Food Biochemistry and Food Processing (2 edition)

BLBS102-c37 BLBS102-Simpson March 21, 2012 14:15 Trim: 276mm X 219mm Printer Name: Yet to Come

718 Part 6: Health/Functional Foods

1,2-Benzoquinone

O O O O O O O O O O

OH

OH

OH

1,4-Benzoquinone

1,2-Napthaquinone

Lawsone

Alizarin

Figure 37.10.Structures of some common quinones.

1,2-benzo- and 1,4-benzo- quinones and naphthaloquinones

(Fig. 37.10). Because of their high coloring power, quinones

are used as dyes.

Quinones are used for the commercial scale production of hy-

drogen peroxide (H 2 O 2 ) by the hydrogenation of anthraquinones

to hydroquinones, and subsequent transfer of hydrogen (H 2 )to

O 2 (Schreyer et al. 1972, Drelinkiewicz and Waksmundzka-Gora ́

2006).

For example:

2-ethyl-9,10-anthraquinone+H 2

→2-ethyl-9,10-anthrahydroquinone

dihydroanthraquinone+O 2 →anthraquinone+H 2 O 2

Quinones can also react and form conjugates with amino

acids, and the products formed can impact the flavor and color

of foods (Bittner 2006).

In nature, some quinones serve as important constituents of

biomolecules (e.g., vitamin K 1 ); some like ubiquinone and plas-

toquinone in mitochondria participate in electron transfer reac-

tions in aerobic respiration, while plastoquinone in chloroplasts

are involved in electron transfer reactions between photosystems

1 and 2 in photosynthesis.

Quinones and Health

Quinones and related compounds (e.g., tertiary butyl hydro-

quinone or TBHQ) have antioxidant properties and the ter-

penes of hydroquinone are thought to be more potent than

the more common antioxidants such asα-tocopherol (Delgado-

Vargas and Paredes-Lopez 2003). Some other quinones like the ́

napthoquinones have antibacterial activity and can inhibit var-

ious strains of aerobic and anaerobic microorganisms (Didry

et al. 1986, Riffel et al. 2002). Some have also been shown to

have anticancer or antitumor activities (Smith 1985). For exam-

ple, dietary intake of certain quinone derivatives was reported

to play a role in the prevention of breast cancer (Zhang et al.

2009). Ironically, certain quinones and their derivatives have

also been shown to be mutagenic or carcinogenic (Zhang et al.

2009). In this regard, it is reported that extended exposure to

some of these compounds increases the incidence of breast can-

cer. Some metabolic products of quinones are also known to be

toxic, and the toxicity appears to arise from either the aryla-

tion of sulfhydryls compounds or the production of free radicals

and/or reactive O 2 species (Smith 1985).

XANTHONES

Properties and Functions

Xanthones are a group of heat stable organic compounds with

9H-xanthen-9-one (xanthone) as the core structure (Fig. 37.11).

Xanthones occur naturally in tropical plants and about two

Xanthone

(a.k.a. 9H-xanthen-9-one)

Xanthydrol

OH

OOH

HO OH

O

H 3 C

O

Mangostin

O

O

O

Figure 37.11.Structures of some common xanthones.