Nutrient composition and polyphenol profile of annual sunflower leaves (Helianthus annuus L.)

Abstract

Goal. To study the nutritional value and polyphenolic composition of annual sunflower leaves (Helianthus annuus L.) for their further use as a phytogenic antioxidant additive for poultry feed. Methods. The chemical composition of phytoraw material (crude protein, crude fat, crude fiber, calcium, phosphorus, vitamin E, and b-carotene) was evaluated according to generally accepted met­hods. The quantitative content of individual groups of polyphenols was determined spectrophotometrically: the volume of hydroxycinnamic acids — in terms of chlorogenic acid, the volume of phenolic compounds — in gallic acid, flavonoids — in rutin. Results. It was established that sunflower leaves had a high content of b-carotene (260.2–291.6 µg/g) and the natural antioxidant vitamin E (37.4%). The protein content was fixed at the level of 16.2%, the fiber content was 4.2%. A significant amount of calcium and phosphorus accumulated in sunflower raw materials — 2.03% and 0.28%, respectively. The total content of hydroxycinnamic acids in terms of chlorogenic acid in sunflower leaves was 3.15%, the total content of phenolic compounds in terms of gallic acid was 1.60%, and flavonoids in rutin equivalent was 1.78%. Conclusions. The presence of polyphenolic compounds and the confirmed nutritional value of sunflower leaves give reasons to consider it not only as a valuable component of feed but also as a source of natural antioxidants.