Studies on color change of seed coat of edible beans during maturation

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H02146
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 38040:Bioorganic chemistry-related
• Research Institution: Nagoya University
• Principal Investigator: YOSHIDA Kumi 名古屋大学, 情報学研究科, 教授 (90210690)
• Co-Investigator(Kenkyū-buntansha): 尾山 公一 名古屋大学, 物質科学国際研究センター, 技師 (80402460)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: Vigna angularis / Glycinbe max / Glycine soja / catechinopyranocyanidin / cyanidin 3-glucoside / 2-flavenol / anthocyanin biosynthesis

Outline of Final Research Achievements

We conducted a research on the unexplored mechanism of pigmentation in colored edible beans: one was red adzuki beans (Vigna angularis) and the other was black soybeans (Glycine max). Matured small red beans contain almost no anthocyanins, and the chemical structure of the pigment responsible for azuki color in an-paste was unknown. The new pigments, catechinopyranocyanidins A and B, were isolated from the seed coat, and their complete structures, including chiral cetres, were determined. On the other hand, seed coat pigment of the black soybean is cyanidin 3-glucoside (Cy3G), which is the most abundant pigment in plants. Inspired by the phenomenon that the seed coat turns black within a day after the immature green bean is removed from the pod, we found a new biosynthetic pathway for Cy3G. In the immature seed coat, a colorless precursor, glycosylated flavanol compound was already contained and this is rapidly converted to give Cy3G.

Free Research Field

天然物化学

Academic Significance and Societal Importance of the Research Achievements

赤小豆の種皮色素は、その赤色から長い間アントシアニンであると誤解されてきた。実際、食品化学の教科書などにもアントシアニンであるとの記載がなされていた。今回、糖を含まない水にほとんど溶けない紫色色素のカテキノピラノシアニジン類が明らかになったことで、その誤解が解かれ、製餡加工工程における餡の紫色着色の科学的解明が進む。
また、黒大豆の種皮色素において、従来教科書に記載されていた生合成経路と異なる新しい生合成経路が見つかり、今後、アントシアニンの生合成研究の不明点などの解明が進む。