Fig. 7: The structures of purified compounds.

The chemical structures of the four purified compounds: a 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (compound 1), b 5-(Hydroxymethyl)furfural (compound 2), c 2-(2-formyl-5-(hydroxymethyl)-1H-pyrrol-1-yl) propanoic acid (compound 3), and d 4-[formyl-5-(methoxymethyl)-1H-pyrrol-1-yl] butanoic acid (compound 4).