CHEMICAL CHARACTERIZATION OF COMMON MILKWEED (ASCLEPIAS SYRIACA L.) ROOT EXTRACTS AND THEIR INFLUENCE ON MAIZE (Zea mays L.), SOYBEAN (Glycine max (L.) Merr.) AND SUNFLOWER (Helianthus annuus L.) SEED GERMINATION AND SEEDLING GROWTH

The Asclepias syriaca L. is an invasive weed species which continuously occurs in numerous populations in the ruderal and agricultural land in Serbia. The aim of the study was to examine the antioxidant capacity of the A. syriaca water and methanol extracts and investigate the effects of the selected extracts towards the seed germination, growth, seedlings development and oxidative stress parameters of maize (Zea mays L.), soybean (Glycine max (L.) Merr.) and sunflower (Helianthus annuus L.). The water extract exhibited the higher total tannin content and superoxide free radical scavenging activity, while the methanol extract had a higher antioxidant capacity (measured by FRAP, DPPH and ABTS assays). The total tannin content ranged from 0.252 (methanol extract) to 0.805 (water extract) mg GAE/g. The water extract showed a significant germination inhibition in the tested plants, while no inhibition was noted in the case of the methanol extract compared with the control. However, both of the tested extracts types significantly reduced shoot and root length in case of all the tested plants.