antioxidant slides lecture.ppt

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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.



Nomenclature and Chemical Structure

Chemical Name (primary antioxidant):1,3-di(3-methoxybenzyl) thiourea (3MBTU)

NHNH

S

O

CH3

O

CH3



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



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



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



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



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



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



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

antioxidant slides lecture.ppt

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