Chemisches Laboratorium Dr. Hermann Ulex Nachf.

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Composition of commercial Cape chamomile oil
(Eriocephalus punctulatus / Eriocephalus tenuifolius)

Hanco-Gisbert Mierendorff, Elisabeth Stahl-Biskup , Maarten A. Posthumus and Teris A. van Beek

ABSTRACT

Cape chamomile oil obtained from the herb Eriocephalus punctulatus DC (Asteraceae) was analysed by means of GC and GC-MS. It was proven to consist of about 50 aliphatic esters together amounting to more than 50% of the oil. 2-Methylbutyl 2-methylpropanoate, 2-methylbutyl 2-methylbutanoate, 2-methylpropyl 2-methylpropanoate, and 7-methyl-2octyl acetate were the main components. In the terpenoid portion (about 37%) linalyl acetate and a-pinene are the major compounds. In the higher boiling fraction the artedouglasia oxides A-D, several davanones and laciniata furanones, oxygenated sesquiterpenes previously found in Artemisia species, could be detected in amounts of 5.9%, 0.4% and 1.4%, respectively. Commercial samples of different years showed almost identical compositions.

KEY WORDS

Eriocephalus punctulatus, Asteraceae, essential oil, commercial Cape chamomile oil, 2-methylbutyl 2-methylpropanoate, artedouglasia oxide, davanone, laciniata furanone

Introduction

Eriocephalus punctulatus DC (Asteraceae), ”Cape chamomile“, is an endemic plant growing on the north-east slopes of the Drakensberge in the Province Freestate (South Africa). It is a white flowering small shrub with fleshy, gland dotted leaves. Although in folk medicine several species of Eriocephalus are traditionally used as diaphoretics and diuretics¹ there have been few publications concerning special uses of E. punctulatus; local people appreciate its benefit in the treatment of stomach diseases or for the fumigation of huts².

Twenty years ago a practically feasible method of vegetative propagation was developed and a few hundred genetically identical plants have been produced for plantings in the Amatola mountains, Ciskei.³ Nowadays commercial Cape chamomile oil is produced from cultivars in the Cape Province (South Africa). Due to its pleasant odour the oil has been used as a fragrance in cosmetics and toiletries; it is increasingly employed in aromatherapy.

The blue colour of the commercial Cape chamomile oil is striking and one associates it automatically with the European chamomile oil from Matricaria recutita L. (Asteraceae). In both oils the blue colour is caused by azulene derivatives in the oils which are formed by a decomposition of proazulenes during steam distillation. Aside from the blue colour these two oils have nothing in common.

To this date only few components have been identified in Cape chamomile oil. 2-Methylbutyl isobutyrate, 2-methylpropyl isobutyrate, p-cymene, a-pinene, 2-methylbutyl isovalerate, 3-methylbutyl isobutyrate were reported to be the main components besides eight minor components.^{6, 7} In Table I the previously published components are labelled with asterisks.

Table 1. Constituents of commercial Cape chamomile oil (Eriocephalus punctulatus DC)

Compound name

RI

Percentage

2-Methyl-1-butanol *

801

0.4

2-Methylpropyl acetate

810

t

3-Methyl-2-butyl acetate

850

t

Propyl 2-methylpropanoate

866

t

2-Methylpropyl propanoate

873

t

3-Methylbutyl acetate

878

t

2-Methylbutyl acetate

879

0.1

2-Methylpropyl 2-methylpropanoate *

909

5.3

Ethyl 3-methyl-2-butenoate

911

t

Tricyclene

917

t

a-Thujene

922

t

2-Methylpropyl methacrylate

926

0.1

a-Pinene *

932

1.9

Camphene

942

0.7

Verbenene

945

t

3-Methylbutyl propanoate

952

t

2-Methylbutyl propanoate

955

0.2

Sabinene

963

0.1

b-Pinene *

966

0.3

(E,Z)-1,2-Diethylidenecyclopentane

969

t

Dehydroxylinalool oxide A

977

0.5

b-Myrcene

979

0.1

2-Methylpropyl 2-methylbutanoate *

986

1.4

2-Methylpropyl 3-methylbutanoate *

989

1.2

3-Methylbutyl 2-methylpropanoate *

995

2.6

2-Methylbutyl 2-methylpropanoate *

1002

21.2

a-Terpinene

1005

0.4

p-Cymene *

1007

2.0

1,8-Cineole

1013

0.2

Limonene *

1015

0.7

3-Methylbutyl methacrylate

1019

t

2-Methylbutyl methacrylate

1021

0.2

2-Heptyl acetate

1022

0.1

cis-Arbusculone

1026

t

2-Methylpropyl angelate

1030

1.6

(E)-b-Ocimene

1033

t

2-Methylbutyl butanoate

1037

0.1

trans-Arbusculone

1039

t

g-Terpinene

1043

1.0

trans-Sabinene hydrate / 7-Methyl-2-octanol**

1046

0.7

Butyl angelate

1055

0.8

2-Nonanone / p-Cymenene **

1066

0.1

Butyl tiglate

1068

0.1

Terpinolene *

1072

0.3

cis-Sabinene hydrate

1075

0.1

Linalool

1077

0.5

3-Methylbutyl 2-methylbutanoate

1082

1.3

2-Methylbutyl 2-methylbutanoate

1087

5.6

2-Methylbutyl 3-methylbutanoate *

1089

1.1

Hexyl 2-methylpropanoate

1092

t

2,2,3-Trimethyl-3-cyclopentene-1-acetaldehyde

1097

t

cis-p-Menth-2-en-1-ol

1099

0.2

Camphor

1111

1.4

trans-Pinocarveol / trans-p-Menth-2-en-1-ol **

1116

0.1

2-Octyl acetate

1121

0.4

Menthone

1125

0.1

3-Methylbutyl angelate

1128

0.3

2-Methylbutyl angelate

1134

3.5

Borneol

1143

1.4

Terpinen-4-ol *

1156

1.7

Pentyl angelate

1162

1.3

a-Terpineol *

1166

0.2

Pentyl tiglate

1174

0.2

7-Methyl-2-octyl acetate

1187

4.5

cis-Carveol

1200

0.0

Nerol

1207

0.1

Pulegone

1209

0.1

2-Nonyl acetate

1221

0.6

Geraniol

1234

t

Linalyl acetate

1241

4.4

Bornyl acetate

1266

0.3

Thymol

1267

t

Diosphenol

1273

t

Carvacrol

1277

t

trans-Sabinene hydrate acetate

1281

t

(E,E)-2,4-Decadienal

1288

t

Myrtenyl acetate

1304

t

Eugenol

1327

t

a-Terpinyl acetate

1332

t

Neryl acetate

1344

0.6

a-Longipinene

1347

0.2

Geranyl acetate

1362

0.5

2-Phenylethyl 2-methylpropanoate

1368

0.5

Longicyclene

1370

0.3

a-Copaene

1374

1.4

Modhephene

1376

t

a-Isocomene

1383

0.1

b-Elemene / a-Funebrene** / Lyratyl acetate **

1387

0.4

Longifolene

1401

0.2

Unknown MW=220 (A) / 2-Methylbutyl benzoate **

1409

0.1

b-Caryophyllene

1414

0.6

b-Copaene

1424

t

a-Humulene

1447

0.1

Unknown MW=206 (B) / allo-Aromadendrene **

1452

0.4

Unknown MW=202 (C) / 3-Methylbutyl phenylacetate **

1460

0.3

2-Methylbutyl phenylacetate

1464

0.7

Unknown MW=234 (D)

1469

0.1

a-Selinene

1478

0.1

Bicyclogermacrene

1489

0.2

a-Muurolene

1493

0.1

Laciniata furanone G

1498

0.2

Artedouglasia oxide C

1500

1.7

Laciniata furanone F

1503

0.4

Artedouglasia oxide A

1511

2.2

Laciniata furanone E

1514

0.3

1,4-Dimethylazulene

1517

0.3

Laciniata furanone H

1522

0.5

a-Calacorene

1526

t

Artedouglasia oxide D

1532

0.7

Isodavanone

1537

0.2

Davanone B

1542

0.2

Artedouglasia oxide B

1553

1.3

Davanone D

1557

t

Spathulenol

1561

1.1

Caryophyllene oxide

1566

0.8

b-Copaen-4-a-ol

1572

0.5

Viridiflorol

1578

0.3

Unknown MW=250 (E)

1586

0.2

Unknown MW=222 (F)

1589

0.1

Unknown MW=218 (G)

1598

0.1

Unknown MW=222 (H)

1608

0.6

Caryophylla-3(15),7(14)-dien-6-ol

1614

0.9

Chamazulene

1700

0.2

94.4

*previously mentioned / ** co-eluted / t = < 0.05%

Mass spectra: EI-Mode, 70eV, (m/z)

(A) 220(28), 177(64), 149(100), 135(47), 107(37), 93(47), 91(37), 43(66)
(B) 206(28), 96(100), 82(32), 81(67), 68(88), 67(47), 55(32), 41(34)
(C) 202(8), 159(75), 115(27), 97(31), 71(39), 70(26), 43(200), 41(20)
(D) 234(13), 161(100), 109(83), 105(71), 93(69), 91(64), 43(63), 41(60)
(E) 250(3), 177(70), 138(68), 124(93), 96(74), 81(84), 43(100), 41(69)
(F) 222(5), 109(67), 105(51), 95(58), 93(64), 81(51), 43(100), 41(68)
(G) 218(8), 105(66), 95(72), 93(100), 91(88), 67(70), 43(73), 41(88)
(H) 222(6), 204(55), 189(32), 161(100), 121(77), 105(59), 95(46), 43(98)

Results and Discussion

GC analysis of 5 commercial samples produced from harvests in 1997- 2001 revealed the Cape chamomile oil to consist of about 220 compounds (Figure 1). 104 of them were elucidated by GC-MS analysis and by comparison of retention indices. If available co-chromatography of authentic substances was performed. The results are listed in Table I which shows the data of sample 2 produced in 1999. Besides 123 identified components, 8 additional components with percentages above 0.1% are listed whose identity remained unknown. Their ms data are given below Table 1 (A)-(H). The components listed in Table 1 cover 92-94% of each oil sample. The remaining portion of 6-8% is distributed over about 100 peaks below 0.1% each.

Aliphatic esters are the dominant group in the oils amounting to more than 50% with 2 -methylbutyl 2-methylpropanoate (21.2%) being the main component. Further important esters are 2-methylbutyl 2-methylbutanoate (5.6 %), previously described as 2-methylbutyl isovalerate3 , 6, 7, 2-methylpropyl 2-methylpropanoate (5.3%), 7-methyl-2-octyl acetate (4.5%), 3-methylbutyl 2-methylpropanoate (2,6%). Furthermore 28 minor aliphatic esters were detected among them 5 angelates and 2 tiglates (in total 7.8 %).

The terpenoid portion consisted of 27 oxygenated monoterpenes (together 11.2%) and 15 monoterpene hydrocarbons (together 7.7%) with linalyl acetate and a-pinene, respectively, as dominant compounds. Furthermore 16 sesquiterpene hydrocarbons (together 4.5%) and 16 oxygenated sesquiterpenes (in total 11.3%) were detected. The presence of the artedouglasia oxides (A-D, together 5.9%), davanones (0.4%) and laciniata furanones (1.4%) reminds one of the sesquiterpene fractions of oils which have been isolated from Artemisia species^{10, 11.}

In Table II the 25 most abundant components (equal to or larger than 0.1%) of the oils of the five investigated samples are listed including a calculation of the percentage ranges and the mean percentages. With regard to the peak pattern as well as to the peak percentages, the table reflects a good correspondence of the commercial Cape chamomile oils produced in the years 1997-2001.

Table 2. Percentage composition of 5 commercial Cape chamomile oils (25 most abundant components)

It was mentioned above that 1,4-dimethylazulene (0.3%) and chamazulene (0.2%) were proven to be artefacts formed during steam distillation. In spite of their low percentages in the oils they are responsible for the typical blue colour of the oils. Aside from colour no further chemical similarity with German chamomile oil could be found. The latter consists mainly of sesquiterpenes of the bisabolane type and other sesquiterpenoids. There is a closer correspondence to Roman chamomile oil, which is known to consist mainly of propionates, butyrates, isobutyrates, angelates, tiglates, and further aliphatic esters.

Experimental

Commercial samples of Cape chamomile oil were provided by Grassroots Natural Products, Gouda 6821, South Africa. Sample 1997(A), sample 1999 “Berger” (B), sample June 1999 (C), sample 2000 (D), sample 2001 (E). For GC and GC-MS the oils were dissolved in n-hexane (5.0%).

Gas Chromatography

A Hewlett-Packard 5890 Series II equipped with a FID (250°C) and a Phenomenex column ZB-1, 30 m x 0.25 mm, 0.25 µm film thickness was applied. The injection (1 µL) was carried out with a Hewlett-Packard 7673 automatic-sampler using the split mode (ratio 1:10) at 250°C. The carrier gas N2 was pressure controlled with a flow of 1 mL/min (45°C). The temperature program was 3°C/min from 45°C to 230°C. The relative amounts of individual compounds are based on the peak area obtained without FID response factor correction. Retention indices of the components were determined relative to n-alkanes.

Gas chromatography-mass spectrometry

A Hewlett-Packard 5890 Series II equipped with a Chrompack column CP-Sil 5, 30 m x 0.25 mm, 0 .25 µm film thickness, carrier gas He, flow 0.9 mL/min., temperature program: 5°C/min from 45°C to 220°C, injector (split 1:10): 220°C, coupled with a Hewlett-Packard MSD 5970 B detector; injection volume 1 µL. Mass spectra were recorded in the scan mode (solvent cut) at 70 eV over the mass range 39-310 Da.

Component Identification

The constituents of the essential oil were identified by matching their 70eV EI mass spectra and retention indices with reference libraries .

Acknowledgements - the authors thank:

• Grassroots Natural Products, Gouda, South Africa, for providing the commercial oil samples.
• G.P. Lelyveld for synthesizing numerous esters in order to definitely identify them in the oils .
• W. A. König for running the GC-MS analyses and providing several ms reference spectra.
• Dr. Maurice C.R. Franssen and Ms. Karin Boer for the chemical synthesis of 7-methyl-2 -octanol and 7-methyl-2-octyl acetate.

References

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9. Joulain D, König WA. The Atlas of Spectral Data of Sesquiterpene Hydrocarbons. E.B. -Verlag: Hamburg ,1998.
10. Weyerstahl P, Marschall-Weyerstahl H, Schröder M, Kaul VK. Liebigs. Ann. Chem. 1988; 917 -918.
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12. Lawrence BM. Perfum. Flav. 1998; 23: 49-50.

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