48Phytochemicals in

Mediterranean Diet: TheInteraction Between Tomato

and Olive Oil BioactiveCompounds

Rita Pernice, Paola Vitaglione, Raffaele Sacchi, and Vincenzo Fogliano

Dipartimento di Scienza degli Alimenti, Universita di Napoli “Federico II”

Parco Gussone, Ed. 84-80055 Portici (NA), Italy

48.1 Introduction 53

48.2 Tomato and Olive Oil Phytochemicals 56

48.3 Physiological Effects 58

48.4 Conclusions 60

References 61

48.1 INTRODUCTION

The word “phytochemicals” is commonly used to indicate thousands of chemically

different natural metabolites used in medicine and food preparations (Table 48.1).

Natural medicines have been used from the infancy of human history for their

53

Handbook of Food Products Manufacturing. By Y. H. HuiCopyright # 2007 John Wiley & Sons, Inc.

pharmacological activity against many diseases or as simple folk remedy. Traditionally

these medicines were obtained from plants, herbs, roots, and seeds, which could be

used in their primary form or combined into mixtures. Nowadays, these preparations

can be also formulated in pills, tablets, or liquids and are commercially available as

natural medicines especially in Asian countries (Table 48.2).

Traditional Chinese medicine uses antioxidant-rich medicinal plants for the prevention

of many diseases. These medicinal plants have a concentration of phenolic compounds

TABLE 48.1 Main Classes of Phytochemicals (Craig 1997).

Phytochemicals Foods

Allyl sulfides Garlic and onion

Phytates Grains and legumes

Glucarates Citrus, grain, and solanaceous vegetables

Lignans Flax and soybeans

Isoflavones Soybeans

Saponins Legumes

Indoles, isothiocyanates, and dithiolthione Cruciferous vegetables

Ellagic acid Grapes, strawberries, raspberries, and nuts

Phthalides and polyacetylenes Umbelliferous vegetables

Flavonoids, carotenoids, and terpenoids Various plants and vegetables

Other phenolic compounds Various plants and vegetables

TABLE 48.2 Plants Found in Herbalists’ Shop in Jordan (Afifi and others 2000).

Family Name Scientific Name Parts Used Recommended Uses

Boraginaceae Echium judaeum Roots Nervosity, hyperactivity, general

weakness, dermatological

disorders

Cruciferae Brassica campestris Seeds,

leaves, roots

Hypercholesteremia, inflammation

Cucurbitaceae Cucurbita maxima Seeds Ulcer, diabetes

Fagaceae Quercus coccifera Fruits Kidney sands and stones, post

delivery syndrome

Labiateae Menta piperita Leaves, stem Common cold, cough, influenza,

constipation, nervosity

Ocium basilicum Leaves Common cold, cough, influenza,

kidney sands, and stones,

gynaecological disorders,

alopacia

Leguminosae Glycyrrhiza glabra Roots Common cold, cough, influenza,

constipation, kidney sands, and

stones

Liliaceae Aloe vera Leaves, juices Abdominal pain, diabetes,

weaning

Punicaceae Punica granatum Fruits, roots,

and stem coat

Common cold, cough, influenza,

ulcer

Rosaceae Rosa damescana Flowers Common cold, cough, influenza,

abdominal pain, gall-bladder

stones, general weakness

Rutaceae Citrus aurantium Leaves, flowers fruits,

peel, fruits

Weakness in myocardium,

gynaecological disorders

Umbrelliferae Petroselinum

sativum

Leaves, steam Urinary tract infections, arthritis

54 PHYTOCHEMICALS IN MEDITERRANEAN DIET

(phenolic acids, flavonoids, tannins, coumarins, lignans, quinines, stilbenes, and curcumi-

noids) significantly higher than vegetables and fruits (Cai and others 2004).

The dietary intake phytochemicals in Western countries is related more to the con-

sumption of fruits and vegetables than to the use of specific medicinal plants or extracts.

In the last decade soybeans and related products, traditionally consumed especially in

Asia, have been conquering Western markets thanks to their biological effects on

humans. The positive effects on health exerted by these foods (Table 48.3), previously

attributed only to their high isoflavones content (genistein, daidzein, glycitein), are

recently thought to be due to the combination of many compounds such as proteins,

amino acids, peptides, saponins, phytic acids, trypsin inhibitors, fiber, and isoflavones

(Barnes and others 1998; King and Bignell 2000; Fukui and others 2002).

Beside the bioactive vegetable compounds naturally present in foods and medicinal

plants, the phenomenon of phytochemical-rich ingredients used as components of commer-

cial food preparation is becoming of nutritional relevance. Many phytochemicals have been

used by food industries to increase the shelf-life of their products. For example, meat indus-

tries largely add phytochemical mixtures to prevent the oxidation of its products.

Lipid oxidation is the most important factor implicated in meat spoilage during storage,

and thus in the reduction of its shelf-life due to off-flavor and off-color development

(Pearson and others 1983). The losses of nutritional value and functionality (Matsushita

1975) could be reduced using synthetic antioxidants (BHA, BHT, and citric acid) but

many investigations performed in model systems showed that natural antioxidants are

as effective as synthetic antioxidants in retarding oxidation (MacNeil and others 1973;

Madsen and Bertlesen 1995). Nissen and co-workers (2000) showed that rosemary

extract had the same efficacy of BHT and octyl gallate in protecting the dehydrated

chicken meat against oxidative deterioration, followed by tea and coffee extract, while

grape skin extract was the less efficient among the tested extracts. Moreover, consumers

are more willing to accept natural extracts than synthetic antioxidants.

Addition and integration of phytochemicals, especially antioxidants, for technological

and nutritional purposes is a fascinating field of food technology. From this point of view

TABLE 48.3 Protective Effects Reported for Soy Isoflavones.

Cancer Epidemiological studies show a protective effect of soy consumption against

hormone-dependent cancer of the breast and prostate (Barnes and others 1998)

and against bowel, stomach, olon, rectum, and lung cancer (Messina and

Messina 1991; Messina and others 1994; Adlercreutz and others 1995; Herman

and others 1995)

Heart disease Soy protein has a hipocholesterolemic effect (Fukui and others 2002) and may

reduce the risk of atherosclerosis (Anderson and others 1995; Potter 1995) and

of coronary heart diseases (Anderson and others 1999; Hermansen and others

2001; Nicolosi and others 2001; Hasler 2002). Isoflavones are thought to be an

important hypocholesterolemic component in soy protein (Anthony and others

1996,1997; Kirk and others 1998; Ni and others 1999)

Osteoporosis Isoflavones protect against osteoporosis (Potter and others 1998; Wiseman 2000;

Scheiber and others 2001)

Antioxidative

effect

Isoflavones acts as antioxidants and scavengers of reactive oxigen species (ROS)

and reactive nitrogen species (RNS) (Arora and others 1998; Yen and Lai 2003)

Other Soy isoflavones also exhibit biological activities such as inhibition of cell prolifer-

ation (Coward and others 1993; Fotsis and others 1995) and enzyme-inhibitory

effects (Keung and others 1993)

48.1 INTRODUCTION 55

many traditional recipes of the Mediterranean diet give unexpected opportunities when the

behavior of antioxidant compounds during the technological processes is considered. In

Mediterranean countries the large consumption of tomatoes and virgin olive oil, which

are present in many traditional recipes, ensures a high intake of antioxidant phytochemicals,

such as carotenoids and polyphenols, respectively. This is due to the high natural occur-

rence of these compounds, but also, as we will show in the following pages, to the type

of processes usually adopted for the preparation of these food.

In this chapter we discuss phytochemicals present in these staple foods of Mediterra-

nean diet, tomato and olive oil, focusing our attention on their natural content in raw

materials and the positive influence of technological processes from the nutritional

point of view.

48.2 TOMATO AND OLIVE OIL PHYTOCHEMICALS

The widespread use of tomatoes and tomato-based products in Mediterranean diet make

this fruit an important source of minerals, vitamins, and healthy phytochemicals such as

carotenoids and flavonoids. The concentration of secondary metabolites in tomatoes

depends on many factors. Carotenoid biosynthesis is influenced by the variety, cultivation

area, stage of ripening at harvest, agronomical practices (i.e., irrigation, fertilization, etc.),

and the storage conditions. Leonardi and co-workers (2000) reported that the concen-

tration of carotenoids in commercial tomatoes ranges from 0.6 to 13 mg per 100 g of

green salad and full ripe cherry tomatoes, respectively. On the other hand, flavonoid bio-

synthesis is poorly correlated with ripening stage, while it seems more dependent on cli-

matic and solar radiation conditions; in fact, tomatoes leading to the same variety results

richer in flavonoids when grown in Mediterranean area than fruits cultivated in North

Europe (Stewart and others 2000).

Since tomatoes are an excellent source of carotenoids, but a modest source of flavo-

noids, there is considerable interest in the production of fruits containing increased

levels of flavonoids with a consequent wider range of potential health beneficial proper-

ties. Several breeding companies and research institutes obtained tomato mutants contain-

ing higher levels of carotenoids and flavonoids than commercial varieties.

Tomato micronutrient content is also influenced by industrial process, which represents

another important factor determining antioxidant intake considering that more than 75%

of tomatoes consumption derives from processed products. All tomato-based products

undergo a more or less severe thermal treatment, which can affect the stability of

tomato bioactive compounds. It is generally accepted that carotenoids are poorly affected

by processing; on the other hand, data for flavonoids are not conclusive, also because fla-

vonoids are mainly located in the skins, which are usually discarded in processed toma-

toes. In fact, while literature data (Crozier and others 1997; Stewart and others 2000)

report that industrial canning causes a severe reduction of flavonols content, a recent

work performed by our group showed that, when tomatoes are canned without the previous

peeling, no thermal degradation of flavonoids was observed (Pernice and others in press).

As far as olive oil phytochemicals the absolute concentration of phenolic compounds is the

result of complex interactions between several factors, including cultivar, ripening degree,

climate, and extraction process (Caponio and others 1999; Fogliano and others 1999). The

amount of phenolic compounds is also affected by oxidative and hydrolytic modification

during storage (Della Medaglia and others 1996).

56 PHYTOCHEMICALS IN MEDITERRANEAN DIET

The phenolic fraction consists of the so-called secoiridoid derivatives, formed by

p-hydroxyphenylethanol ( p-HPEA) or by dihydroxyphenylethanol (DHPEA) linked to

elenolic acid. Phenolic compounds, particularly o-dihydroxy derivatives, have strong anti-

oxidative activity and are essential to preserve the fatty acid moiety of VOO from oxi-

dative damage during processing and storage (Baldioli and others 1996; Litridou and

others 1997). Furthermore, o-dihydroxyphenolic compounds contribute to the stability

of the oil, due to their ability to donate a hydrogen atom and form an intramolecular hydro-

gen bond between their hydroxyl group and phenoxyl radicals (Visioli and Galli 1998).

In the last few years, we have investigated the effect of industrial process and

home cooking on the interactions between carotenoid and flavonoid of tomatoes and poly-

phenol of virgin olive oil in tomato sauces. Home-made tomato sauces are prepared by

mixing 3–5% of extra-virgin olive oil to fresh or canned tomatoes and cooking them for

a period ranging from few minutes to many hours, as it happens in traditional recipes of

southern Italy. During thermal treatment phytochemicals degradation could be expected.

However, the presence of a two phase-system (oil-in-water), causes a peculiar phase

partition of virgin olive oil polyphenols, as well as tomato carotenoids and flavonoids.

A model system study (Graziani and others 2003) showed that, heating in

laboratory-scale conditions, a mixture of tomato and 5% olive oil, the latter had a protec-

tive effect on tomato antioxidants (Table 48.4). Lipid matrix favored the extraction and the

detection of tomato carotenoids (Fig. 48.1) and at the same time olive oil phenolic

TABLE 48.4 Effect of Heating Time on Lycopene Concentration in Peeled

Tomato Puree and in Peeled Tomato Puree Added of 5% Virgin Olive Oil.

Lycopene Concentration (mg/100 g of Dry Matter)

Heating Time Peeled Tomato Puree

Peeled Tomato

Pureeþ 5% Virgin Olive Oil

0 61.12+ 3.7 70.37+ 5.5

0.5 59.26+ 3.7 62.96+ 5.6

1 55.56+ 1.8 64.81+ 7.1

2 53.70+ 5.5 62.95+ 3.7

4 46.30+ 1.8 59.26+ 3.6

9 37.04+ 3.7 59.26+ 3.8

0

1

2

3

4

5

6

7

mg

of c

arot

enoi

ds

nt 2h 4h 8h

Figure 48.1 Effect of heating time on carotenoid repartition in an oil-tomato mixture. The gray bars cor-

respond to oil carotenoids while the white ones correspond to tomato carotenoids; “nt” is for not thermal

treated samples.

48.2 TOMATO AND OLIVE OIL PHYTOCHEMICALS 57

compounds protected carotenoids from oxidation thus resulting in an enhanced antioxi-

dant activity of the heated mixture (Fig. 48.2). Accordingly, Anese and co-workers

(2002) showed that using industrial-like treatment on tomato–olive oil system there

were no significant change in lycopene concentration.

The positive interaction between the various classes of antioxidants in this system have

implications in the stability and storage of tomato sauces, and these findings are very

important from the stand point of the physiological effects that these compounds may

have on humans.

48.3 PHYSIOLOGICAL EFFECTS

The in vivo physiological effects of carotenoids are related to their bioavailability. Many

studies demonstrated that the uptake of carotenoids is greater from heat processed than

from unprocessed tomato, and that the absorption efficiency is also affected by the contem-

porary presence in the diet of other food components such as dietary fats and proteins

(Dimitrov and others 1988; Rock and Swendseid 1992; Stahl and Sies 1992; Gartner

and others 1997). Giovannucci and co-workers (1995) found that the intake of tomato

sauce was significantly correlated with lycopene concentrations in plasma, while the

administration of tomato juice did not cause any increase of lycopene plasma concen-

trations. A slight increase was also correlated to the intake of fresh tomatoes. These find-

ings were attributed to the common practice to consume tomato sauce and fresh

tomatoes together with oil. The fat matrix has two positive effects on carotenoid bioavail-

ability: in the stomach it favors carotenoid extraction from food matrix. In the upper gut

the presence of oil stimulates the excretion of biliary acids, the consequent formation of

chylomicrons and therefore the absorption of all lipophilic phytochemicals.

On the basis of this consideration an antioxidant-rich functional food (FF) constituted

by a tomato puree mixed with 10% extra-virgin olive oil was produced in an industrial

plant and a pilot bioavailability study of carotenoids was performed. For this purpose

five healthy volunteers (2M and 3F) that were asked to consume 100 g/day of the FF

(23 mg carotenoids/day) for a week were enrolled. The control group was constituted

of three volunteers (2M and 1F) that did not consume the FF. Blood samples were

drawn before (T0), after a week of FF administration (T7) and after a week of wash-out

(T14). Serum samples collected were analyzed for carotenoid composition. In particular

0

0.05

0.1

0.15

mm

ol t

rolo

x/10

0g

nt 2h 4h 8h

Figure 48.2 Antioxidant activity of water and oil phases measured during heating in a tomato olive oil

system. Note: The grey bars correspond to oil antioxidant activity while the white ones correspond to

tomato antioxidant activity; “nt” is for not thermal treated samples.

58 PHYTOCHEMICALS IN MEDITERRANEAN DIET

all-trans- and 5-cis-lycopene, lutein and b-carotene were quantified by HPLC as described

by Holloway and others (2000).

The results (showed in Figure 48.3) demonstrate that in all the subjects that consumed the

FF, an increase of the bioactive compounds directly related to FF antioxidant contents was

found. In particular after the week of administration, b-carotene and lutein levels doubled

the basal levels (0.28 + 0.17 mg/mL vs. 0.12+ 0.09 mg/mL and 0.22+ 0.13 mg/mL

vs. 0.10+ 0.08 mg/mL respectively) while all-trans lycopene levels were four-fold

higher (0.50 + 0.15 mg/mL vs. 0.16+ 0.03 mg/mL). After the wash-out period the caro-

tenoid serum concentration come back to the basal levels (p , 0.05).

Heating tomatoes in the presence of fat increases the bioavailability of carotenoids, but

it is important to underline that the composition of fat can also affect this parameter.

On this regard, Lee and others (2000) carried out a study to value the effect of cooking

tomatoes with two different oils, extra-virgin olive oil and sunflower oil, on plasma

lycopene concentration and plasma antioxidant activity. Six subjects (5F and 1M) were

asked to consume for a week, 200 g of tomato soup (33 mg lycopene) and 230 g of

0

0.1

0.2

0.3

0.4

0.5

0.6

All-tr

ans l

yc.

5-cis

lyc.

b-car

oten

e

Lutein

Seru

m c

arot

enoi

d le

vels

(µg/

mL

)Se

rum

car

oten

oid

leve

ls (

µg/m

L)

0

0.1

0.2

0.3

0.4

0.5

0.6

All-tr

ans l

yc.

5-cis

lyc.

b-ca

rote

ne

Lutein

a a a

a b a

a b a

a b a

a b a

a a a

a a a a a a

Figure 48.3 Top Panel: average serum carotenoid concentration in subjects that consumed the FF.

Bottom Panel: average serum carotenoid concentration in subjects of control group. Shaded bars T0;

black bar T7; pointed bar T14.

48.3 PHYSIOLOGICAL EFFECTS 59

canned tomatoes (13 mg lycopene) with 20 mL of extra-virgin olive oil, followed by three

weeks of washout, then they were supplemented for another week with the same amount of

tomato products plus 20 mL of sunflower oil. The results (Table 48.5) showed that the

supplementation of tomato products (about 46 mg/day of lycopene) with olive oil and

sunflower oil produced respectively 80% and 70% increase of the plasma lycopene

levels. The increase was not significantly different between the two oils. On the contrary,

plasma antioxidant activity (measured with FRAP assay) increased only with consumption

of tomato products with olive oil, while with sunflower oil the plasma antioxidant

activity is slightly below the control level. Again, this result is likely due to the

amazing integration between the antioxidant component of olive oil and that of tomato.

48.4 CONCLUSIONS

The link between diet and chronic diseases is very well documented. Medical research is

focused on prevention of major chronic diseases to reduce the current high cost of medical

care. As a consequence, nowadays major attention is referred to food components note for

their capability to exert positive effects on human health, such as phytochemicals, whose

activities have been demonstrated by many scientific studies. Among phytochemicals,

antioxidants have been hypothesized to play a major role as an enhanced production of

free radicals and/or significant decrease of antioxidant defence is correlated to many

diseases (Weisburger 1999). Moreover, antioxidant-rich foods have been shown more

effective than pills, tables and other synthetic nutraceuticals.

In recent years, the consumer demand of enjoyable foods that are able to satisfy senses,

but also maintain an healthy status, is continuously increasing. This tendency is coupled

with the large diffusion of Mediterranean diet in the world, as this alimentary regime is

considered a model for a healthy diet. Mediterranean diet is characterized by a greater

intake of cereal, fruit, and vegetables respect to animal-derived foods, thus assuring a

large intake of bioactive compounds. Among the staple foods of Mediterranean diet

tomatoes and virgin olive oil represent an optimal antioxidant mixture by nutritional

and technological point of view.

The phytochemicals presence in raw foods and their capability to undergo to the

industrial processing should be taken in serious account by the food industry. In fact,

the selection of antioxidant-rich raw foods, and better control of processing conditions

could ensure the highest bioactive compound content in the final products, thus increasing

the functionality of the offered products also thanks to a particular interaction and

synergism among food compounds that improve the bioavailability (Beecher 1998).

As consequence the bioavailability of phytochemicals used as food ingredients, and the

choice of food matrix, must be carefully considered.

TABLE 48.5 Effect of Supplementation of Tomato Products with Olive Oil and

Sunflower Oil (Lee and others 2000).

Tomato Products with

Olive Oil

Tomato Products with

Sunflower Oil

Baseline Week 1 Week 4 Week 5

Dietary lycopene ,5 46 + 10 ,3 46 + 12

Plasma lycopene (mmol/L) 0.66+ 0.26 1.20 + 0.20 0.67 + 0.27 1.14 + 0.35

Plasma antioxidant activity

(mmol/L)

930+ 150 1118 + 184 1049 + 186 1009 + 181

60 PHYTOCHEMICALS IN MEDITERRANEAN DIET

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