Edible Flowers of Onions (Allium L.) as a Source of Biologically Active Substances

The paper reports the results of a comparative study of biologically active substances content in the flowers of 10 perennial onion species, namely Allium aflatunense B. Fedtsch., A. altaicum Pall., A. flavum L., A. microdictyon Prokh., A. nutans L., A. obliquum L., A. ramosum L., A. rosenbachianum Regel, A. schoenoprasum L., and A. senescens L. var. glaucum Regel (A. senescens ssp. glaucum (Schrad.) N. Friesen). Freshly harvested raw material in the period of mass flowering was analysed. Dry matter content was determined by drying 1 g of raw material at 100–105°C to constant weight. The amount of phenolic compounds, pectins, total sugars and carotenoids was measured spectrophotometrically using the SF-56 (Russia) and Agilent 8453 (United States) instruments. For the first time, data on the quantitative content of the main groups of secondary metabolites in onion flowers were obtained. It has been demonstrated that under the forest-steppe conditions of western Siberia the flowers of Allium species contain 10.7–22.5% of dry matter, 6.6–26.2% of total sugars, 3.3–18.6% of pectin substances, 3.6–10.6% of phenolic compounds, 3.0–23.4 mg % of carotenoids (on absolutely dry basis) and 35.4–157.8 mg % of ascorbic acid (on wet weight basis). The highest amounts were observed in A. rosenbachianum, A. flavum and A. aflatunense. The observed high variability in the accumulation of biologically active substances can be explained by species and different weather conditions during the growing season. The present study has revealed the high potential of onion flower as a source of various bioactive compounds which could serve as food supplements among other uses.