Furpenthiazinate is a yellow pigment
formed by the Maillard reaction
between cysteine and furfural under strongly acidic conditions. Here,
we describe the conditions and mechanism of pigment formation in a
model system and in an acid hydrolyzate of food and analyze its biological
properties. A reaction solution containing 32 mM cysteine and 128
mM furfural or 64 mM cysteine and 256 mM furfural in the presence
of 2–6 M hydrochloric acid that was heated to 110 °C for
1–2 h yielded approximately 3 mM furpenthiazinate. Nuclear
magnetic resonance analysis of furpenthiazinate prepared using 1-13C or 5-13C d-ribose suggests that it
was formed through the condensation of cysteine and two C5 chains
derived from pentose with the dehydration and elimination of formic
acid. Furpenthiazinate was detected in mieki, a seasoning,
and some acid hydrolyzates of food, and it did not show antibacterial
or mutagenic activity.