FUNCTIONAL MINOR CONSTITUENTS IN OILS AND FATS: UPDATE 2006
PT Gee and SH Goh
Palm Nutraceuticals Sdn. Bhd. and Forest Research Institute of Malaysia
Abstract: Minor components in oils and fats are of interest as vitamins, antioxidants and biologically active molecules
that confer quality and other useful properties to the oils. Unique structural moieties in some oils are perceived to
promote health and have become popular nutraceuticals.
General
Oils and fats are a very important part of food,
providing energy-dense macronutrient food, essential
fatty acids, medium for lipid soluble vitamins and a
variety of micronutrients. While fat provides delightful
characteristics to food preparations and sensory
requirements, the nutrients and micronutrients present
are being emphasized in recent times. Oils high in
monounsaturated fatty acids (e.g. from olive,
palmolein, high oleic sunflower and canola) have been
much of demand, saturated fats have been considered
ample from foods, while excessive consumption of
polyunsaturated fatty acids have been subject to
caution. Notably trans-fats from hydrogenation have
been subject of elimination from the diet because of
confirmed health risks while long chain 3 fatty acids
(e.g. from marine foods) are much sought after despite
their relative scarcity.
Different oils and fats are now known to provide
not only fatty and glyceride structural variety but also
varying and differing amounts of numerous
micronutrients. These micronutrients may be vitamins,
antioxidants, phytonutrients or natural products that
can be of significance because of biological activities.
Fat-soluble or partially-soluble components such as carotene, CoQ10, phytosterols, vitamin E or tocopherol, vitamin D, vitamin K, niacin and Bvitamins (and folate) have received some attention but
almost all do not appear to reduce the risk of various
cancers in 8-year trials; heart health however show
varying degrees of benefits. It is not known if it is a
problem of dosage or that longer-term trials are
required or that diets of subjects are already optimal so
as not to be able to show effects. -Carotene, however,
has shown negative effects in lung cancer for smokers
although it reduces precancerous lesions in oral cancer.
Water soluble vitamin C, glucosinates, isoflavones,
flavonoids and various antioxidants from food sources
are still highly regarded. Natural products acting as
antioxidants, oestrogen-mimics, TNF, NF-κB and
COX inhibitors or other signalling molecules can
inhibit procarcinogens and tumour promoters. A lot of
phytomicronutrients hold promise for reducing risk of
various cancers perhaps from such bioactivities or
other epigenetic factors but the specifics still remain
unknown. Among the list of compounds are curcumin,
diindoylmethane, selected sesquiterpenoids and
diterpenoids, various flavonoids, glucosinolates,
isoflavones (e.g. genistein), isothiocyanates, lycopene
and other carotenoids, some polyphenolics (e.g. EGCG
and other catechins), resveratrol, natural salicylates,
selenium, tocotrienols and several triterpenoids (Fig. 1)
[Chuah et al, 2005].
Palm Oil
Virgin palm oil containing 600-1000 ppm vitamin E
and 500-700 ppm provitamin A (carotenoids) is
undoubtedly the richest source of these valuable minor
components. The vitamin E content is of special
interest as it is the most valuable component (currently
the value of vitamin E alone exceeded the price of the
palm oil it is derived from) and more so, it contains the
full spectrum tocotrienols (α-, β-, γ- & δ-tocotrienols)
but also contains α-tocopherol (constituting about 22%
of the total vitamin E). The scarcity of natural sources
R
O
HO
H
O
MeO
OMe
O
Tocopherols (, R=H; , R=Me)
R
Curcumin
HO
OH
HO
OH
O
Tocotrienols (, R=H; , R=Me)
Vitamin A (retinol)


Lycopene
- & -carotenes
Figure 1. Common lipid-soluble vitamins and micronutrients
Malaysian Oil Science and Technology 2005 Vol. 14 No. 2
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Functional Minor Constituents in Oils and Fats: Update 2006
and the recent scientific reports on both
chemoprevention and chemotherapy potentials of
tocotrienols shall provide a new dimension to the palm
oil industry.
The structural difference between tocopherol and
tocotrienol is that the former has a saturated phytyl tail
whereas the latter has a farnesyl tail (three isoprene
units). However, high field NMR indicated that the
farnesyl tail curls and forms an arc over the chroman
ring (Atkinson, 2006). This is rather unexpected as the
trans conformation of isoprene units normally behave
similar to the saturated hydrocarbon chain except it is
slightly shorter due to the presence of three double
bonds.
The proposed curl structure through
intramolecular proton interactions shall change the
physical appearance of tocotrienol and have an impact
on the membrane behaviour (Fig. 2). This may also
partly explain the observation that tocotrienols (which
has higher mobility) can penetrate deeper in the skin
than the α-tocopherol (Fig. 3).
Current knowledge indicates that α-tocopherol as
vitamin E plays little or no role in the chemo-prevention
and chemotherapy of degenerative diseases. The term
vitamin E is a misnomer here and refers to α-tocopherol.
In addition, meta-analysis of 19 previous clinical trials
indicated that supplementation with excessive dosages of
α-tocopherol increased the all-cause mortality ((Miller
III et al , 2005) and the HOPE-TOO clinical trial also
reported that α-tocopherol supplementation increased the
risk of heart failure (Lonn, 2003).
On the other hand, scientific evidences are
indicating that tocotrienols play their roles in chemoprevention and chemotherapy, not just as an antioxidant
or vitamin E but more importantly, in molecular
signalling and/or signal transduction. This clearly
differentiated tocotrienols from α-tocopherol; even tocopherol may be more beneficial than α-tocopherol.
Reviews on the multiple therapeutic potentials are
available (Sen et al, 2006; Gee, 2005).
Researchers from Tohuku University, Japan
reported that tocotrienols are anti-angiogenic by
regulating intracellular fibroblast growth factor
signalling (Inokuchi et al, 2003; Miyazawa et al, 2004).
Angiogenesis is a requirement for cancer cells
proliferation and growth. The same group of researchers
had also reported that tocotrienols inhibit DNA
polymerase-λ (Mizushima et al, 2006) and telomerase
activities (Miyazawa et al, 2006), thereby suppressing
cancer growth. The order potency of anti-angiogenesis,
inhibition of polymerase-λ and inhibition of telomerase
activities are identical, δ-T3 > β-T3 > γ-T3 > α-T3.
NOE
HO
O
Figure2. Conformation of -tocotrienol from through-space NOE interactions (Atkinson, 2006)
Figure 3. -Tocopherol (darker) and -tocotrienol (lighter) in membranes (Atkinson, 2006)
Malaysian Oil Science and Technology 2006 Vol. 15 No. 1
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Functional Minor Constituents in Oils and Fats: Update 2006
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Figure 4. Various studies on dose-benefits of vitamin E (-tocopherol)
Numerous reports have been published on the roles of
tocotrienols in inducing apoptosis and S-phase arrest
on cancer cells.
So far, tocotrienols were reported to have
anticancer properties for cancers of breast (both
oestrogen receptor positive and negative, see
Schwenke, 2002 for review), prostate (Conte et al,
2004), liver, lung (Wada et al, 2005) and skin (He et
al, 1997; Mo et al, 1999). More promising results
have been reported from the Ohio State University on
the mechanisms of tocotrienols in neuroprotection and
protection against stroke (Sen et al, 2000; Khanna et
al, 2003, 2005). α-Tocotrienol has the highest potency
in neuroprotection against glutamate-induced toxicity.
The roles of tocotrienols in cardiovascular
diseases prevention are likely to encompass
anti-inflammatory,
immuno-therapy
and
antihypertension to reversing atherosclerosis. For too long
there has been an overemphasis in the reduction of
LDL-cholesterol despite the lack of support from
overall
mortality
data
(excepting
familial
hypercholesterolemia), thus the changing strategy for
cardiovascular diseases prevention is towards
inhibition of cholesterol oxidation and reduction of
vascular inflammation (Yoshikawa, 2006).
Malaysian Oil Science and Technology 2006 Vol. 15 No. 1
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Functional Minor Constituents in Oils and Fats: Update 2006
some useful constituents that may protect against
coronary artery wall production of inflammatory
mediators (TNF- and VCAM-1). Recently
oleocanthal has been serendipitously discovered as a
novel anti-inflammatory agent from freshly pressed
olives. The throat-irritating dialdehyde compound
inhibits cyclooxygenase enzymes COX1 and COX2.
Olive oil actually contains very little of antioxidants
while the extra virgin oils have a little but most (as
much as 500 times more) remain in the water extracts.
Olive Oil
Olive oils, especially the extra virgin varieties, have
healthful microconstituents. Apart from commonly
encountered
flavonoids,
its
main
phenolic
micronutrient (oleuropein) prevents inflammationinduced bone loss in the ovariectomised rat; the main
polyphenol is based on hydroxytyrosol (Fig. 5). The
Mediterranean diet which incorporates fish, vegetables
and fruits, wine and olive oil is considered healthy.
Only extra virgin olive oil, not the refined oil, has
hydroxytyrosol unit
tyrosol unit
HO
O
O
secoiridoid
unit
O
HO
O
OH
CHO
OH
glucose
unit
Oleuropein
CHO
HO
O
O
O
OH
OH
Oleocanthal
Figure 5. Antioxidant phenolic constituents from olive
HO
OH
HO
O
O
OH
4
HO HO
6
OH O
Genistein
OH
OH
8
O
OH
OH
OH
OH
HO
OH
4,6- and 4,8-linked Epicatechin Dimers in Cocoa
Resveratrol
OH
Figure 6. Representative epicatechin dimers in cocoa, genistein and resveratrol
Cocoa and Chocolate
Natural chocolate, especially dark chocolate, made
from cocoa beans have the most complex mixtures of
phenolic compounds, flavonoids and polyphenols,
chemically in the form of monomers, dimers, trimers
and oligomers, which are useful antioxidants and
phytonutrients. Epicatechin, catechin, procyanidins,
quercetin, naringenin, hydroxy- and dihydroxycinnamoyl-amino acids have been characterised [Stark
et al, 2005]. Much hope has been placed on the
antioxidants on protecting LDL-cholesterol and
prevention of artery blockages with trials being
planned or already ongoing. Lowered platelet activity
has been found for those eating 25 g of dark chocolate
of good quality can containing 85% cocoa. It is noted
that chocolate flavonoids are sensitive to oxidation and
need processing care. This will be against indulgence
to most commercial chocolates that may lose their
health value for being overloaded with sugary calories
and oily nuts apart from the fact that careful processing
is required to preserve cocoa micronutrients.
Furthermore, the real cocoa may only be present as
minor flavourings and cocoa butter is predominantly
being substituted with cheap hydrogenated fats and
unhealthy fillings.
Sesame Oil
Sesame is unique because of the presence of powerful
unique antioxidants that allows the highly
polyunsaturated oil to remain fairly resistant to
oxidation. The seed is rich in high quality proteins, B
and E vitamins, sesamin (lignan), and minerals (iron
and calcium) and it is stated “sesame is a food that can
improve mankind’s energy and vitality” – Hippocrates.
Sesamolin, sesamolinol and sesamol are antioxidants
or pro-antioxidants and together with other
constituents may be responsible for use in traditional
medicines valued by ancient Egyptians, Chinese and
Indians (Fig. 7).
Malaysian Oil Science and Technology 2006 Vol. 15 No. 1
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Functional Minor Constituents in Oils and Fats: Update 2006
O
O
O
O
H
H
H R
O
H
O
O
O
O
O X
Y
O
(+)-Sesamin, R=H
Sesaminol, R=OH
O
O
Sesamolin, X,Y=CH2
Sesamolinol, X=H, Y=CH3
O
MeO
HO
O
-Oryzanol (Campesteryl ferulate)
(mixed with Cycloartenyl ferulate and
24-Methylene-cycloartenyl ferulate)
Figure 7. Structures of oryzanol, sesamin and derivatives
nutritional calcium because of ready absorption by
Soybean, Canola, Corn, Sunflower, Rice
calcium-binding proteins. Short and medium chain
Bran, Cottonseed and Other Oils
saturated fatty acids are readily absorbed, as are
All plant oils have varying amounts of tocopherols,
essential, long-chain 3 fatty acids; minerals, vitamins
sterols and other minor components. Soybean in fact
A and D and other nutrients are copiously available.
provides a source of natural -tocopherol and sterols
Vitamin D is now receiving increasing attention for the
that are mainly stripped off during refining; notably
new generation spending too much time indoors. Apart
soybean also provides isoflavones. Rice bran oil, like
from the fear of saturated fats, which are actually
palm oil, provides both tocopherols and potentially
beneficial, butter is now considered a better alternative
useful tocotrienols; oryzanol is also a characteristic
to margarines because of the absence of trans fats and
antioxidant (Fig. 7).
lack of minerals and vitamins. Ruminant fats are also
A comparison of main antioxidants in some oils
noted to provide conjugated linoleic acid (CLA) that
can be made as follows: Rice Bran Oil (80 T, 340 T3,
has cytotoxic and anti-obesity properties [Smedman,
2000 oryzanol, total 420 + 2,000 ppm), Palm 190 -T,
2005] although clinical trials have not provided
convincing results thus far.
710 T3, total 900 ppm, Soybean 1,000 -T, Canola 650
Eggs have for some time been cautioned because
-T, Sunflower 530 -T and Olive 50 ppm -T
of the perceived high cholesterol levels despite the
[Gunstone, 2003; Koh and Lim, 1998]. The change of
wealth of nutrients (phospholipids, proteins, vitamins,
perception in that excessive polyunsaturated linoleic
minerals, etc) present. Recently however, eggs are
acid and partial hydrogenation is undesirable has
considered as total nutrition and 1-2 eggs per day are
caused N. American consumers to switch to more
considered to provide almost complete daily needs
monounsaturated oils including peanut, cottonseed and
while better feed materials have ensured desirable fats
palmolein. Peanut oil remains a potential danger to
and other nutrients in the eggs.
allergic reactions of residual proteins and of aflatoxins
Temperate fishes from unpolluted seas
from bad nuts while cottonseed oil may be of concern
traditionally provide long chain 3 essential oils and
due to its genetic modification. Cottonseed oil,
vitamins A and D.
however, is thermally stable and has more vitamin E
than corn and soybean oils. Corn is exceptional in
having high -tocopherol (corn oil 3x> sesame oil
Exotic Oils: Wheat Germ and Sea
1.5x> linola oil) and the latter two oils have relatively
Buckthorn
low -tocopherol. The - and -isomers are being
Vitamin E (-tocopherol) was originally identified
investigated for better properties than -tocopherol, the
from wheat germ oil, the content in which exceeds
-analog may have anti-arthritic potential.
those in other common oils (e.g. 5x> sunflower, 10x>
corn oil, 15x> soybean oil). Wheat germ also remains
an important source of minerals and other
Dairy, Animal Fats and Fish Oils
micronutrients.
Useful nutrients, notably from milk and cheese, are
much sought after; dairy is traditionally the source of
Malaysian Oil Science and Technology 2006 Vol. 15 No. 1
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Functional Minor Constituents in Oils and Fats: Update 2006
Sea Buckthorn berries on cold-press provides a
remarkable oil which has fish oil glycerides and an
extremely rich mixture of vitamins (A, B, D, E and K),
antioxidants and flavonoids. The vitamin E content is
double that of wheat germ oil.
Abbreviations
COX = Cyclooxygenase; EGCG = epigallocatechin
gallate, usually considered as obtained from green tea;
LDL = low density lipoprotein (commonly known as
bad cholesterol); NMR = Nuclear Magnetic
Resonance; NF-κB = Nuclear factor-κB; T =
tocopherol; T3 = tocotrienol; TNF = tumour necrosis
factor, considered to be involved in atherosclerosis and
heart failure; VCAM = vascular adhesion molecule,
high levels are usually found in heart patients; 3 =
important class of essential fatty acid, 3-position
counted from the CH3-end of carbon chain, long chain
polyunsaturated 3 fatty acids usually from marine
sources.
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[Received and edited in July, 2006]
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