INVESTIGATION OF CHANGES IN THE BIOACTIVE PROPERTIES AND PHENOLIC COMPOSITIONS OF DIFFERENT LAYERS OF THE LEEK PLANT

Background. Leek is one of the most widely cultivated winter vegetables in Turkey and Western Europe, with large-scale production in Turkey, France, Belgium and Poland. Material and methods. The bioactive properties and phenolic compounds of leek layers, numbered from the outermost to the innermost, were determined using spectrophotometric and chromatographic methods, respectively. Results. Total phenol and flavonoid contents were highest in the outermost (1st layer) and innermost (9th layer) parts of the leek, while intermediate layers (3rd–4th layers) showed comparatively lower levels. Total phenol content ranged from 90.92 mg GAE/100 g (4th layer) to 177.13 mg GAE/100 g (9th layer), and total flavonoid content ranged from 171.84 mg/100 g (4th layer) to 340.58 mg/100 g (1st layer). The predominant phenolic compounds were quercetin, kaempferol, cinnamic acid, gallic acid and catechin. Quercetin content ranged from 49.09 mg/100 g (1st layer) to 207.56 mg/100 g (7th layer), and kaempferol from 35.52 mg/100 g (1st layer) to 291.81 mg/100 g (8th layer). Cinnamic acid content ranged from 5.22 mg/100 g (1st layer) to 184.40 mg/100 g (9th layer). Gallic acid and 3,4-dihydroxybenzoic acid levels ranged from 39.39 mg/100 g (5th layer) to 75.67 mg/100 g (3rd layer) and from 2.22 mg/100 g (8th layer) to 47.57mg/100g (9th layer), respectively. Conclusion. Both the outermost and innermost layers exhibited the highest total phenol and flavonoid contents. The higher concentration in the outermost layer compared to the innermost layer may be attributed to a relative decrease in water content, which concentrates bioactive compounds.