FLAVOUR AND FRAGRANCE JOURNAL, VOL. 8,257-260 (1993)

Chemical Composition of the Essential Oil of Ageratum conyzoides L. (Asteraceae) from RCunion

Robert Vera Luboratoire Agrochimie, Facultd des Sciences, Universitk de La Rkunion, F-97489 Saint-Denis Cedex, Reunion,

Indian Ocean

The essential oil of Ageratum conyzoides L. (Asteraceae) growing in Reunion (Indian Ocean) was investigated using capillary GC and GC-MS. Two main components 7-methoxy-2,2-dimethylchromene (Precocene I) and p- caryophyllene, a large number of terpenoids and some chromenes are reported. Two new compounds, coumarin and phytol (a diterpene alcohol), were identified.

KEY WORDS Ageratum conyzoides L. Asteraceae Essential oil Chromenes Terpenoids

INTRODUCTION

Ageratum conyzoides L. (Asteraceae), a weed usually called 'Herbe h bouc' or 'Herbe babouc', grows wild throughout Reunion and other tropical countries. In Reunion a leaves or roots infusion is said to possess vermifuge properties. Stems and leaves are used against idammatory stomach or intestine diseases. A poultice of leaves is reported to possess wound-healing properties. The plant is used in folk medicine in Asia, South America and Africa as a cure for numerous Previous investigations of Ageratum conyroides L. have revealed the presence of chromenes (benzopyrans) ,'-lo terpenoids 11-15 and flavonoid corn pound^'^>'^ A number of biological activities have been associated with the plant. The essential oil displayed antibacterial activities l8 and fungi- cide ro rties,lg and has been used as an insecti- cide. While the oils obtained from the same plant remain chemically constant in successive crops, one outstanding feature is the difference observed in the composition for different geographical origins. ''-'' We therefore report results for samples growing in Reunion.

J : p "

EXPERIMENTAL

Plant Material Fresh stems and leaves of Ageratum conyzoides

L. were obtained from wild plants growing in

Sainte-Marie district in the north of Reunion. An herbarium sample is kept in the Plant Physiology Department, Facultt des Sciences, Universitt de La Rtunion (Voucher RV no. 18).

Essential Oil The leaves and stems were subjected to hydro-

distillation in a modified Clevenger apparatus for 5 hours to yield 0.2% (v/w) of a brown essential oil which was lighter than water and had a nauseating odour. The essential oil was dried over anhydrous sodium sulphate and stored in the re- frigerator.

Analysis Capillary gas chromatography was carried out

on a Intersmat IGC 120 PL with a FID. Separation was performed on a fused-silica capillary column (50 m X 0.32 mm i.d.) coated with 0.52 pm of methyl silicone phase. The column temperature was held at 70°C for 5 min and raised to 250°C at 2"C/min. Helium at a pressure of 0.5 bar was used as camer gas. Typically 0.1 pI of sample was injected using a conventional split system with a split ratio of 1/50. Peak areas and retention times were calculated with a Shimadzu CR6A integra- tor. Kovhts retention indices (KI) of compounds were determined relatively to the retentions times of a series of n- araffin hydrocarbons with a logarithmic scale. 8,21

0882-5734/93/0502574404S07.00 @ 1993 by John Wiley & Sons, Ltd.

Received I1 January 1993 Accepted I I May I993

258 R. VERA

Combined gas chromatography-mass spectro- metry was recorded on a Hewlett Packard 5890 series I1 gas chromatograph linked to a Hewlett Packard 5995 mass spectrometer. The GC column was a 25 m X 0.32 mm id., fused-silica capillary column coated with 0.52 pm of 5% phenyl methyl

silicone gum phase. Same above conditions rela- tive to injection and programmed temperature were used here. Unknown compounds were iden- tified using the WileylNBS Registry of Mass Spectral Data and by comparison of their Kovhts indices with the l i t e r a t ~ r e . ~ - * ~

Table 1. GC-MS qualitative and quantitative analysis of Ageratum conyzoidcs L. essential oil in elution order on methyl silicone column

Compounds identification" Essential oil YO* Kovhts index m / z (EI)C

a-Pinene Camphene B-Pinene B-M yrcene 2-Carene Limonene Terpinolene Linalol 2-Methylbmethylenescta-l,7diene-3-one Borneo1 Bornyl formate Bornyl acetate l-Hydroxy-2-acetyl-4-methylbenzene Eugenol aCubebene $-Cubebene B-Caryoph yllene a-Bergamotene p-Farnesene Coumarin a-Humulene 7-Methoxy-2,2-dimethylchromene (Recocene I) Germacrene-D y-Cadinened a-Muurolene

(2)-Nerolidol Caryophyllene oxide Dihydrodemethoxyencecalin Unknown Unknown Unknown 6-Cadinol Demethoxyencecalin Ageratochromene (Precocene 11) Unknown 2,2-Dimethyl-7-methoxy-6-vin lchromene

Dihydroencecalin Phytol isomer" Eicosane

exo-2-Hydroxycineole acetate J

0.21 1.53 0.12 0.16 0.54 0.17 0.01 0.04 0.15 0.25 0.46 0.77 0.03 0.40 0.07 1.23 11.21 0.05 0.29 0.52 2.53 70.56 3.16 1.26 0.19 0.08 0.19 0.81 0.04 0.59 0.15 0.20 0.13 0.18 0.10 0.18 0.10 0.44 0.14 0.46 0.08 0.13 0.32 0.06

926 938 964 979 993 1017 1074 1081 1104 1140 1203 1262 1281 1326 1362 1375 1431 1433 1435 1435 1435 1445 1468 1482 1484 1493 1503 1505 1538 1542 1549 1557 1568 1586 1609 1611 1614 1617 1617 1634 1658 1761 1935 uwx)

93, 91, 92, 77, 41, 39, 79 93, 121, 41, 39, 79, 67, 107 93.41, 69, 39, 79, 7l 41.93, 69,39 93, 121, 136,91,77,79, 39,41 68,67, 93.39, 41, 53, 79 93, 121, 136,39,41 71, 43, 41, 93, 55, 69 69, 41, 39, 53, 79, 77 95, 41, 110, 43. 39, 55 95, 121, 41, 93, 136, 43 95,43,93, 121,41, 136, 108 135, 150, 1M,77 164, 149, 77, 103, 131, 55 105, 161, 119, 41, 93, 91, 81 161, 105, 91.41, 119, 81 41,93, 91,69, 133, 79, 105, 39, 55 93, 119,41,91,69 69.41, 93.55 118, 146,90,89,63, 62 93,41, 80, 121 175, 132, 190, 176, 160,77 161, 105,91,41, 119 161. 105, 93, 91, 41, 119 105, 161, 93, 94, 119, 204 41, 93, 55, 69 43, 161, 207,41, 105, 93 161,204, 119, 134, 105,41 161.204, 105,81,41, 119 41,69,43,93,71,55,67, 107 43, 41, 79,93,69 189, 145, 190, 171,204 151.41, 109 119, 161, 41, 105, 43, 204 41, 136, 79, 69, 91, 55 161, 43, 119, 41, 105, 95, 204 187. 144.43, 188, 115 205, 161, 220, 206, 91, 190 41,43, 55,71,69, 109, 135 201, 185,216,202, 115, 128 43, 108, 71, 93,41 219,201, 189, 220,234 71,43, 57,41, 55, 123, 69, 81, 68 57,43, 71, 85,41,55,99,56

"Identification using the WileylNBS Registry of Mass Spectral Data. *Composition calculated from the peak area. 'Main fragments in decreasing order. dTentative identification.

ESSENTIAL OIL OF AGERATUM CONYZOIDES 259

Table 2. Comparative percentage composition of the essential oils of Agerahun wnyzoidcr L. from different origins

CameroonI2 Fiji" Fiji" Ghanal5 India4 Nigeria" Rtunion V i ~ t n a m ' ~ (Suva) (Nadi)

Yields (YO)

Main components Precocene I Precocene I1 f3-Casyoph yllene Farnesene isomers Elemene (a, f3, y) Cubebene (a, f3) Humulene Germacrene-D Cadmene Nerolidol Caryophyllene oxide

0.70 0.13 0.21 0.13 0.u) 0.06 0.20 -

81 ,o 37.5 0.2 21.3

10.5 21.9 0.3 5.3 0.5 0.4 - 0.4 0.9 2.4 0.9 0.5 - 0.4 0.2 , - 0.2 0.4

59.3 0.3

16.0 3.4 0.3 0.6 1.7 1.0 0.2

0.6 -

80.3 10.1 - 75.4 7.0 7.1 0.3 - 0.7 - 0.04 - 0.8 - 1.3 0.3 -

- - -

- -

82.2 0.7 1.9 0.4 0.1 0.1 0.2

traces

0.1 0.5

-

70.6 29.0 0.44 31.1

11.2 16.9 0.08 2.3 - 1 .o 1.3 2.4 2.5 - 3.2 - 1.3 - 0.15 - 1.30 2.4

RESULTS

GC and GC-MS led to the identification of 38 compounds depicted in Table 1. They are arranged according to their order of elution on the methyl silicone phase and their linear retention indices are indicated. The main constituents, such as 7- methoxy-2,2-dimethylchromene (Precocene I), p- caryophyllene, and minor constituents, such as ageratochromene (Precocene 11) and farnesene isomers, have been reported in classical analyses of the essential oil. Since chromenes (benzo- pyrans) are characteristic constituents of the Ageratum genus, the detection of a large number of terpenoids in the oil is interesting. We iden- tified two new compounds, coumarin and phytol, not previously reported in Ageratum conyzoides

. L. essential oil.

Comparison of Essential Oils from Different Origins (Table 2)

Numerous reports on A. conyzoides L. essen- tial oil, especially on those used for medicinal purposes, have been published. It should be noted that, except for samples from India and Vietnam, A. conyroides L. oils contain Precocene I as the major component. In the case of Fiji (Suva) and Vietnam, it appears that the amounts of Precocene I and Precocene I1 are roughly com- parable. In contrast, the composition of the oil from India reported by von Rudloff and Sood4 is rich in Precocene 11 and virtually devoid of Perco- cene I. It is interesting to note that p-

caryophyllene and farnesene isomers are present in all samples. On the other hand the results shown in Table 2 suggest that the other com- pounds seem to be dependent on the origins of samples. For example, all African essential oils contain nerolidol but no y-cadinene.

Acknowledgements-The author wishes to thank Dr Giam- paoli, Laboratoire ArBmes, ENSIA, Massy, France for kindly recording the GC-MS of the oil. He also acknowledges the collaboration of Mr I Laakso, Department of Pharmacy, University of Helsinki, Finland for mass-speara data of chromenes.

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