Effect of different extraction techniques on total phenolic and flavonoid content of spring onions

Abstract

Spring onions are a popular and very common vegetable in the human diet during the early spring months. In the Serbian markets there are an offer of green onion (Allium cepa) and spring garlic (A. sativum), while in better supplied markets the assortment also includes A. ursinum, popularly known as wild garlic, ramsons or bear’s garlic. In this paper, the influence of two extraction techniques, with application of 80% MeOH (solvent extraction and ultrasound-assisted extraction (UAE) on the content of total phenolics (TPC) and flavonoids (TFC) in samples of spring onions (A. cepa and A. ursinum) was investigated, with the aim to find an extraction technique that would ensure more efficient isolation of these bioactive compounds, which would enable a more precise assessment of the quality of the examined plants. Total phenolic content (TPC) was determined using the standard spectrophotometric Folin-Ciocalteu method. The obtained results are expressed as mg of ferulic acid equivalents (FAE) per g of fresh weight. The content of total flavonoids (TFC) was determined by the standard spectrophotometric aluminum chloride method, and the obtained results were expressed as mg of quercetin equivalent (QE) per gram of fresh weight. The lowest content of TPC (0.79 mg/g FAE) and TFC (0.10 mg/g QE) was determined in A. cepa using solvent extraction, while the highest content of TPC (4.32 mg/g FAE) and TFC (0.64 mg/g QE) was obtained in A. ursinum, by using UAE. Spring onions available in the Serbian market, in addition to being popular vegetables, are also a good source of bioactive compounds with potential phytotherapeutic effects