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Natural Product Research: Formerly Natural Product Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gnpl20
Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity a
a
a
Xiong Liu , Dongliang Yang , Jiajia Liu & Na Ren
a
a
Click for updates
Department of Pharmaceutical Engineering, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Hunan, P.R. China Published online: 17 Feb 2015.
To cite this article: Xiong Liu, Dongliang Yang, Jiajia Liu & Na Ren (2015): Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity, Natural Product Research: Formerly Natural Product Letters, DOI: 10.1080/14786419.2015.1012716 To link to this article: http://dx.doi.org/10.1080/14786419.2015.1012716
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. 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 &
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Natural Product Research, 2015 http://dx.doi.org/10.1080/14786419.2015.1012716
SHORT COMMUNICATION Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
Xiong Liu, Dongliang Yang, Jiajia Liu* and Na Ren Department of Pharmaceutical Engineering, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Hunan, P.R. China (Received 25 November 2014; final version received 25 January 2015)
I
II
Antioxidant activity III
(IC50=25 mg/mL)
IV
V
Voacanga seeds VI
Antimicrobial activity (oils exhibited different antimicrobial activities)
VII
Essential oils
In this study, essential oils from Voacanga africana seeds at different extraction stages were investigated. In the chemical composition analysis, 27 compounds representing 86.69– 95.03% of the total essential oils were identified and quantified. The main constituents in essential oils were terpenoids, alcohols and fatty acids accounting for 15.03– 24.36%, 21.57 – 34.43% and 33.06– 57.37%, respectively. Moreover, the analysis also revealed that essential oils from different extraction stages possessed different chemical compositions. In the antioxidant evaluation, all analysed oils showed similar antioxidant behaviours, and the concentrations of essential oils providing 50% inhibition of DPPH-scavenging activity (IC50) were about 25 mg/mL. In the antimicrobial experiments, essential oils from different extraction stages exhibited different antimicrobial activities. The antimicrobial activity of oils was affected by extraction stages. By controlling extraction stages, it is promising to obtain essential oils with desired antimicrobial activities. Keywords: Voacanga africana seeds; essential oils; chemical composition; antioxidant activity; antimicrobial activity
1. Introduction Voacanga africana (Voacanga chalotiana Pierre ex Stapf) is an evergreen tree, belonging to the family Apocynaceae. It is mainly distributed in rainforests at the West Africa. Its seeds are traditionally used against leprosy, diarrhoea, generalised oedema, convulsions in children, mental disorders and diuretic (Marnewick 2009). In 2011, Su et al. investigated the chemical constituents of essential oil from V. africana seeds (Su et al. 2011). The results revealed that the main component of the oils was fatty acids. However, to date, studies about the antioxidant
*Corresponding author. Email: [email protected] q 2015 Taylor & Francis
2
X. Liu et al.
activity and antimicrobial activity of this essential oil have rarely been carried out. Hydrodistillation is one of the widely used methods to obtain essential oils (Avci et al. 2014). Zheljazkov et al. (2013) have found that the distillation time was a crucial determinant of yield and composition of essential oils. Essential oils obtained from different extraction stages may possess different chemical compositions and biological activities. Based on this hypothesis, the aim of this study was to investigate the influence of hydrodistillation stages on the chemical composition and biological activity of essential oils from Voacanga seeds.
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
2. Results and discussion In our experiments, essential oils extracted between 0 –60, 60– 120, 120 – 180, 180 –240, 240– 300 and 300 – 360 min were named as I, II, III, IV, V and VI, respectively. As a control, the total essential oil extracted between 0 and 360 min was also investigated and was named as VII. 2.1. Yields of essential oils from different extraction stages The seeds produced light yellow oils with irritating smell. The mean values of yields for oils I, II, III, IV, V, VI and VII were 0.181‰, 0.126‰, 0.115‰, 0.131‰, 0.055‰, 0.023‰ and 0.512‰, respectively. It can be seen that the yields of oils decreased remarkably after stage IV. This result revealed that most of oils were extracted in stages I– IV. The sum yield of oils I, II, III, IV, V and VI was 0.631‰, which was much higher than the yield of total oils VII (0.512‰). 2.2. GC –MS analysis The chemical compositions of the essential oils were analysed by GC –MS and the results are shown in Table S1. In total, 27 compounds representing 86.69 – 95.03% of the total essential oils were identified and quantified. The dominant compounds identified and quantified were terpenoids, alcohols and fatty acids, accounting for 15.03 –24.36%, 21.57 – 34.43% and 33.06 – 57.37%, respectively. The contents of terpenoids in essential oils followed an order of V . VI . VII . II . III . I . IV. Essential oil V contained the highest content of terpenoids (24.36%), while oil IV contained the lowest (15.03%). The major terpenoids of oils were (2 )-belemene (0.9 –1.47%), a-cedrene (7.01 –12.11%), b-cedrene (2.02 –3.41%) and thujopsene (0.64 – 1.15%). The contents of alcohols in essential oils had the following order: I . II . VI . III . V . VII . IV. The highest content of alcohols (34.43%) was found in oil I, while the lowest content of alcohols (21.57%) was found in oil IV. The major alcohols identified and quantified were ethylhexanol (tr-7.5%), a-terpineol (tr-2.11%), 8b-H-cedran-8-ol (19.91 – 30.3%) and cedrol (tr-0.33%). The contents of fatty acids followed an order of IV . III . II . I . VII . V . VI. Essential oil IV contained the highest content of fatty acids (57.37%), while oil VI contained the lowest (33.06%). The major fatty acids of oils were nhexadecanoic acid (22.05 – 35.51%), 9,12-octadecadienoic acid (Z,Z)-(1.34 – 3.74%), 9octadecenoic acid, (E)-(8.03 –12.26%) and octadecanoic acid (1.10 – 1.98%). Besides these dominant compounds, some other constituents such as 3-ethylpyridine (0 – 1.46%), 1,3diethylbenzene (0 – 0.67%) and naphthalene (tr-2.92%) were also identified and quantified. Overall, essential oils obtained from stages I, II, III, IV, V, VI and VII possessed different chemical compositions and contents. For instance, oil IV contained the lowest content of terpenoids and alcohols, as well as the highest content of fatty acids. From Table S1, it can also be seen that some components detected in the early extraction stages, such as a-pinene and 3ethylpyridin, disappeared in total oil VII. This is probably because these compounds escaped from the oil collector during the long extraction process (0 – 360 min). This phenomenon could help explain the result that the sum yield of oils I– VI was much higher than the yield of oil VII.
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
Natural Product Research
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3.3. Antioxidant capacity As shown in Table S2, the IC50 values of essential oils approximately followed an order of V . VI . VII . II . III . I . IV. Essential oils V and VI showed slightly higher antioxidant activities. In the chemical composition analysis, the results revealed that oils V and VI contained higher content of terpenoids, which have been reported to be responsible for antioxidant activities (Mohamed et al. 2014). The higher content of terpenoids was a possible reason responsible for the higher antioxidant activities of oils V and VI. The statistical analysis indicated that the antioxidant activities between oils I, II, III, IV, VI and VII, between oils II, V, VI and VII showed no significant difference ( p . 0.05). This result suggested that there are probably similar amounts and/or combinations of antioxidants extracted in these stages (Gawde et al. 2014). In general, oils from different extraction stages showed similar antioxidant behaviours. The IC50 values of essential oils were about 25 mg/mL, which were much higher than that of the control standard ascorbic acid (IC50 ¼ 14 mg/mL). All oils showed low antioxidant activities. 3.4. Antimicrobial assay The MIC values of essential oils for Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Proteus vulgaris, Pseudomonas aeruginosa, Escherichia coli and Candida albicans were investigated and the results are shown in Table S3. Oils I, II and III showed identical activity against B. subtilis and MIC for all oils being 128 mg/mL. Besides, oil IV also showed considerable activity with an MIC of 256 mg/mL. All analysed oils showed considerable activity against P. vulgaris with the max MIC of 256 mg/mL. Among them, oil III was the most active with MIC at 64 mg/mL. For P. aeruginosa, oils IV, V and VII showed considerable activity with MICs of 128, 64 and 256 mg/mL, respectively. For S. aureus, all oils exhibited considerable activity except oils I and V. Among them, oil III was the most active oil with MIC at 64 mg/mL. All analysed oils showed considerable activity against S. epidermidis with the minimum MIC for oil IV was 64 mg/mL. Oils I and II exhibited activity against E. coli with MICs of 256 and 512 mg/mL, respectively. Other oils exhibited low activity against E. coli with MIC . 1024 mg/ mL. For C. albicans, oil II was the only oil with MIC . 1024 mg/mL and oil VII was the most active oil with MIC of 64 mg/mL. The Mueller– Hinton broths introduced with Tween 80 (5%) showed no toxicity towards the microorganisms. The oils were much less effective than the antibiotic or antimycotic used as reference standards against all microorganisms tested. In summary, oils extracted in the early stages showed good activity against B. subtilis and E. coli. According to the results discussed in Section 2.2, some components, such as a-pinene and 3-ethylpyridin, were only present in oils extracted in the early stages. These minor constituents in oils might play a critical role in antimicrobial activity, possibly by producing a synergistic effect with other constituents. These components may be a factor resulting in B. subtilis and E. coli being most sensitive to oils extracted in the early stages. All oils showed considerable activity against P. vulgaris and S. epidermidis. This result indicated that the activity of oils against them was not significantly affected by extraction stages. For P. aeruginosa and S. aureus, the antimicrobial activity of oils was affected by extraction stages. The most active oils were obtained in the middle extraction stages. For C. albicans, oil II was the only oil showing low antimicrobial activity with MIC . 1024 mg/mL. Based on the results discussed earlier, it can be concluded that the antimicrobial activity of oils could be affected by extraction stages. It is promising to obtain essential oils with desired antimicrobial activities by controlling extraction stages. Many researchers have reported that essential oils rich in terpenoids showed good antimicrobial activity (Nissen et al. 2010; Da Silva et al. 2014). In our experiments, the contents of terpenoids in oils ranged from 15.03% to 24.36%. The different contents of terpenoids may be
4
X. Liu et al.
a factor resulting in the different antimicrobial activities. In addition, the different chemical compositions and contents of alcohols and fatty acids is probably another important factor affecting the antimicrobial behaviour of oils. Some minor constituents in oils might also play a critical role in antimicrobial activity, possibly by producing a synergistic effect with other constituents (Liu et al. 2009). At present, the mode of action of oils from Voacanga seeds on microorganisms is not fully understood. Further studies are needed for more extensive interpretation of these differences.
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
3. Conclusion In summary, the influence of hydrodistillation stages on the chemical composition and biological activity of essential oils from V. africana seeds was investigated. The essential oils obtained from different extraction stages showed similar antioxidant behaviours and different antimicrobial activities. The results of our studies suggested that it is promising to obtain essential oils with desired antimicrobial activities by controlling extraction stages. Supplementary material Experimental details relating to this paper are available online, alongside Tables S1 – S3. References ¨ zc elik H. 2014. Essential oil composition of Cymbocarpum erythraeum (DC.) Boiss. from Avci AB, Korkmaz M, O Turkey. Nat Prod Res. 28:636–640. doi:10.1080/14786419.2014.891116. Da Silva JKR, Pinto LC, Burbano RMR, Montenegro RC, Guimara˜es EF, Andrade EHA, Maia JGS. 2014. Essential oils of Amazon Piper species and their cytotoxic, antifungal, antioxidant and anti-cholinesterase activities. Ind Crop Prod. 58:55–60. doi:10.1016/j.indcrop.2014.04.006. Gawde A, Cantrell CL, Zheljazkov VD, Astatkie T, Schlegel V. 2014. Steam distillation extraction kinetics regression models to predict essential oil yield, composition, and bioactivity of chamomile oil. Ind Crop Prod. 58:61–67. doi:10.1016/j.indcrop.2014.04.001. Liu JJ, Yang DL, Zhang Y, Yuan Y, Cao FX, Zhao JM, Peng XB. 2009. Chemical component and antimicrobial activity of volatile oil of Calycopteris floribunda. J Cent South Univ Technol. 16:931–935. doi:10.1007/s11771-0090155-7. Marnewick JL. 2009. African natural plant products: new discoveries and challenges in chemistry and quality. ACS symposium series. Chapter 20, Voacanga africana: chemistry, quality and pharmacological activity. Washington, DC: American Chemical Society; p. 363–380. Mohamed AA, Ali SI, El-Baz FK, Hegazy AK, Kord MA. 2014. Chemical composition of essential oil and in vitro antioxidant and antimicrobial activities of crude extracts of Commiphora myrrha resin. Ind Crop Prod. 57:10–16. doi:10.1016/j.indcrop.2014.03.017. Nissen L, Zatta A, Stefanini I, Grandi S, Sgorbati B, Biavati B, Monti A. 2010. Characterization and antimicrobial activity of essential oils of industrial hemp varieties (Cannabis sativa L.). Fitoterapia. 81:413– 419. doi:10.1016/j. fitote.2009.11.010. Su Y, Chen X, Bai K, Liu H, Li H. 2011. GC-MS study on chemical constituents of essential oil from seeds of Voacanga africana Stapf. Chin J Pharm Anal. 31:496–498. Zheljazkov VD, Astatkie T, Jeliazkova EA, Tatman AO, Schlegel V. 2013. Distillation time alters essential oil yield, composition and antioxidant activity of female Juniperus scopulorum trees. J Essent Oil Res. 25:62–69. doi:10. 1080/10412905.2012.744704.
Natural Product Research: Formerly Natural Product Letters Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gnpl20
Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity a
a
a
Xiong Liu , Dongliang Yang , Jiajia Liu & Na Ren
a
a
Click for updates
Department of Pharmaceutical Engineering, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Hunan, P.R. China Published online: 17 Feb 2015.
To cite this article: Xiong Liu, Dongliang Yang, Jiajia Liu & Na Ren (2015): Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity, Natural Product Research: Formerly Natural Product Letters, DOI: 10.1080/14786419.2015.1012716 To link to this article: http://dx.doi.org/10.1080/14786419.2015.1012716
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. 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 &
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Natural Product Research, 2015 http://dx.doi.org/10.1080/14786419.2015.1012716
SHORT COMMUNICATION Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition, antioxidant activity and antimicrobial activity
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
Xiong Liu, Dongliang Yang, Jiajia Liu* and Na Ren Department of Pharmaceutical Engineering, College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Hunan, P.R. China (Received 25 November 2014; final version received 25 January 2015)
I
II
Antioxidant activity III
(IC50=25 mg/mL)
IV
V
Voacanga seeds VI
Antimicrobial activity (oils exhibited different antimicrobial activities)
VII
Essential oils
In this study, essential oils from Voacanga africana seeds at different extraction stages were investigated. In the chemical composition analysis, 27 compounds representing 86.69– 95.03% of the total essential oils were identified and quantified. The main constituents in essential oils were terpenoids, alcohols and fatty acids accounting for 15.03– 24.36%, 21.57 – 34.43% and 33.06– 57.37%, respectively. Moreover, the analysis also revealed that essential oils from different extraction stages possessed different chemical compositions. In the antioxidant evaluation, all analysed oils showed similar antioxidant behaviours, and the concentrations of essential oils providing 50% inhibition of DPPH-scavenging activity (IC50) were about 25 mg/mL. In the antimicrobial experiments, essential oils from different extraction stages exhibited different antimicrobial activities. The antimicrobial activity of oils was affected by extraction stages. By controlling extraction stages, it is promising to obtain essential oils with desired antimicrobial activities. Keywords: Voacanga africana seeds; essential oils; chemical composition; antioxidant activity; antimicrobial activity
1. Introduction Voacanga africana (Voacanga chalotiana Pierre ex Stapf) is an evergreen tree, belonging to the family Apocynaceae. It is mainly distributed in rainforests at the West Africa. Its seeds are traditionally used against leprosy, diarrhoea, generalised oedema, convulsions in children, mental disorders and diuretic (Marnewick 2009). In 2011, Su et al. investigated the chemical constituents of essential oil from V. africana seeds (Su et al. 2011). The results revealed that the main component of the oils was fatty acids. However, to date, studies about the antioxidant
*Corresponding author. Email: [email protected] q 2015 Taylor & Francis
2
X. Liu et al.
activity and antimicrobial activity of this essential oil have rarely been carried out. Hydrodistillation is one of the widely used methods to obtain essential oils (Avci et al. 2014). Zheljazkov et al. (2013) have found that the distillation time was a crucial determinant of yield and composition of essential oils. Essential oils obtained from different extraction stages may possess different chemical compositions and biological activities. Based on this hypothesis, the aim of this study was to investigate the influence of hydrodistillation stages on the chemical composition and biological activity of essential oils from Voacanga seeds.
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
2. Results and discussion In our experiments, essential oils extracted between 0 –60, 60– 120, 120 – 180, 180 –240, 240– 300 and 300 – 360 min were named as I, II, III, IV, V and VI, respectively. As a control, the total essential oil extracted between 0 and 360 min was also investigated and was named as VII. 2.1. Yields of essential oils from different extraction stages The seeds produced light yellow oils with irritating smell. The mean values of yields for oils I, II, III, IV, V, VI and VII were 0.181‰, 0.126‰, 0.115‰, 0.131‰, 0.055‰, 0.023‰ and 0.512‰, respectively. It can be seen that the yields of oils decreased remarkably after stage IV. This result revealed that most of oils were extracted in stages I– IV. The sum yield of oils I, II, III, IV, V and VI was 0.631‰, which was much higher than the yield of total oils VII (0.512‰). 2.2. GC –MS analysis The chemical compositions of the essential oils were analysed by GC –MS and the results are shown in Table S1. In total, 27 compounds representing 86.69 – 95.03% of the total essential oils were identified and quantified. The dominant compounds identified and quantified were terpenoids, alcohols and fatty acids, accounting for 15.03 –24.36%, 21.57 – 34.43% and 33.06 – 57.37%, respectively. The contents of terpenoids in essential oils followed an order of V . VI . VII . II . III . I . IV. Essential oil V contained the highest content of terpenoids (24.36%), while oil IV contained the lowest (15.03%). The major terpenoids of oils were (2 )-belemene (0.9 –1.47%), a-cedrene (7.01 –12.11%), b-cedrene (2.02 –3.41%) and thujopsene (0.64 – 1.15%). The contents of alcohols in essential oils had the following order: I . II . VI . III . V . VII . IV. The highest content of alcohols (34.43%) was found in oil I, while the lowest content of alcohols (21.57%) was found in oil IV. The major alcohols identified and quantified were ethylhexanol (tr-7.5%), a-terpineol (tr-2.11%), 8b-H-cedran-8-ol (19.91 – 30.3%) and cedrol (tr-0.33%). The contents of fatty acids followed an order of IV . III . II . I . VII . V . VI. Essential oil IV contained the highest content of fatty acids (57.37%), while oil VI contained the lowest (33.06%). The major fatty acids of oils were nhexadecanoic acid (22.05 – 35.51%), 9,12-octadecadienoic acid (Z,Z)-(1.34 – 3.74%), 9octadecenoic acid, (E)-(8.03 –12.26%) and octadecanoic acid (1.10 – 1.98%). Besides these dominant compounds, some other constituents such as 3-ethylpyridine (0 – 1.46%), 1,3diethylbenzene (0 – 0.67%) and naphthalene (tr-2.92%) were also identified and quantified. Overall, essential oils obtained from stages I, II, III, IV, V, VI and VII possessed different chemical compositions and contents. For instance, oil IV contained the lowest content of terpenoids and alcohols, as well as the highest content of fatty acids. From Table S1, it can also be seen that some components detected in the early extraction stages, such as a-pinene and 3ethylpyridin, disappeared in total oil VII. This is probably because these compounds escaped from the oil collector during the long extraction process (0 – 360 min). This phenomenon could help explain the result that the sum yield of oils I– VI was much higher than the yield of oil VII.
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
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3.3. Antioxidant capacity As shown in Table S2, the IC50 values of essential oils approximately followed an order of V . VI . VII . II . III . I . IV. Essential oils V and VI showed slightly higher antioxidant activities. In the chemical composition analysis, the results revealed that oils V and VI contained higher content of terpenoids, which have been reported to be responsible for antioxidant activities (Mohamed et al. 2014). The higher content of terpenoids was a possible reason responsible for the higher antioxidant activities of oils V and VI. The statistical analysis indicated that the antioxidant activities between oils I, II, III, IV, VI and VII, between oils II, V, VI and VII showed no significant difference ( p . 0.05). This result suggested that there are probably similar amounts and/or combinations of antioxidants extracted in these stages (Gawde et al. 2014). In general, oils from different extraction stages showed similar antioxidant behaviours. The IC50 values of essential oils were about 25 mg/mL, which were much higher than that of the control standard ascorbic acid (IC50 ¼ 14 mg/mL). All oils showed low antioxidant activities. 3.4. Antimicrobial assay The MIC values of essential oils for Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Proteus vulgaris, Pseudomonas aeruginosa, Escherichia coli and Candida albicans were investigated and the results are shown in Table S3. Oils I, II and III showed identical activity against B. subtilis and MIC for all oils being 128 mg/mL. Besides, oil IV also showed considerable activity with an MIC of 256 mg/mL. All analysed oils showed considerable activity against P. vulgaris with the max MIC of 256 mg/mL. Among them, oil III was the most active with MIC at 64 mg/mL. For P. aeruginosa, oils IV, V and VII showed considerable activity with MICs of 128, 64 and 256 mg/mL, respectively. For S. aureus, all oils exhibited considerable activity except oils I and V. Among them, oil III was the most active oil with MIC at 64 mg/mL. All analysed oils showed considerable activity against S. epidermidis with the minimum MIC for oil IV was 64 mg/mL. Oils I and II exhibited activity against E. coli with MICs of 256 and 512 mg/mL, respectively. Other oils exhibited low activity against E. coli with MIC . 1024 mg/ mL. For C. albicans, oil II was the only oil with MIC . 1024 mg/mL and oil VII was the most active oil with MIC of 64 mg/mL. The Mueller– Hinton broths introduced with Tween 80 (5%) showed no toxicity towards the microorganisms. The oils were much less effective than the antibiotic or antimycotic used as reference standards against all microorganisms tested. In summary, oils extracted in the early stages showed good activity against B. subtilis and E. coli. According to the results discussed in Section 2.2, some components, such as a-pinene and 3-ethylpyridin, were only present in oils extracted in the early stages. These minor constituents in oils might play a critical role in antimicrobial activity, possibly by producing a synergistic effect with other constituents. These components may be a factor resulting in B. subtilis and E. coli being most sensitive to oils extracted in the early stages. All oils showed considerable activity against P. vulgaris and S. epidermidis. This result indicated that the activity of oils against them was not significantly affected by extraction stages. For P. aeruginosa and S. aureus, the antimicrobial activity of oils was affected by extraction stages. The most active oils were obtained in the middle extraction stages. For C. albicans, oil II was the only oil showing low antimicrobial activity with MIC . 1024 mg/mL. Based on the results discussed earlier, it can be concluded that the antimicrobial activity of oils could be affected by extraction stages. It is promising to obtain essential oils with desired antimicrobial activities by controlling extraction stages. Many researchers have reported that essential oils rich in terpenoids showed good antimicrobial activity (Nissen et al. 2010; Da Silva et al. 2014). In our experiments, the contents of terpenoids in oils ranged from 15.03% to 24.36%. The different contents of terpenoids may be
4
X. Liu et al.
a factor resulting in the different antimicrobial activities. In addition, the different chemical compositions and contents of alcohols and fatty acids is probably another important factor affecting the antimicrobial behaviour of oils. Some minor constituents in oils might also play a critical role in antimicrobial activity, possibly by producing a synergistic effect with other constituents (Liu et al. 2009). At present, the mode of action of oils from Voacanga seeds on microorganisms is not fully understood. Further studies are needed for more extensive interpretation of these differences.
Downloaded by [University of Nebraska, Lincoln] at 22:35 11 April 2015
3. Conclusion In summary, the influence of hydrodistillation stages on the chemical composition and biological activity of essential oils from V. africana seeds was investigated. The essential oils obtained from different extraction stages showed similar antioxidant behaviours and different antimicrobial activities. The results of our studies suggested that it is promising to obtain essential oils with desired antimicrobial activities by controlling extraction stages. Supplementary material Experimental details relating to this paper are available online, alongside Tables S1 – S3. References ¨ zc elik H. 2014. Essential oil composition of Cymbocarpum erythraeum (DC.) Boiss. from Avci AB, Korkmaz M, O Turkey. Nat Prod Res. 28:636–640. doi:10.1080/14786419.2014.891116. Da Silva JKR, Pinto LC, Burbano RMR, Montenegro RC, Guimara˜es EF, Andrade EHA, Maia JGS. 2014. Essential oils of Amazon Piper species and their cytotoxic, antifungal, antioxidant and anti-cholinesterase activities. Ind Crop Prod. 58:55–60. doi:10.1016/j.indcrop.2014.04.006. Gawde A, Cantrell CL, Zheljazkov VD, Astatkie T, Schlegel V. 2014. Steam distillation extraction kinetics regression models to predict essential oil yield, composition, and bioactivity of chamomile oil. Ind Crop Prod. 58:61–67. doi:10.1016/j.indcrop.2014.04.001. Liu JJ, Yang DL, Zhang Y, Yuan Y, Cao FX, Zhao JM, Peng XB. 2009. Chemical component and antimicrobial activity of volatile oil of Calycopteris floribunda. J Cent South Univ Technol. 16:931–935. doi:10.1007/s11771-0090155-7. Marnewick JL. 2009. African natural plant products: new discoveries and challenges in chemistry and quality. ACS symposium series. Chapter 20, Voacanga africana: chemistry, quality and pharmacological activity. Washington, DC: American Chemical Society; p. 363–380. Mohamed AA, Ali SI, El-Baz FK, Hegazy AK, Kord MA. 2014. Chemical composition of essential oil and in vitro antioxidant and antimicrobial activities of crude extracts of Commiphora myrrha resin. Ind Crop Prod. 57:10–16. doi:10.1016/j.indcrop.2014.03.017. Nissen L, Zatta A, Stefanini I, Grandi S, Sgorbati B, Biavati B, Monti A. 2010. Characterization and antimicrobial activity of essential oils of industrial hemp varieties (Cannabis sativa L.). Fitoterapia. 81:413– 419. doi:10.1016/j. fitote.2009.11.010. Su Y, Chen X, Bai K, Liu H, Li H. 2011. GC-MS study on chemical constituents of essential oil from seeds of Voacanga africana Stapf. Chin J Pharm Anal. 31:496–498. Zheljazkov VD, Astatkie T, Jeliazkova EA, Tatman AO, Schlegel V. 2013. Distillation time alters essential oil yield, composition and antioxidant activity of female Juniperus scopulorum trees. J Essent Oil Res. 25:62–69. doi:10. 1080/10412905.2012.744704.
