Paper presented at the IFEAT Int. Conference in Cape Town

Paper presented at the IFEAT Int. Conference in Cape Town, South Africa, 27 Nov.- 1 Dec. 2006: ‘The Industryin Sub-Saharan Africa and the Indian Ocean Islands’. Pages 98-109 in the printed Conference Proceedings._________________________________________________________________________________BUCHU OIL IN SOUTH AFRICADr. Matthias W. EsterhuysenPuris Natural Aroma Chemicals,P.O. Box 12127, Die Boord, 7613, South Africa[ matthias@puris.co.za ]‘Buchu’ is the common name for the essential oils obtained from Agathosma betulina, A. crenulataand a hybrid (A. betulina x crenulata). These perennial shrubs are indigenous and unique to SouthAfrica, which is the sole producer of buchu oil.Buchu oils possess a characteristic aroma and flavour due to the presence of unique, high impactsulphur compounds and are employed in a wide variety of F&F applications.In the past, raw material for distillation was obtained exclusively by harvesting wild growing plants.Today, plantation grown material is the dominant source and, progressively, the desirably lowpulegone content A. betulina is displacing plantations of A. crenulata and the hybrid.Buchu oil production estimatesIn 2006 Prediction for 2008Total oil production ~ 5 tonnes ~ 7.5 tonnesFrom A betulina 65% Bulk of productionFrom A. crenulataand hybrids35% Low proportion of totalThe paper will sequentially deal with:• Background on the plant• The essential oil chemistry• The history of oil production• The industry today• The future - new challenges and opportunitiesThe Characteristics of Buchu PlantsThe word ‘buchu’ is a traditional collective name for fragrant ‘fynbos’ plant species that are classifiedunder the genus Agathosma, whose name is derived from the Greek words, ‘Agathos’, meaningpleasant and ‘osme’, meaning fragrance.The genus Agathosma belongs to the family Rutaceae, which contains all Citrus species. There arearound 150 Agathosma species, which are all endemic to the Cape Floral Kingdom [1] .The Cape Floral Kingdom is by far the smallest, and most diverse in species of the six floral kingdomson earth, and it is also the only one contained in its entirety in one country. For example, the speciesdensity of the Cape Floral Kingdom is ca. 1,300 species / 10,000 km 2 , whereas the floral kingdom thatis second richest in species, the Amazonian Floral Kingdom, has a species density of only some 400species / 10,000 km 2 .98

The Cape Floral Kingdom, often also referred to as ‘Fynbos’ due to the fine shrubby nature of most ofits ca. 8,700 species, ranges over a narrow band (~60km wide) along the South Western Cape coastlinefrom ~200km north of Cape Town to Port Elizabeth, ~700km to the east of Cape Town. In general‘Fynbos’ vegetation is characterised by many low bushy shrub-like plants and few trees [2] .Natural occurrenceTypical Fynbos scene The natural ranges for A. betulina and A.crenulata are, however, much smaller than thetotal Cape Floral Kingdom range and also aregeographically separated:• Natural A. betulina occurs in mountainousregions from Gouda northwards to Piketberg,Aurora in the west to the Cederbergmountains northeast of Piketberg [3] .• A. crenulata is found naturally in an evensmaller area, ranging from the HottentotsHolland mountains around Somerset-West inthe south to the mountains around Tulbagh,~100km to the north.• The natural occurrence of the third “species”,A. betulina x crenulata (or hybrid buchu), isrelatively unclear.Two phenotypically indistinguishable chemotypes of A. betulina have been described [3] :• an isomenthone chemotype that is mainly found in the wild in the Piketberg region, and• a diosphenol chemotype that occurs naturally only in the eastern portion of A. betulina’srange, in the Cederberg mountains.The hybridThere is a school of thought that ascribes the emergence of the hybrid, A. betulina x crenulata, to theplanting of cultivated A. betulina and A. crenulata plants in the same fields by early buchu farmers.Another school of thought describes it not as a true hybrid species, but rather as a unique population orchemotype of A. crenulata (since phenotypically, adult A. betulina x crenulata plants usually havemuch more in common with A. crenulata than A. betulina, and the chemistry of its essential oil is99

much closer related to that of A. crenulata, although it does contain elements of A. betulina oil aswell). A third school of thought doubts its existence altogether, ascribing the chemistry of a buchu oilcontaining characteristics of both species to the distillation of both A. betulina and A. crenulata plantsin one batch. Since the identification of all the components found in buchu oil in 1975 [4] and thedevelopment of accurate analytical GC analyses of buchu oils obtained from single plants withinSouth Africa in the early 1990s, it has been shown that A. betulina x crenulata certainly does exist.Whether it is a true hybrid, or a population / chemotype of A. crenulata still remains unclear.It has to be stressed that, due to cultivation of buchu, and the small area in which it successfully grows,the natural ranges of each of the species described here do not reflect the cultivated ranges well. Theold habit of obtaining buchu seeds or plant material only from a certain area as an assurance of itsgenetic identity is therefore a very risky venture indeed.Morphological characteristicsThe three species of buchu that are currently cultivated for essentialoil production are perennial shrubs with woody branches and smalldotted leaves and they are sometimes difficult to distinguish fromeach other within the first year of growth.At the mature stage:• A. betulina displays a round leaf and is commonly knownas ‘round leaf buchu’; while• A. crenulata has an oval leaf and is called as such.Botanical drawings of buchu leafshapes for commercial species A. betulinaA. crenulata100

Species identity in plantationsBecause vegetative propagation wasnot developed until recently, all ofthe early buchu plantations wereestablished using individualseedlings and there has often beengreat confusion regarding geneticidentity of many plantations [6] .In particular, A. crenulata and thehybrid A. betulina x crenulata plantsare practically identical, even beyondthe seedling stage.To add to this confusion, the two phenotypically indistinguishable chemotypes of A. betulina (adiosphenol and an isomenthone chemotype), with drastically different essential oil compositions, areoften found mixed in plantations.These factors, together with competitive behaviour of some oil distillers and the lack of sufficientanalytical facilities, have caused great confusion regarding the production of the individual species andchemotypes of buchu oil. Many a farmer has ended up with a beautiful field of cultivated A. crenulataplant material instead of the more valuable A. betulina that he intended to cultivate, ditto regarding thechemotypes of A. betulina.Furthermore, these confusions have even filtered through to the oil market with the result that eventoday some of the largest traditional users of buchu oil for flavour and fragrance applications havespecifications for ‘Betulina buchu oil’, which is in fact obtained from A. crenulata, or worse a ‘secret’mixture of A. betulina and A. crenulata.The species buchu oil that a client requires is sometimes not mentioned at all, thus putting the onus onthe distiller to exhaustively match a specific client’s specification. Even when ‘Betulina buchu oil’ isrequested, the chemotype is never known until a sample is approved. Clearly this situation is not ideal.Interestingly, it is our experience that very rarely are pure forms of either chemotypes of A. betulinarequired.There is currently no ISO standard for buchu oil(s), and only general CAS and FEMA numbers (CAS:68650-46-4; FEMA: 2169) are assigned to ‘Buchu oil’, representing all the various types and speciesof buchu oil available.Essential oil chemistryModern gas-chromatographic analyses have made the identification of the exact species / chemotypeof buchu plant material a routine exercise.A. betulina (both chemotypes), A. crenulata and A. betulina x crenulata essential oils all containnearly the same chemical components, but in greatly varying amounts:• The main flavour contributors in buchu oils are the unique high-boiling 8-mercapto-pmenthan-3-one(FEMA 3177) isomers and their acetates, 8-acetylthio-p-menthan-3-one(FEMA 3809) [4,7,8] .101

• Other major components in buchu oils, pinene (α- and β-), myrcene, d-limonene,menthone/isomenthone, ocimene, linalool, pulegone and diosphenols play minor, but notinsignificant, roles in the organoleptic properties of buchu oils.It is only the greatly varying concentrations of diosphenols vs. menthone/isomenthone that sets the oilsof the different chemotypes of A. betulina apart. Both, however, owe their uniquely buchucharacteristic organoleptic properties to their 8-mercapto-p-menthan-3-one isomer content (for whichbuchu is the only botanical source of this important sulphur containing high-impact aroma chemical).By GC (FID) analysis, commercial A. betulina essential oils are generally characterised by relativelylarge amounts of d-limonene, menthone/isomenthone or diosphenols (0-45% combined Ψ-diosphenoland diosphenol and/or menthone/isomenthone with the relative concentration of one, at the expense ofthe other), relatively small amounts of pulegone (typically

GC trace of the essential oil of A. betulina (isomenthone chemotype).In addition to containing all of the above-mentioned compounds (in different amounts), A. crenulataessential oils also contain the high olfactory impact cis/trans-8-acetylthio-p-menthan-3-one isomers.By GC (FID) analysis a typical commercial A. crenulata essential oil contains 10-20% limonene, 5-15% menthone/isomenthone, 35-55% pulegone, 0-5% diosphenols (combined Ψ-diosphenol anddiosphenol), 0.5-3.5% cis/trans-8-mercapto-p-menthan-3-one isomers in a 8:1 to 4:3 trans:cis isomerratio, and the unique cis/trans-8-acetylthio-p-menthan-3-one isomers, 1-6%, in a ~10:1 trans:cisisomer ratio.GC trace of the essential oil of A. crenulata.103

A. betulina x crenulata essential oils tend to show a lot of variation in their chemical compositions,presumably due to the degree of hybridization and/or the chemotype of A. betulina genetic materialthat was involved in the crossing. These oils are nevertheless generally characterized by GC (FID) ashaving a medium limonene level (15-25%), varying concentrations of menthone/isomenthone (0-20%), with correspondingly inversely varying diosphenol (Ψ-diosphenol and diosphenol combined)concentrations (0-20%), medium to high pulegone concentrations (15-40%), varying amounts ofcis/trans-8-mercapto-p-menthan-3-one isomers (in a 1:4 to 3:4 trans:cis isomer ratio, but always moretrans than cis isomers present) and varying amounts of cis/trans-8-acetylthio-p-menthan-3-oneisomers (0.1-2%, in the same 8:1 trans:cis isomer ratio found in A. crenulata oil).GC trace of the essential oil of A. betulina x crenulata (typical)Although the identity of each of the compounds found in buchu oils has been known since 1975 [4] , itwas not until 1996 that the exact chemotaxonomy of the various buchu oils was described [3] . Untilthen the chemical composition of a general ‘buchu oil’, which could chemically look like any of theoils described above (or any mixture of them), was greatly dependant on the initial historicalagricultural source of the oil. In that the unique olfactory properties of each individual type of buchuoil was never formally described, due to the failure of buchu oil distillers to recognize or haveknowledge of the various types of buchu oils available, the use of each type of buchu oil forspecialized applications is poorly developed, thereby limiting the use of buchu oil to fewerapplications than their potential.Oils from specific species / chemotypes or blends of species / chemotypes may indeed have a desiredeffect in specific applications. Furthermore, inconsistencies in chemical compositions, and thereforealso olfactory characteristics, of general ‘buchu oils’, as a result of the variations in oils and thehistorical inability to accurately determine and control any such variations, have certainly also brandedbuchu oil as a raw material of inconsistent quality in the past. Large scale harvesting / poaching ofbuchu from wild sources, where many uncontrollable factors (e.g. wild fires, droughts, pests etc.)come to play, furthermore, made the availability of buchu plant material inconsistent, to say the least.When combining variablility of supply with great variations in composition / quality, it becomesobvious why buchu oil remained a niche product in the flavour and fragrance industry for such a long104

time. The reasons for buchu oil’s inconsistencies, however, become much clearer when its initialhistory as a herbal remedy, and not a flavour and fragrance ingredient, is considered.The History of Buchu’s UseAs a medicinal herbBuchu has an ancient history as a natural herbal remedy in the San-Khoi healing culture. Traditionalceremonial and cosmetic uses of buchu as a body perfume in the form of dried crushed leaves mixedwith animal fats have been documented. It is not known which species were employed but, due to theirpleasant aromas compared to other species in the Agathosma genus, A. betulina and A. crenulata arelikely candidates.The modern history of buchu dates from the 17 th and 18 th centuries when the Khoikhoi introducedbuchu to the Dutch settlers in the Cape as a herbal remedy. Buchu’s purported medicinal uses causedits spread to Europe [10] and the first record of buchu export is by Reece & Co. who shipped driedbuchu leaves to England in 1821. By the late 19 th century large volumes of dried buchu plant materialwere exported to England and the USA; for example in 1873, imports were 153 tons by England and27 tons by the USA. Initially ‘buchu’ (of unspecified species) was mainly used in the form ofinfusions or tinctures and found widespread use as a natural health tonic for just about any afflictionthat affects mankind, including rheumatism, cholera, bladder diseases, stomach complaints, dropsy,dyspepsia, vesicle catarrh, cystitis, gout, PMS and hypertension [10] .Advert for buchu in the Franklin Gazette (USA), 1883105

It is interesting to note that to this day buchu remains a well-known herbal medicine in South Africaand to some extent in Europe. However, medicinal use today is very small compared to what isconsumed by the international flavour and fragrance industry.As an essential oilAround 1900, buchu was found to produce an essential oil upon steam distillation. With the aroma ofbuchu in a useable form as the essential oil, the interesting flavour and fragrance properties of buchu,found widespread application in formulations in post-WWII Europe, most notably for its cassischaracteristic at certain concentrations.With the advent of modern analytical methods (GC and GC-MS), in the late 1960s, the main flavourcontributing components in buchu oils could be identified successfully. Almost simultaneously in1971, Lamparsky et al (Givaudan) [7] and Sundt et al (Firmenich) [8] independently described thecis/trans-8-mercapto-p-menthan-3-one isomers in buchu oil as the source of its cassis flavour.The chemical nature of these compounds, relatively simple sulphur-containing monoterpenes,facilitated their synthesis from readily available raw materials. In 1971, Firmenich registered a patentdescribing the synthesis of nature identical cis/trans-8-mercapto-p-menthan-3-one [9] . Suddenly buchuoil was no longer required to impart a good cassis aroma, with the result that usage drasticallydecreased and the buchu oil market crashed. This period in buchu’s history saw widespread neglectand removal of the few established buchu plantations that existed to supply the market.However, renewed emphasis on natural flavours and fragrance raw materials in the EU during the1990s created a new demand for buchu oils, the only known natural source of cis/trans-8-mercapto-pmenthan-3-oneand cis/trans-8-acetylthio-p-menthan-3-one.At roughly the same time, EU legislation restricting the use of raw materials that naturally containpulegone came into force, with the result that the popularity of A. crenulata (35-55% pulegone) inflavour and fragrance applications decreased dramatically. On the eve of the introduction of new EUlegislation further restricting the levels of pulegone in flavour and fragrance formulations, this effect isstill observed today in the ever-dwindling sales of pure A. crenulata oils, as well as a perceiveddecline in the demand for A. betulina x A. crenulata (15-40% pulegone) oils.The demand for A. betulina oils, which are low in pulegone but have comparable flavour properties toA. crenulata or A. betulina x A. crenulata oils, thus became unnaturally high around the turn of themillennium, causing production to lag behind and the oil prices to sky-rocket. On the production sidepoorly developed and neglected farming practices, confusion regarding the species of buchu thatshould be propagated, and inconsistent supply and quality issues were added causes in the highhistorical price of buchu oils. This situation, however, has steadily changed for the better in the past 5years.The Buchu Oil Industry TodayWidespread A. betulina (low pulegone) plantings and the modernisation of buchu farming in the past 5years have set the stage for a reliable supply of excellent quality buchu oils.In a response to the high demand for buchu oil, the total available oil volumes are estimated to havealmost doubled between 2003 and 2006, and, based on knowledge of new plantations, production in2008 is likely to reach around 7.5 tonnes. (The grouping of buchu oil exports under “Aromatic plant106

extracts” in the South African harmonized tariff code system, however, does make the estimation ofthe total production an inaccurate exercise.)Estimated production of buchu oil2003 2006 2008(predicted)tonnes 3.5 5 7.5Currently, A. crenulata and hybrid / blended oils still account for ca. 35% of sales. However, thisproportion will progressively decrease along with selective new planting of A. betulina.With the decrease in popularity of A. crenulata oil, a surplus of cultivated A. crenulata plant materialis already experienced and it has caused the price of this oil to plummet in the past 3 years.Currently A. crenulata oil is viewed as a natural source for buchu’s unique cis/trans-8-mercapto-pmenthan-3-oneand cis/trans-8-acetylthio-p-menthan-3-one isomers. Production of a ‘buchu sulphurfraction’ in which the pulegone level is, relative to the levels of the flavour contributing sulphurcompounds, equally low as it is in A. betulina oil has been developed in South Africa and since 2004this speciality fraction of buchu oil has been commercially available.In order to limit poaching of wild buchu plant material from the wild, its cultivation, harvesting (fromthe wild especially), and processing is carefully monitored by the governmental Cape NatureConservation Group. In spite of measures to combat poaching and theft of buchu plant material, it wasa common occurrence, mainly as a result of unscrupulous distillers who purchased poached / stolenmaterial, thus effectively encouraging the depletion of the wild buchu stock. With the recent emphasison mass cultivation of buchu as opposed to harvesting from the wild the needs of the buchu market areincreasingly met by cultivated material, thereby decreasing the prevalence of poaching of wild plantmaterial and thereby preserving the surviving wild population.Feedstock sourcing: plantations versus wild harvesting (est.)2003 season sourcing 2006 season sourcingSpecies From the wild From plantations From the wild From plantationsA. betulina 30% 70% 15% 85%A. crenulata 10% 90% - 100%Hybrib - 100% - 100%Formal cultivation of buchu, however, brings another factor affecting buchu oil quality into play,namely agricultural residues. In areas where A. betulina buchu is found naturally (Piketberg/Citrusdal)agricultural residues are not a great concern. Buchu has few natural pests in these areas and performswell unaided by any pesticides / acaracides when cultivated from seedlings. However, when buchu ispropagated vegetatively, as has been recently developed, or is cultivated under hydroponic conditions,or even when it is cultivated in areas far outside of its natural range, it is far more sensitive to attacksfrom pests and diseases. As no pesticides / acaracides have been officially approved for use on buchuplant material, its spraying is technically illegal. However, there is no doubt that producers spray theirplants when under threat to protect their sizeable investment.Buchu oil distillers that are HACCP certified conduct, as part of their HACCP procedures, routineanalysis for pesticide / acaracide contamination in buchu oils. EU legislation outlawing the sourcing offlavour and fragrance ingredients from suppliers that are not HACCP accredited has thus far led to the107

HACCP certification of only two of the eight companies that are known to produce buchu oilregularly.The Future of the Industry – challenges and opportunitiesFrom a buchu oil production point of view, especially the observed and further expected growth inavailable plant material volumes – as well as the greatly improved degree of sophistication in oilproduction, analysis, processing – the future looks promising.There are, nevertheless, serious challenges facing the industry as a whole. The largest concern is theexplosive rate at which plant material / oil production is set to increase in the near future, juxtaposedagainst a sluggishly growing traditional oil market. To ensure ongoing stability and growth in thebuchu oil industry, marketing, pricing and raw materials must be managed with utmost care andresponsibility.As buchu oil has historically been treated as an expensive niche flavour and fragrance raw material, itsapplication in formulations has been very limited. With the increase in volumes of buchu plantmaterial, there is no doubt that demand / supply forces will cause the price for buchu oil to decreaseover the next few years. How quickly the flavour and fragrance market for buchu oil can respond interms of increased usage is unknown at this stage.The potential uses for buchu oil are legion, as again demonstrated by G. Mosciano’s panel evaluationof buchu oil in the most recent issue of Perfumer and Flavourist [11] . Should the supply of buchu oilsurpass the demand by quite a large margin, the oil price will be placed under such pressure that acrash in the buchu oil price may occur. In the long run such a situation will be in nobody’s bestinterest. Responding to sudden decreases in the plant material price, and fearing a crash in the plantmaterial price, buchu farmers have already threatened to hold back their plant material in order torealize higher prices. Although this is no solution to the problem for any of the affected parties, andcertainly adds to previous perceived instability in the buchu oil market, it will most probably be ashort-term effect re-alignment. As the raw material supply stabilizes it is up to the end-users of buchuoil, together with inputs from suppliers (who in turn require support from farmers) to find a healthysupply / demand price scenario for buchu oil on the long run. With the promise of still larger volumesof oil coming to the market in the near future, with a potential for huge further growth, and theplethora of applications buchu oil may be used for, the eventual outcome for buchu oil may be anextremely positive one indeed.Ever tightening restrictions viz. the pulegone contents in finished consumer products affects the use ofbuchu oils, all of which contain pulegone in varying (2 - 50%) amounts. The use of natural buchusulphur fractions, in which the ratio of the flavour-active sulphur compounds (cis/trans-8-mercapto-pmenthan-3-oneand cis/trans-8-acetylthio-p-menthan-3-one) to pulegone is greatly increased, is aneffective and proven measure to decrease the amount of pulegone in finished products that require orwill benefit from buchu oil’s unique flavour / fragrance contribution.Matthias Esterhuysen is Technical Director of Puris Natural Aroma Chemicals(Pty) Ltd, a company that specializes in the production of buchu oil and theisolation of its unique aroma constituents. He obtained his Ph.D. in chemistry atthe University of Stellenbosch in 2002 and then spent a year as a post-doctoralfellow at the Philipps University in Marburg, Germany. Matthias joined Puris in2003 and has focused on the commercial implementation of buchu oil chemistry.108

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