Investigation of the extraction dynamic of the biologically active substances of the raspberry (Rubus idaeus L.) shoots

The study has the intent of exploring the dynamics of biologically active substance (BAS) extractions from red raspberry (R. idaeus) shoots in order to determine the appropriate extraction frequency. A secondary objective is to assess the relationship between extract antioxidant activity and BAS content.

The focus of the study revolved around R. idaeus shoots, and the spectrophotometric method of analysis was applied to determine the amount of the catechins, polyphenols, hydroxycinnamic acids derivatives and flavonoids, while the gravimetric method was used to determine the dry residue of the extracts and the potentiometric method applied for evaluating antioxidant activity.

The polyphenols amount was 1.74±0.03, 0.58±0.01 and 0.016±0.005%, catechins – 1.50±0.02, 0.50±0.01 and 0.11±0.01%, flavonoids – 0.08±0.005, 0.046±0.005 and 0.016±0.002%, hydroxycinnamic acids derivatives – 0.24±0.005, 0.078±0.005 and 0.017±0.002%, organic acids – 0.15±0.005, 0.05±0.005 and 0.01±0.002, dry residue – 2.14±0.005, 0.72±0.01 and 0.16±0.005%, antioxidant activity – 94.80±1.90, 47.40±0.95 and 7.90±0.16 mM-eqv./m for the 1^st, 2^nd and 3rd extraction, respectively. The optimal extraction frequency of raspberry shoots with distilled water was two times. The highest value of Peasorn‘s correlation coefficient was between the antioxidant activity and catechins (r = 0.9813) and the lowest in the case of organic acids (r=0.9112).

The appropriate extraction frequency of R. idaeus shoots with distilled water was two times. The antioxidant method of determination extraction frequency was not inferior to the traditional method. The catechins dominated in the extracts from R. idaeus shoots. A significant positive correlation was content of catechins and antioxidant activity.