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Research Article | | Peer-Reviewed

Thermal Conversion of Pregeijerene into Geijerene in Essential Oil of Chromolaena Odorata L. King & Robinson (Asteraceae)

Esse Leon Wognin*,  Amenan Evelyne Tanoh,  Acafou Thierry Yapi,  Kidjegbo Augustin Toure,  Tomi Felix,  Zanahi Felix Tonzibo
Published in Science Journal of Chemistry (Volume 12, Issue 6)
Received: 5 November 2024     Accepted: 9 December 2024     Published: 30 December 2024
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Abstract

It is well-known that geijerene is mostly associated with pregeijerene. These terpenes are believed to be thermoconvertible by a type of sigmatropic transposition order supra or antarafaciale. Our contribution to the study of the molecular pair consisted on a combination of statistical and analytical approach to the chemical composition of Chromolaena odorata essential oil. A compilation of chemical compositions of the samples obtained by steam distillation and analyzed by GC, presented a variation of this binomial proportions in different countries. For Ivory Coast, the results of analysis of 71 samples showed a dominance of geijerene proportion. We carried out a two-stage sampling by chemical variability factors (effects of site and period). We chose, at random, three different samples we submitted separately to chromatographic analysis (GC) and spectroscopic analysis (13C-NMR). It appears from this study that pregeijerene and geijerene were found in the essential oil with a relationship characterized by a polynomial degree 6 between these both molecules. Then during the chromatographic analysis, thermal conversion of pregeijerene into geijerene with the ratio 85.8% was observed. This result supported the idea of the coexistence of pregeijerene and geijerene in the essential oil of Chromolaena odorata. We intend to help clarify the kinetics and complete thermodynamics of this equilibrium.

Published in Science Journal of Chemistry (Volume 12, Issue 6)
DOI 10.11648/j.sjc.20241206.14
Page(s) 144-152
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2024. Published by Science Publishing Group
Previous article
Keywords

Chromolaena Odorata, Essential Oil Composition, Statistical Approach, Thermal Conversion, Geijerene, Pregeijerene

1. Introduction
It has been reported in literature that the geijerene is currently associated with the pregeijerene
[1-8, 9-16]
. In 1968, Jones and Sutherland have suggested that the pregeijerene isolated from geijera parviflora would be the precursor of geijerene
[7]
. In addition, this precursor would result from of hedycaryol by the loss of an isopropylhydroxyl group
[4, 9]
. The exact stereochemistry of these two hydrocarbons was reported by Coggon et al., through X-ray crystallography. It is worth noting that, despite the presence of two asymmetric carbons, the geijerene is inactive
[4, 13]
. The thermal isomerization reaction is one of the most remarkable trans-trans-1, 5-cyclodecadieniques systems; it is a sigmatropic transposition [3, 3] supra or antarafaciale
[4]
. The pregeijerene would rearrange themselves into geijerene, then the geijerene would be an artifact resulting from pregeijerene by thermal transposition (Owolabi et al., 2010)
[2]
. Theoretical calculations undertaken by Owolabi et al.
[2]
, have confirmed the hypothesis of the thermal conversion of pregeijerene to geijerene proposed by Jones and Sutherland and noted by AM Adio
[2, 7, 12]
.
After these precursors, recently, several scientific works have been done to solve the problem of pregeijerene and geijerene. This work deals with the theoretical, spectroscopic and biological aspects of these both molecules. According to Owolabi, ΔrG0 = -4.16 kcal obtained by calculations, would be compatible with almost complete conversion of pregeijerene to geijerene. Jared et al.
[11]
, used the 13C-NMR to elucidate the structures of these two molecules, basing their work on the numbering of Jones and Sutherland
[2, 10, 7]
. Furthermore, recent studies have shown that citrus roots infected with nematodes (D. Abbreviatus) product geijerene and pregeijerene
[11]
. The thermal conversion of pregeijerene into geijerene was studied. Taking account all stages of the production process, retention and chromatographic analysis of essential oil, only hypotheses have been put on the steps where the thermal conversion takes place: some have applied for the distillation step and other than the gas chromatography analysis in comparison with 13C-NMR analysis
[5, 7]
.
This study, consist to model and quantify the relationship between pregeijerene and geijerene in essential oil and their thermal conversion during gas chromatography.
2. Materials and Methods
2.1. Plant Material
Leaves from eight harvest localities were collected from May to November during three years (2007, 2008 and 2009) in
(1) Toumodi (6°55′ N, 5°03′ W) (9 Samples),
(2) Dougba (6°39'0" N, 5°7'60" W) (10 Samples),
(3) Yamoussoukro (6°49'0" N, 5°16'60" W) (17 Samples),
(4) Zambakro (6°43'60" N, 5°25'0" W) (9 Samples),
(5) Toumbokro (6°55'60" N, 5°30'0" W) (9 Samples),
(6) Attiegbakro (6°46'0" N, 5°7'0" W) (2 Samples),
(7) Tiebissou (7°9'47" N, 5°13'14" W) (6 Samples), and
(8) Tie-N’Diekro (7°25'16" N, 4°45'59" W) (9 Samples),
From ‘Region du Belier’ (6°49'60" N, 5°10'0" W) in the center of Ivory Coast (Figure 1)
[17]
.
Figure 1. Sampling locations of Chromolaena odorata leaves from “Region du Belier” in Ivory Coast.
2.2. Essential-Oil Isolation
From May to November 2007 to 2009, fresh Chromolaena odorata leaves were collected at various sites in the “Belier Region” in the central part of Ivory Coast: Toumodi, Dougba, Yamoussoukro, Zambakro, Toumbokro, Attiegbakro, Tiebissou and Tie-N diékro. For each site and each year, samples were repeated several times. These fresh leaves were placed in a pressure cooker containing water under a grid. The pressure cooker was connected to a Clevenger apparatus, and the device boiled for 03 hours. Condensation separated the essential oil from the aqueous phase. This is the hydrodistillation method. Extracted essential oils were dried over anhydrous sulphate magnesium and kept in the dark vials at +4°C prior to analysis.
2.3. GC-FID Analysis
The oil samples were analyzed with a Perkin Elmer Clarus 500 apparatus equipped with FID and two fused-silica cap. columns (50mх0.22mm i.d., film thickness 0.25mm), an apolar BP-1 (polydimethylsiloxane) and a polar BP-20 (polyethylene glycol) column. The oven temperature was programmed rising from 60 to 220° at 2°/min and then held isothermal at 220° for 20 min; injector temperature, 250°; detector temperature, 250°; carrier gas, He (0.8 ml/min); split ratio, 1/60. Retention indices (RIs) were determined relative to the tR of a series of n-alkanes with linear interpolation using the software Target Compounds from Perkin Elmer.
2.4. 13C-NMR Analysis
The 13C-NMR spectra were recorded with a Bruker AVANCE 400 Fourier Transform spectrometer operating at 100.63 MHz and equipped with a 5-mm probe, in CDCl3, with all shifts referred to internal Me4Si. The 13C-NMR spectra of the oil samples were recorded with the following parameters: pulse width, 4 ms (flip angle 45°); acquisition time, 2.7 s for 128 K data table with a spectral width of 25000 Hz (250 ppm); CPD (Composite Pulse Decoupling) mode decoupling; digital resolution, 0.183 Hz/pt. The number of accumulated scans was 2000–3000 for each sample, depending on the available amount of oil (when available, 45 –50 mg of essential oil in 0.5 ml of CDCl3).
2.5. Identification of Components
The identification of the individual components was based
i) on the comparison of the GC retention indices (RIs) for the polar and apolar columns, determined relative to the retention time (tR) of a series of n-alkanes with linear interpolation, with those of reference compounds
[18]
;
ii) for investigated samples, on the comparison of chemical shift values in the 13C-NMR spectra of the essential oils with those of reference spectra compiled in a laboratory-built library, following a computerized method developed in our laboratories, using home-made software. In the investigated samples, individual components were identified by 13C-NMR at contents as low as 0.3–0.4%. The 13C spectra were recorded with the following parameters: pulse angle 45°; acquisition time = 2.7 s corresponding to an acquisition of 128 K with a spectral width (SW) of 24,000 Hz (approximately 240 ppm); relaxation time D1 = 0.1 s; digital resolution of 0.183 Hz/pt. To record the spectra of the essential oils (or chromatography fraction), a mass of 40 to 70 mg of essential oil or 9 to 50 mg of chromatography fraction was dissolved in 0.5 mL of CDCl3. The number of accumulations is between 2000 and 5000 for each recording. The signal data (FID) is multiplied before the Fourier transform by an exponential function (LB = 1.0 Hz). The following parameters were used for the spin echo experiments (JMOD programme) (5 mm probe): pulse duration = 8.6 μs (pulse angle 90°); repetition time between two experiments = 4.7 s; time [1/J(C,H)] calculated for a coupling constant J(C,H) = 140Hz: 7.1 ms. To record 2D NMR spectra involving heteronuclear correlations (HSQC, HMBC) or homonuclear correlations (COSY, NOESY), we used the pulse sequences defined by the Brücker programmes.
2.6. Quantification of Components
The relative contents of the oil constituents were expressed as percentage obtained by peak-area normalization without using correction factors.
2.7. Statistical Analysis
The correlation matrix was performed with Xlstat-Pro7.5.2 (Adinsoft, France) and the trendlines by excel of office 2013. The use of the solver of excel 2013 solved the equations. This solver has also helped to calculate the theoretical content of geijerene, using of the trend curves equations.
2.8. Determination of the Rate of Thermal Conversion from Pregeijerene into Geijerene
In chemistry, a quantitative or total reaction is a chemical reaction with an equilibrium constant very large in front of 1: K≫1. This is also equivalent to ∆rG0<0
[19]
. An incomplete reaction is one that cannot be complete. It has an associated equilibrium constant. It can also be a total reaction whose evolution has not yet had time to be completed. In this case, when the reaction is incomplete, the value of the rate of reaction may be less than the maximum value of the rate of reaction. To measure the evolution of the reaction in relation to the maximum evolution, we can therefore define a rate of reaction progress, a dimensionless quantity which represents the fraction of reactants that have reacted in relation to the fraction that would have disappeared if the reaction had been complete. This rate of progress can be different from the rate of conversion α for each of the reactants. The conversion rate of reactant A is equal to the ratio of the number of moles of A remaining to the number of moles of A initially present
[20]
. We therefore write:
α=nAtransformednAinitial=nA0-nAnA0(1)
We can also replace quantities of matter by concentrations.
The theoretical study of the thermoconversion of pregeijerene into geijerene meets all the above conditions
[2]
. This equilibrium being displaced in favor of geijerene, we have modeled the thermal conversion of pregeijerene to geijerene by a quantative reaction. The evolution table, which we have adopted, is presented as below:
datet=0t≠0 Pregeijerene⟶GeijerenePregNMRGeijNMRPregGC   GeijGC  (2)
In this model, [Preg]N.M.R and [Geij]N.M.R represent respectively the initial concentrations of pregeijerene and geijerene. These are those obtained by 13C-NMR, therefore, at low temperatures when thermoconversion is prohibited. Similarly, [Preg]G.C and [Geij]G.C represent the concentrations, at any given date, of pregeijerene and geijerene, therefore, at high temperatures when thermoconversion is permitted. These are those obtained by the G.C. The rate of conversion of pregeijerene is defined as follows, according to (1):
α=PregeijerenetransformedPregeijereneinitial=PregN.M.R-PregG.C.PregN.M.R(3)
3. Results
3.1. Presentation, Manipulation and Comparative Study of the Content of the Molecular Binomial in Samples
All the 71 samples were submitted to GC-FID analysis to determine retention index (RIs) on two columns of different polarity.
Among them, some samples, selected on the basis of their chromatographic profile, were also analyzed by 13C-NMR. Therefore, the oil components were identified by comparison of their RIs and 13C-NMR chemical shift values with those of authentic samples compiled in our laboratory-made libraries. For the study, only pregeijerene and geijerene contents were highlighted for eight locations of harvest: the predominant molecule geijerene is associated with pregeijerene as minority molecule (Table 1). Table 1 shows the proportions of the pregeijerene and geijerene molecules.
Table 2 compares the levels of the two molecules in essential oil samples from different countries.
Table 3 compares the percentages of the molecular pair after chromatographic analysis (GC) and after spectroscopic analysis (13C-NMR).
Table 4 compares the decrease in pregeijerene with the increase in geijerene, for each validation sample.
3.2. Mathematical Modeling Between Content of Pregeijerene and Geijerene
All the trend line equations and their correlation coefficients for the effect of harvest location are summarised in Table 5.
Table 6 presents the model validation tests according to the two variability factors.
3.3. Determination of Conversion Rate of Pregeijerene into Geijerene
Table 7 shows the proportion of the thermal conversion of pregeijerene into geijerene to validate the sense of the chemical transformation observed during the GC analysis. It also shows the conversion rate of pregeijerene established clearly during the GC analysis.
4. Discussion
Table 1 shows the proportions of the pregeijerene and geijerene molecules. It can be seen that the proportion of geijerene is always higher than that of pregeijerene. During gas chromatography, some of the pregeijerene is converted to geijerene as a result of the temperature rise. This observation does not seem to be saw out elsewhere.
Scheme 1. Biosynthesis of pregeijerene and Cope rearrangement between pregeijerene and geijerene
[4].
Scheme 2. Pregeijerene and geijerene structures with Jones and Sutherland numbering
[11].
Table 1. Pregeijerene and geijerene contents from differents locations of Chromolaena odorata harvests.

Compound name and classa)

RIapolarb)

RIpolarc)

Content (%)d)

harvesting sites

Toumodi

Dougba

Yamoussoukro

Zambakro

Toumbokro

Attiegbakro

Tiebissou

Tie-N'Diekro

number of samples

(9 samples)

(10 samples)

(17 samples)

(9 samples)

(9 samples)

(2 samples)

(6 samples)

(9 samples)

Geijerene

1134

1327

16.9±3.2

13.6±3.1

17.6±6.2

19.7±4.3

16.3±6.8

10.9±1.2

15.5±6.7

9.9±4.2

Pregeijerene

1276

1569

1.9±0.3

1.5±0.5

1.1±1.0

2.0±0.6

2.0±1.4

2.1±0.2

1.7±0.8

0.9±0.5
a)Order of elution and contents determined on the apolar and polar column (BP-1 and BP-20); b)RIapolar: Retention index determined on the apolar column (BP-1); c)RIpolar: Retention index determined on the polar column (BP-20); d)Contents are given as mean±standard deviation.
Table 2. Average proportions of pregeijerene and geijerene in different countries.

Countries

Benin_1

Benin_2

Togo_1

Togo_2

Nigeria

Congo_1 (forest)

Congo_2 (savannah)

India

Thaïland

Ivory Coast

Geijerene (y)

11.4

12.0

19.4

27.0

4.7

4.2

4.4

1.4

3.1

15.7

Pregeijerene (x)

19.9

14.6

10.5

0.1

2.8

14.8

33.3

14.2

17.6

1.5

Ratio (y/x)

0.5

0.8

1.8

270

1.7

0.3

0.1

0.1

0.2

10.5
x and y are the average percentages of molecules in the essential oil
Table 3. Contents of pregeijerene and geijerene in the samples of validation.

Samples

Components

GC

13C-NMR

Content (%)

Ratio y/x

Content (%)

Ratio y/x

Toumbokro (2007)

Geijerene (y)

16.9

6.3

16.1

0.2

Pregeijerene (x)

2.7

3.4

Yamoussoukro (2008)

Geijerene (y)

19.3

9.7

13.7

0.6

Pregeijerene (x)

2.0

7.6

Tiebissou (2009)

Geijerene (y)

3.2

16

1.8

<0.2

Pregeijerene (x)

0.2

< 0.3
x: content of pregeijerene in the essential oil (%); y: content of geijerene in the essential oil (%)
Table 4. Comparative study of the decrease in pregeijerene and the increase in geijerene for validation samples.

Samples

Decrease in pregeijerene

Increase in geijerene

Toumbokro (2007)

16.1-2.7 = 13.4

16.9-3.4 = 13.5

Yamoussoukro (2008)

13.7-2.0 = 11.7

19.3-7.6 = 11.7

Tiebissou (2009)

1.8-0.2 = 1.6

>3.2-0.3 = 2.9
Table 5. Model equations relating the proportions of pregeijerene and geijerene.

Chemical variability factor

Dependent variables

Model equation

R2

Site effect

Toumodi

y = 10118x6 - 108013x5 + 477353x4 - 106x3 + 106x2 - 106x + 291745

0.9935

Dougba

y = 301.06x6 – 2891.8x5 + 11332x4 - 23194x3 + 26148x2 - 15383x + 3695.1

0.9968

Yamoussoukro

y = 36.113x6 – 388.82x5 + 1676.4x4 – 3658.8x3 + 4165.2x2 – 2218.8x + 375.45

0.9895

Zambakro

y = -220.69x6 + 2375.4x5 - 10433x4 + 23840x3 - 29716x2 + 18991x – 4775.4

0.9997

Toumbokro

y = -3.2201x6 + 42.951x5 – 217.58x4 + 523.04x3 – 605.67x2 + 298.1x – 20.702

0.6621

Tiebissou

y = -225.42x5 + 1724.4x4 – 4939.6x3 + 6397.5x2 - 3432x + 424.65

1.0000

Tié-N'Diékro

y = 910.57x6 – 4820.3x5 + 9907.4x4 - 10010x3 + 5161.5x2 – 1249.1x + 111.48

0.9976

Period effect

2007

y = 79.807x6 – 839.05x5 + 3583.3x4 – 7944.9x3 + 9623.5x2 – 6009.5x + 1512.5

0.8573

2008

y = -16.767x6 + 157.03x5 - 588x4 + 1115.8x3 – 1115.8x2 + 553.58x – 95.977

0.9746

2009

y = -25.51x6 + 153.29x5 – 350.56x4 + 379.95x3 – 197.48x2 + 52.704x – 1.5694

0.9829

Organ effect

Feuille

y = -7.108x6 + 9.108x5 – 4.108x4 + 1.108x3 - 107x2 + 604570x + 6.7037

0.9939
x: content of pregeijerene in the essential oil (%); y: content of geijerene in the essential oil (%)
Table 6. Results of the validation of polynomial models.

Factor of variability

Samples

Components

Real value of x and y (%)

Equation of the model

Calculated value of y (%)

Accuracy (%)

Effetc of period

2007

Geijerene

16.9

y = 79.807x6 - 839.05x5 + 3583.3x4 - 7944.9x3 + 9623.5x2 - 6009.5x + 1512.5

18.31

8

Pregeijerene

2.7

2008

Geijerene

19.3

y = -16.767x6 + 157.03x5 - 588x4 + 1115.8x3 - 1115.8x2 + 553.58x - 95.977

18.3

5

Pregeijerene

2.0

2009

Geijerene

3.2

y = -25.51x6 + 153.29x5 - 350.56x4 + 379.95x3 - 197.48x2 + 52.704x - 1.5694

3.6

12.5

Pregeijerene

0.2
x: content of pregeijerene in the essential oil (%); y: content of geijerene in the essential oil (%)
Table 7. Conversion rate of the pregeijerene during the GC.

harvesting sites

Toumbokro

Yamoussoukro

Tiebissou

Average conversion rate α (%)

83.2

85.4

88.9

Average conversion rate (%)

85.8
Indeed, a compilation of the chemical compositions of samples obtained by hydrodistillation and analysed by GC (Table 2) shows a variability in the proportions of this binomial in different countries. Average proportions were used for Ivory Coast.
Table 2 compares the levels of the two molecules in essential oil samples from different countries. Observation of this table shows that in Benin and Togo, the proportions of the two molecules are significant, while in Congo, India and Thailand, pregeijerene is higher than geijerene. However, our samples clearly show a dominance of the geijerene proportion, which is less noticeable in the Nigerian essential oil with relatively low proportions of both molecules. In addition, two-stage sampling per chemical variability factor (site effect and period effect) was carried out. Three different samples were selected at random and subjected separately to chromatographic analysis (GC) and spectroscopic analysis (13C-NMR).
The results of the analyses, for the molecular pair, are shown in Table 3. This table compares the percentages of the molecular pair after chromatographic analysis (GC) and after spectroscopic analysis (13C-NMR). This observation shows that the molecular pair is present in each of the samples, regardless of the method of analysis. Manipulation of this table resulted in Table 4, which compares the decrease in pregeijerene with the increase in geijerene, for each validation sample. We observe that, for each validation sample: - in GC, the percentage of geijerene is higher than that of pregeijerene; - in 13C-NMR, the percentage of pregeijerene is higher than that of geijerene. In addition, for each validation sample (with the exception of Tiebissou where the exact value of geijerene could not be determined in NMR), the decrease in pregeijerene is equal to the increase in geijerene, when we change the values of these two molecules from NMR (cold) to GC (hot). We therefore suspect a thermoconversion of pregeijerene to geijerene.
We considered all the data from which a correlation between the pregeijerene and the geijerene is 0.581 (This value seems low, but it is significant, depending on the software used). Since the correlation between pregeijerene and geijerene levels is significant, we wanted to determine the mathematical model linking these levels from the trend curves. All the trend line equations and their correlation coefficients for the effect of harvest location are summarized in Table 5. The levels of the molecular pair in the three validation samples were used to validate the mathematical model obtained from the trend curves. Table 6 presents the model validation tests according to the two variability factors mentioned above. The calculated values of the geijerene percentage are of the same order of magnitude as the experimental percentages when the polynomial model is of degree 6. These models are validated: there is indeed a polynomial link of degree 6 between the pregeijerene and geijerene percentages.
Table 7 shows the proportion of thermal conversion of pregeijerene to geijerene in order to validate the direction of the chemical transformation observed in the GC analysis. It also shows the rate of conversion of pregeijerene clearly established in the GC analysis. It can be seen that at least 83% and at most 89% of the pregeijerene was converted to geijerene during the chromatographic analysis. These results make it possible to model, quantify and validate the thermal conversion, in part, of pregeijerene to geijerene during the chromatographic analysis. Overall, the trend function is a polynomial of degree 6 for all the harvesting sites, with the exception of Tiebissou. If we look at the correlation coefficients, we can see that pregeijerene and geijerene are strongly linked regardless of the harvesting site. However, the harvesting period allowed us to carry out our comparative study with a random selection of three validation samples (Table 3).
The thermal conversion of pregeijerene has been clearly established (scheme 1-2)
[4, 7, 12]
. The structures of pregeijerene and geijerene are known, as is the reaction mechanism for converting pregeijerene to geijerene (scheme 1-2)
[4, 7, 10-12]
. However, what is less well known is the stage at which the thermal conversion takes place, let alone the rate of conversion of pregeijerene to geijerene. Because of the high temperature at which the conversion takes place (120-170°C), it is unlikely to be during steam distillation (which takes place at a temperature below 100°C), as claimed by Bissangou and Ouamba
[5]
.
5. Conclusions
Our contribution to the study of the thermal conversion of pregeijerene to geijerene in the chromatographic analysis is based on a statistical approach, using the essential oil of Chromolaena odorata. Therefore, we have carried out a two-stage sampling. The 71 samples were collected from eight sites during three successive years. These samples were analysed by GC-MS. A validation sample was submitted separately to GC and 13C-NMR. The results show that, for the essential oil of Chromolaena odorata in Ivory Coast, during the chromatographic analysis in gas phase, 85.8% of pregeijerene is thermally converted to geijerene. This rate also translates the possibility of an equilibrium reaction for the duration of the rise in temperature during the chromatography. However, the comparative analysis of the results by GC and 13C-NMR, reinforces our idea of the co-existence of the pregeijerene and the geijerene in Chromolaena odorata. This work has shown that geijerene, present in the chromatographic profile of Chromolaena odorata essential oil, is partly due to the thermal conversion of pregeijerene. So, geijerene is, in part, an artifact.
We intend to help clarify the kinetics and complete thermodynamics of this equilibrium.
Abbreviations

GC

Gas Chromatographic

13C-NMR

Carbon-13 Nuclear Magnetic Resonance

FID

Flame Ionisation Detector

RI

Retention Index

CPD

Composite Pulse Decoupling
Author Contributions
Esse Leon Wognin: Conceptualization, Data curation, Formal Analysis, Investigation, Methodology, Software, Writing – original draft
Amenan Evelyne Tanoh: Conceptualization, Formal Analysis, Investigation, Methodology, Visualization, Writing – original draft
Acafou Thierry Yapi: Resources, Visualization
Kidjegbo Augustin Touré: Data curation, Formal Analysis, Methodology, Software, Supervision
Tomi Felix: Supervision
Zanahi Felix Tonzibo: Conceptualization, Supervision, Validation, Writing – original draft, Writing – review & editing
Conflicts of Interest
The authors declare no conflicts of interest.
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    Wognin, E. L., Tanoh, A. E., Yapi, A. T., Toure, K. A., Felix, T., et al. (2024). Thermal Conversion of Pregeijerene into Geijerene in Essential Oil of Chromolaena Odorata L. King & Robinson (Asteraceae). Science Journal of Chemistry, 12(6), 144-152. https://doi.org/10.11648/j.sjc.20241206.14

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    Wognin, E. L.; Tanoh, A. E.; Yapi, A. T.; Toure, K. A.; Felix, T., et al. Thermal Conversion of Pregeijerene into Geijerene in Essential Oil of Chromolaena Odorata L. King & Robinson (Asteraceae). Sci. J. Chem. 2024, 12(6), 144-152. doi: 10.11648/j.sjc.20241206.14

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    Wognin EL, Tanoh AE, Yapi AT, Toure KA, Felix T, et al. Thermal Conversion of Pregeijerene into Geijerene in Essential Oil of Chromolaena Odorata L. King & Robinson (Asteraceae). Sci J Chem. 2024;12(6):144-152. doi: 10.11648/j.sjc.20241206.14

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  • @article{10.11648/j.sjc.20241206.14,
  author = {Esse Leon Wognin and Amenan Evelyne Tanoh and Acafou Thierry Yapi and Kidjegbo Augustin Toure and Tomi Felix and Zanahi Felix Tonzibo},
  title = {Thermal Conversion of Pregeijerene into Geijerene in Essential Oil of Chromolaena Odorata L. King & Robinson (Asteraceae)
},
  journal = {Science Journal of Chemistry},
  volume = {12},
  number = {6},
  pages = {144-152},
  doi = {10.11648/j.sjc.20241206.14},
  url = {https://doi.org/10.11648/j.sjc.20241206.14},
  eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.sjc.20241206.14},
  abstract = {It is well-known that geijerene is mostly associated with pregeijerene. These terpenes are believed to be thermoconvertible by a type of sigmatropic transposition order supra or antarafaciale. Our contribution to the study of the molecular pair consisted on a combination of statistical and analytical approach to the chemical composition of Chromolaena odorata essential oil. A compilation of chemical compositions of the samples obtained by steam distillation and analyzed by GC, presented a variation of this binomial proportions in different countries. For Ivory Coast, the results of analysis of 71 samples showed a dominance of geijerene proportion. We carried out a two-stage sampling by chemical variability factors (effects of site and period). We chose, at random, three different samples we submitted separately to chromatographic analysis (GC) and spectroscopic analysis (13C-NMR). It appears from this study that pregeijerene and geijerene were found in the essential oil with a relationship characterized by a polynomial degree 6 between these both molecules. Then during the chromatographic analysis, thermal conversion of pregeijerene into geijerene with the ratio 85.8% was observed. This result supported the idea of the coexistence of pregeijerene and geijerene in the essential oil of Chromolaena odorata. We intend to help clarify the kinetics and complete thermodynamics of this equilibrium.
},
 year = {2024}
}

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  • TY  - JOUR
T1  - Thermal Conversion of Pregeijerene into Geijerene in Essential Oil of Chromolaena Odorata L. King & Robinson (Asteraceae)

AU  - Esse Leon Wognin
AU  - Amenan Evelyne Tanoh
AU  - Acafou Thierry Yapi
AU  - Kidjegbo Augustin Toure
AU  - Tomi Felix
AU  - Zanahi Felix Tonzibo
Y1  - 2024/12/30
PY  - 2024
N1  - https://doi.org/10.11648/j.sjc.20241206.14
DO  - 10.11648/j.sjc.20241206.14
T2  - Science Journal of Chemistry
JF  - Science Journal of Chemistry
JO  - Science Journal of Chemistry
SP  - 144
EP  - 152
PB  - Science Publishing Group
SN  - 2330-099X
UR  - https://doi.org/10.11648/j.sjc.20241206.14
AB  - It is well-known that geijerene is mostly associated with pregeijerene. These terpenes are believed to be thermoconvertible by a type of sigmatropic transposition order supra or antarafaciale. Our contribution to the study of the molecular pair consisted on a combination of statistical and analytical approach to the chemical composition of Chromolaena odorata essential oil. A compilation of chemical compositions of the samples obtained by steam distillation and analyzed by GC, presented a variation of this binomial proportions in different countries. For Ivory Coast, the results of analysis of 71 samples showed a dominance of geijerene proportion. We carried out a two-stage sampling by chemical variability factors (effects of site and period). We chose, at random, three different samples we submitted separately to chromatographic analysis (GC) and spectroscopic analysis (13C-NMR). It appears from this study that pregeijerene and geijerene were found in the essential oil with a relationship characterized by a polynomial degree 6 between these both molecules. Then during the chromatographic analysis, thermal conversion of pregeijerene into geijerene with the ratio 85.8% was observed. This result supported the idea of the coexistence of pregeijerene and geijerene in the essential oil of Chromolaena odorata. We intend to help clarify the kinetics and complete thermodynamics of this equilibrium.

VL  - 12
IS  - 6
ER  -

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