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Characterization and antioxidant activity of the volatile oils of Thymus Syriacus Boiss. var syriacus and Thymbra spicata L. grown wild in Kurdistan-Iraq

Published online by Cambridge University Press:  17 March 2010

D. M. Jamil ,
J. E. Brown ,
D. Driscoll  and
N. K. Howell
D. M. Jamil
Affiliation:
Division of Nutritional Sciences, University of Surrey, Guildford GU2 7XH, Surrey, UK
J. E. Brown
Affiliation:
Division of Nutritional Sciences, University of Surrey, Guildford GU2 7XH, Surrey, UK
D. Driscoll
Affiliation:
Division of Chemical Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, Surrey, UK
N. K. Howell
Affiliation:
Division of Nutritional Sciences, University of Surrey, Guildford GU2 7XH, Surrey, UK
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Abstract

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Proceedings of the Nutrition Society , Volume 69 , Issue OCE1: Over- and undernutrition: challenges and approaches. 29 June–2 July 2009 , 2010 , E104
Copyright
Copyright © The Authors 2009

Herbs and their essential oils are known for their antimicrobial and antioxidant properties in biological systems(Reference Yanishlivea, Marinova and Pokorny1,Reference Lee, Umano and Shibamoto2). Thyme (Thymus syriacus Boiss. var syriacus) and thymbra (Thymbra spicata L.) grow wild in Kurdistan-Iraq and because of their abundance in the region and use in foods their volatile oils (VO) were extracted by hydro-distillation(Reference Hanci, Sahin and Ylmaz3), chemically characterised (by GC and GC–MS) and evaluated for their antioxidant activities (using the Cu2+-mediated LDL oxidation method(Reference Esterbauer, Gebicki and Puhl4,Reference Brown and Kelly5)). The kinetics of LDL oxidation was monitored by the change in absorbance of conjugated dienes (234 nm) over time (14 h) at 30°C. The antioxidant efficacy of the VO of each herb and their major and minor terpen(oid)s were measured by their ability to extend the lag phase of oxidation v. control(Reference Esterbauer, Gebicki and Puhl4,Reference Brown and Kelly5).

The VO yield of thymbra and thyme was significantly higher (4.15 (sd 0.15) % and 3.75 (sd 0.10) %) in samples grown at higher altitudes (1100 m and 900 m) compared with those grown at lower altitudes (670 m and 400 m; (2.72 (sd 0.08) % and 2.52 (sd 0.12) % respectively; P<0.05). The principal components identified in the VO of thyme and thymbra are shown in Table 1. Clear differences were observed for their terpen(oid) content, with the main difference observed in the content of thymol and carvacrol, although the level of γ-terpinene was also much higher in thymbra. Altitude had little effect on VO composition.

Table 1. Major terpen(oid) identified in thyme and thymbra (n 6)

The VO of thyme and thymbra showed clear antioxidant activity by extending lag phase by 43 and 49% respectively at 1 μm (Table 2). Pure samples of thymol and carvacrol were shown to be more effective than thyme and thymbra VO by an order of >10-fold. The other pure standards tested however were less efficacious. The effectiveness of the compounds tested as antioxidants in this system were thymol>carvacrol>γ-terpinene>α-terpinene>borneol>β-caryophyllene. Interestingly, α-pinene, myrcene and p-cymene were found to be pro-oxidant at the concentrations tested.

Table 2. Effects of thyme and thymbra VO and synthetic terpenoids on extending lag phase to oxidation of copper-mediated LDL oxidation (% increase compared with control oxidation; control lag phase 151 (sd 12) min)

*Means for two determinations.

These findings may have important implications for the more general use of these herbs in foods.

References

1. Yanishlivea, NV, Marinova, E & Pokorny, J (2006) Eur J Lipid Sci Technol 108, 776–793.CrossRefGoogle Scholar
2. Lee, SJ, Umano, K, Shibamoto, T et al. (2005) Food Chem. 91, 131–137.CrossRefGoogle Scholar
3. Hanci, S, Sahin, S & Ylmaz, L (2003) Nahrung 47, 252–255.CrossRefGoogle Scholar
4. Esterbauer, H, Gebicki, J, Puhl, H et al. (1992) Free Radic Biol Med 13, 341–390.CrossRefGoogle Scholar
5. Brown, JE & Kelly, MF (2007) Eur J Lipid Sci Technol 109, 66–71.CrossRefGoogle Scholar
Figure 0

Table 1. Major terpen(oid) identified in thyme and thymbra (n 6)

Figure 1

Table 2. Effects of thyme and thymbra VO and synthetic terpenoids on extending lag phase to oxidation of copper-mediated LDL oxidation (% increase compared with control oxidation; control lag phase 151 (sd 12) min)