 ± 3.0 dyne/cmDensity = 1.171 ± 0.06 g/cm3
Average Mass = 316.423591 Da
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A Note About The Structure Of
The Antioxidant
Vacuum free energy (AM 1) favors, by over 6 kcal/mol, the
extended trans-trans form of 3MBTU. NMR results are in
agreement with the trans-trans conformation of the molecule
being preferred in non-polar solvents. In this configuration,
the sulfur atom is highly exposed and available to participatein redox reactions. This characteristic of the molecule would
most likely contribute to its high antioxidant efficiency.
Sul fur atomH ighly exposed and therefore readily
available to participate in redox
reactions
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Initial Identification Of
Antioxidant Activity• Meadowfoam (Limnanthes alba) seed oil is highly
stable to oxidation.
• The addition of crude Meadowfoam seed oil to
other oils imparts enhanced oxidation stability to
the mixture (Isbell et al., 1999). This indicates that
crude Meadowfoam seed oil contains anantioxidant
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Ability Of 3MBTU To Protect Oils
From Oxidation
OSI is measured by heating the oil to a definite temperature (110 oC
or 130 oC for these experiments). As the oil is heated gases are
produced into the headspace above the oil. Theses gases are
captured and dissolved in water thereby changing the conductance
of the aqueous system. The oil eventually “fatigues” and there is a
very rapid rise in conductance. The time required to fully fatigue
(i.e. complete thermal stress of the oil) is called the OSI or Oxidative
Stability Index. It is measured in hours, the longer the OSI time the
more stable the oil.
Oxidative stability index (OSI) values
were determined on 5.00 g samples
in triplicate according to AOCS
method Cd 12b-92 (AOCS, 1993) at
110 and 130 oC
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0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
H o u r s
OSI (Hrs. @ 110 degrees C)
OSI 36.5 34.2 18.6 26.0 6.9
4265 (0.9%) 4160 (0.9%) BHA (1.0%) BHT (1.0%) CONTROL
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0.0
20.0
40.0
60.0
80.0
100.0
120.0
140.0
O S I ( h r s ) @ 1 1
0 o C
Crambe Oil
(refined) = COr
COr + 0.01% AO COr + 0.02% AO COr + 0.1% AO COr + 0.5% AO COr + 1.0% AO
Crambe (refined) + AO 4160
activity as a function of concentration