Comparative antioxidant evaluation of the essential oils from chamomile's commercial samples

Aromatic plants such as Matricaria recutita L. (Syn. Chamomilla recutita L. Rauch) and Anthemis nobilis L. (Syn. Chamaemelum nobile L. All.) are popular medicinal agents used as anti-inflammatories, mild sedatives and anti-ulcer remedies [1]. Both species belong to the Asteraceae family and are known as German chamomile and Roman chamomile, respectively, and many times sold under the generic name chamomile, together with other related species.

In the present work, the essential oils, isolated from chamomile commercial samples (Matricaria recutita or mixture of Chamaemelum mixtum and C. fuscatum), were evaluated for prevention of lipid peroxidation, using the TBARS method, scavenging the hydroxyl radical and the stable radical 2,2-diphenyl-1-picryl-hydrazyl and for inhibition of 5-lipoxygenase. The percentage of antioxidant activity was calculated using methanol as negative control. α-Tocopherol was used as positive control, for TBARS and DPPH, manitol for scavenging the hydroxyl radical method and nordihydroguaiaretic acid (NDGA) for inhibitory activity of 5-lipoxygenase. The chemical composition of these oils was analysed by GC and GC/MS.

Apart from the difference in oil colour obtained from the M. recutita sample (blue) and mixture of Chamaemelum mixtum and C. fuscatum (yellow), these oils showed also marked differences in their composition. The main component of Chamaemelum mixture oils was a yet unidentified component whereas α-bisabolol oxide dominated M. recutita oils.

These oils possess a low ability from preventing lipid peroxidation. The maximum percentage found for Matricaria and the Chamaemelum oils was 49 % at 50 mg/L and 20 % at 250 mg/L, respectively. At higher concentrations these oils seemed to possess a pro-oxidant activity.

The IC₅₀ found, with the DPPH method, for M. recutita oil was 950 mg/L, while for the Chamaemelum mixture the parameter was not determined because the highest percentage was only 2 % at the maximum concentration tested (1500 mg/L).

The oils' best ability to scavenge OH radicals was 51 %, at 50 mg/L, for M. recutita oil and 60 %, at 25 mg/L, for the Chamaemelum mixture oil.

Considering the concentration tested (500 mg/L), the inhibitory activity of 5-lipoxygenase of M. recutita oil (42 %) was significantly better than that of the Chamaemelum mixture (19 %).

Acknowledgements: This study was partially funded by IFADAP under research contract AGRO 800.

References: [1] Wang, Y. et al. (2005) J. Agric. Food Chem. 53: 191–196. [2] Ma, C.M. et al. (2007) Phytochem. Anal. 18: 42–49.