Chemistry of Antioxidants from Labiatae Herbs - American Chemical

Chapter 16

Chemistry of Antioxidants from Labiatae Herbs Nobuji Nakatani

Downloaded by EAST CAROLINA UNIV on March 22, 2016 | http://pubs.acs.org Publication Date: May 5, 1994 | doi: 10.1021/bk-1994-0547.ch016

Department of Food and Nutrition, Osaka City University, Sumiyoshi, Osaka 558, Japan

Antioxidants have been widely used to delay or prevent oxidation of fats and oils in a variety of foods. In the process of lipid oxidation, many radical species, such as lipid alkoxyl radical, are generated and cause not only food deterioration but D N A , cell and tissue damage. Great interest in this process has prompted us to search for antioxidants from natural sources and to elucidate their chemistry for further research concerning chemoprevention of inflammation, tumors and aging. In our search for effective antioxidants we focused on edible plants, especially herbs and spices.

Several studies on the antioxidants of spices had appeared before Chipault et al examined systematically more than 70 spices for antioxidative activity (1). They reported that rosemary and sage were remarkably effective spices. As shown in Table I, we also found that spices belonging to the Family Labiatae exhibited the highest activity in a wide range of polarity. In addition, Myristicaceae and Myrtaceae showed activity in each fraction. Zingiberaceae showed the strongest activity in the slightly polar fraction. Cumin and fennel, Umbelliferae family members, contain effective substances in their polar fractions. Less Polar Antioxidants from Labiatae We chose to search rosemary (Rosmarinus officinalis L.) first for antioxidative compounds (2,3). Active compounds were isolated by a combination of chromatographies from the weakly acidic fraction of n-hexane extract. The HPLC chromatogram is shown in Figure 1. Purification of peak 3 afforded carnosol (1, Figure 2). The most effective compound isolated from Peak 1 was named rosmanol (2), the structure of which was determined by IR, H - and C - N M R analyses. H-H COSY and COLOC spectra (Figure 3) precisely confirmed the H-H, C-H correlation. N O E and long range coupling was measured. Two isomers of rosmanol were isolated and determined to be epirosmanol (3) and isorosmanol (4). Structure correlation between 2 and 3 was confirmed by chemical transformation as shown in Figure 4. 1

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Chemistry of Antioxidants from Labiatae Herbs

Table I. Antioxidant Activities of Spices Methanol extract Spice


Family

Labiatae

Basil Marjoram Oregano Perilla Rosemary Sage Thyme

Zingiberaceae

Cardamom Dried ginger Fresh ginger Turmeric

Myristicaceae Mace Nutmeg Lauraceae

Bay leaf Cinnamon

Plant part

CH C1 extract

EtOAc sol.

H 0 sol.

Leaves Leaves Leaves Leaves Leaves Leaves Leaves

+++ +++ +++ +++ +++ +++ +++

+++ +++ +++ +++ +++ +++ +++

+++ +++ +++ +++ +++ +++ +++

Fruits Rhizomes Rhizomes Rhizomes

-

+++ +++ +++ +++

-

+++ ++

Aril Seeds

+++ +

+++ +++

+++ +++

Leaves Bark

+ —

+++ +

+++

Fruits Floral parts

+++ ++

+++ +++

+++ +++

2

2 2

+++ —

-

Myrtaceae

Allspice Cloves

Umbelliferae

Caraway Coriander Cumin Fennel

Seeds Seeds Seeds Seeds

—

-

-

-

-

++ ++

+++ +++

Star-anise

Fruits

-

-

++

Magnoliaceae

+++: remarkably effective ++: moderately effective +: slightly effective - : ineffective


FOOD PHYTOCHEMICALS II: TEAS, SPICES, AND HERBS

146


1

I

1

1

0

10

20

—ι

'

30

40

m

i

n

Figure 1. H P L C chromatogram of the weakly acidic fraction of n-hexane extract from rosemary (Rosmarinus officinalis L.) Column: Develosil-ODS (φ4.6 χ 250 mm); Solvent: MeOH: H 0 (80:20); Flow rate: 1 ml/min; monitored at 285 nm. Peak 1. isorosmanol+rosmanol; Peak 2. epirosmanol; Peak 3. carnosol; Peak 4. rosmadial. 2




NAKATANI

OH

Ο

7 Figure 2. Antioxidants isolated from Labiatae.

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Figure 3. COLOC spectrum of rosmanol.



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The four diterpene antioxidants (1-4) were also isolated from sage (Salvia officinalis L.). Antioxidant efficacy was measured by the ferric thiocyanate method to reveal much higher activity of all compounds than α-tocopherol, B H A and BHT (Figure 5). Several flavonoids were isolated from sage in addition to the diterpenoids. One of them, a new glucuronoside (F-5, Figure 6) was determined based on spectroscopic methods. Four methylated flavonoids (F-l-F-4) were isolated from the antioxidant active fractions from thyme (Thymus vulgaris L.) (Figure 6) (4). F-4 was also isolated from rosemary and sage. Because the solubility of flavonoids differs in various media, different antioxidant activities have been reported. Five new biphenyls with significant activity were isolated (5-7) and compound 5 was synthesized by Miura et al.

rosmanol

epirosmanol

Figure 4. Structure correlation between rosmanol and epirosmanol.

Figure 5. Antioxidant activity of diterpenoids isolated from rosemary and sage (AOM; α-tocopherol, B H A , BHT, 0.02%; diterpenoids, 0.01%). Ho et al.; Food Phytochemicals for Cancer Prevention II ACS Symposium Series; American Chemical Society: Washington, DC, 1994.


Ferric Thiocvanate Method O.D.


5

Day

Figure 6. Antioxidant activity of flavonoids from Labiatae.


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Polar Antioxidants from Labiatae In practical use, water soluble antioxidants are strongly required. Oregano (Origanum vulgare L.) showed high antioxidative properties in the polar fraction. Purification with polyamide chromatography afforded five phenol carboxylic acid derivatives (8,9). A new glucoside (6), which exhibited remarkable activity, was determined by chemical degradation (Figure 7) and synthesis. Rosmarinic acid and a related new compound (7) were obtained accompanied by protocatequic acid and caffeic acid (9). Marjoram (Origanum majorana L.), a herb close to oregano in botanical classification, contains phenol carboxylic acids in the MeOH extract. As shown in Figure 8, rosmarinic acid and acylated arbutin are major active products in polar fraction. Conclusion Herbs and spices are one of the most important targets to search for natural antioxidants from the point of view of safety. It is expected that natural antioxidants which are investigated for basic and applied experiments will lead to chemoprevention of inflammation, cancer and aging.

OH OH

methylation OCH

3

οII

HO

CH 0-C

OCH

2

3

H O ' V " ^ OH HO^^ 1) alkaline hydrolysis 2) acetylation 3) fractionation

neutral fraction column chromatography recrystallization from MeOH - H 0

acidic fraction recryatallization from HoO

2

A c O ^ V ^ ^ N ^ O — ^ AcO-^^OAc

^

>-CH OAc 2

y

Figure 7. Chemical degradation products of glucoside (6). Ho et al.; Food Phytochemicals for Cancer Prevention II ACS Symposium Series; American Chemical Society: Washington, DC, 1994.


152

A : arbutin HO

OH HO±^

HO


Β : 6-o-p-hydroxybenzoylarbutin OH J ^ O H

H O y ^ - y C O O H

C : rosmarinic acid COOH OH

D : 2-hydroxy-3-(3,4,-dihydroxyphenyl)propionic acid

Thiocyanate Method control α-tocopherol

BHT

O.D.

Figure 8. Antioxidant activity of the phenolic constituents of marjoram. Ho et al.; Food Phytochemicals for Cancer Prevention II ACS Symposium Series; American Chemical Society: Washington, DC, 1994.

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Literature Cited 1. Chipault, J. R.; Hawkins, J. M.; Lundberg, W. O. Food Res. 1952, 17, 46. 2. Inatani, R.; Nakatani, N.; Fuwa, H.; Seto, H. Agric. Biol. Chem. 1982, 46, 1661. 3. Nakatani, N.; Inatani, R. Agric. Biol. Chem. 1984, 48, 2081. 4. Miura, K.; Nakatani, N. Agric. Biol. Chem. 1989, 53, 3043. 5. Miura, K.; Nakatani, N.; Chem. Express 1989, 2, 237. 6. Miura, K.; Inagaki, T.; Nakatani, N. Chem. Pharm. Bull. 1989, 37, 1816. 7. Nakatani, N.; Miura, K.; Inagaki, T. Agric. Biol. Chem. 1989, 53, 1375. 8. Nakatani, N.; Kikuzaki, H. Agric. Biol. Chem. 1987, 51, 2727. 9. Kikuzaki, H.; Nakatani, N. Agric. Biol. Chem. 1989, 53, 519. RECEIVED

October 4, 1993


Chemistry of Antioxidants from Labiatae Herbs - American Chemical

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