SCIENCE &
NUTRITION
35
JUL 2017 FOOD FOCUSTHAILAND
Diabetes can be divided into two groups, type 1 and type 2. The former involves
immune system, whichdestroys islet cells that produce insulin inpancreas.As a result,
insulin production is terminated. The latter involves the body that continues to produce
insulin, but it does not functionproperly due to insulin resistance.
Diabetes can be prevented by reducing sugar absorption through inhibition of
α-amylase and α-glucosidase, the key enzymes that degrade carbohydrate into sugar.
Bothdigestiveenzymescanhydrolyzeα-1-4-glycosidic linkageonpolysaccharide (starch),
producingsmaller sugarunits,whichareabsorbed into intestinewall.Thus, the inhibition
of α-amylase and α-glucosidase can control diabetes by delaying carbohydrate
degradation and glucose absorption. The α-amylase and α-glucosidase inhibitors can
treat hyperglycemia or diabetes by slowing carbohydrates degradation and glucose
absorption. Several medicinal treatments are proposed with effective dose; however,
these synthetic drugs pay theprices as beingexpensive, containing severe sideeffects
andpossessing individualdependent response.Therefore,naturalproducts from functional
foods and bioactive compounds with potential anti-diabetic properties are currently of
interest in term of prevention rather than treatment.
Bioactive compounds in plants are generally polyphenols that defined as phenolic
acids,flavonoids,stilbenes,coumarins, lignansand tannins.Avariety inphenolicsprovides
particular stability, bioavailability and physiological functions, which related to human
health. Previous study has been reported that phenolics regarding their quantities and
types are in directed correlationwith inhibition of key enzymes that control diabetes
[1]
.
Latin–America fruits including açaí fruits (
Euterpe oleracea
L.), Maqui (edible berry)
(
Aristoteliachilensis
L.), gooseberry (
Physalisperuviana
L.) andpapaya (
Caricapapaya
L.) aswell as threenativeAustralianherbs includinganisemyrtle (
Syzygiumanisatum
),
lemonmyrtle (
Backhousiacitriodora
) and tasmanniapepper leaf (
Tasmannia lanceolata
R.)are foundas thedominant sourcesof variousbioactivecompoundswithanti-diabetic
properties
[2]
. The bioactive compounds that have been previously reported regarding
theirbiological functionsagainstα-amylaseandα-glucosidasearemainlyphenolicacids
andflavonoids, inwhich flavonoidsexhibit greater anti-diabeticproperties thanphenolic
acids
[3-4]
.
Flavonoidsarenaturalcompounds thataremainly found inallpartsofplants,especially
photosynthesized plant cells. More than 5,000 flavonoids have been found in nature,
includinganthocyanins,flavanols,flavones,flavanones,flavonolsand isoflavones.Among
theflavonoids family, flavonesandflavonolsarecommonly found in leavesand fruit skin,
in which their levels are depending on light exposure. Flavonoids have variously been
reported thebiochemical activities that dependon their chemical structuresand relative
orientation of various moieties in the molecule. These compounds differently react to
specific locations and types of oxidants; therefore, flavonoids can act as effective
antioxidants. Additionally, flavonoids exhibit pharmacological and medicinal properties
includinganticarcinogenic, anti-inflammatory, antibacterial and antiviral properties.
The comparison in enzyme inhibitions of flavonoids against α-glucosidase and
α-amylase suggested that flavonoids could affect α-glucosidase more effectively than
α-amylase (Table1). It is possible that flavonoids fit into theactive siteof α-glucosidase
Flavonoidsand
Anti -diabetesProperty
Diabetes is a chronic disease, inwhich body cannot produce enough
insulin or respond to the insulin. Diabetes is a public health problem,
because it can cause acute or chronic complications that increase
morbidity andmortality rates.
better than those in theactive siteof α-amylase, thus
making α-glucosidase a better targeted enzyme to
prevent/treat diabetes. Besides, a management for
type 2 diabetes is controlled through inhibition of
α-glucosidase, since α-amylase provides unclear
property for prevent or remedy of diabetes.
Flavonoids including cyanidin, myricetin and
epigallocatechin gallate (EGCG) are the effective
agentsonα-glucosidase inhibitoryactivity. Cyanidin can
bemostly found inblueberry,cranberry,cherry,blackberry
and raspberry. Intake of these anthocyanin-rich fruits
wascorrelatedwithcontrollinghyperglycemia
[5]
.At the
same time, anthocyanin supplementationwas useful
for improving insulin resistance indiabetic patients
[6]
.
Myricetin shows high contents in garlic, onion and
grape seed. Some epidemiological evidences
suggested the lower risk of diabetes with intake of
dietary myricetin. On the contrary, some researches
showed the non-correlation of high consumption of
myricetinagainst hyperglycemiaondiabeticpatients
[7-8]
.
The most effective flavonoid, EGCG, is highly
distributed in tea. The investigation on the effect of
green teaonbloodglucose levelssuggested thatgreen
teaadministrationcoulddecreasebloodglucose level
and control diabetic status
[9]
. Furthermore, green tea
consumption can improve insulin resistance as well
as decrease blood glucose level in clinical trial
[10-12]
.
