In sweet clover, coumarin is rapidly converted to melilotic acid 
and its glucoside (Kosuge and Conn, 1959). It was postulated that 
coumarin was reduced to dihydrocoumarin and the the pyrone ring was 
then opened to form melilotic acid. An enzyme was subsequently 
partially purified from sweet clover which catalyzed this ring opening 
(Kosuge and Conn, 1962). 
Arthrobacter sp. Coumarin 
Rabbit Sweet 
Rat Clover 
H 
=O 
0 
4 
H=CH-C” 
Sou 
o-Coumaric Acid Rat 
Dihyd rin 
avencobaceer sp -~Eghht wt ihydrocoumari 
OH 
NADH 
0 
7 
ee 
H 
Ht 
Melilotic Acid 
Arthrobacter sp. 
HO. 
0 
CHy -CH-C 
| “ox 
NH? 
Tyrosine 
59 
