Effect of the simultaneous extraction of rosemary and spinach leaves on the antioxidant activity of the extracts

Abstract

Several spices and some herbs have received increased attention as sources of effective natural antioxidants. Particularly, rosemary (Rosmarinus officinalis L.) is a Lamiaceae plant with high content of phenolic antioxidant substances, and spinach (Spinacia oleracea L.) is a natural source of carotenoids (lutein and β-carotene) which were also recognized to possess antioxidant activity. In this work the simultaneous extraction of leaves of a rosemary/spinach mixture (50 weight % of each plant) was investigated and compared with the extraction of the separate species. Three different extraction techniques were applied: (i) solid-liquid extraction at ambient pressure and using ethanol or hexane at 50ºC, (ii) accelerated solvent extraction (ASE) with the same liquid solvents but at higher temperatures (100 and 150ºC) and pressure (100 bar); and (iii) supercritical fluid extraction (SFE) with pure CO2 at 40ºC and different pressures (200 and 300 bar). All extracts obtained were studied in terms of the presence of antioxidant substances. Carotenoids and phenolic compounds were identified and quantified by HPLC analysis. Despite the extraction procedure and conditions applied, the results obtained show a linear behavior in terms of extraction yield and composition of key antioxidant compounds. The antioxidant activity of all samples was determined by the DPPH test and the effect of the simultaneous extraction (the mixed spinach/rosemary plant matrix) on the antioxidant activity of the extracts was analyzed and discussed.