Essential oils of Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart from Tunisia: chemical composition and antioxidant activity.

BACKGROUND

Characterisation of the essential oils from O. glandulosum collected in three locations of Tunisia, chemical composition and the evaluation of their antioxidant activities were carried out.

RESULTS

The essential oils from Origanum vulgare L. subsp. glandulosum (Desf.) Ietswaart collected from three localities of north Tunisia-Krib, Bargou and Nefza-were obtained in yields of 2.5, 3.0 and 4.6% (v/w), respectively. The essential oils were analysed by GC and GC/MS and assayed for their total phenolics content, by the Folin-Ciocalteu method, and antioxidant effectiveness, using the 2,2-diphenyl-1-picrylhydrazil (DPPH) radical scavenging assay. The main components of these essential oils, from Nefza, Bargou and Krib, were p-cymene (36%, 40% and 46%), thymol (32%, 39% and 18%), gamma-terpinene (24%, 12% and 16%) and carvacrol (2%, 2% and 15%), respectively). The ability to scavenge the DPPH radicals, expressed by IC(50), ranged from 59 to 80 mg L(-1). The total phenolic content, expressed in gallic acid equivalent (GAE) g kg(-1) dry weight, varied from 9.37 to 17.70 g kg(-1) dw.

CONCLUSIONS

A correlation was identified between the total phenolic content of the essential oils and DPPH radical scavenger capacity. The occurrence of a p-cymene chemotype of O. glandulosum in the northern region of Tunisia is demonstrated.