High angiotensin I-converting enzyme inhibitory activity of Chinese <i>douchi</i> (soy nuggets)


       Angiotensin I-converting enzyme (ACE) plays an important role in the reninangiotensin system that regulates the blood pressure and the blood circulatory system. Many types of Japanese fermented soybean foods are reported to exhibit a much stronger angiotensin I-converting enzyme (ACE)- inhibitory activity than their unfermented equivalents. Although these foods are believed to have originated in China, traditional Chinese fermented soybean foods such as douchi have not been systematically studied. Douchi are used as a seasoning or condiment in everyday Chinese dishes. During the more than 2,000-year history of douchi manufacture, a wide variety of types been produced in China. However, most manufacturing in China has been carried out by small factories using natural fermentation. We obtained 12 douchi samples from different regions of China and classified them by their dominant fermentation microorganism (Table 1). In this study, the ACE-inhibitory activities of aspergillus-type (7), mucor-type (3), and bacterial-type (2) douchi were determined and compared with Japanese hama-natto and itohiki-natto.
  Fig. 1 shows the ACE-inhibitory activities of various douchi extracts compared with those of hama-natto and itohiki-natto, which are known to have strong inhibitory activity. All the samples except one showed similar ACE-inhibitory activity to itohiki-natto. A mucor-type douchi from Sichuan province had about ten times higher activity than itohiki-natto. Studies on the identification of which microbes produce strong ACE inhibitors, and the relationship between their inhibitory activity and processing conditions are now in progress; the results will enable the development of an improved processing method for the production of highly functional foods.

Figure, table


    Table 1.

    Fig. 1.
    Fig. 1. Angiotensin I-converting enzyme (ACE) inhibitory activities of douchi and natto samples.

Japan International Research Center for Agricultural Sciences Food Science and Technology Division

China Agriculture University Japan-China Food Research Center


Technical A



Term of research


Responsible researcher

TATSUMI Eizo ( Food Science and Technology Division )

SAITO Masayoshi ( Food Science and Technology Division )

LI Lite ( China Agricultral University )

FAN Junfeng ( China Agricultral University )

Publication, etc.

Fan, J., Saito, M., Tatsumi, E. and Li, L.(2003): Preparation of angiotensin I-converting enzyme inhibiting peptides from soybean protein by enzymatic hydrolysis. Food Science and Technology Research, 9 (3), 254-256.

Li, L., Yin, L. and Saito, M.(2004): Function of Traditional Foods and Food Culture in China. Japan Agricultural Research Quarterly 38,(4), 213-220.

Japanese PDF

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