Influence of Abiotic Treatments on Isoflavone Accumulation in Soybean Seeds during Germination

Isoflavones, a group of secondary metabolites present in plants and especially abundant in soybeans, are garnering increasing interest because of their medicinal properties. Numerous environmental factors influence isoflavone accumulation in plants. Successful attempts to increase isoflavone contents in soybean seeds have not been widely reported. In this report, we examined an effective method for producing a high amount of isoflavones during soybean seed germination, by treating the seed with 4 abiotic factors. Soybean seeds were exposed to ultrasound (50 Hz) and heat ($40^{\circ}C$) for 30minutes, then germinated for 5 days in darkness. Another sample was subjected to water deficit during germination in darkness, and the other sample was subjected to light conditions during the germination period. The results showed that the ultrasound treatment increased isoflavone content during soybean germination. Three days after germination, the ultrasound-treated seeds presented the highest isoflavone content (6,042.1 ug/g dry weight) compared to the other treatments, which was also 1.3-fold increases over the content of the raw seed's before germination. With respect to each type of isoflavone group, aglycone (partially genistein) content was markedly higher, whereas glucoside was lower than that of the untreated samples. In other experiment, total isoflavone content after heat, water deficit, and light treatments was 5,600.0, 4,740.1, and 5,631.4 ug/g, respectively. These present work suggests that ultrasound treatment is a novel approach for improving the production of isoflavones in soybean seeds during germination.

물리적 요인이 콩 발아 중 isoflavone 함량에 미치는 영향

콩 발아기간 중 몇 가지 물리적 요인(열 처리, 수분공급 제한, 조명 처리, 초음파 처리)이 이소플라본 함량 증대에 미치는 영향에 대하여 알아보았다. 1. 대조군과 함께 4가지 처리는 모두 발아시간이 경과함에 따라 이소플라본 함량이 높아졌다. 2. 초음파 처리가 이소플라본 함량 증대에 가장 큰 효과가 있었으며, 발아기간 중 조명 처리도 유의성이 인정되었다. 3. 열처리도 이소플라본 함량 증대에 유의적인 효과가 있었으나 발아기간 중 부패립이 많이 발생하는 문제가 있었으며, 수분제한은 대조군에 비해 이소플라본 함량이 떨어지는 경향이었다. 4. 이소플라본 종류별 함량을 분석한 결과 malonyl-glucoside가 대체로 총 이소플라본 함량의 85% 이상을 차지하였고 다음으로는 glucoside > aglycone > acetyl-glucoside 순서로 함량이 높았으며, 발아가 진행되면서 aglycone 함량이 증가하는 경향이었다. 이와 같은 결과를 볼 때 발아기간 중 외부의 물리적 요인 처리가 콩 종자의 이소플라본 함량을 증대시킴을 확인할 수 있었다.