Wine Chemistry and Biochemistry

480 N. Terrier et al.

R, R’, R1, R2 as in Figure 3

R3 = OH, OCH 3

R4 = H,OH,OCH 3

R5 = O-Glc, O-acetylGlc, O-p-coumaroylGlc

O

R2

HO

OH

R

OH

OH

R1

O

R2

HO

OH

R’

OH

OH

R1

+ H+

+

O

R2

HO

OH

R

OH

OH

R1

O

R2

HO

OH

R’

OH

OH

R1

O

R2

HO

OH

R

OH

OH

R1

O

R2

HO

OH

R

OH

OH

R1

O

R2

HO

OH

R

OH

OH

R1

+ anthocyanin

+ flavanol

+H 2 O, – H+

–H 2 O,+ H+

proanthocyanidin

proanthocyanidin

flavanol-anthocyanin adduct

hemiketal form

flavylium form

(1)

(2a)

(2b)

(3)

O+

R5

OH

R4

HO

OH

R3

O

R5

OH

R4

HO

OH

R3

OH

O

R2

HO

OH

R

OH

OH

R1

O

R5

OH

R4

HO

OH

R3

OH

O

R2

HO

OH

R

OH

OH

R1

O+

R5

OH

R4

HO

OH

R3

Fig. 9B.5Polymerisation reactions based on acid-catalysed cleavage of proanthocyanidins

R, R’, R1, R2 as in Figure 3

R6 = CH 3 ,COOH,...

R4 = H,OH,OCH 3

R5 = O-Glc, O-acetylGlc, O-p-coumaroylGlc

+ H+

+ anthocyanin

(hemiketal)

+ flavanol

• H 2 O,+ H+

flavanol

flavylium form

(2)

(3a)

(3b)

(3)

R6-CHO

R6-CHOH+

δ−

–H 2 O, + H+

(1)

O

OH

HO

HO R

R2

R1 O

OH

OH

R OH

R2

R1

O

R6

+

O

OH

HO

HO R

R2

R1 O

OH

OH

R OH

R2

R1

O

R6

oxidation

hemiketal form

–H 2 O

xanthene

xanthylium

(4)

(5)

HO

OH

O

OH

OH

OH

R-CH+

HO

OH

O

OH

OH

OH

O

OH

HO

OH

OH

OH

R6-CH

HO O

OH

OH

OH

R3

R4

OH

HO O+

OH

OH

OH

R3

R4

O

OH

HO

OH

OH

OH

R6-CH

HO

OH

O

OH

OH

OH

O

OH

HO

OH

OH

OH

R6-CH

HO

OH

O

OH

OH

OH

Fig. 9B.6Condensation reactions with aldehydes