Extraction and determination of antioxidant properties of essential oils of <i>Ocimum gratissimum</i> and <i>Thymus vulgaris</i> (lamiaceae) or (labiateae)

Leaves collected from two species of Thymus vulgaris and Ocimum gratissimum (Lamiaceae) from Cameroon gave by hydrodistillation method, essential oils yield between 1.3 and 1.6%. Identification of chemical composition by chromatography and chromatography coupled with mass spectrometry was done. It appeared that the majority of compounds of T. vulgaris detected were Thymol (39.2%), p- Cymene (25.36%), λ- Terpinene (16.2%), Lenalool (3.32%), α-Thujene (1, 7%) and Camphene (1.3%). For O. gratissimum, p-cymene (29.6%), λ- terpinene (21.9%), α-Thujene (6.2%), Thymol (5.1%), Myrcene (3.9%) and 1.8- Cineol (2.9%). p- Cymene, λ- terpinene, thymol and α- thujene were found in both species at significant levels. The antioxidant activities of essential oils of the leaves of these two species were highlighted with IC50 for the DPPH method which gave values of 146.33 µg/ml; 121.61 µg/ml and 69.99 µg/ml and for the FRAP method 342.33 µg/ml, 264.93µg/ml, 202.85 µg/ml respectively for O. gratissimum, T.vulgaris and Butyl hydroxy toluene (BHT). These results showed that the essential oils of the leaves of these two plants can be used in the preservation of food against oxidation. For concentration necessary to have a 50% trapping ability, a significant difference (p<0.05) in the increase in average trapping percentages (%IC) of the DPPH radical as a function of BHT concentrations was observed. It can be concluded that the essential oils of the leaves of Ocimum gratissimum and Thymus vulgaris could be used as antioxidants in food products and protect humans against certain chronic diseases.