Synergistic antioxidant activities of essential oils and methanolic extracts of Bunium alpinum and Bunium incrassatum from Algeria
Interest in natural substances such as essential oils and plant extracts is growing more and more. The therapeutic efficacy of plant extracts has been proven. However, this efficiency can be improved by combining several extracts at the same time, as is already applied in multidrug therapy. Today, combinations of plant extracts represent a potential new strategy for developing new antioxidant therapies that will increase their effectiveness, taking advantage of their synergistic effects. The objective of this work was to evaluate the antioxidant activity of EOs and MEs individually from two Apiaceae; Bunium alpinum (BA) and B. incrassatum (BI) as well as the effects of EOs and EMs in combination. The EOs were obtained by hydrodistillation using a Clevenger apparatus, whereas the MEs were prepared by hydro-alcoholic maceration (methanol/water: 1/10 v/v). The antioxidant activity was carried out by two methods: the power reduction test which consists in measuring the reduction of Fe3+ to Fe2+ in the presence of the extracts, which increases the absorbance in the reaction medium at 700 nm. The activity of the combinations was carried out by the DPPH test, this radical placed in the medium with the extracts absorbed at 517 nm, the antioxidant activity can be, then, determined by recording the decrease in the absorbance of the extracts and is compared with the standards (BHT, BHA, tocopherol, quecitin and rutin).Both EOs showed a perfectly dose-dependent ability to reduce Fe3+ by electron transfer reaction with a superiority of MEs. The essential oils of BA and BI were very active by the DPPH test either alone (IC50=0.69 and 0.57μg/ml respectively) or in combination (1.80 μg/ml). While the extracts had lower activities (BA: IC50=21.85±1.32 and BI: 55.77±3.25 μg/ml). Only the combination of essential oils gave a synergistic effect. Based on the results of this study, it is concluded that EOs and MEs of B. alpinum and B. incrassatum exhibit interesting antioxidant activity by both methods. These two extracts can be used as an easily accessible source of natural antioxidants or as a possible food supplement after a study of toxicity and cyto-toxicity of the extracts. Other antioxidant techniques and other types of extracts of these species, abundant in Algeria, can be realized later.