Oregano

The genera Origanum and Lippia

Spiridon E. Kintzios

• Publisher: CRC Press
• Year: 2002
• Print ISBN: 9780415369435
• eBook ISBN: 9781134202546
• Edition: 1
• Topic: Medicine
• Subtopic: Alternative & Complementary Medicine

Oregano: The Genera Origanum and Lippia is an updated analysis of the technical knowledge and market information on the world's most commercially valuable spice. The book treats various aspects of practical significance for the crop's industrialization, such as optimizing germplasm selection and utilization, novel cultivation methods and product pr

Part 1
Introduction

1
Profile of the multifaceted prince of the herbs

Spiridon E. Kintzios

The scope of this volume is to offer an updated and analytic review on the currently available technical knowledge and market information of the world’s commercially most valued spice – oregano. In addition, the book treats in detail various aspects of practical significance for the crop’s industrialization – such as optimizing germplasm selection and utilization, novel cultivation methods and product processing, blending and uses in different countries, along with other market-related issues never included in previous reviews.

Oregano is the common name for a general aroma and flavor primarily derived from more than 60 plant species used all over the world as a spice. The majority of them belong to the Lamiaceae and Verbenaceae families, while a large distinction is made between the European (Origanum sp.) and Mexican (Lippia sp.) oregano.

European oregano is used as a flavoring in meat and sausage products, salads, stews, sauces, and soups. Prior to the introduction of hops, oregano was used to flavor ale and beer. The essential oil and oleoresin, used extensively in place of the plant material, are found in food products, cosmetics, and alcoholic liqueurs. Oregano is also a good salt replacement in tomato-containing recipes. Mexican oregano is used predominantly in flavoring Mexican foods, pizza, and barbecue sauces. Mexican oregano has a somewhat sharper and more pungent flavor than European oregano. The reader will find detailed information on the dietary properties of the spice and the various ways of adding it to foodstuff and beverage preparations. Issues of chemical stability and compatibility to diversified demand specifications will also be examined.

Most widely used is the genus Origanum (family Lamiaceae) (from the Greek words oros – mountain and hill and ganos – ornament). The taxonomy of the genus is rather complicated and a current issue of debate: indeed, Origanum sp. is characterized by a large (and still little investigated) morphological and chemical diversity resulting in the distinction of 49 taxa and 42 species. Respecting Ietswaart taxonomic revision there exist ten sections (Amaracus Bentham, Anatolicon Bentham, Brevifilamentum Ietswaart, Longitubus Ietswaart, Chilocalyx Ietswaart, Majorana Bentham, Campanula ticalyx Ietswaart, Elongatispica Ietswaart, Origanum Ietswaart, Prolaticorolla Ietswaart). Since Ietswaart’s publication, five more species and one more hybrid have been recognized, raising the number of species to 43 and the number of hybrids to 18.

More than 300 scientific names have been given, during the last 150 years, to not more than 70 presently recognized Origanum species, subspecies, varieties and hybrids. This plethora of different names reflects the extent of morphological variation the genus exhibits in nature. The overwhelming majority of the taxa are locally distributed within the Mediterranean region, with nine species being located in Greece and 21 in

Turkey. Sixty per cent of all Origanum taxa are recorded to grow in Turkey, indicating this country as the gene center of Origanum. In addition, 17 hybrids between different species have been described, some of which are known only from artificial crosses. Very complex in their taxonomy, Origanum biotypes vary in respect of either the content of essential oil in aerial parts of the plant or essential oil composition. Essential oil ‘rich’ taxa with essential oil content of more than 2 per cent (most commercially known oregano plants), are mainly characterized either by the dominant occurrence of carvacrol and/or thymol (together with considerable amounts of ϒ-terpinene and p-cymene) or by linalool, terpinene-4-ol and sabinene hydrate as main components. The two most well commercially known ‘oregano’ species are O. vulgare subsp. hirtum (Greek oregano) (as well as winter sweet marjoram or pot marjoram, which is derived from O. heracleoticum and O. onites (Turkish oregano), each having an essential oil content of more than 2 per cent.

The genus Lippia (family Verbenaceae) is the most well known of several plants in Mexico that bear a resemblance to the Mediterranean oregano in terms of flavor and aroma, and the leaves of which have long been established by trade practice to be oregano (curly leaf oregano, Mexican sage, origan, oregamon, wild marjoram, Mexican marjoram, or Mexican wild sage). The genus Lippia Houst. consists of approximately 200 species of which 46 have been chemically examined.

The species mainly used are either Lippia graveolens or L. berlandieri. Because most of the species are aromatic, the studies on the chemistry of this genus are mostly related with the composition of the essential oils and only a very few ones devoted to the nonvolatile constituents. An outstanding feature of Lippia is the difference observed in the essential oil composition reported for the same species from different geographic origins. The mono- and sesquiterpenoids found in the essential oils for all but two of the Lippia species investigated so far are quite common and widespread in the plant kingdom, the exceptions being L. integrifolia (Gris.) Hieron. which produces ketones based on the unique sesquiterpene skeletons named lippifoliane and integrifoliane and L. dulcis Trev. which contains (+)-hernandulcin, a sesquiterpenoid 1500 times sweeter than sucrose. Iridoids glucosides, phenylpropanoids, naphthoquinoids and flavonoids are the four types of significant non-volatile secondary metabolites reported in Lippia.

The Origanum species are perennial herbs native to the dry, rocky calcareous soils in the mountainous areas of southern Europe and south-west Asia, and the Mediterranean countries. The perennial, erect plants reach a height of 0.8 to 1 m and have pubescent stems, ovate, dark green leaves, and white or purple flowers. The root structure of oregano is such that it binds the soil and keeps it from washing away on steep slopes. European oregano is primarily produced in Greece, Italy, Spain, Turkey, and the United States. The Lippia species are small shrubs with larger leaves than the Origanum species and come primarily from Mexico.

The reported life zone for Origanum vulgare is 5–28 °C with an annual precipitation of 0.4–2.7 m and a soil pH of 4.5–8.7. Although much of the commercial material is collected from wild plants, fields can be seeded or established from transplants on light, dry, well-drained soils that are somewhat alkaline. Harvesting can take place two to six times per year. The Lippia species are predominantly collected as wild plants in Mexico.

Information is provided, in a very detailed manner, on structural dynamics of Origanum in order for the reader to get a picture about the construction and operation of the specific tissues composing the plant fundamental organs (leaf, stem, root).

Particular attention is given to glandular (peltate, capitate Type I and II) hairs and nonglandular hairs, their ontogenetic patterns from a protodermal initial cell and the topology of essential oil biosynthesis. Such data (e.g. knowing the structural components participating in a certain metabolic process as well as their temporal alterations and modifications) can be utilized for other fields of Origanum research.

There are a number of publications referring to the chemisty of Origanum which is known widely in the world of herbs and spices for its volatile oils. Oregano is the commercial name of those species that are rich in the phenolic monoterpenoids, mainly carvacrol, occasionally thymol, while marjoram is the commercial name of those that are rich in bicyclic monoterpenoids cis- and trans-sabinene hydrate. Besides the qualitative variation of the volatile compounds at the infrageneric level, there is considerable quantitative variation at the infraspecific level. Remarkable chemical variations have not only been observed between but also within populations and accessions. The seasonal variation of essential oil yield and composition has received less attention. There is yet limited knowledge in the biosynthesis of the essential oil compounds and their inheritance, which would be useful for a more effective selection and establishing a targeted breeding program. For all these reasons, wild collection accompanied with quality and species maintaining assurance systems (sustainability, GHP) and/or field production of reliable genotypes are the future methods of choice for quality products. The enormous inter- and infraspecific chemical polymorphism of Oregano sp. offers a wide range for selection towards the production of specific monoterpenes as fine chemicals, new odor and flavor profiles a.s.o. In the present book, a detailed chemotaxonomic account of Origanum taxa is presented by group and by section. Origanum species are rich in other compounds as well, such as various phenolics, lipids and fatty acids, flavonoids and anthocyanids. In a separate chapter, main breeding targets and quality criteria are set out and various breeding methods are discussed.

It is generally accepted that the Greek oregano has the best essential oil quality, the main constituents of which are carvacrol (the compound responsible for characterizing a plant as of the oregano type) and/or thymol, accompanied by p-cymene and ϒ-terpinene. Mexican oregano oil contains approximately equal amounts of carvacrol and thymol and smaller amounts of 1,8-cineole and other compounds. The basic composition of the oil varies with the plant source and geographical growth area.

Although oregano has been known and used for centuries, it gained only lately mass popularity, largely due to its relationship to marjoram (O. marjorana), the popular and botanical terms for both species having long been confused. And while sweet marjoram was one of the most popular herbs during the Middle Ages, oregano was scarcely cultivated, probably due to the plant’s tendency to compete against other plants growing nearby. On the other hand, wild oregano has been traditionally collected in Mediterranean countries and in Mexico for use in many of the favorite dishes (e.g. for tomato-based sauces, lamb, seafood, chili peppers and almost any garlic flavored dish). The rest of the world discovered oregano after Second World War, with the expansion of pizza consumption (and in a lesser-degree, Mexican-style foods). Oregano consumption boomed from almost nil to a consumption volume of over 500 000 tons, demonstrating a per capita increase of importation into the United States of 3800 per cent from 1940 to 1985. Product prices depend heavily on quality. The overall market of oregano is expanding becoming thus by far the largest selling herb today. Latest estimates put worldwide production of oregano at about 10 000 tons. Turkey has a dominant position in the worldwide trade of oregano (over 2/3 of the total production), followed by Mexico, Greece and other Mediterranean countries. Greece has long been a leading source and its product has traditionally commanded the highest prices, nevertheless not always sufficiently meeting demand. Though Italy harvests large amounts of oregano, most of it is consumed domestically. The Mediterranean-type of product, as compared to the Mexican, is a smaller leaf of somewhat lighter green color and milder, sweeter flavor. As compared to sweet marjoram, however, it is much strongly flavored. The harvesting and processing of oregano is similar in Mediterranean and Mexican areas. In a separate chapter, a comparative demonstration is given of cultivation practices of oregano in different producing countries, such as Turkey, Hungary, Germany, Israel, Slovenia, the Federal Republic of Yugoslavia and Albania.

Cultivation of oregano can be a profitable business. Growers currently enjoy increased market prices due to the limited product availability, as a result of the exhaustion of wild oregano populations due to intensive collection. A recent survey in Greece (Papanagiotou et al., 2001) indicated that for a given average yield of 1850 kg per hectare and an average product price of 4.1 € per kg, the net profit for the grower is 2500 € per hectare, a value considerably higher then for most crop and horticultural species. Labor (1260 man-hours/hectare) was estimated to reach 64 per cent of the total production cost.

The herb is often sold by mesh size, indicating average particle size. In United States oregano imports are roughly equal from both Mediterranean and Mexican species. The Mexican Oregano is a much stronger, more robustly, ‘wild’ flavored oregano. After cleaning, the leaves of Mediterranean oregano come into a size of 30 or 60 mesh, with larger leaf particles giving the choicest, more refined appearance. In Mexico, shippers often refer to their most refined product as ‘Greek cut.’ In the United States the herb is offered as ground or whole leaf oregano (although not always in the original whole form). Beyond that, various mesh sizes may also be available, each being the most appropriate choice for a particular use. Other important species collected and marketed as European oregano include Thymus capitatus (Spanish oregano), Origanum syriacum (Origanum maru – Syrian marjoram or zatar) and Origanum virens. Additional species used in Mexican oregano include Lippia palmeri and Lippia origanoides.

The original fresh material is the essential factor determining the quality of the dried herbs. Nevertheless, the drying method, type of packaging, and storage conditions also has clear effects on the microbiological quality of the herbs. An exemplary investigation is the Finnish Herb Study, presented in detail in this volume.

As a medicinal plant, European oregano has traditionally been used as a carminative, diaphoretic, expectorant, emmenagogue, stimulant, stomachic, and tonic. In addition, it has been used as a folk remedy against colic, coughs, headaches, nervousness, toothaches, and irregular menstrual cycles. Turkish villagers have traditionally used kekik water, the aromatic water obtained after removing essential oil from the distillate of oregano herbs, which has in recent years become a commercial commodity. Origanum oil is a powerful disinfectant, and carvacrol and thymol are considered to be anthelmintic and antifungal agents. The documented insecticidal and allelopathic properties of the species suggest its potential value as a biological control agent. Antibacterial/fungicidal properties are reviewed in detailed as is the use of the genus as a food ingredient, either for its antioxidant properties or its distinctive flavor. Especially, the monoterpenic phenol carvacrol, the main constituent of commercial oreganos should be given special emphasis since its low toxicity and surprisingly high and diverse biological activities render this simple molecule a promising lead for the development of novel medicines not only for humans but also for animals and plants. Carvacrol-rich oils are also used for their high potency especially as antibacterial and antifungal agents. The use of carvacrol-rich oils as ingredients in animal feed and for the preservation of food against bacterial or fungal spoilage and as antioxidants appears to increase. The Lippia species of oregano are generally recognized as safe for human consumption as natural flavorings/seasonings, and the Origanum species are generally recognized as safe as natural extracts/essential oils. However, oregano is one of the most common foodstuffs, which have the ability to cause aversions during pregnancy. In addition, and according to some reports, oregano intake can cause systemic allergic reactions. These items are particularly treated with.

Although the monograph documentation of O. vulgare was submitted to German Ministry of Health, the stuff responsible for phytotherapeutic medicinal domain – Commission E evaluated Origani vulgaris herba negatively (Banz. Nr. 122 from 6th July 1988), because of lack of scientific proofs for a number of indication areas (Blumenthal, 1998). Nevertheless, many of the studies confirmed benefit effects of oregano for human health. In this volume, extensive reference is provided on the bioactive/pharmacological properties of the Origanum genus, such as antioxidant and antimicrobial action and its use for the treatment of a vast list of ailments, such as respiratory tract disorders like cough or bronchial catarrh (as expectorant and spasmolitic agent), in gastrointestinal disorders (as choleretic, digestive, eupeptic and spasmolitic agent), as an oral antiseptic, in urinary tract disorders (as diuretic and antiseptic) and in dermatological affections (alleviation of itching, healing crusts, insect stings), viral infections and even cancer. Oregano, its essential oil ...

Table of contents

• COVER PAGE
• TITLE PAGE
• COPYRIGHT PAGE
• PREFACE TO THE SERIES
• ACKNOWLEDGEMENTS
• CONTRIBUTORS
• PART 1: INTRODUCTION
• PART 2: BOTANY
• PART 3: TAXONOMY AND CHEMISTRY
• PART 4: CULTIVATION AND BREEDING
• PART 5: PHARMACOLOGY
• PART 6: USES OF OREGANO IN THE FOOD INDUSTRY
• PART 7: BIOTECHNOLOGY
• PART 8: MISCELLANEOUS