Analysis of bioactive compounds and antioxidant activities of cultivated garlic (allium sativum l.) and red onion (allium cepa l.) in algeria

Abstract

In all times, humankind has used several species of the genus Allium as food, spice, or herbal remedy. Some of these species have been cultivated, such as garlic (Allium sativum) or onion (Allium cepa). Today, their value for human health care is one of the most important aims of research. Up to now, many applications of Allium species are known for the use of phyto-pharmaceutical preparations. Therefore, the present study aimed to determine the phytochemical profile of cultivated garlic (Allium sativum), and red onion (Allium cepa) in Algeria, both quantitatively (total phenolic, total flavonoids, condensed and hydrolysable tannins contents) and qualitatively (phytochemical screening), to characterize the phenolic compounds using HPLC method and to evaluate the antioxidant properties using DPPH assay. Red onion gave the higher amounts of total phenolic compounds (86±1.00mg GAE/100g DM), flavonoids (43.33±0.57mg QE/100 g DM), condensed tannins (4.4±0.52 mg CE/100g DM) and hydrolyzable tannins (0.22±0.04mg TAE/100g DM) compared to garlic (45±1.00mg GAE/100g DM, 34.66±0.57mg QE/100g DM, 6.8±0.34mg CE/100g DM and 0.05±0.01mg TAE/100g DM) respectively. Five compounds were found in red onion extract and one compound in garlic extract after chromatographic analysis of the samples. Furthermore, red onion possessed the higher antioxidant activity (IC50= 420.9±5.00 µg/ml) as compared to garlic (919.87±4.43 µg/ml). These findings provide ample evidence of the existence of bioactive compounds in garlic and red onion, both of which are rich in phenolics primarily flavonoids and tannins, have strong antioxidant activity, and can be further consumed directly or as food products.