Food Biochemistry and Food Processing (2 edition)

BLBS102-c43 BLBS102-Simpson March 21, 2012 14:30 Trim: 276mm X 219mm Printer Name: Yet to Come

822 Part 8: Food Safety and Food Allergens

Figure 43.2.Scheme for the biosynthesis of serotonin from

tryptophan.

ingest or consume. Well-known food sources of tyramine include

fermented, pickled and aged foods, marinated foods, smoked

foods, chocolate, alcoholic beverages, and spoiled foods. Its

production and accumulation in the body have been linked to

elevated blood pressure and headaches.

Serotonin, known systematically as 5-hydroxytryptamine,

is synthesized froml-tryptophan by a series of reactions

(Fig. 43.2), including hydroxylation, decarboxylation, and

deamination steps. These reactions involve the participation

of several enzymes, including tryptophan hydroxylase (TPH),

5-hydroxytryptophan decarboxylase, and monoamine oxidase

(MAO). Serotonin is a neurotransmitter found mostly in the

gastrointestinal tract (GIT), the CNS, and platelets of animals

including humans. In the GIT, serotonin acts to regulate intesti-

nal movements; in the CNS, serotonin performs various func-

tions, including the regulation of appetite, mood, and sleep,

as well as muscle contraction and some cognitive functions

Figure 43.3.Scheme for the synthesis of adrenaline (epinephrine)

from tyrosine.

(Berger et al. 2009). Platelet-related serotonin is involved in

haemostasis and liver regeneration (Lesurtel et al. 2006). In

plants, serotonin is thought to be produced as a mechanism

for obviating the build-up of toxic ammonia. This involves

the coupling of NH 3 to the indole ofl-tryptophan followed

by decarboxylation into tryptamine and subsequently by cy-

tochrome P450 (Cyt P 450 ) monooxygenase-mediated hydroxy-

lation to serotonin. Plant sources of serotonin include mush-

room, tomato, plantain, banana, plum, kiwifruit, walnut, and

hickory. Excessive levels of serotonin can be toxic to humans

and is manifested by specific cognitive, autonomic, and somatic

effects that may range from nondetectable to fatal (Boyer and

Shannon 2005).

Tryptamines are a group of alkaloid compounds found in

plants, animals, and fungi. Well-known tryptamines include

serotonin and melatonin. These compounds are known for their

psychotropic effects and this forms the basis of their use by some

people; examples include psilocybin (from “magic mushrooms”)