DETERMINATION OF CAFFEIC ACID IN THE DIGESTIVE JUICE OF SILKWORM LARVAE AND ITS ANTIBACTERIAL ACTIVITY AGAINST THE PATHOGENIC STREPTOCOCCUS-FAECALIS AD-4

Caffeic acid (CA) was identified as an antibacterial substance in the digestive juice of silkworm larvae. Concentrations of CA in the digestive juice decreased from 460 ppm to 3 ppm as the starvation period of the larvae was prolonged from 1 hr to 12 hr. The specimens of digestive juice (ca. pH 10.0) containing 460 ppm and 222 ppm of CA had antibacterial activity against Streptococcus faecalis AD-4, a pathogenic intestinal bacterium affecting silkworm larvae, and an alkaline medium (pH 10.0) containing 500 ppm of authentic CA also exhibited antibacterial activity. These findings suggest that CA plays an important role in the defense mechanism of silkworm larvae against the bacterial infection. © 1979 Taylor & Francis Group, LLC.