Investigation of phenols in soybean seeds
Introduction. Recent investigations have revealed the therapeutic properties of biologically active substances of soybean seeds. The literature gives data on their content of flavonoids, vitamins, lipids; but soybean phenolic compounds have not been adequately investigated. Objective. To investigate the accumulation of a number of phenolic compounds (tannins and phenolcarboxylic acids) in soybean seeds. Material and methods. The investigation was concerned with the seeds of five soybean varieties: Soprosoy (Burundi), Okskaya (Russia), 740-1 (Sweden), Severnaya zvezda (Belarus), Gisa-111 (Iraq). The absorption spectra of aqueous extracts from soy seeds were recorded on a Lambda 950 spectrophotometer. The pH was established using an Aquilon-410 ionomer. The levels of tannins and simple phenols were determined by potentiometric titration; those of phenolcarboxylic acids were spectrophotometrically estimated in the ultraviolet region. Results. The seeds of cultural soybean varieties, which were examined during experiments, did not vary widely. The pH range for all the extracts was 6.7-6.9. The content of tannin was low (0.20 to 0.41%). That of phenolcarboxylic acids varied over a wide range from 14.38 to 4.66%. Conclusion. The levels of tannins and phenolcarboxyli acids in soybean seeds from different countries were investigated. The findings showed that all seeds contained a low amount of tannins (below 0.5%). The varieties differed in the content of phenolcarboxylic acids in the seeds.