Phytochemicals and Bioactive Compounds in Tropical and Subtropical Fruits - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 62

cholesterol-lowering properties. Beveridge et al. (1964)
tested the effect of different amounts of

to hemoglobin A1c (HbA1c), independent of the carbo-
hydrate intake, total energy intake, and other factors re-
garding lifestyle and diabetes management. Results also
showed that severe ketoacidosis risk fell significantly with
higher fiber intake. Therefore, it is reasonable to assert that
higher fiber intake is independently related to a reduction
in HbA1c levels in people with Type I diabetes (Buyken
et al., 1998).

-sitosterol on
serum cholesterol levels in 85 students on a diet rich in
butterfat, and results gave a decreasing effect on plasma
cholesterol with intakes of 300 mg/950 kcal of β -sitosterol.

β

Diabetes lowering effect
Phenolics
Flavonoids, especially quercetin, have been reported to pos-
sess antidiabetic activity; Vessal et al. (2003) reported that
quercetin brings about the regeneration of pancreatic islets
and probably increases insulin release in streptozotocin-
induced diabetic rats.

Antiulcer activity
Some recent reports have indicated that many flavonoids
possess antiulcerogenic activity. Oral treatment with the
ether fraction of the flavonoid extract demonstrated a good
level of gastric protection. Mucous content was increased
and accompanied by proportionate increase in proteins and
hexosamines (Alarcon et al., 1994).
Hydroxy ethyl rutosides, gossypin, naringin, naringenin,
and (

Dietary fiber
Water-soluble fiber and foods rich in soluble fiber are at-
tributed to reducing postprandial glucose excursions and
improve insulin profiles. Soluble fiber sources, such as
pectin, which is abundant in most tropical and subtropical
fruits, have been attributed with hypoglycemic properties
(Madar et al., 1988a, 1988b). The rate of glucose absorption
and uptake in the body is dependent on the composition and
structure of the food consumed. Although every component
of a food, such as water fat and protein, does influence the
rate of carbohydrate absorption, fiber content is a major de-
terminant in the postprandial glucose response (Nishimune
et al., 1991).
One of the numerous mechanisms that have been
proposed by which fiber affects carbohydrate metabolism
postulates increased viscosity of the gastrointestinal con-
tents to be a major factor affecting the rate of absorption.
Highly viscous chime slows gastric emptying and reduces
the rate of intestinal absorption of glucose (Meyer et al.,
1988). A diet rich in highly viscous methylcellulose
significantly lowered blood glucose levels in rats when
compared to methylcellulose of low viscosity (Topping
et al., 1988), which was attributed to the increased transit
time from the stomach to the intestines, delaying absorp-
tion of nutrients and the unavailability of starch and sugars
trapped in the methylcellulose matrix. A combination
of slowing of gastric emptying and hindered intestinal
absorption appears to be responsible for the decreases in
postprandial glucose levels.
A study by Buyken et al. (1998) examined the relation
between intake of fiber (total, soluble, and insoluble) and
HbA1c in 2065 people with Type I diabetes and associa-
tions with severe ketoacidosis and severe hypoglycaemia in
2,687 people with Type I diabetes. The study showed that
total fiber intake in grams per day was inversely related

)-cyanidanol-3 were shown to exhibit antiulcer ac-
tivity. Quercetin, rutin, and kaempferol administered in-
traperitoneally (25-100 mg/kg) inhibited dose-dependent
gastric damage produced by acidified ethanol in rats.
Flavone was inactive while naringin was active at a higher
dose (200 mg/kg). Quercetin, kaempferol, morin, myrcetin,
and rutin when tested were found to inhibit the mucosal con-
tent of platelet activating factor (PAF) in a dose-dependent
manner, suggesting that the protective role of these sub-
stances may be mediated by endogenous PAF (Parmar and
Parmar, 1998).
A study carried out on the unripe plantain banana found
the active antiulcerogenic ingredient to be a flavonoid leu-
cocyanidin. In this study, dried unripe plantain banana pow-
der, the extracted leucocyanidin, and a purified synthetic
leucocyanidin demonstrated a significant protective effect
against aspirin-induced erosions (David et al., 1999). The
possible mechanism of action of this group of compounds
may be through their ability to reduce acid secretion from
gastric parietal cells (Beil et al., 1995).

+

Other health benefits
Phenolics
Isoflavones have a structure similar to human estrogen,
which suggests the possibility of estrogen-like biological
activities. Isoflavones, however, exhibit antagonist estro-
gen activity, resulting in lower overall exposure to estro-
gen in premenopausal-women (Cassidy et al., 1994). Cells
that have phytoestrogen receptors may be influenced by
these molecules and therefore may aid in the reducing
menopause-related problems.