THE QUANTIFICATION OF SOME BIOACTIVE COMPOUNDS IN THE FRUITS OF FOUR BLACKBERRY (Rubus fruticosus L.) CULTIVARS, PROPAGATED BY TISSUE CULTURE

The goal of the research was the quantitative determination of biochemical compounds (ascorbic acid, reducing sugars, tannins and titratable acidity) in Rubus fruticosus L. fruits – blackberries ('Melana', 'Triple Crown', 'Arapaho' and 'Thornfree'), propagated by tissue culture and cultivated under the ecological conditions of the Republic of Moldova. The spectrophotometric determination of ascorbic acid revealed that the highest content of this phytocompound was quantified in the 'Arapaho' blackberries, 48.28 mg/100 g, followed by the 'Thornfree' cultivar (41.69 mg/100 g), which is an amount about twice as high as in the 'Melana' blackberries (23.8 mg/100 g). The high amount of vitamin C in the researched blackberries makes them comparable to raspberries and gooseberries. The content of reducing sugars varied between 4.72% and 7.26%. The 'Triple Crown' cultivar was characterized by the maximum amounts of these biochemical compounds, and the lowest amounts were found in the fruits of the 'Thornfree' blackberry cultivar. The evaluation of the titratable acidity showed that the highest index of this parameter was recorded in the 'Melana' blackberries (0.74% / 0.77% as compared with malic / citric acid. The quantification of the tannins revealed that the fruits of the 'Triple Crown' cultivar have the lowest tannin content (1.97%), the amount being more than twice lower than the maximum amount (4.16%), recorded in the blackberries of the 'Thornfree' cultivar. The results of the study led to the conclusion that the fruits of Rubus fruticosus L., obtained from plants which had been micropropagated in the Embryology and Biotechnology Laboratory (NBGI) and grown under the conditions of the Republic of Moldova are a good source of biologically active substances and can be proposed for commercial production as a promising organic food product.