Agriculture Reference
In-Depth Information
suggested to be a potential compound for treatment of the
infection by HSV-2 and ADV-3 (Chiang et al., 2002).
carcinogenic components into less toxic materials or pre-
vent their biological actions and flavonoids have been re-
ported to possess the ability to act in all the three ways
(Manthey et al., 2001).
Many fruits (including tropical and subtropical) con-
tain ellagic and chlorogenic acids, which serve as potential
chemopreventers against several carcinogens (Huang et al.,
1992). Quercetin and rutin have the capability of inhibit-
ing colonic neoplasia induced by azoxymethanol (Lehrian
et al., 1978). It has been suggested that regular consump-
tion of tannins may induce the development of a defensive
mechanism by animals and human beings to lower the risk
of cancer. This may include utilization of very special-
ized tannin-binding proteins. For example, the mammalian
herbivores produced salivary proteins with a high affin-
ity for tannins (Lueck, 1970). Conversely, some tannins
may exert anticarcinogenic effects by acting as free radical
scavengers.
Phenolic antioxidants including simple phenols, aldehy-
dic secoiridoids, avonoids, and lignans have shown ability
to inhibit reactive oxygen species attack on salicylic acid,
2-deoxy-guanosine. There is also evidence that reactive
oxygen species are involved in the etiology of fat-related
neoplasms such as cancer of the breast and colorectum
(Lustre and Issenberg, 1970).
Most flavonoids have demonstrated ability to inhibit
proliferation in many kinds of cancerous cell lines. Kan-
daswami et al. (1991) reported that flavonoids (quercetin
and taxifolin) have antiproliferative effects on squamous
cell carcinoma HTB43 Diosmin; a flavonoid found in cit-
rus fruit was reported to exhibit antiproliferative activity in
Caco-2 and HT-29 colon cancer cell lines, although with
less efficacy than quercetin (Kuntz et al., 1999).
Phytoestrogens are a group of polyphenolic nonsteroidal
compounds of plant origin. The four main groups of
compounds currently recognized as phytoestrogens are
isoflavones, stilbenes, coumestans, and lignans (Moon
et al., 2006). These phytochemicals are some of the most
prevalent compounds found in fruits and are generally con-
centrated in the fruit skin (Moon et al., 2006).
The effects of phytoestrogen may vary with menopausal
status, and it is speculated that before menopause, they act
as antiestrogens, staving off breast cancer by blocking the
action of some of the body's naturally occurring estrogens.
After menopause, when production of endogenous estrogen
dramatically decreases, phytoestrogens may provide some
hormone activity without raising breast cancer risk. In men,
phytoestrogens appear to act as blockers of testosterone, the
male hormone that can spur the growth of prostate tumors
(Adlecreutz, 1995).
Carotenoids
Lower serum lycopene levels have been reported in human
immunodeficiency virus (HIV) positive women (Coodley
et al., 1995). The low serum lycopene levels in these
groups may be part of the compounding factors exacerbat-
ing their immune system failure, though additional research
is needed for establishing a conclusive relationship.
Anti-inflammatory activity
Phenolics
A number of flavonoids are reported to possess anti-
inflammatory activity. Hesperidin, a citrus flavonoid, pos-
sesses significant anti-inflammatory and analgesic effects
(Shahidi et al., 1998). Dopamine, a predominant cate-
cholamine, demonstrated anti-inflammatory activity and
protection against intestinal injury (Alanko et al., 1992).
Antitumor activity
Phenolics
Flavonoids may act at the different development stages
of malignant tumors by protecting DNA against oxidative
damage, inactivating carcinogens, inhibiting the expression
of the mutagenic genes and enzymes responsible for activat-
ing procarcinogenic substances, and activating the systems
responsible for xenobiotic detoxification (Bravo, 1998).
Carotenoids
Carotenoid fractions extracted from Valencia orange peel
showed the hypophasic carotenoids to be mainly violax-
anthin, zeaxanthin, and lutein. The Valencia orange peel
extract showed high cytotoxic activity against three hu-
man tumor cell lines (squamous cell carcinoma HSC-2 and
HSC-3, submandibular gland carcinoma HSG) and human
promyelocytic leukemic HL-60 cells than against three nor-
mal human oral cells (gingival fibroblast HGF, pulp cell
HPC, and periodontal ligament fibroblast HPLF), suggest-
ing a tumor-specific cytotoxic activity (Molnar et al., 2005).
Anticancer activity
Phenolics
Cancer may be controlled by a variety of means, includ-
ing suppression, blockage, and transformation. Suppress-
ing agents prevent the formation of new cancers from
procarcinogens; blocking agents prevent carcinogenic com-
pounds from reaching critical initiation sites; and trans-
formation
agents
act
to
facilitate
the
metabolism
of
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