Déterpénation de l'huile essentielle d'Origanum majorana L. et évaluation desd activités biologiques

Abstract

The purpose of this work is the study of the deterpenation of the Origanum Majorana essential oil, and the evaluation of the effect of this treatment on the biological efficiency of this volatile component. The aerial part of this plant was extracted in 135 min by hydrodistillation giving a yield of 1.7%. Deterpenation was achieved by distillation under reduced pressure (10 mmHg). Qualitative and quantitative analyses were performed by gas chromatography coupled to mass spectrometry (GC-MS) and by Fourier transform infrared (FT-IR). 99.93% of the total quantity of raw essential oil (REO) are identified, representing 38 compounds. Terpin-4-ol (27.32%), γ-terpinene (15.67%) and α-terpinene (11.08%) are the majority constituents. REO contains a complex mixture of oxygenated monoterpenes (47.36%), hydrocarbon monoterpenes (50.70%) and a small amount of hydrocarbon sesquiterpenes (4.94%). A qualitative and quantitative change in the chemical profile after fractionation by reduced pressure distillation was observed. The first fraction (F1) consists of 16 compounds, of which γ-terpinene (27.53%), α-terpinene (21.15%) and sabinene (11.17%) are the main constituents. The second fraction (F2) is characterized by 17 compounds consisting mainly of terpinene-4-ol (54.39%), cis-sabine hydrate (10.00%) and beta-fenchylic alcohol (9.63%). Finally, 22 compounds were identified in the third fraction (F3) such as: terpinen-4-ol (48.60%), cis-sabine hydrate (5.79%) and α-terpinolene (3.43%) are the main components. The increase in the quantity of oxygenated terpenes and the interesting decrease in the concentration of hydrocarbon terpenes in F2 and F3 make it possible to classify them as deterpened fractions of essential oils. The antioxidant activity was performed using the DPPH test. REO, F1, F2 and F3 have weak antioxidant effects. The total polyphenol assay results show that samples from REO, F1, F2 and F3 are low in polyphenols with values ranging from 4.72 to 8.22 µg EAG/mL EO. The antibacterial test reveals that marjoram essential oils are similarly active in the growth of Gram + bacteria (Staph 2), Gram - bacteria (AH2, E.coli, S.typhi, P.aeru, V.algi, V.angui) and yeast (C.albi). REO and F3 are classified as sensitive antibacterial agent with inhibition diameters of (11.7 to 15.0 mm) and (11.3 to 13.7 mm) respectively. F1 (8.0 to 10.0 mm) shows the lowest inhibitory power against the development of bacteria. F2 is the most active fraction with respect to all strains tested with diameters of the inhibition zones between 15.7 and 21 mm, it can be classified as a highly sensitive or extremely sensitive antibacterial substance. The study of antifungal activity against A. niger shows that REO (36.56%) and F1 (8.76%) have very low levels of inhibition of fungal growth compared to F2 (100%) and F3 (85.09%). The results of the antifungal activity obtained against R.oryzae, R.stolonifier and A. penicillioides corroborate those previously observed against A. niger except for REO which follows the following inhibition order: R.oryzae (85.84%) > R.stolonifier (53.40%) > A. penicillioides (29.95%).