A modification of the method for determining the total content of phenolic compounds in plant tissue extracts with the Folin-Denis reagent and the Folin-Ciocalteu reagent has been carried out, allowing to establish the correspondence of the results obtained when using them. The method using the Folin-Denis reagent is adapted for conducting determinations in microvolumes. For the method using the Folin-Ciocalteu reagent, the concentration of the latter (0.4 N, a 5-fold dilution of the standard reagent) and the composition of the reaction mixture were selected, using which the optical densities of the reduction products of the Folin-Denis and Folin-Ciocalteu reagents containing polyphenols in ethanol extracts from wheat, buckwheat and calus tissue of tea were almost the same. The absorption spectra of the reduction products of these reagents by gallic acid, rutin, (-)-epicatechin, as well as ethanol extracts from wheat, buckwheat, and tea calus tissue, were located in the same region (680–770 nm) and had similar characteristics. Calibration graphs of the dependence of the optical density of solutions on the concentration of standard substances (gallic acid, (-)-epicatechin, rutin), constructed using the Folin-Denis and Folin-Ciocalteu reagents, had a linear character within the concentration range of 10–100 μg/ml and practically coincided. The results of determining the content of phenolic compounds in ethanol extracts of plants, differing in their ability to accumulate, showed very similar and statistically significant values when using these two reagents.
The data on the morphophysiological characteristics of young three-leaf shoots (flashes, the first collection wave) of Camellia sinensis L. cultivars Kolhida and Kimyn, cultivated in the conditions of Russia subtropics (Krasnodar region, Sochi), the accumulation of photosynthetic pigments (chlorophylls a and b), phenolic compounds, including flavanes, and antiradical activity of extracts obtained from them are presented. It has been shown that the Kolhida cultivar is characterized by the formation of larger leaves compared to those of the Kimyn cultivar, as well as a high accumulation of photosynthetic pigments in them. At the same time, in the leaves of both tea representatives, the total content of chlorophylls a and b was higher compared with the stems. A similar tendency is characteristic for the accumulation of the phenolic compounds sum and flavanes, whereas the number of proanthocyanidins (soluble and insoluble) in the stems exceeded that in the leaves by 2–3 times. Both cultures had the same ability to form all forms of phenolic compounds, which is consistent with the data on the activity of L- phenylalanine ammonia-lyase – the key enzyme of their metabolism. It was established that the antiradical activity of extracts obtained from tea leaves was, on average, 30–40% higher than that of the stems and correlated with the content of phenolic compounds in them.
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