Table Of ContentMint
The Genus Mentha
Medicinal and Aromatic Plants — Industrial Profiles
Individual volumes in this series provide both industry and academia with in-depth coverage of
one major genus of industrial importance.
Series Edited by Dr. Roland Hardman
Volume 1 Volume 16
Valerian, edited by Peter J. Houghton Mistletoe, edited by Arndt Büssing
Volume 2 Volume 17
Perilla, edited by He-ci Yu, Tea, edited by Yong-su Zhen
Kenichi Kosuna and Megumi Haga Volume 18
Volume 3 Artemisia, edited by Colin W. Wright
Poppy, edited by Jenö Bernáth Volume 19
Volume 4 Stevia, edited by A. Douglas Kinghorn
Cannabis, edited by David T. Brown Volume 20
Volume 5 Vetiveria, edited by Massimo Maffei
Neem, edited by H.S. Puri Volume 21
Volume 6 Narcissus and Daffodil, edited by
Ergot, edited by Vladimír Krˇen and Gordon R. Hanks
Ladislav Cvak Volume 22
Volume 7 Eucalyptus, edited by
Caraway, edited by Éva Németh John J.W. Coppen
Volume 8 Volume 23
Saffron, edited by Moshe Negbi Pueraria, edited by Wing Ming Keung
Volume 9 Volume 24
Tea Tree, edited by Ian Southwell and Thyme, edited by E. Stahl-Biskup and
Robert Lowe F. Sáez
Volume 10 Volume 25
Basil, edited by Raimo Hiltunen and Oregano, edited by Spiridon E. Kintzios
Yvonne Holm Volume 26
Volume 11 Citrus, edited by Giovanni Dugo and
Fenugreek, edited by Angelo Di Giacomo
Georgios Petropoulos Volume 27
Volume 12 Geranium and Pelargonium, edited by
Ginkgo biloba, edited by Maria Lis-Balchin
Teris A. Van Beek Volume 28
Volume 13 Magnolia, edited by Satyajit D. Sarker
Black Pepper, edited by P.N. Ravindran and Yuji Maruyama
Volume 14 Volume 29
Sage, edited by Spiridon E. Kintzios Lavender, edited by Maria Lis-Balchin
Volume 15 Volume 30
Ginseng, edited by W.E. Court Cardamom, edited by P.N. Ravindran
Mint
The Genus Mentha
Edited by Brian M. Lawrence
Medicinal and Aromatic Plants — Industrial Profiles
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Library of Congress Cataloging-in-Publication Data
Lawrence, Brian M.
Mint : the genus mentha / Brian M. Lawrence.
p. cm.
Includes bibliographical references and index.
ISBN-13: 978-0-8493-0779-9 (alk. paper)
ISBN-10: 0-8493-0779-1 (alk. paper)
1. Mints (Plants) I. Title.
SB295.M5L38 2006
633.8’2--dc22 2006014190
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Preface to the Series
There is increasing interest in industry, academia, and the health sciences in medicinal and
aromaticplants.Inpassingfromplantproductiontotheeventualproductusedbythepublic,
manysciencesareinvolved.Thisseriesbringstogetherinformationthatiscurrentlyscattered
through an ever-increasing number of journals. Each volume gives an in-depth look at one
plant genus, about which an area specialist has assembled information ranging from the
production of theplantto market trends and quality control.
Manyindustriesareinvolved,suchasforestry,agriculture,chemicals, food,flavor,bever-
age,pharamaceutical,cosmetics,andfragrance.Theplantrawmaterialsareroots,rhizomes,
bulbs,leaves,stems,barks,wood,flowers,fruits,andseeds.Theseyieldgums,resins,essential
(volatile) oils, fixed oils, waxes, juices, extracts, and spices for medicinal and aromatic
purposes. All these commodities are traded worldwide. A dealer’s market report for an
item may say‘‘drought inthe countryof origin has forced up prices’’.
Natural products do not mean safe products, and account of this has to be taken by the
above industries, which are subject to regulation. For example, a number of plants that are
approvedfor use inmedicine must not be used in cosmetic products.
The assessment of ‘‘safe to use’’ starts with the harvested plant material, which has to
comply with an official monograph. This may require absence of, or prescribed limits of,
radioactivematerial,heavymetals,aflatoxin,pesticideresidue,aswellastherequiredlevelof
active principle. This analytical control is costly and tends to exclude small batches of plant
material.Large-scale,contracted,mechanizedcultivationwithdesignatedseedorplantletsis
now preferable.
Today,plantselectionisnotonlyfortheyieldofactiveprinciple,butfortheplant’sabilityto
overcomedisease,climaticstress,andthehazardscausedbymankind.Suchmethodsasinvitro
fertilization,meristemcultures,andsomaticembryogenesisareused.Thetransferofsections
of DNA isgivingrise tocontroversy in thecase ofsomeend uses of theplant material.
Some suppliers of plant raw material are now able to certify that they are supplying
organically farmed medicinal plants, herbs, and spices. The Economic Union directive
CVO=EU No. 2092=91 details the specifications for the obligatory quality controls to be
carried out at all stages of production and processing oforganicproducts.
Fascinating plant folklore and ethnopharmacology lead to medicinal potential. Examples
arethemusclerelaxantsbasedonthearrowpoison,curare,fromspeciesofChondrodendron,
and the antimalarials derived from species of Cinchona and Artemisia. The methods of
detection of pharmacological activity have become increasingly reliable and specific, fre-
quently involving enzymes in bioassays and avoiding the use of laboratory animals. By
using bioassay-linked fractionation of crude plant juices or extracts, compounds can be
specifically targeted which, for example, inhibit blood platelet aggregation, or have antitu-
mor,orantiviral,oranyotherrequiredactivity.Withtheassistanceofroboticdevices,allthe
members of a genus may be readily screened. However, the plant material must be fully
authenticated by a specialist.
The medicinal traditions of ancient civilizations such as those of China and India have a
largearmamentariumofplantsintheirpharmacopoeiasthat areusedthroughout Southeast
Asia.AsimilarsituationexistsinAfricaandSouthAmerica.Thus,averyhighpercentageof
the world’s population relies on medicinal and aromatic plants for their medicine. Western
medicine is also responding. Already in Germany all medical practitioners have to pass an
examination in phytotherapy before being allowed to practice. It is noticeable that medical,
pharmacy, and health-related schools throughout Europeand theUnited States are increas-
ingly offering training inphytotherapy.
Multinational pharmaceutical companies have become less enamored of the single com-
pound, magic-bullet cure. The high costs of such ventures and the endless competition from
‘‘me-too’’ compounds from rival companies often discourage the attempt. Independent
phytomedicine companies have been very strong in Germay. However, by the end of 1995,
11(almostall)hadbeenacquiredbythemultinationalpharmaceuticalfirms,acknowledging
the laypublic’s growing demand for phytomedicinesin the Western world.
The business of dietary supplements in the Western world has expanded from the health
store to the pharmacy. Alternative medicine includes plant-based products. Appropriate
measurestoensuretheirquality,safetyandefficacyeitheralreadyexistorarebeinganswered
bygreatedlegislativecontrolbysuchbodiesastheU.S.FoodandDrugAdministrationand
the recently created European Agency for the Evaluation of Medicinal Products based in
London.
IntheUnitedStates,theDietarySupplementandHealthEducationActof1994recognized
the class of phytotherapeutic agents derived from medicinal and aromatic plants. Further-
more, under public pressure, the U.S. Congress set up an Office of Alternative Medicine,
which in 1994 assisted the filing of several Investigational New Drug (IND) applications,
required for clinical trials of some Chinese herbal preparations. The significance of these
applications was that each Chinese preparation involved several plants and yet was handled
as aSingle IND. Ademonstration of thecontribution toofficialy ofeach ingredientof each
plant was not required. This was a major step toward more sensible regulations in regard
to phytomedicines.
MythanksareduetothestaffofCRCPresswhohavemadethisseriespossibleandespecially
to thevolume editorsand their chapter contributors forthe authoriative information.
Dr. RolandHardman
Preface
All species and natural hybrids of Mentha are essential oil bearing. Today, taxa of Mentha,
either native or naturalized, are ubiquitous and found on all continents except Antarctica.
Becauseofthearomaticpropertiesofthesetaxa,somehavebeenusedtraditionallyformore
than 2000 years.
MenthaisthemostimportantgenusintheLabiatae(Lamiaceae)familybecauseitcontainsa
number of taxa the essential oils of which have achieved high economic value. These oils are
cornmint(thesourceofnaturalmenthol),peppermint,Scotchspearmint,andNativespearmint.
The amount of the oils produced annually is in excess of 23,000 metric tonnes with a value
exceeding $400 million. This makes them the most economically important essential oils pro-
duced.Mintoilsareproducedindifferentpartsoftheworld.Forexample,thelion’sshareof
peppermint oil, Native spearmint, and Scotch spearmint oil is produced in North America,
whereasalmostallthecornmintoilandnaturalmentholareproducedinChinaandIndia.
ThecorrecttaxonomicsourceofcornmintoilisMenthacanadensisL.notthesynonymsM.
arvensisL.,M.arvensisf.piperascensMalinv.exHolmes,M.haplocalyxBriq.,etc.Similarly,
thecorrecttaxonomicsourceofScotchspearmintoilisM.(cid:2)gracilisSoleandnotM.cardiaca
GerardeexBaker.Finally,thecorrecttaxonomicsourceofMenthacitrataoilisM.aquatica
L.var.citrata(Ehrh.)Fresen.notM.citrataEhrh.Therefore,thecorrecttaxonomicnomen-
claturehas been used throughoutthis treatise.
For an essential oil to be natural and genuine, it must be isolated from a whole plant or
plantpartofknowntaxonomicoriginbyphysicalmeansonly.Thephysicalprocessesusedto
isolate essential oils areas follows:
1. Hydrodistillation(waterdistillation)inwhichtheplantmaterial(herbageinthecaseof
Menthaspecies)isimmersedinwater,theheterogeneousmixtureisboiled,andtheoilis
condensed and separated from the steam and oil vapor mixture.
2. Water and steam distillation in which water is boiled in a container with the herbage
heldabovetheboilingwateronagridsothatthewetsteamcanreleasetheoilinvapor
form,which iscondensed and separated aswith water distillation.
3. Normalsteam distillationin which thesteam is produced ina satellitesteam generator
(boiler)andpassedthroughthebottomofacontainerofherbagetoyieldasteamandoil
vapormixture, which iscondensed and separated.
4. Hydrodiffusionisamodificationofthesteamdistillationprocess inwhichthesteamis
passed through the top of a container of herbage, thus allowing the steam to percolate
down through the plant material by gravity, after which the oil vapor and steam are
condensed and separated.
5. Expression (also known as cold processing) in which the oil-bearing part of the plant
is compressed to remove the oil. This process is mainly used to isolate oils from
thepeelsofCitrustaxa.AnessentialoilcannotbeobtainedbysupercriticalCO extraction,
2
although it is sometimes erroneously referred to that way in the literature, because
extraction processesproduce extracts irrespectiveof the solvent type orvolatility.
Ashortsummaryof the chaptersthat appear inthe text follows:
TheMenthagenusiscomplex asmore than3000epithetsofMentha havebeenpublished,
although a redefinition of the genus has revealed that it contains 18 species and 11 hybrids
(Tucker and Naczi).
AnatomicallyMenthataxacontainbothcapitateandpeltateglandulartrichomeslikeother
members of the Labiatae family. Studies on biosynthesis and biotechnology have led to a
betterunderstandingofthephysiology,molecularbiology,andtissueculturepotentialforthe
production of oil of the important Mentha taxa (Maffei etal.).
The four economically important Mentha taxa are cultivated extensively (a) in the United
States (peppermint, Scotch, and Native spearmint); (b) in India (cornmint, peppermint,
Scotch spearmint, and Native spearmint); and (c) in China (cornmint and Native and Scotch
spearmint).Theircultivationpracticesaredissimilarasarethecontrolmeasuresusedtocombat
diseaseandinsectinfestation(Morris,USA;Kumaretal.,India;andLiuandLawrence,China).
The isolationofmintoils frommintherbageismorecomplexthandescribedearlier. Asa
result, the theoretical aspects of distillation must be applied if efficient cost-effective oil
isolation isto be realized (Denny and Lawrence).
The number and type of components that have been isolated from the commercially
important oils (also including pennyroyal and Mentha citrata) and their quantitative differ-
encesfound inthesame taxagrownindifferent environments areofimportance tothemint
oiluser.Theenantiomericdistributionofthemainconstituentscanalsoassistinthechoiceof
oil supplier (Lawrence).
Theoilsproducedfromthe18Menthaspeciesand11hybrids,eithercultivatedorcollected
from their naturalized habitats, reveal a wide compositional diversity within the genus. In
addition,similaritiesanddifferencesbetweenoilcompositionsfoundeitherwithinorbetween
a species or hybrid shed light on the widespread occurrence of infraspecific chemical differ-
encesandthefactthatcompositioncannotbeusedsolelytocharacterizeaspeciesorhybrid
(Lawrence).
The annual production statistics for peppermint, Native, and Scotch spearmint oils pro-
ducedintheUnitedStatesrevealthechangesinproductionregionsovertheyears.Also,the
qualitycontrolaspectsincludinggaschromatographicprofileswillassisttheusersincharac-
terizing their oils of choice (Sheldon).
Mentholisanextremelyimportantflavorchemicalthatcanbeproducedbyfreezecrystalliza-
tion from cornmint oil. This same enantiomerically pure compound can also be produced
syntheticallyeitherfrompulegone,piperitone,d-3-carene,thymol,andN,N-diethylgeranylamine
(Hopp and Lawrence).
The important mint oils in commerce are sometimes found stretched, diluted, or adulter-
ated with single compounds, similar oils, or fractions thereof. The resultant mixture is no
longerapuregenuineoil.Theuseofblendsofoilsofdifferentgeographicaloriginwithalabel
of the most expensive origin or the standardization of an oil to ameliorate year-to-year oil
composition variation isfairly widespread (Lawrence).
Asmintoilsandtheirmajorisolateshaveawiderangeofuse,anassessmentoftheirsafety,
biological, and toxicological properties reveals that much work has been completed on
menthol and pulegone. The methods of determining these properties provide an insight into
the conclusions drawn from such studies (Hayeset al.).
Theantibacterialandantifungalpropertiesofmintoilsandsomeoftheirisolateshavebeen
the subject of study over the years because of their use as preservatives. As expected, the
majority of the work has been directed toward controlling the microbes that cause food
spoilage (Deans).
Mint oils and menthol are widely used in the flavor industry where they are integral
components of the flavor systems used in confection, alcoholic beverage, and tobacco
industries. They are also widely used in the fragrance industry in personal care and oral
care products and, to a lesser extent, in fine fragrances. An almost equivalent use of these
materialscanbefoundinthepharmaceuticalindustry,particularlyinnonprescriptionprod-
ucts. A more recent use of the commercially important mint oils and the lesser-known mint
oils is inaromatherapy (Tucker).
Acknowledgments
The editor would like to thank Professor K.H.C. Baser (Anadolou University, Turkey) for
providing data, a summary of which was used in his manuscript ‘‘Essential Oils of Mentha
species from Northern Turkey’’ [J. Essent. Oil Res., 11, 579–588 (1999)]. Thanks are also
extended to Professor E.H. Graven (University of Fort Hare), for providing compositional
data on South African peppermint oil; J. Thacker (Prairie Aromatic Natural Oils, Ltd.,
Canada)for statistical data on Scotch spearmint oil production in Canada;and M.Monroe
(QuestInternational, U.K.) for providing dataon mint oils.
The editor would like to acknowledge the skillful assistance of Ken Baker (R.J. Reynolds
TobaccoCo.)whopainstakinglycomputerizedandclarifiedthephotosanddiagramsusedin
the various chapters. The following people are thanked for supplying copies of some of the
photos used:
Chapter 6. Figure 6.1, Ramon Bordas (Distilaciones Bordas Chinchurreta SA, Spain);
Figure 6.4, Ian Blair (A.M. Todd Co., USA); Figure 6.4 Richard Carrington (I.P. Callison
&Sons,USA);Figure6.5andFigure6.6,BobLundy(NewhouseManufacturingCo.,USA).
Chapter5,Figure5.1andFigure5.2,DavidMoyler(FuerstDayLawson,U.K.).
Finally, the editor is grateful for assistance in typing the chapters Ann G. Niten (Typing
Service)andfortheexcellentproofreadingandeditingskillsofJudith A.Lawrence(Journal
ofEssential Oil Research).
