This article was downloaded by: [Selcuk Universitesi] On: 02 February 2015, At: 10:09 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Natural Product Research: Formerly Natural Product Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gnpl20
Chemical composition, phytotoxic and antifungal properties of Ruta chalepensis L. essential oils a
b
c
d
Wafa Bouabidi , Mohsen Hanana , Samia Gargouri , Ismail Amri , e
e
f
Tarek Fezzani , Mustapha Ksontini , Bassem Jamoussi & Lamia e
Hamrouni a
Faculty of Sciences of Tunis, El Manar II, 2092 Tunis, Tunisia
b
Plant Molecular Physiology Laboratory, Biotechnology Center in Borj-Cedria Technopol, BP. 901, 2050 Hammam-Lif, Tunisia
Click for updates
c
Plant Protection Laboratory, National Institute of Agronomical Research of Tunisia, Rue Hédi Karray 2049, Tunisia d
Faculty of Sciences of Bizerta, Bizerta 7021, Tunisia
e
Ecological Forestry Laboratory, National Institute of Rural Engineering, Water and Forest Researches, P.B. 10, 2080 Ariana, Tunisia f
Laboratory of Chemistry, Higher Institute of Education and Continual Formation, Tunis, Tunisia Published online: 02 Jan 2015.
To cite this article: Wafa Bouabidi, Mohsen Hanana, Samia Gargouri, Ismail Amri, Tarek Fezzani, Mustapha Ksontini, Bassem Jamoussi & Lamia Hamrouni (2015): Chemical composition, phytotoxic and antifungal properties of Ruta chalepensis L. essential oils, Natural Product Research: Formerly Natural Product Letters, DOI: 10.1080/14786419.2014.980246 To link to this article: http://dx.doi.org/10.1080/14786419.2014.980246
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
Downloaded by [Selcuk Universitesi] at 10:09 02 February 2015
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Natural Product Research, 2014 http://dx.doi.org/10.1080/14786419.2014.980246
SHORT COMMUNICATION Chemical composition, phytotoxic and antifungal properties of Ruta chalepensis L. essential oils Wafa Bouabidia, Mohsen Hananab*, Samia Gargouric, Ismail Amrid, Tarek Fezzanie, Mustapha Ksontinie, Bassem Jamoussif and Lamia Hamrounie
Downloaded by [Selcuk Universitesi] at 10:09 02 February 2015
a
Faculty of Sciences of Tunis, El Manar II, 2092 Tunis, Tunisia; bPlant Molecular Physiology Laboratory, Biotechnology Center in Borj-Cedria Technopol, BP. 901, 2050 Hammam-Lif, Tunisia; cPlant Protection Laboratory, National Institute of Agronomical Research of Tunisia, Rue He´di Karray 2049, Tunisia; d Faculty of Sciences of Bizerta, Bizerta 7021, Tunisia; eEcological Forestry Laboratory, National Institute of Rural Engineering, Water and Forest Researches, P.B. 10, 2080 Ariana, Tunisia; fLaboratory of Chemistry, Higher Institute of Education and Continual Formation, Tunis, Tunisia (Received 7 July 2014; final version received 21 October 2014)
The chemical composition, and phytotoxic and antifungal activities of the essential oils isolated by using hydrodistillation from the aerial parts of Tunisian rue were evaluated. Significant variations were observed among harvest periods. The analysis of the chemical composition by gas chromatography/mass spectrometry showed that 2undecanone (33.4– 49.8%), 2-heptanol acetate (13.5– 15.4%) and a-pinene (9.8– 11.9%) were the main components. The antifungal ability of rue essential oils was tested by using disc agar diffusion against ten plant pathogenic fungi. A high antifungal activity was observed for the essential oil isolated at flowering developmental phase. Furthermore, rue essential oils showed high level of herbicidal activity against several weeds. Keywords: biological activity; chemotype; fungi; Rutaceae; volatile compounds; weeds
1. Introduction Ruta chalepensis L. essential oils possess useful biological activities and antioxidant properties that may be utilised in the food-processing industry and biopesticide exploitation (Fakhfakh et al. 2012). R. chalepensis (Rutaceae) or fringed rue is a very strong smelling perennial *Corresponding author. Email: [email protected] This work was presented to the 5th International Congress on Medicinal and Aromatic Plants, CIPAM 2014, 17 – 20 March 2014, Zarzis-Dejerba, Tunisia. q 2014 Taylor & Francis
2
W. Bouabidi et al.
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herbaceous shrub growing in dry and calcareous rocky areas and widely diffused in the Mediterranean area, with glabrous, alternate bi-pennatisect leaves, narrow oblong-lanceolate or obovate segments, and inflorescence in cymose (Ben Bnina et al. 2010; Fakhfakh et al. 2012). Locally known under the common name ‘fedjel’, this ancient medicinal plant is still used in the traditional medicine of many countries as a laxative, anti-inflammatory, analgesic, antispasmodic, abortifacient, antiepileptic, emmenagogue and for dermatopathy treatment (Al-Said et al. 1990; Ben Bnina et al. 2010). However, as far as we know, there have been few reports (Bouajaj et al. 2014) on the antifungal and weed killer activities of R. chalepensis. Therefore, this study was carried out to determine the phytotoxic and antifungal activities of the essential oils isolated by using hydrodistillation from the aerial parts of R. chalepensis during two different phases of the plant development. In addition, the yields, chemical compositions and physico-chemical properties of essential oils were analysed and compared with respect to harvest periods. 2. Results and discussion 2.1. Yield variability and physico-chemical properties of essential oils The oil yields obtained varied considerably with respect to harvest periods. The highest oil yield of 0.7% was obtained in flowering phase in April, while the lowest yield of 0.5% was obtained in post-flowering phase in December. Few or no modification was observed in physico-chemical properties of essential oils with respect to harvest periods. Indeed, density, refraction index and colour (yellow) did not vary significantly between different periods of harvest. Only acid index has been increased at the flowering phase. 2.2. Chemical composition The total number (19) of identified components did not vary among periods, representing 95.6– 99.1% (December and April, respectively) of the total oils (Table S1). Nevertheless, the essential oil collected in December displayed the poorest quality; it contained the lowest amount of 2undecanone (33.5%). All the essential oils analysed were characterised by the predominance of ketonic compounds (39.3 – 57.9 – 60.3%), particularly the 2-undecanone (33.4 – 49.8%). Similarly, according to Fakhfakh et al. (2012), regardless of the plant location or the extraction method, the compositions of the Tunisian R. chalepensis essential oils were dominated by ketones and esters. 2-Heptanol acetate, an alcoholic fraction, was also found in considerable amounts in our investigated samples (14 –16%). The hydrocarbon monoterpenes represent 14.5 –17.9% of the total oil, and a-pinene was the major compound of this fraction (10 –12%). Our results agreed with Saidani-Tounsi et al. (2011) who reported that the 2-undecanone was the main compound in the chemical composition of the essential oil of R. chalepensis growing in Tunisia; moreover and according to Saidani-Tounsi and co-workers, 2-undecanone was shown to be the unique component (100%) of the essential oil obtained from flowers. In addition, chemical composition analysis revealed a slight difference between the essential oils of R. chalepensis collected during the three different dates. Indeed, the flowering phase (April) was richer in 2-undecanone (49.8%) than the essential oil of R. chalepensis collected in December (33.5%) and February (46.4%). 2.3. Herbicidal effects of the oils Our results showed that herbicidal activity varies according to the dose of the oil and the weed species, and that the essential oils display inhibitory effects on both germination (Table S2) and seedling growth of weeds. Different degrees of inhibition were observed in comparison
Downloaded by [Selcuk Universitesi] at 10:09 02 February 2015
Natural Product Research
3
with control and 2,4-D isooctyl ester samples. In other respects, we could not find any significant differences between the three harvest periods on the herbicidal activities. At the dose of 2 mL/mL, essential oils inhibit, at least 90%, the germination rate of all the weeds, and there was no significant difference between the three collection dates, even some variation was seen in their chemical composition (particularly the 2-undecanone content). At low doses (in the range of 0.5 – 1 mL/mL), the oil partially inhibits germination capacity, affects the kinetics of germination by delaying the onset of germination and reduces the growth of aerial parts and roots of plantlets. However, the inhibitory effects of essential oils and 2,4-D isooctyl ester on seed germination of the tested weeds were the same. The herbicidal effects of some essential oils and their pure constituents against weeds have been previously reported (Harminder et al. 2006; Emine et al. 2007), and their effects are generally attributed to their major components. In general, there is a correlation between the herbicidal effects and percentage of some major components. The essential oils of R. chalepensis contain mainly 2-undecanone, 2-heptanol acetate and a-pinene (Table S1). However, no studies so far have been made on the herbicidal effects of 2-undecanone and 2-heptanol acetate. Nevertheless, it has been reported that apinene, one of the major components of Ruta essential oil, has strong phytotoxic effect against various plant species and causes uncoupling oxidative phosphorylation by acting as protonophoric agent such 2,4-dinitrophenol (Abrahim et al. 2003). Other report showed that apinene inhibits early root growth and causes oxidative damage in root tissue (Harminder et al. 2006). The herbicidal effects of R. chalepensis essential oils can be attributed to their high level of oxygenated components (59.2 – 78.4%). Therefore, we can conclude that the herbicidal activity of R. chalepensis observed in our study is due to the presence of monoterpenes, either hydrocarbons or oxygenated monoterpenes. Although the herbicidal mechanism of the oils was not investigated in this study, it is well known that monoterpenes in essential oils have phytotoxic effects that may cause anatomical and physiological changes in plant seedling leading to accumulation of lipid globules in the cytoplasm, reduction in some organelles such mitochondria, possibly due to inhibition of DNA synthesis or disruption of membranes surrounding mitochondria and nuclei (Nishida et al. 2005). 2.4. Antifungal activity of essential oil The antifungal activity assays of the essential oils extracted from the leaves of R. chalepensis collected at 3 different dates against 10 agriculturally important fungal species revealed a broad spectrum of antifungal activity (Table S3). However, the inhibition effects of essential oils on the growth of tested fungi were lower than benomyl (a commercial fungicide). The oil of R. chalepensis collected in April was active against all the tested fungi, but the oil extracted in December and February were active only against Alternaria sp. and Microdochium nivale. Furthermore, our results indicated that the oil extracted in April was more effective than the oils extracted in December and February. The major components of the essential oils are most probably responsible for the antimicrobial activity. The essential oils of R. chalepensis contain mainly 2-undecanone, 2-heptanol acetate and a-pinene. The latter component has already been proved to possess antibacterial activity. Other studies have indeed shown that essential oils containing relatively high amount of oxygenated monoterpenes possess antifungal activity (Kordali et al. 2008; Bouajaj et al. 2014). Besides, it should be noted that minor components in essential oils, as well as synergistic and/or antagonistic interaction between the volatile components, could also affect the antifungal properties of the essential oils of R. chalepensis which were found in this study to be rich in oxygenated compounds representing 59.13 –78.39% of total oils. Other studies have indeed shown that essential oils containing relatively high amount of oxygenated monoterpenes possess antifungal activity (Kordali et al. 2008). In the view of these findings, the antifungal
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W. Bouabidi et al.
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activity of Ruta essential oils extracted in April can be attributed to their high levels of oxygenated monoterpenes. Zunino and Zygadlo (2004) indicated that mycelial growth inhibition is caused by the monoterpenes present in essential oils. These components would increase the concentration of lipidic peroxides such as hydroxyl, alkoxyl and alkoperoxyl radicals and thereby bring about cell death. For Sharma and Tripathi (2006), the essential oils would act on the hyphae of the mycelium, provoking exit of components from the cytoplasm, the loss of rigidity and integrity of the hyphal cell wall, resulting in its collapse and death of the mycelium.
3. Conclusion In our study, the first qualitative and quantitative analysis of R. chalepensis oils showed significant variations in the yield of essential oils among harvest periods: oil collected during April (flowering stage which is characterised by a high metabolic activity) showed the best yields whereas oil collected during December showed the least. Ruta oils displayed a high antifungal activity against plant pathogenic fungi and phytotoxic effects against weeds. Based on the present results, the essential oils could be suggested as alternative pesticides and herbicides. Indeed, our study supports the application of certain essential oils to control plant pathogens such as fungi and weeds. However, in spite of considerable data on the pesticidal properties of essential oils and their constituents, surprisingly few pest control products based on plant essential oils have appeared in the market place. Further studies are required to determine the cost, applicability, safety and phytotoxicity of these agents as potential herbicides and fungicides in integrated pest management strategy.
Supplementary material Experimental details relating to this paper are available online, alongside Tables S1 – S3.
References Abrahim D, Francischini AC, Pergo EM, Kelmer-Bracht AM, Ishii-Iwamoto EL. 2003. Effects of a-pinene on the mitochondrial respiration of maize seedlings. Plant Physiol Biochem. 41:985– 991. Al-Said M, Tariq M, Al-Yahya MA, Rafatullah S, Ginnawi OT, Ageel AM. 1990. Studies on Ruta chalepensis, an ancient medicinal herb still used in traditional medicine. J Ethnopharmacol. 28:305– 312. Ben Bnina E, Hammami S, Daamii-Remadi M, Ben Jannet H, Mighri Z. 2010. Chemcial composition and antimicrobial effects of Tunisian Ruta chalepensis L. essential oils. J Soc Chim Tunis. 12:1–9. Bouajaj S, Romane A, Benyamna A, Amri I, Hanana M, Hamrouni L, Romdhane M. 2014. Essential oil composition, phytotoxic and antifungal activities of Ruta chalepensis L. leaves from High Atlas Mountains (Morocco). Nat Prod Res. 28:1910–1914. Emine S, Saban K, Recep K, Cakire AYK. 2007. Chemical compositions, antimicrobial and herbicidal effects of essential oils isolated from Turkish Tanacetum aucheranum and Tanacetum chiliophyllum var. chiliophyllum. Biochem Syst Ecol. 35:569– 581. Fakhfakh N, Zouari S, Zouari M, Loussayef C, Zouari N. 2012. Chemical composition of volatile compounds and antioxidant activities of essential oil, aqueous and ethanol extracts of wild Tunisian Ruta chalepensis L. (Rutaceae). J Med Plant Res. 6(4):593–600. Harminder PS, Daisy RB, Shalinder K, Komal A, Ravinder KK. 2006. a-Pinene inhibits growth and induces oxidative stress in roots. Ann Bot. 98:1261 –1269. Kordali S, Cakir A, Ozer H, Cakmaci R, Kesdek M, Mete E. 2008. Antifungal, phytotoxic and insecticidal properties of essential oil isolated from Turkish Origanum acutidens and its three components, carvacrol, thymol and pcymene. Bioresour Technol. 99:8788–8795. Nishida N, Tamotsu S, Nagata N, Saito C, Sakai A. 2005. Allelopathic effects of volatile monoterpenoids produced by Salvia leucophylla: inhibition of cell proliferation and DNA synthesis in the root apical meristem of Brassica campestris seedlings. J Chem Ecol. 31:1187–1203.
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Saidani-Tounsi M, Aidi-Wannes W, Ouerghemmi I, Msaada K, Smaoui A, Marzouk B. 2011. Variation in essential oil and fatty acid composition in different organs of cultivated and growing wild Ruta chalepensis L. Ind Crops Prod. 33:617–623. Sharma N, Tripathi A. 2006. Fungitoxicity of the essential oil of Citrus sinensis on post harvest pathogens. World J Microbiol Biotechnol. 2:587–593. Zunino MP, Zygadlo JA. 2004. Effect of monoterpenes on lipid oxidation in maize. Planta. 219:303–309.
Natural Product Research: Formerly Natural Product Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gnpl20
Chemical composition, phytotoxic and antifungal properties of Ruta chalepensis L. essential oils a
b
c
d
Wafa Bouabidi , Mohsen Hanana , Samia Gargouri , Ismail Amri , e
e
f
Tarek Fezzani , Mustapha Ksontini , Bassem Jamoussi & Lamia e
Hamrouni a
Faculty of Sciences of Tunis, El Manar II, 2092 Tunis, Tunisia
b
Plant Molecular Physiology Laboratory, Biotechnology Center in Borj-Cedria Technopol, BP. 901, 2050 Hammam-Lif, Tunisia
Click for updates
c
Plant Protection Laboratory, National Institute of Agronomical Research of Tunisia, Rue Hédi Karray 2049, Tunisia d
Faculty of Sciences of Bizerta, Bizerta 7021, Tunisia
e
Ecological Forestry Laboratory, National Institute of Rural Engineering, Water and Forest Researches, P.B. 10, 2080 Ariana, Tunisia f
Laboratory of Chemistry, Higher Institute of Education and Continual Formation, Tunis, Tunisia Published online: 02 Jan 2015.
To cite this article: Wafa Bouabidi, Mohsen Hanana, Samia Gargouri, Ismail Amri, Tarek Fezzani, Mustapha Ksontini, Bassem Jamoussi & Lamia Hamrouni (2015): Chemical composition, phytotoxic and antifungal properties of Ruta chalepensis L. essential oils, Natural Product Research: Formerly Natural Product Letters, DOI: 10.1080/14786419.2014.980246 To link to this article: http://dx.doi.org/10.1080/14786419.2014.980246
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
Downloaded by [Selcuk Universitesi] at 10:09 02 February 2015
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Natural Product Research, 2014 http://dx.doi.org/10.1080/14786419.2014.980246
SHORT COMMUNICATION Chemical composition, phytotoxic and antifungal properties of Ruta chalepensis L. essential oils Wafa Bouabidia, Mohsen Hananab*, Samia Gargouric, Ismail Amrid, Tarek Fezzanie, Mustapha Ksontinie, Bassem Jamoussif and Lamia Hamrounie
Downloaded by [Selcuk Universitesi] at 10:09 02 February 2015
a
Faculty of Sciences of Tunis, El Manar II, 2092 Tunis, Tunisia; bPlant Molecular Physiology Laboratory, Biotechnology Center in Borj-Cedria Technopol, BP. 901, 2050 Hammam-Lif, Tunisia; cPlant Protection Laboratory, National Institute of Agronomical Research of Tunisia, Rue He´di Karray 2049, Tunisia; d Faculty of Sciences of Bizerta, Bizerta 7021, Tunisia; eEcological Forestry Laboratory, National Institute of Rural Engineering, Water and Forest Researches, P.B. 10, 2080 Ariana, Tunisia; fLaboratory of Chemistry, Higher Institute of Education and Continual Formation, Tunis, Tunisia (Received 7 July 2014; final version received 21 October 2014)
The chemical composition, and phytotoxic and antifungal activities of the essential oils isolated by using hydrodistillation from the aerial parts of Tunisian rue were evaluated. Significant variations were observed among harvest periods. The analysis of the chemical composition by gas chromatography/mass spectrometry showed that 2undecanone (33.4– 49.8%), 2-heptanol acetate (13.5– 15.4%) and a-pinene (9.8– 11.9%) were the main components. The antifungal ability of rue essential oils was tested by using disc agar diffusion against ten plant pathogenic fungi. A high antifungal activity was observed for the essential oil isolated at flowering developmental phase. Furthermore, rue essential oils showed high level of herbicidal activity against several weeds. Keywords: biological activity; chemotype; fungi; Rutaceae; volatile compounds; weeds
1. Introduction Ruta chalepensis L. essential oils possess useful biological activities and antioxidant properties that may be utilised in the food-processing industry and biopesticide exploitation (Fakhfakh et al. 2012). R. chalepensis (Rutaceae) or fringed rue is a very strong smelling perennial *Corresponding author. Email: [email protected] This work was presented to the 5th International Congress on Medicinal and Aromatic Plants, CIPAM 2014, 17 – 20 March 2014, Zarzis-Dejerba, Tunisia. q 2014 Taylor & Francis
2
W. Bouabidi et al.
Downloaded by [Selcuk Universitesi] at 10:09 02 February 2015
herbaceous shrub growing in dry and calcareous rocky areas and widely diffused in the Mediterranean area, with glabrous, alternate bi-pennatisect leaves, narrow oblong-lanceolate or obovate segments, and inflorescence in cymose (Ben Bnina et al. 2010; Fakhfakh et al. 2012). Locally known under the common name ‘fedjel’, this ancient medicinal plant is still used in the traditional medicine of many countries as a laxative, anti-inflammatory, analgesic, antispasmodic, abortifacient, antiepileptic, emmenagogue and for dermatopathy treatment (Al-Said et al. 1990; Ben Bnina et al. 2010). However, as far as we know, there have been few reports (Bouajaj et al. 2014) on the antifungal and weed killer activities of R. chalepensis. Therefore, this study was carried out to determine the phytotoxic and antifungal activities of the essential oils isolated by using hydrodistillation from the aerial parts of R. chalepensis during two different phases of the plant development. In addition, the yields, chemical compositions and physico-chemical properties of essential oils were analysed and compared with respect to harvest periods. 2. Results and discussion 2.1. Yield variability and physico-chemical properties of essential oils The oil yields obtained varied considerably with respect to harvest periods. The highest oil yield of 0.7% was obtained in flowering phase in April, while the lowest yield of 0.5% was obtained in post-flowering phase in December. Few or no modification was observed in physico-chemical properties of essential oils with respect to harvest periods. Indeed, density, refraction index and colour (yellow) did not vary significantly between different periods of harvest. Only acid index has been increased at the flowering phase. 2.2. Chemical composition The total number (19) of identified components did not vary among periods, representing 95.6– 99.1% (December and April, respectively) of the total oils (Table S1). Nevertheless, the essential oil collected in December displayed the poorest quality; it contained the lowest amount of 2undecanone (33.5%). All the essential oils analysed were characterised by the predominance of ketonic compounds (39.3 – 57.9 – 60.3%), particularly the 2-undecanone (33.4 – 49.8%). Similarly, according to Fakhfakh et al. (2012), regardless of the plant location or the extraction method, the compositions of the Tunisian R. chalepensis essential oils were dominated by ketones and esters. 2-Heptanol acetate, an alcoholic fraction, was also found in considerable amounts in our investigated samples (14 –16%). The hydrocarbon monoterpenes represent 14.5 –17.9% of the total oil, and a-pinene was the major compound of this fraction (10 –12%). Our results agreed with Saidani-Tounsi et al. (2011) who reported that the 2-undecanone was the main compound in the chemical composition of the essential oil of R. chalepensis growing in Tunisia; moreover and according to Saidani-Tounsi and co-workers, 2-undecanone was shown to be the unique component (100%) of the essential oil obtained from flowers. In addition, chemical composition analysis revealed a slight difference between the essential oils of R. chalepensis collected during the three different dates. Indeed, the flowering phase (April) was richer in 2-undecanone (49.8%) than the essential oil of R. chalepensis collected in December (33.5%) and February (46.4%). 2.3. Herbicidal effects of the oils Our results showed that herbicidal activity varies according to the dose of the oil and the weed species, and that the essential oils display inhibitory effects on both germination (Table S2) and seedling growth of weeds. Different degrees of inhibition were observed in comparison
Downloaded by [Selcuk Universitesi] at 10:09 02 February 2015
Natural Product Research
3
with control and 2,4-D isooctyl ester samples. In other respects, we could not find any significant differences between the three harvest periods on the herbicidal activities. At the dose of 2 mL/mL, essential oils inhibit, at least 90%, the germination rate of all the weeds, and there was no significant difference between the three collection dates, even some variation was seen in their chemical composition (particularly the 2-undecanone content). At low doses (in the range of 0.5 – 1 mL/mL), the oil partially inhibits germination capacity, affects the kinetics of germination by delaying the onset of germination and reduces the growth of aerial parts and roots of plantlets. However, the inhibitory effects of essential oils and 2,4-D isooctyl ester on seed germination of the tested weeds were the same. The herbicidal effects of some essential oils and their pure constituents against weeds have been previously reported (Harminder et al. 2006; Emine et al. 2007), and their effects are generally attributed to their major components. In general, there is a correlation between the herbicidal effects and percentage of some major components. The essential oils of R. chalepensis contain mainly 2-undecanone, 2-heptanol acetate and a-pinene (Table S1). However, no studies so far have been made on the herbicidal effects of 2-undecanone and 2-heptanol acetate. Nevertheless, it has been reported that apinene, one of the major components of Ruta essential oil, has strong phytotoxic effect against various plant species and causes uncoupling oxidative phosphorylation by acting as protonophoric agent such 2,4-dinitrophenol (Abrahim et al. 2003). Other report showed that apinene inhibits early root growth and causes oxidative damage in root tissue (Harminder et al. 2006). The herbicidal effects of R. chalepensis essential oils can be attributed to their high level of oxygenated components (59.2 – 78.4%). Therefore, we can conclude that the herbicidal activity of R. chalepensis observed in our study is due to the presence of monoterpenes, either hydrocarbons or oxygenated monoterpenes. Although the herbicidal mechanism of the oils was not investigated in this study, it is well known that monoterpenes in essential oils have phytotoxic effects that may cause anatomical and physiological changes in plant seedling leading to accumulation of lipid globules in the cytoplasm, reduction in some organelles such mitochondria, possibly due to inhibition of DNA synthesis or disruption of membranes surrounding mitochondria and nuclei (Nishida et al. 2005). 2.4. Antifungal activity of essential oil The antifungal activity assays of the essential oils extracted from the leaves of R. chalepensis collected at 3 different dates against 10 agriculturally important fungal species revealed a broad spectrum of antifungal activity (Table S3). However, the inhibition effects of essential oils on the growth of tested fungi were lower than benomyl (a commercial fungicide). The oil of R. chalepensis collected in April was active against all the tested fungi, but the oil extracted in December and February were active only against Alternaria sp. and Microdochium nivale. Furthermore, our results indicated that the oil extracted in April was more effective than the oils extracted in December and February. The major components of the essential oils are most probably responsible for the antimicrobial activity. The essential oils of R. chalepensis contain mainly 2-undecanone, 2-heptanol acetate and a-pinene. The latter component has already been proved to possess antibacterial activity. Other studies have indeed shown that essential oils containing relatively high amount of oxygenated monoterpenes possess antifungal activity (Kordali et al. 2008; Bouajaj et al. 2014). Besides, it should be noted that minor components in essential oils, as well as synergistic and/or antagonistic interaction between the volatile components, could also affect the antifungal properties of the essential oils of R. chalepensis which were found in this study to be rich in oxygenated compounds representing 59.13 –78.39% of total oils. Other studies have indeed shown that essential oils containing relatively high amount of oxygenated monoterpenes possess antifungal activity (Kordali et al. 2008). In the view of these findings, the antifungal
4
W. Bouabidi et al.
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activity of Ruta essential oils extracted in April can be attributed to their high levels of oxygenated monoterpenes. Zunino and Zygadlo (2004) indicated that mycelial growth inhibition is caused by the monoterpenes present in essential oils. These components would increase the concentration of lipidic peroxides such as hydroxyl, alkoxyl and alkoperoxyl radicals and thereby bring about cell death. For Sharma and Tripathi (2006), the essential oils would act on the hyphae of the mycelium, provoking exit of components from the cytoplasm, the loss of rigidity and integrity of the hyphal cell wall, resulting in its collapse and death of the mycelium.
3. Conclusion In our study, the first qualitative and quantitative analysis of R. chalepensis oils showed significant variations in the yield of essential oils among harvest periods: oil collected during April (flowering stage which is characterised by a high metabolic activity) showed the best yields whereas oil collected during December showed the least. Ruta oils displayed a high antifungal activity against plant pathogenic fungi and phytotoxic effects against weeds. Based on the present results, the essential oils could be suggested as alternative pesticides and herbicides. Indeed, our study supports the application of certain essential oils to control plant pathogens such as fungi and weeds. However, in spite of considerable data on the pesticidal properties of essential oils and their constituents, surprisingly few pest control products based on plant essential oils have appeared in the market place. Further studies are required to determine the cost, applicability, safety and phytotoxicity of these agents as potential herbicides and fungicides in integrated pest management strategy.
Supplementary material Experimental details relating to this paper are available online, alongside Tables S1 – S3.
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