Chemical compositions and antioxidant/anti-inflammatory activities of steam distillate from freeze-dried onion ( Allium cepa L.) sprout

Freeze-dried onion sprout was steam-distilled, and the distillate was extracted with dichloromethane (volatile sample). Water sample I was obtained from the residual aqueous solution in the extractor. The filtrate and the methanol extract of filtrand from the residual aqueous solution in the steam distillation flask were named water sample II and methanol sample, respectively. Among the total of 71 components identified in the volatile sample, 24 were sulfur-containing compounds, which comprised 36.87% of the total volatile chemicals identified. The volatile sample inhibited hexanal oxidation for 40 days by >99% at levels >100 microg/mL. The volatile sample and water sample II exhibited moderate antioxidant activity in a malonaldehyde/gas chromatography assay and thiobarbituric acid assay, whereas water sample I did not show appreciable activity. The volatile sample, water sample I, and water sample II exhibited anti-inflammatory activity with a dose-related response in the lipoxygenase inhibitor screening assay. However, the methanol sample did not show appreciable activity in either antioxidant or anti-inflammatory tests. The results suggest that onion sprouts can be an excellent food source.