Preliminary screening of antioxidant activity of some plant extracts in rapeseed oil

The antioxidant activity (AA) of acetone extracts of sage (Salvia officinalis L.), sweet grass (Hierocloe odorata Wahlnb.), sea buckthorn leaves (Hipophae rhamnoides L.), costmary (Balsamita major Desf., syn. Chrysanthemum balsamita L.), Roman camomile (Anthemis nobilis L.), and tansy (Tanacetum vulgare L.) were tested in refined, bleached and deodorised rapeseed oil at 40 degrees C. The concentrations of the extracts added were in the range from 0.02 to 0.20% (w/w). The rate of oxidation was assessed by the measurement of peroxide value (PV) and calculation of such characteristics as induction period (IP), when PV reaches 20 meq kg(-1), protection factor (PF), which is the ratio of IP of the sample viith additive with IP of the sample without additive, and AA (the ratio of IP increase of the sample with extract with the IP increase of the sample with butylated hydroxytoluene). Sage and sweet grass extracts were found to be most effective in stabilising rapeseed oil, followed by tansy, Roman camomile, costmary and sea buckthorn in a decreasing order. The IP of rapeseed oil increased with extract concentration. AA's of the extracts added at different concentrations were the following: sage, sweet grass (0.05, 0.1 and 0.2%) and tansy (0.2%) - very high, (PF > 3); tansy and Roman camomile (0.1%) - medium (PF = 2-2.5), tansy (0.05%), Roman camomile (0.02 and 0.05%) and sea buckthorn (0.1 and 0.2%) low (PF = 1.5-2.0), tansy (0.02%) - very low (PF = 1.0-1.5). The extracts of sea buckthorn (0.02 and 0.05%) slightly increased the formation of peroxides in rapeseed oil as compared with pure oil. (C) 2000 Elsevier Science Ltd. All rights reserved.