Chemical Compound	R1	R2	R3	R4	R5	R6
p-Coumaric acid	CH=CH–COOH	H	H	OH	H	H
Homovanillic acid	CH2–COOH	H	H	OH	OCH3	H
Phloroglucinol aldehyde	CHO	OH	H	OH	H	OH
4-Hydroxybenzoic acid	COOH	H	H	OH	H	H
Hippuric acid	CO–NH–CH2–COOH	H	H	H	H	H
Ferulic acid	CH=CH–COOH	H	OCH3	OH	H	H
4-Hydroxybenzaldehyde	CHO	H	H	OH	H	H
Protocatechuic acid	COOH	H	H	OH	OH	H
Caffeic acid	CH=CH–COOH	H	H	OH	OH	H
Vanillic acid	COOH	H	H	OH	OCH3	H