Extraction, antioxidant and antilisterial activities of polysaccharides from the flower of viper's bugloss.

The objective of the present research was to investigate the effect of microwave-assisted extraction (MAE) conditions on the extraction yield, antioxidant properties and antilisterial activities of the polysaccharides from the flowers of viper's bugloss (Echium vulgare L.). The four extraction variables, time (40-100min), microwave power (200-800W), temperature (30-70°C), and the ratio of water to raw material (10-70), were optimized using response surface methodology. The experimental data were matched to a second-order polynomial equation. The optimal conditions for MAE of polysaccharides (EVFP) were time 73.8min, microwave power 769.2W, temperature 42.3°C and the ratio of water to raw material 61.4, where the actual yield of EVFP 25.11±0.87% was obtained (versus the value predicted by the model 25.36%). The results indicated that EVFP has significant radical (·OH and ·DPPH) scavenging abilities in vitro assay. Moreover, the antilisterial activity was confirmed against four species of Listeria. EVFP, at a concentration of 5mg/mL, demonstrated great antilisterial properties against Listeria ivanovii and Listeria monocytogenes, with inhibition zones of 10.76±0.32mm and 8.64±0.47mm, respectively.