In order to determine the further metabolites, Polyporus sp.
S133 was grown in phthalic acid and then the extract were subjected
to GC/MS. In phthalic acid grown culture, we found one
fraction (compound V), which had a GC retention time of 11.3 min.
GC/MS revealed this metabolite to have a molecular ion [M+] at
m/z 370 and fragment ion [M+-15] at 355, representing a probable
loss of CH3. The mass spectral fragmentation pattern suggested
that this metabolite was protocatechuic acid. This indicates that 1-
hydroxy-2-naphthoic acid was converted into protocatechuic acid
via phthalic acid.