Role of Flavones and Related Compounds in Retarding Lipid

1 R o l e of Flavones a n d Related C o m p o u n d s i n Retarding L i p i d — O x i d a t i v e Flavor Changes i n Foods

Phenolic, Sulfur, and Nitrogen Compounds in Food Flavors Downloaded from pubs.acs.org by 118.121.38.137 on 09/19/15. For personal use only.

DAN E. PRATT Department of Foods and Nutrition, Purdue University, West Lafayette, Ind. 47907

The term f l a v o n o i d is g e n e r a l l y used t o denote the group of p l a n t phenols c h a r a c t e r i z e d by the carbon skeleton C -C -C . The b a s i c s t r u c t u r e of these compounds c o n s i s t s of two aromatic r i n g s l i n k e d by a three carbon aliphatic chain which normally has been condensed t o form a pyran or l e s s commonly a furan ring. As the name i m p l i e s flavone may be considered the general type compound of the f l a v o n o i d group. Based chiefly on the o x i d a t i o n s t a t e of the a l i p h a t i c fragment, these compounds may be subdivided i n t o s e v e r a l groups (1, 2, 3). The widest and most inclusive classification (2) places the flavonoids i n t o three c l a s s e s : 1) The anthoxanthins include all flavonoids t h a t possess a carbonyl group in the 4 - p o s i t i o n . The center condensed r i n g may be e i t h e r the pyran or furan s t r u c t u r e ; or in one case (the chalcones) the a l p h a t i c fragment i s not condensed i n t o a ring. 2) The flavans i n c l u d e flavonoids t h a t do not possess a carbonyl in the 4 - p o s i t i o n . The center condensed ring is always i n t a c t and i s the pyran s t r u c t u r e . 3) The anthocyanins are f l a v y l i u m salts. These may be considered as flavans in the highest s t a t e of o x i d a t i o n . These three c l a s s e s may be further d i v i d e d as shown in Figures 1 and 2. Several phenolic compounds t h a t are not flavonoids, but are c l o s e l y r e l a t e d t o flavonoids b i o s y n t h e t i c a l l y and i n t h e i r d i s t r i b u t i o n , must a l s o be considered. These compounds are i n the cinnamic acids (3-phenyl propenoic a c i d d e r i v a t i v e s ) , e s t e r s of cinnamic acids and hydroxy and/or methoxy d e r i v a t i v e o f coumarin. In the p l a n t kingdom, the angiosperms account for 6

3

6

1

2

PHENOLIC, SULFUR, AND NITROGEN COMPOUNDS IN FOOD FLAVORS

A.


TYPE COMPOUND

ANTHOXANTHINS

DESCRIPTION OF CLASS H y d r o x y l a t e d and/or methoxylated derivatives of flavone The 3-hydroxyf1avones a r e commonly r e f e r r e d t o as flavonols.

2.

Flavanones

H y d r o x y l a t e d and/or methoxylated derivatives of f l a v a none ( 2 , 3 - d i h y d r o f l a v o n e ) . The 3 - h y d r o x y f l a v a n o n e s a r e commonly r e f e r r e d t o as flavanonols.

3.

Isoflavones

Analogous t o t h e f l a v o n e s w i t h the aromatic r i n g l i n k e d t o carbon 3 i n s t e a d o f carbon 2.

OCM3 4.

Chalcones

H y d r o x y l a t e d and/or methoxyl a t e d d e r i v a t i v e s o f two a r o m a t i c r i n g s l i n k e d by a three carbon a l i p h a t i c fragment.

4' Figure I.

Classification of flavonoids

1.

PRATT

A.

ANTHOXANTHINS DESCRIPTION OF CLASS

TYPE COMPOUND


5.

3

Fhvones and Related Compounds

H y d r o x y l a t e d and/or methoxyl a t e d d e r i v a t i v e s of benzalcoumranone.

Aurones

a:>o B.

FLAVANS f

3,7,4 -Hydroxyflavans which may a l s o be h y d r o x y l a t e d a t the 5, 3 , and/or 5 p o s i tions .

Catechins

f

HO

f

(χχο Leucoanthocyanins

H y d r o x y l a t e d and/or methoxyl a t e d d e r i v a t i v e s of 3,4-dihydroxyflavan.

OH

Figure 1.

Classification of flavonoids (continued)


Cinnamic

acids

(3-phenylproponoic a c i d

derivatives)


CH-COOH

Quinic

acid

(1,3,4,5-tetrahydroxycyclohexanecarboxylic a c i d ) ,

Quinic

a c i d e s t e r s o f c i n n a m i c a c i d s , and coumarins

( h y d r o x y and/or methoxy d e r i v a t i v e s o f c o u m a r i n ) .

00°

Figure 2. Classification of related compounds


1.

PRATT

Ffovones and Related Compounds

5

between 250 and 300 thousand s p e c i e s . Of t h i s number l e s s t h a n 400 s p e c i e s a r e c u l t i v a t e d o r g a t h e r e d as human f o o d s . These 400 s p e c i e s i n c l u d e 33 o f t h e 51 o r d e r s and 89 o f t h e 279 f a m i l i e s . A l l p a r t s o f p l a n t s a r e e a t e n - r o o t s , stems, l e a v e s , f l o w e r s , f r u i t , and seeds - b u t i n most s p e c i e s t h e e d i b l e p o r t i o n s are r e s t r i c t e d t o one p a r t . F l a v o n o i d s and r e l a t e d com pounds have been i s o l a t e d f r o m , o r d e t e c t e d i n about o n e - h a l f o f t h e s e e d i b l e p l a n t s , b u t n o t always i n t h e edible portions. The same compound, o r group o f com pounds, are n o t always p r e s e n t t h r o u g h o u t t h e p l a n t . Flavonoids occur i n a l l types of higher p l a n t t i s s u e - wood, b a r k , stems, l e a v e s , f r u i t , r o o t s , f l o w e r , p o l l e n and s e e d s . T a b l e I shows t h e g e n e r a l d i s t r i b u t i o n o f f l a v o n o i d s and c i n n a m i c a c i d s i n tlie v a r i o u s p a r t s o f the p l a n t . C e r t a i n groups o f f l a v o n o i d s are more c h a r a c t e r i s t i c o f some t i s s u e s t h a n others. I n f r u i t b e a r i n g p l a n t s , however, t h e same groups o f f l a v o n o i d s t h a t o c c u r i n t h e l e a v e s a l s o o c c u r i n t h e f r u i t i n a l e s s e r amount. A n t h o c y a n i n s a r e t y p i c a l l y i n f r u i t s , f l o w e r s , and some l e a v e s . The g r e a t e s t n a t u r a l s o u r c e o f f l a v a n s - c a t e c h i n s and l e u c o a n t h o c y a n i n s - a r e from woods and b a r k s . How e v e r , t h e s e do o c c u r i n non-woody t i s s u e as t e a l e a v e s , c o c o a b e a n s , and f r u i t p u l p s . C h a l c o n e s and aurones a r e c h i e f l y found i n f l o w e r p e t a l s , and t o a l e s s e r e x t e n t i n l e a v e s and stems o f some s p e c i e s b u t a r e n o t as w i d e l y d i s t r i b u t e d as o t h e r groups o f f l a v o n o i d compounds. F l a v o n e s and f l a v o n o n e s a r e p r e s e n t in many p l a n t t i s s u e s and cannot be c o n s i d e r e d as com ponents o f any one t y p e o f t i s s u e . Perhaps t h e g r e a t e s t s t i m u l u s t o t h e s t u d y o f f l a v o n o i d s and r e l a t e d compounds came w i t h t h e d e v e l o p ment o f paper chromatography and i t s e v o l u t i o n i n t o t h i n - l a y e r techniques. Paper chromatography p r o v i d e d the f i r s t s a t i s f a c t o r y procedures o f surveying p l a n t t i s s u e s f o r the presence of f l a v o n o i d s (4). These compounds p o s s e s s j u s t t h e r i g h t range 6Έ s o l u b i l i t y c h a r a c t e r i s t i c s f o r ease i n s e p a r a t i o n (5, 6) and most o f them p o s s e s s c h a r a c t e r i s t i c s p e c t r a i n u l t r a v i o l e t a n d / o r v i s i b l e r e g i o n s (6, 1). N e a r l y t h i r t y y e a r s ago paper chromatography was employed f o r t h e s e p a r a t i o n o f f l a v o n o i d s . There have been many e x c e l l e n t r e v i e w s on t h e s u b j e c t (5, (3, 8_, —* i £ ' ϋ . ) · The s e l e c t i o n o f a s p e c i f i c c h r o m a t o g r a p h i c p r o c e d u r e depends on t h e o b j e c t i v e s o f an i n v e s t i g a t i o n . The i s o l a t i o n and p u r i f i c a t i o n o f a f l a v o n o i d (or a c i n n a m i c a c i d ) can be a c h i e v e d b y v a r i o u s p r e p a r a t i o n techniques u s i n g e i t h e r one- or two-dimensional p r o cedures. In p r e p a r a t i v e p r o c e d u r a l work i n our


6

PHENOLIC, SULFUR, A N D NITROGEN COMPOUNDS I N FOOD FLAVORS

l a b o r a t o r y has u s u a l l y been b y s e r i e s o f o n e - d i m e n s i o n a l techniques. In e i t h e r case, s e v e r a l separations a r e r e q u i r e d and s e v e r a l d e t e c t i o n t e c h n i q u e s must be used. Many o f t h e f l a v o n o i d s and r e l a t e d compounds have strong antioxidant c h a r a c t e r i s t i c s i n lipid-aqueous and l i p i d f o o d systems (Tables I I , H I , F i g u r e 3 ) . As may be seen c e r t a i n f l a v o n e s , f l a v o n o l s , f l a v o n o n e s , f l a v a n o n a l s , and c i n n a m i c a c i d d e r i v a t i v e s have c o n siderable antioxidant a c t i v i t y . The v e r y low s o l u b i l i t y o f t h e s e compounds i n l i p i d s i s o f t e n c o n s i d e r e d a d i s a d v a n t a g e and i s c o n s i d e r e d a s e r i o u s d i s a d v a n t a g e i f an aqueous phase i s a l s o p r e s e n t (12). However, f l a v o n o i d s suspended i n t h e aqueous phase o f a l i p i d aqueous system o f f e r a p p r e c i a b l e p r o t e c t i o n t o l i p i d o x i d a t i o n (13, 14, 15, 16, 17, 1 8 ) . A l s o , L e a and Swoboda (12J7 n e a r l y twenty y e a r s ago, found t h a t f l a v o n o l s were e f f e c t i v e a n t i o x i d a n t s when suspended i n l i p i d systems. The a n t i o x i d a n t a c t i v i t y was measured u s i n g 20 mg. o f l i n o l e i c a c i d , 200 mg. o f Tween 40, and 1 m l . o f 0.02% B - c a r o t e n e i n c h l o r o f o r m . The c h l o r o f o r m was removed b y e v a p o r a t i o n on a w a t e r - b a t h a t 5 0 ° C . , u s i n g a rotary evaporator. 50 m l . o f oxygenated water was added, and 5 m l . a l i q u o t s o f t h i s e m u l s i o n were p l a c e d i n spectrometer tubes w i t h 2 m l . o f the a n t i o x i d a n t s o l u t i o n under t e s t . For the c o n t r o l , 2 m l . o f d e i o n i z e d , d i s t i l l e d w a t e r , o r e t h a n o l , as a p p r o p r i a t e , were added t o t h e e m u l s i o n . Readings a t 470 nm. were taken immediately. The t u b e s were s t o p p e r e d , and p l a c e d i n a w a t e r - b a t h a t 50 C . Readings o f t h e o p t i c a l d e n s i t y were t a k e n a t r e g u l a r i n t e r v a l s u n t i l t h e c o n t r o l was b l e a c h e d . The a n t i o x i d a n t i n d e x was c a l c u l a t e d by d i v i d i n g the l o s s o f o p t i c a l d e n s i t y o f the c o n t r o l a t t h e end o f t h e i n d u c t i o n p e r i o d , b y t h e l o s s o f o p t i c a l d e n s i t y o f the t e s t s o l u t i o n at t h a t time. Polyphenolic antioxidants, sparingly soluble i n l i p i d systems, have been c o n v e r t e d i n t o r e a d i l y f a t s o l u b l e form b y a l k y l a t i o n or e s t e r i f i c a t i o n w i t h l o n g chain f a t t y acids or a l c o h o l s . Such a p r o c e d u r e o f f e r s promising r e s u l t s with f l a v o n o i d s . The a c t i o n f l a v o n o l a n t i o x i d a t i o n i s b i - m o d a l . F l a v a n o l s are known t o form complexes w i t h m e t a l s . C h e l a t i o n occurs at the 3-hydroxy, 4-keto grouping a n d / o r a t t h e 5 - h y d r o x y , 4 - k e t o g r o u p , when t h e A r i n g i s k y d r o x y l a t e d i n t h e 5 p o s i t i o n . An o - q u i n o l g r o u p i n g on t h e B - r i n g can a l s o demonstrate m e t a l - c o m p l e x i n g a c t i v i t y (19, 20). However, t h e major v a l u e o f f l a v o n o i d s and c i n n a m i c a c i d s i s i n t h e i r p r i m a r y

1.

PRATT

TABLE I .

The G e n e r a l D i s t r i b u t i o n o f F l a v o n o i d Compounds i n P l a n t T i s s u e s

Plant Tissue Wood

R e l a t i v e C o n c e n t r a t i o n o f Compounds Catechins ^ Leucoanthocyanins > f l a v o n o l s > cinnamic a c i d s A s wood b u t g r e a t e r t o t a l q u a n t i t y Flavonols c i n n a m i c a c i d s > c a t e c h i n s #w Leucoanthocyanins Cinnamic a c i d s > c a t e c h i n s ^ L e u c o a n t h o c y a n ins > flavonols

Bark Leaf Fruit Phenolic, Sulfur, and Nitrogen Compounds in Food Flavors Downloaded from pubs.acs.org by 118.121.38.137 on 09/19/15. For personal use only.

7

Fhvones and Related Compounds

TABLE I I ,

Antioxidant A c t i v i t y o f Flavones A n t i o x i d a n t index Compound (5 χ 1CT M)

Aglycones: Quercetin (3,5,7,3·,4·-Pentahydroxy) Fisetin (3,7,3 ,4 -Tetrahydroxy) Myricetin (3,5,7,3 ,4 ,5 -Hexahydroxy) Robinetin (3,7,3',4*,5'-Pentahydroxy) Rhammnetin ( 3 , 5 , 3 , 4 - T e t r a h y d r o x y 7-Methoxy) Glycosides: Quercetin ( Q u e r c e t i n 3-Rhamnoside) Rutin ( Q u e r c e t i n 3-Rhamnoglucoside) 1

TABLE I I I .

3.8

1

1

1

3.8

1

4.5

1

4.5 3.6

1

3.7 1.6

A n t i o x i d a n t A c t i v i t y o f Flavanones A n t i o x i d a n t Index Compound (5 χ 10 M)

Aglycones: Naringenin (5,7,3*-Trihydroxy) Dihydroquercetin (3,5,7,3 ' , 4 '-Pentahydroxy) Hesperitin (5,7,3*-Trihydroxy-4 -Methoxy) Glycosides : Hesperidin ( H e s p e r i t i n 7-Rhamnoglucoside) Neohesperidin (Hesperitin 7-glucoside)

1.6 3.8 1.2

1

1.2 1.3

—

8


Compound

Structure

Antioxidant Index (5 χ 10~ M) %

Hesperidin Methyl Chalcone

1.3

*C ^ O H M


OH

R-%hamnoglucoside D-Catechin

3.5

Chlorogenic Acid

3.7 OH

G H ^

U

V ^ O O H ^-~CH=CH-C00

C a f f e i c Acid

3.6 OH

CH=CH-C00H

Quinic A c i d

1.5

Nu

7^ COOH

OH

Propyl G a l l a t e

2.1 OH HO ^

^-C00C H 3

7

OH

Figure 3. Antioxidant indices of some flavonoids and related compounds


1. PRATT

Flavones and Related Compounds

9

a n t i o x i d a n t a c t i v i t y ( i . e . , as f r e e r a d i c a l a c c e p t o r s and as c h a i n - b r e a k e r s ) . The major e v i d e n c e t h a t t h e s e compounds work m a i n l y as p r i m a r y a n t i o x i d a n t s i s t h e i r a b i l i t y t o work e q u a l l y w e l l i n m e t a l c a y a l y z e d and u n c a t a l y z e d systems. They a r e a l s o e f f i c i e n t a n t i o x i d a n t s i n systems c a t a l y z e d b y r e l a t i v e l y l a r g e m o l e c u l e s , such as heme and o t h e r p o r p h y i n compounds. They are a l s o e f f e c t i v e against lipoxygenase catalyzed r e a c t i o n s . These compounds cannot be e n f i s a g e d as f o r m i n g complex es w i t h f l a v o n o l s . In a d d i t i o n , h e s p e r i t i n ( 5 , 7 , 3 ' t r i h y d r o x y - 4 ' me t h o x y f l a v o n e ) which p o s s e s s e s an a c t i v e m e t a l - c o m p l e x i n g s i t e has demonstrated n e g l i b i b l e antioxidant a c t i v i t y . The p o s i t i o n and t h e degree o f h y d r o x y l a t i o n i s o f p r i m a r y importance i n d e t e r m i n i n g a n t i o x i d a n t a c t i vity. There i s g e n e r a l agreement t h a t o r t h o - d i h y d r o x y l a t i o n o f the Β r i n g c o n t r i b u t e s markedly t o the a n t i o x i d a n t a c t i v i t y o f f l a v o n o i d s (12, 13, 14, 21, 22, 23, 24). The p a r a - q u i n o l s t r u c t u r e οΈ t E ê Β r i n g T i a F l > e e n sïïbwn t o i m p a r t even g r e a t e r a c t i v i t y them t h e o r t h o q u i n o l s t r u c t u r e ; w h i l e t h e meta c o n f i g u r a t i o n has no e f f e c t on a n t i o x i d a n t a c t i v i t y (21). However, p a r a and meta h y d r o x y l a t i o n o f t h e Β r i n g a p p a r e n t l y does n o t o c c u r commonly i n n a t u r e . A l l f l a v o n o i d s with the 3 ' , 4 - d i h y d r o x y c o n f i g u r a t i o n possess antioxidant a c t i v i t y . Two ( r o b i n e t i n and m y r i c e t i n ) have an a d d i t i o n a l h y d r o x y l group a t the 5 p o s i t i o n , which i n c r e a s e s the a n t i o x i d a n t a c t i v i t i e s over those of the corresponding flavones w i t h t h e 5 - h y d r o x y l g r o u p , f i s e t i n and q u e r c e t i n . Two f l a v a n o n e s ( n a r i n g e n i n and h e s p a r i t i n ) h a v i n g a s i n g l e h y d r o x y l group on t h e Β r i n g p o s s e s s e s o n l y s l i g h t antioxidant a c t i v i t y . H y d r o x y l a t i o n o f the Β r i n g i s a major c o n s i d e r a t i o n f o r a n t i o x i d a n t a c t i v i t y . Meta 5 , 7 - h y d r o x y l a t i o n o f t h e A r i n g a p p a r e n t l y has l i t t l e , i f any, e f f e c t on a n t i o x i d a n t a c t i v i t y . T h i s i s e f i d e n c e d b y t h e f i n d i n g s t h a t q u e r c e t i n and f i s e t i n have r e l a t i v e l y t h e same a c t i v i t y and m y r i c e t i n p o s s e s s e s t h e same a c t i v i t y as r o b i n e t i n . Heimann and h i s a s s o c i a t e s (23, 24) r e p o r t e d t h a t meta 5 , 7 - h y d r o x y l a t i o n lowered a n t ï b x ï c t a n t a c t i v i t y . To t h e c o n t r a r y , Mehta and S e s h a d r i (22) found q u e r c e t i n t o be a more e f f e c t i v e a n t i o x i d a n t than 3 , 3 , 4 - t r i h y d r o x y f l a v o n e . Data from our l a b o r a t o r y s u p p o r t t h e f i n d i n g o f Mehta and S e s h a d r i . The importance o f o t h e r s i t e s o f h y d r o x y l a t i o n were s t u d i e d b y L e a and Swoboda (12); Mehta and S e s h a d r i (22); Simpson and U r i (21); and U r T (25). The two former groups found q u e r c e t a g e t i n (3,¥75,7,3,4'-hexa1

1

1

1

1

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PHENOLIC, SULFUR, AND NITROGEN COMPOUNDS I N FOOD FLAVORS

h y d r o x y f l a v o n e ) and g o s s y p e t i n ( 3 5 , 7 , 8 , 3 , 4 ' - h e x a h y d r o x y f l a v o n e ) t o be v e r y e f f e c t i v e a n t i o x i d a n t s . U r i (25) found t h a t t h e o r t h o - d i h y d r o x y g r o u p i n g on one r i n g and t h e p a r a d i h y d r o x y g r o u p i n g on the o t h e r ( i . e . , 3 , 5 , 8 , 3 * 4 ' - and 3 , 7 , 8 , 2 , 5 - p e n t a h y d r o x y vlavones) produced v e r y potent a n t i o x i d a n t s . These f o u r p o l y h y d r o x y f l a v o n e s are t h e most p o t e n t f l a v o n o i d s , as a n t i o x i d a n t s , y e t r e p o r t e d i n non-aqueous s y s t e m s . Simpson and U r i (21) found 7-n-butoxy-3,2 ,5 -trihyd r o x y f l a v o n e t o be t h e most e f f e c t i v e a n t i o x i d a n t o f 30 f l a v o n e s s t u d i e d i n aqueous e m u l s i o n s o f m e t h y l linoleate. The 3 g l y c o s i d e s p o s s e s s a p p r o x i m a t e l y t h e same a n t i o x i d a n t a c t i v i t y as t h e c o r r e s p o n d i n g a g l y c o n e when t h e g l y c o s y l s u b s t i t u t i o n i s w i t h m o n o s a c c h a r i d e . In t h e c a s e o f r u t i n where t h e s u b s t i t u t i o n i s w i t h a disaccharide antioxidant a c t i v i t y i s reduced. The a n t i o x i d a n t c a p a c i t y o f a commercial p r e p a r a t i o n o f r u t i n i s c o n s i d e r a b l y lower t h a n t h e c o r r e s p o n d i n g aglycone, q u e r c e t i n . K e l l e y and Watts (19) s t u d i e d t h e a n t i o x i d a n t e f f e c t o f s e v e r a l f l a v o n ô T d s and found r u t i n womewhat i n f e r i o r t o q u e r c e t i n and q u e r c i t r i n b u t t h e d i f f e r e n c e s were n o t as g r e a t as we have f o u n d . Chromatographic p u r i f i c a t i o n and t h e use o f s e v e r a l c o m m e r c i a l l y a v a i l a b l e samples (to e l i m i n a t e t h e e f f e c t o f p o s s i b l e contamination) d i d not a l t e r the f i n d i n g . K e l l e y and Watts (19), u s i n g a c a r o t e n e - l a r d system a l s o found t h a t q u e r c i t r i n had a p p r o x i m a t e l y the same p r o t e c t i o n as q u e r c e t i n . C r a w f o r d e t a l , (26) found t h a t m e t h y l a t i o n o f t h e 3 - h y d r o x y l group o f q u e r c e t i n o n l y s l i g h t l y lowered a n t i o x i d a n t a c t i v i t y . However, c o n s i d e r a b l e importance has been a t t a c h e d t o t h e f r e e 3 - h y d r o x y l b y o t h e r s (12, 21, 22, 2 3 ) . Mehta and S e s h a d r i (22) p o s t u l a t e d t h a t t E e " ^ h y d r o x y 1 and t h e 2,3 double"T>ond a l l o w e d t h e m o l e c u l e t o undergo i s o m e r i c changes t o d i k e t o forms w h i c h would p o s s e s s a h i g h l y r e a c t i v e - C H group ( p o s i t i o n 2 ) . D i h y d r o q u e r c e t i n was found t o have t h e same a n t i o x i d a n t a c t i v i t y as q u e r e c t i n i n d i c a t i n g e i t h e r t h a t t h e 2 , 3 , d o u b l e bond i s n o t o f major importance t o antioxidant a c t i v i t y or t h a t conversion of d i h y d r o q u e r c e t i n t o q u e r c e t i n t o o k p l a c e w h i l e t h e compound was i n c o n t a c t w i t h t h e o x i d i z i n g f a t . Mehta and S e s h a d r i (22) s u g g e s t e d t h a t c o n v e r s i o n might a c c o u n t f o r t h e a n t i o x i d a n t a c t i v i t y o f d i h y d r o q u e r c e t i n . Howe v e r , c h r o m a t o g r a p h i c t e s t s demonstrated t h a t d i h y d r o q u e r c e t i n i s not converted t o q u e r c e t i n by the h y d r o l y s i s p r o c e d u r e , nor c o u l d q u e r c e t i n be c h r o m a t o g r a p h i c a l l y d e t e c t e d i n t h e c a r o t e n e - l a r d system i n which d i h y d r o q u e r c e t i n was u s e d as a n t i o x i d a n t . Dihydrof

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q u e r c e t i n was s t i l l p r e s e n t a f t e r 12 h o u r s i n t h e system. Perhaps t h e g r e a t e s t p o t e n t i a l s o u r c e o f f l a v o n o i d s f o r f o o d a n t i o x i d a n t s i s from wood as a b y - p r o d u c t o f lumber and p u l p i n g o p e r a t i o n s . Whole b a r k o f t h e D o u g l a s f i r c o n t a i n s about f i v e p e r c e n t d i h y d r o quercetin ( 3 , 4 , 7 , 3 ' , 4 pentohydroxyflavonone). The c o r k f r a c t i o n , r e a d i l y s e p a r a t e d from t h e b a r k , c o n t a i n up t o 22% d i h y d r o q u e r c e t i n ( 2 7 ) . K i r t h (28) r e p o r t e d t h a t a p p r o x i m a t e l y 150 m î T l i o n pounds o f d i h y d r o q u e r c e t i n are p o t e n t i a l l y a v a i l a b l e a n n u a l l y i n Oregon and Washington a l o n e . Q u e r c e t i n ( 3 , 5 , 7 , 3 *4' p e n t o h y d r o x y f l a v o n e ) has been p r o d u c e d c o m m e r c i a l l y as an a n t i o x i d a n t from wood s o u r c e s ( 2 9 ) . Quercetin i s p r e s e n t i n much l o w e r amounts i n wood and b a r k t h a n i s d i h y d r o q u e r c e t i n b u t q u e r c e t i n c a n be o b t a i n e d i n q u a n t i t y by o x i d a t i o n o f d i h y d r o q u e r c e t i n . As m e n t i o n e d e a r l i e r o t h e r p l a n t c o n s t i t u e n t s w h i c h m i g h t be e x p e c t e d t o show a n t i o x i d a n t powers w o u l d be p r i m a r i l y p h e n o l i c compounds, e x p e c i a l l y o - and p - d i h y d r o x y p h e n o l s such as t h e h y d r o x y c i n n a m i c a c i d s , c a f f e i c and f e r u l i c a c i d s . While t h e s e a c i d s u s u a l l y o c c u r i n p l a n t t i s s u e as w a t e r s o l u b l e e s t e r s , commonly c h l o r o g e n i c a c i d o r d a f f e o y l q u i n i c a c i d , and s u g a r e s t e r s , t h e y have a l s o been i s o l a t e d as complex l i p o p h i l i c e s t e r s o f g l y c e r o l , l o n g - c h a i n d i o l s , and -w-hydroxy a c i d s . These l i p o p h i l i c e s t e r s have b e e n r e v e a l e d as a n t i o x i d a n t s i n a comprehensive i n v e s t i g a t i o n o f t h e a n t i o x i d a n t s i n o a t s (30, 3 1 , 32, 3 3 ) . The c a f f e o y l e s t e r s have c o n s i d e r a b l y more a n t i o x i d a n t a c t i v i t y t h a n do t h o s e o f f e r r u l i c a c i d . Other l i p i d - s o l u b l e e s t e r s o f f e r u l i c a c i d w i t h c y c l o a r t e n o l and o t h e r t r i t e r p e n o i d s have been shown b y Ohta e t a l . (34) t o o c c u r i n r i c e b r a n o i l , w h i l e a f e r u l a t e o f d i H y d r o x y - B - s i t o s t e r o l has been i s o l a t e d from m a i z e b y Tamura e t a l . ( 3 5 ) . Wheat has a l s o been shown t o c o n t a i n s i m i l a r s t e r o i d e s t e r s (36). The p r e s e n c e o f two i s o m e r s o f c h l o r o g e n i c a c i d , a l s o f e r u l i c a c i d , and s e v e r a l o t h e r p h e n o l i c a c i d s , has been c o n f i r m e d i n hexane d e f a t t e d s o y f l o u r b y A r a i et a l . (37).

Literature Cited 1. 2. 3.

Geissman, T . A . and Hinreiner, E . Botan. Rev. (1952) 18:77. B a t e - S m i t h , E. C. Advances in Food R e s e a r c h . (1954) 5:261. Geissman, T . A . "The C h e m i s t r y of F l a v o n o i d Com―


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p o u n d s " , C h a p t e r 1. ( E d i t e d b y T . A . Geissman) The M a c m i l l a n Company, New Y o r k . (1962). 4 . B a t e - S m i t h , E . C . Chem. I n d . R . (1956) 32. 5 . Harborne, J. B. J. Chromatography. (19591) 2:581. 6 . M a b r y , T. J., Markham, K . R . and Thomas, M. B. "The Systematic Identification of Flavonoids". Springer-Verlag, Berlin (1970). 7 . J u r d , L. "The C h e m i s t r y o f F l a v o n o i d Compounds", Chapter 5. ( E d i t e d b y T . A . Geismann) The Mac millan Company, New Y o r k . (1962). 8. H a r b o r n e , J. B. J. Chromatography (1958) 1:473. 9 . Thompson, J. F., Honda, S. I., H u n t , G. Ε., K r u p k a , R. M., Morris, C. J., Powell, Jr., L. Ε., Silber stein, O. O., Towers, G. Η. Ν., and Z a c h a r i u s , R. M . B o t a n . Rev. (1959) 25:1. 1 0 . Seikel, M. K. "The C h e m i s t r y o f F l a v o n o i d Com pounds", Chapter 3 ( E d i t e d b y T . A . Geissman) The M a c m i l l a n Company, New Y o r k . (1962). 1 1 . Seikel, M. K. " B i o c h e m i s t r y of P h e n o l i c Compounds", C h a p t e r 2 ( E d i t e d b y J. B. Harborne) Academic P r e s s , New Y o r k . (1964). 1 2 . L e a , C . H . and Swoboda, P . A . T . Chem. I n d . (1956) 1426. 1 3 . Pratt, D. E. and W a t t s , B. M. J. Food Sci. (1964) 29:27. 1 4 . Pratt, D. E. J. Food Sci. (1965) 30:737. 15. Cofer, A . Unpublished data. (1961) Florida State University. 16. C o f e r , A . Unpublished data. (1963) Florida State University. 17. Cofer, A . Ph.D. Thesis. (1965) Florida State University. 1 8 . Ramsey, M. B. and W a t t s , Β . M . Food T e c h n o l . (1963) 17:1056. 1 9 . Kelley, G . G . and W a t t s , Β . M . Food R e s e a r c h (1957) 22:308. 2 0 . D e W i t t , K . W. Chem. I n d . (1955) 1551. 21. S i m p s o n , T . H . and Uri, N . Chem. I n d . (1956) 2 2 . M e h t a , A . C . and S e s h a d r i , T. R. J. Sci. I n d . Research (1959) 18B: 2 4 . 2 3 . Heimann, W . , Heimann, Α . , Gremminger, M . and Holman, Η. H . F e t t e u. S o i f e n (1953) 55:394. 2 4 . Heimann, W. and Reiff, F. F e t t e u. S o i f e n (1953) 55:451. 2 5 . Uri, N. 1 9 6 1 . Mechanism of antioxidation. " A u t o x i d a t i o n a n d A n t i o x i d a n t s " , Chapter 4 ( E d i t e d b y W. O. L u n d b e r t ) Interscience Publishers, New Y o r k . 2 6 . C r a w f o r d , D. L., S i n n h u b e r , R. O. and Aft. H . J. Food Sci. (1962) 26:139.

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27. H e r g e r t , H. L. and K u r t h , E . F . T a p p i (1952) 35:59. 28. Kirth, E. F. I n d . E n g . Chem: (1953) 45:2096. 29. Anon. Chem. E n g . News (1958) 36 (No. 7 ) , 58. 30. D a n i e l s , D. G. H., K i n g , H . G . C . and M a r t i n , H . F . Sci. Food A g r . (1963) 14:385. 31. D a n i e l s , D . G . H . and M a r t i n , H. F. Chem. I n d . (1964) 2058. 32. D a n i e l s , D . G. H . and M a r t i n , H. F. J. Sci. Food Agr. (1967) 18:589. 33. D a n i e l s , D. G. H . and M a r t i n , H. F. J. Sci. Food Agr. (1968) 19:710. 34. Ohta, G. and Shimuzu, M . Pharm. Bull. (Tokyo) (1957) 5:40. 35. Tamura, T . , Sakaedani, N . and Matsumoto, T . Nippon Kagaku Z a s s h i (1958) 29:1011. 36. Tamura, T . , H i b i n o , T., Yokoyama, D. and Matsumoto, T. Nippon Kagaku Z a s s h i (1959) 80:215. 37. Arai, S., S u z u k i , H., F u j i m a k i , M . and Sakurai, Y. A g r . Biol. Chem. (Tokyo) (1966) 30:364.

Role of Flavones and Related Compounds in Retarding Lipid

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