Extraction of Phenolic and Flavonoid from Seeds of Black Soybean (Glycine max L.)

Aims: The study was conducted on black soybean seeds (Glycine max. L) to optima the conditions of some factors affecting the extracted yield of polyphenol compounds.

Study Design: The factors include the types of solvent used (methanol, ethanol and acetone); solvent concentrations (40, 50, 60, 70, 80 and 90 % v/v); ratio of sample and solvent (1:4,1:6, 1:8, 1:10) and cycle of extractions (2, 3, 4); extract times (2, 3, 4h) and temperature (30, 40, 50, 60 oC). The efficiency of polyphenol extract was shown by the content of total phenolic (TPC) and flavonoid (TFC).

Place and Duration of Study: Department of Biotechnology and Food technology, Thai Nguyen University of Agriculture and Forestry, Viet Nam, from March 2021 to March 2022.

Methodology: The black soybean seeds were pulverized by a mill and defatted using the Soxhlet system with hexane for 10 hrs as described by Weidner et al. (2012). TPC was determined by the Folin-Ciocalteu method of Susu Giang et al (2013). TFC was determined by colorimetric method as described by Ozsoy et al (2008).

Results: The results showed that the extraction efficiency was high when using 70% acetone solvent; the appropriate ratio of soybean and solvent was 1:10 with 3 cycles of extraction. The extraction efficiency can be improved when extracting samples at temperature at 60oC for 4 hours, TPC and TFC content reached about 5.02±0.04 mgGAE/g and 2.74±0.03 mgQE/g.

Conclusion: 70% acetone is the most suitable solvent to extract polyphenols from black soybean. The ratio of sample in solvent is 1:10 (w/v), three times of extraction in 4 hours for each extraction cycle at 60°C for the highest extraction efficiency of TPC and TFC, reaching 7.02 ±0.04 mgGAE/g and 2.74±0.03 mgQE/g, respectively.