Table II.

Basic structures of the typical active components of polyphenols most commonly occurring in leaf extracts

Group		Structure	Common residues and representatives
1	Phenolic acids
1.1	Hydroxybenzoic acids		R1 = R2 = OH, R3 = H Protocatechuic acid R1 = R2 = OH = R3 = OH Gallic acid
1.2	Hydroxycinnamic acids		R1 = OH Coumaric acid R1 = R2 = OH Caffeic acid R1 = OCH3, R2 = OH
2	Flavonoids
2.1	Anthocyanins
2.2	Flavanols		R1 = R2 = OH, R3 = H Catechin R1 = R2 = R3 = OH Gallocatechin
2.3	Flavones		R1 = R2 = OH Luteolin
2.4	Flavonols		R1 = R2 = OH, R3 = H Quercetin R2 = OH, R1 = R3 = H Kaempferol
2.5	Proanthocyanidins		Trimeric Procyanidin