Chapter 6
Natural Antioxidants from Spices
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Nobuji Nakatani Department of Food and Nutrition, Osaka City University, Sumiyoshi, Osaka 558, Japan
There is currently great worldwide interest in finding new and safe antioxidants from natural sources to prevent o x i dative deterioration of foods and to minimize oxidative damage to living cells. Our study has focused on spice c o n stituents or isolates which are functional antioxidants yet do not have the overpowering or undesireable organoleptic properties of the whole spice. New antioxidative compounds were isolated from various spices and herbs and their struc tures were determined by chemical and spectroscopic means. Examples of new antioxidants include: phenolic diterpenes from rosemary and sage, phenolic carboxylic acids from oregano, biphenyls and flavonoids from thyme, phenolic amides from pepper and chili pepper, and diarylheptanoids from ginger. All the phenolic compounds have antioxidant activities that are more effective than the natural occur ring antioxidant, α-tocopherol, and are comparable to the synthetic antioxidants, BHA and BHT. In addition to anti oxidant activity, this study assessed the stability and utility of these compounds in food systems.
M u c h research is concerned with finding ways to prevent or to delay the deterioration of foods. O n e of the principle causes of food deterioration is the oxidation of fats and oils. E v e n a 1% oxygen level can cause reactions that produce undesirable flavor, rancid odor, discoloration and other spoilage. In particular, lipids containing large amounts of unsaturated fatty acids can be easily 0097-6156/92/0507-0072$06.00/0 © 1992 American Chemical Society
In Phenolic Compounds in Food and Their Effects on Health II; Huang, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1992.
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6. NAKATANI
Natural Antioxidants front Spices
73
oxidized to lipid peroxide or hydroperoxide, which then rapidly decomposes by radical chain reaction to give lower molecular compounds such as aldehyde, ketone, epoxide, carboxylic acid and others. These compounds contribute to food rancidity. This process is outlined i n Figure 1. These lipid peroxides damage not only foods but also living organisms. Various efforts have been made to m i n i mize the oxidation reaction i n foods such as by reducing the amount of oxygen i n the headspace of food, filling with inert gas or addition of antioxidants. Antioxidants from Natural Souces Synthetic antioxidants such as tert - b u t y l - 4 - h y d r o x y a n i s o l ( B H A ) and / i ? y / - b u t y l - 4 - h y d r o x y t o l u e n e ( B H T ) , and to a lesser extent natural antioxidants as α - t o c o p h e r o l , have been widely used to depress rancidity of fats and oils. The use of synthetic a n t i oxidants as food additives is restricted i n several countries, because of the possibility they could cause an undesirable effect on the enzymes of human organs. Consequently, many reseachers have searched for antioxidative compounds from natural sources. F o r example, tocopherols and flavonoids are abundant plant c o n s t i tuents, nordihydroguaiacol ( N D G A ) is found i n creosote bush (Larrea divancate ), gossypolin cotton seed and sesamol i n sesame o i l and orizanol i n rice germ. Antioxidants from Spices O u r attention for the developement of safe and effective a n t i o x i dants has been focused on edible plants, especially spices, because man has used them not only for flavoring foods but also for a n t i septic or medicinal properties, since the prehistoric era (Table Ï ) . Researchers such as Chipault et al. examined more than 70 spices for antioxidative activity. They reported that rosemary and sage were remarkably effective antioxidants and that oregano, thyme, nutmeg, mace and turmeric also retarded the oxidation of lard. In an oil—in—water emulsion, clove showed extremely high antioxidant activity, and to a lesser degree did turmeric, allspice, mace, r o s e mary, nutmeg, ginger, cassia, cinnamon, oregano, savory and sage ( 1, 2). The practical effectiveness of ground spices was examined i n different types of food (J). Other studies have been concerned with the antioxidative effect of spices and spice extracts Results of these studies have promoted research to isolate active components. Herrmann reported the activity of labiatic acid (rosmar— inic acid), caffeic acid and other phenolic carboxylic acids from
In Phenolic Compounds in Food and Their Effects on Health II; Huang, M., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1992.
74
PHENOLIC COMPOUNDS IN FOOD AND THEIR EFFECTS ON HEALTH II
l i p i d polymer polymerization decomposition lipid
epoxide *
l i p i d peroxide
hydrocarbon
decomposition aldehyde ketone alcohol
carboxylic acid Figure
1.
O x i d a t i o n process of
lipid.
Taxonomical c l a s s i f i c a t i o n of
spices
Labiatae
b a s i l , marjoram, mint, oregano, rosemary, sage, savory, thyme
+%
Solanaceae
c h i l i , paprika, red pepper
I
Pedaliaceae
sesame
Campanulatae
Compos i taie
chamomile, chicory, tarragon
Piperales
Piperaceae
cubeba, long pepper, pepper
Myristicaceae
mace, nutmeg
Lauraceae
bay l e a f , cassia, cinnamon
Magnoliaceae
star-anise
Crueiferae
mustard, wasabi
Myrtaceae
a l l s p i c e , clove
Umbel1iferae
anise, caraway, celery, c h e r v i l , coriander, cumin, d i l l , fennel, parsley
Liliaceae
g a r l i c , onion
Iridaceae
saffron
icoty^
Table I .
Scitamineae
Zingiberaceae
cardamom, ginger, turmeric
I
Orchidales
Orchidaceae
vanilla
α ι—ι cCCe Tubiflorae
1 r-H
iospermae
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lactone
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