Phytochemicals and Bioactive Compounds in Tropical and Subtropical Fruits - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 50

4
Phytochemicals and Bioactive Compounds
in Tropical and Subtropical Fruits

Ssonko Umar Lule and Wenshui Xia

INTRODUCTION
Phytochemicals are nonnutritive plant compounds that play
a protective or disease-preventive role in the body of human
beings. These compounds are not required by the human
body for sustaining life but are necessary for a healthy
body. Some of the well-known phytochemicals in fruits are
carotenoids, phytosterols, and phenolic compounds. Phyto-
chemicals occur in most fruits, and the known phytochem-
icals are more than a thousand in number.
Bioactive compounds usually refer to nonessential
biomolecules that are present in foods and exhibit the ca-
pacity to modulate one or more metabolic processes, which
result in the promotion of better health. Owing to their
various forms, bioactive compounds follow many different
metabolic processes during which they may impart benefi-
cial effects to body tissues. These compounds are predomi-
nantly found in plants, particularly in fruits and vegetables;
unlike phytochemicals, which only come from plant origin,
some compounds found in animal products also qualify to
be bioactive compounds, such as bioactive peptides in fer-
mented milk products and omega-3 polyunsaturated fatty
acid found in certain fish species. But for the purpose of this
chapter, we will be discussing bioactive compounds of plant
origin only and thus we will use the terms phytochemicals
and bioactive compounds interchangeably.
Phytochemicals and/or bioactive compounds come in a
variety of forms, and some tropical fruits have higher con-
centrations of a particular bioactive compound than the
others. This chapter discusses the occurrence, main forms,
significance, and health benefits of bioactive compounds
found in tropical and subtropical fruits.

Common forms of phytochemicals/bioactive
compounds
The common forms of occurrence of bioactive com-
pounds give the basis of categorizing the thousands of
bioactive compounds found in fruits, of which cate-
gories include phenolic compounds, carotenoids, phytos-
terols, dietary fiber (soluble and insoluble), and fructo-
oligosaccharide. Usually, these compound categories do not
usually occur as piecemeal in a given fruit but rather in a
mixture.

PHENOLIC COMPOUNDS
Phenolic compounds occur naturally in fruits as well as
in processed products from fruits, such as fruit juices
and canned, frozen, dehydrated, and fermented products.
Phenolic compounds are the most widely distributed cat-
egory among the different categories of phytochemicals
or bioactive compounds. This category comprises numer-
ous organic compounds with one or more hydroxyl groups
on the aromatic ring(s) ranging from simple compounds,
known as simple phenols, to complex ones, referred to as
polyphenols.

Simple phenols
Phenolic acids in the form of substituted derivatives of
hydroxybenzoic and hydroxycinnamic acids are the pre-
dominant phenolic acids in fruits. These derivatives differ
in patterns of hydroxylations and methoxylations of their
aromatic rings.