Highbush Blueberry (Vaccinium corymbosum L.) Leaves Extract and Its Modified Arginine Preparation for the Management of Metabolic Syndrome—Chemical Analysis and Bioactivity in Rat Model

Growing blueberry (Vaccinium corymbosum L., Highbush blueberry) as a berry crop is developing dynamically, especially in warm temperate, subtropical, and tropical regions of the world. When blueberry is cultivated on plantations, the bushes are pruned annually, and tons of leaves become waste. Thus, the aim of the present study was to create a preparation from blueberry leaves, study their chemical composition and determine their potential as a dietary supplement for the prophylactic and correction of the metabolic syndrome. Several schemes for obtaining extracts from blueberry leaves have been developed, including one with addition of arginine. A total of 18 phenolic substances were identified and quantified in the extracts by TLC and HPLC methods. Chlorogenic acid, hyperoside, and rutin were shown to be dominating constituents. Quantitative determination of hydroxycinnamic acid derivatives, flavonoids and other phenolics in the extracts was performed by spectrophotometric method. The extracts administration led to a significant decrease in the level of glucose, insulin and triacylglycerols in blood serum of adult mature inbred rats with insulin resistance induced by the fructose-enriched diet. The most promising one was the extract modified with arginine. The determined hypoglycemic and hypolipidemic activity of chemically standardized extracts from highbush blueberry leaves indicate the potential of this crop residue in utilization as a dietary supplement recommended in prevention of ailments associated with metabolic syndrome.