Study of the antioxidant activity of plant extracts and their effect on the growth of lactic acid bacteria isolated from koumiss

Abstract

This article describes the effect of plant extracts on the growth and reproduction of lactic acid bacteria (LAB), Lactobacillus acidophilus 0015k-1 and Lactobacillus delbrueckii subsp. bulgaricus 018k-3, isolated from the traditional fermented milk drink, Koumiss. In this study, analyses were carried out on plant extracts of Rubus caesius L. (gray blackberry), Rubus idaeus L. (common raspberry) and Punica granatum (common pomegranate). The focus was on the antioxidant activity as measured by the electroanalytical technique, amperometry and the content of polyphenols as detected by photometry.

Antioxidant activity was measured using amperometry - calibration standards of quercetin were used to construct a calibration curve with which the activity of the antioxidant analytes in the test samples could be analysed. It was determined that blackberries had the highest content of antioxidants at 3.30mg/g followed by pomegranates (2.40mg/g) and then raspberries (2.37mg/g). The total polyphenol content again demonstrated blackberries in the lead (8.20%) followed by raspberries (2.99%) and pomegranates (2.78%).

To test the prebiotic activity of aqueous plant extracts, LAB were cultured in milk with and without plant components (10%, 15% and control samples) until a clot was formed. The CFU titer was determined for each sample. The results of the in-vitro test showed a significant growth of bacterial colonies in samples containing plant extracts (10%) compared to control samples. However, a slight inhibition of LAB