Project of Irina Koleva
Project title: Isolation, analysis and evaluation of compounds having antioxidative properties from Bulgarian Siderites species

Bulgarian plants belonging to the genus Sideritis (Lamiaceae) are the focus of this research project. They are used in Bulgarian and other folk medicines. Several species and chemotypes were investigated with respect to their antioxidant properties with the consideration of their possible utilisation as natural antioxidants in foods and cosmetics. Rapid screening methods for evaluation of the antioxidant activity of the obtained extracts, fractions and pure isolates have been evaluated and improved. These methods were applied for an initial evaluation of different extracts and the data compared to those of well-known synthetic and natural antioxidative compounds. By bioassay guided fractionation active constituents responsible for the activities of interest were isolated and their structures elucidated. Several methods for the assessment of antioxidant activity were used to examine in detail the respective properties of the products studied.

Several novel techniques for the LC on-line detection of antioxidants were developed. An example of an on-line chromatogram can be found on the right. In the upper image the normal UV profile can be seen. In the lower image, the radical scavenging activity of each compound can be observed. Note that minor constituents can contribute to the overall radical scavenging effect.