Study on the antioxidant activity of extracts from native Salvia species from Iran

This research was carried out in order to identify and introduce potential sources of natural antioxidants in native species of Salvia from Labiatae family. Sixteen native species of Salvia, at the stage of flowering, grown in different parts of Iran, were collected, identified, dried and the ground leaves were used for the experiments. Moisture contents of the samples were determined at 100 °C. Extraction was carried out using a polar (ethanol) and a nonpolar (hexane) solvent, separately. The yield of the herbs were determined after evaporating solvents. Antioxidant activities of ethanolic and hexanic extracts of different species were evaluated in RBD soybean oil containing no added antioxidant. In the oven test, soybean oil samples containing 0.1% and 0.2% of the herb extracts were placed in the oven at 60 °C and the progress in oxidation of the oil was examined by determination of peroxide value (PV) and anisidine value (AV) at different intervals. A sample of soybean oil was taken as andrdquocontrolandrdquoand several synthetic and natural antioxidants (standards) including TBHQ (200 ppm), AP (200ppm), commercial rosemary extract (1000 ppm) and BHA (200 ppm) were used for comparison. Furthermore, oxidative stability of soybean oil containing herb extracts as well as standard antioxidants and andrdquocontrolandrdquowas evaluated by OSI method at 110°C. Results showed that on average the moistuer content of the native Salvia species was about 5% and average yields for ethanolic and hexanic extracts were about 10% and 3%, respectively. The highest (17.0%) and lowest (5.1%) yields for ethanolic extracts were for S. sahendica and S. aethiopis species, respectively, whereas for hexanic extracts S. mirzayanii (8.3%) and S. chorassanica (0.7%) had the highest and lowest yields, respectively. In the oven test, the order of antioxidant activity for standard antioxidants was: TBHQAPRosemary BHA. Generally, increase in the concentration of the herb extracts (especially ethanolic) resulted in higher antioxidant activity and also ethanolic extracts showed better antioxidant activity than hexanic extracts. Results of PV and AV determinations were in good agreement in almost all cases. In OSI test some differences in antioxidant activity were observed as compared to oven test , which was due to the application of higher temperature in the former. In the case of standards, BHA was not active at 110°C but TBHQ was the most active, and AP and Rosemary were partially active. ککFor the sake of comparison and concluding, Salvia species examined were classified into three categories with high, intermediate and low antioxidant activites. The overall scores from different tests were indicative of S. verticillata, S. multicaulis and S. glutinosa as potent sources of natural antioxidants, whereas S. lerifolia and S. mirayanii had weak antioxidant acitivity. Other Salvia species examined including S. plaestina, S. viridis, S. hypoleuca, S. limbata, S. sahendica, S. spinosa, S. aethiopis , S. chorassanica, S. rhytidea, S. nemorosa, and S. syriaca had intermediate antioxidant activity. There are about 50 more native Salvia species in Iran which can be studied in a comprehensive research project with extensive laboratory facilities in order to identify the species with significant antioxidant activity. Following the screening of the potent species , purification of the extracts, isolation and identification of active components will lead to better understanding of the nature of these compounds and the possibility of their utilization in different industries.