1
Inhibition Of Diabetes Related Glucosidases By Extract Of Fruits From
Myrtaceae Plants Growing In The Atlantic Forest Region In Brazil
Simone Muniz Pacheco1, Mauricio Seifert2, Rafael de Almeida Schiavon3, Rejane Giacomelli Tavares4,
Leonardo Nora5
1
Department of Ciência e Tecnologia Agroindustrial, Universidade Federal de Pelotas, Rio Grande do Sul, Brazil
[email protected]
2
Department of Ciência e Tecnologia Agroindustrial, Universidade Federal de Pelotas, Rio Grande do Sul, Brazil
3
Department of Ciência e Tecnologia Agroindustrial, Universidade Federal de Pelotas, Rio Grande do Sul, Brazil
4
Department of Ciências Químicas, Farmacêuticas e de Alimentos, Universidade Federal de Pelotas, Rio Grande do Sul,
Brazil
[email protected]
5
Department of Ciência e Tecnologia Agroindustrial, Universidade Federal de Pelotas, Rio Grande do Sul, Brazil
2
3
Abstract
There is a great diversity of plants that produce small edible fruit growing in the Atlantic Forest region of Brazil. Several
of these plants are used by the local population for primary health care but so far few scientific studies support the use of
these plants in traditional medicine. Therefore the present study was undertaken to evaluate the fruit of Myrtaceae family,
for their potential as adjuvants in the management of postprandial hyperglycemia. The evaluation was based on their
inhibitory activity on α-glycosidase and α-amylase, antioxidant activity and content of phenolic and flavonoid compounds.
Extracts of P. cattleianum, S. cumini, E. pyriformis distinctly inhibited α-amylase activity and extract of P. cattleianum
inhibited α-glucosidase activity, with either maltose or sucrose as substrate. By its antioxidant activities and capacity to
inhibit carbohydrate digestive enzymes, P. cattleianum, S. cumini and E. pyriformis could be good candidates to manage
postprandial hyperglycemia.
Keywords: phenolic, α-glucosidase, α-amylase, hyperglycemia.
1. Introduction
Chronic hyperglycemia due to carbohydrate metabolism alterations is the main characteristic of type 2 diabetes
mellitus (T2DM). Frequently this disease does not present many symptoms and can remain many years without diagnosis
and treatment, leading to complications (Brazilian Society of Diabetes, 2014). Recommendations to prevent disease or to
delay the complications include a healthy diet, regular physical exercise and normal weight (lifestyle change) (Bahadoran,
Mirmiran, & Azizi, 2013; Xiao, 2015).
Several drugs are indicated to treat T2DM such as glucosidase inhibitors (eg. acarbose, miglitol, voglibose)
(Bahadoran, Mirmiran, & Azizi, 2013; Lordan et al., 2013). These drugs can slow down glucose uptake, but they may
generate adverse reactions such as hypoglycemia, weight gain, gastrointestinal disorders and cardiovascular effects
(Aruselvan et al., 2014; Carpéné et al., 2015).
Phenolic compounds from plants are a potential source of antihyperglycaemic compounds, capable of slowing down
the absorption of glucose with minimum side effects (Correia et al., 2012; Podsędek et al., 2014).
Among the glucosidase enzymes are pancreatic α-amylase (EC 3.2.1.1) that hydrolyses starch releasing maltose and
maltotriose, and α-glucosidase (EC 3.2.1.20) that hydrolyses oligosaccharides and disaccharides releasing glucose.
Thereby inhibitors of these enzymes change the glucose influx through the gastrointestinal tract to blood flow, delaying its
absorption and decreasing postprandial hyperglycemia (Kazeem, Adamson, & Ogunwande, 2013; Lordan et al., 2013;
Miao et al., 2014).
Consumption of fruits rich in phenolic compounds is associated with health benefits and there is evidence that some
fruit extracts inhibit enzymes involved in the carbohydrate metabolism (Boath, Stewart, & McDougall, 2012; Correia et
al., 2012). Therefore, the consumption of certain fruits could help in the prevention and treatment of hyperglycemia and
T2DM.
Several in vitro studies report inhibition of α-glucosidase and α-amylase by fruit extracts. According to McDougall
et al. (2005), strawberry and raspberry extracts were better α-amylase inhibitors and blueberry and blackcurrant extracts
were more effective as α-glucosidase inhibitors. The authors suggest that anthocyanins and soluble tannins contribute to
α-glucosidase and α-amylase inhibition, respectively. Boath, Stewart and McDougall (2012) observed that blackcurrant
and rowanberry fruit extracts inhibit α-glucosidase, similarly to acarbose. According to McDougall et al. (2005), the main
compounds of blackcurrant and rowanberry are anthocyanins and chlorogenic acid, respectively. Correia et al. (2012)
showed that tropical fruit residues (seeds, peels and residual pulp generated as by-products of the fruit processing industry)
containing phenolic compounds (cyanidin, quercetin, ellagic acid and proanthocyanidins) inhibit the activity of αglucosidase and α-amylase.
Fruits from the Atlantic Forest region in Brazil are commonly used in folk medicine to treat hyperglycemia, but
without scientific evidence supporting treatment effectiveness. Therefore, this study was performed to characterize fruits
from plants (Psidium cattleianum, Campomanesia xanthocarpa, Eugenia pyriformis, Eugenia uniflora and Syzygium
cumini) that grow in the Southern region of the Brazilian Atlantic Forest, through determination of inhibitory potential of
α-amylase and α-glucosidase, their contents of total phenolics and total flavonoids, and antioxidant activity.
2. Materials and Methods
2.1 Analytical reagents and chemicals
Except acarbose (Bayer Glucobay 100) and the glucose assay kit (Labtest: Glicose GOD #134), all the other products
were purchased from Sigma-Aldrich: Intestinal acetone powders from rat (#I1630), α-amylase from Bacillus licheniformis
(#A3403), sucrose (#S7903), D-(+)-maltose monohydrate from potato (#M5885), ascorbic acid (#A7506), DPPH: 3,5dinitrosalicylic acid, 2,2-diphenyl-1-picrylhydrazyl (#D9132), trichloroacetic acid (#T0699), ABTS: 2,2’-azino-bis(3ethylbenzothiazoline-6-sulfonic acid) diammonium salt (#A1888), (+)-catechin hydrate (#C1251), gallic acid monohydrate
(#398225), soluble starch (S9765), Folin-Ciocalteu (#F9252), methanol (#322415), ethanol (#459844).
4
2.2 Plant material
The fully ripe fruit from Psidium catteianum (red fruit, accesses 44 and 87 and yellow fruit, access 'bicudo'),
Campomanesia xanthocarpa, Eugenia pyriformis (accesses 3, 4, 11 and 15) and Eugenia uniflora (access 156) were
harvested from the experimental field (Active Germplasm Bank) at 'Embrapa Clima Temperado', Pelotas, RS, Brazil. The
fully ripe fruit from Syzygium cumini was harvested from the experimental field at 'Universidade Federal de Pelotas', Capão
do Leão, RS, Brazil. About 3 kg of each fruit were harvested between November (2013) and March (2014).
Only commonly edible parts were used for the analyses – whole fruit for P. catteianum and C. xanthocarpa; peel and
pulp for E. pyriformis, E. uniflora and S. cumini. Fruits were selected, processed, freeze-dried and stored at − 20 °C.
2.3 Preparation of fruit extracts
Extracts were based on the modified method of Alothman, Bhat, and Karim (2009) with modifications. Freezedried fruits were ground to a fine powder in a ball mill (Marcone MA350) with liquid nitrogen and mixed (1:3, weight (w)
/ volume (v) ratio) with the extraction solvent (methanol:water, 80:20, v/v ratio). Samples were incubated for 3 h in a water
bath with stirring and heating (40 ºC). Extracts were filtered (Buchner funnel) vacuum concentrated at 40 ºC using a rotary
evaporator (La Borota 4000 Heidolph), freeze-dried, and stored at − 20 ºC.
2.4 Determination of total phenolic content
Total phenolics were determined by using the Folin-Ciocalteu method described by Swain and Hillis (1959). The
absorbance was measured at 725 nm in a spectrophotometer (Spectrophotometer UV/VIS 6705 Jenway). Results were
expressed as mg of gallic acid equivalents (GAE) per 100 g of sample (fresh fruit).
2.5 Determination of total flavonoids
The total flavonoid content was measured according to the method described by Zhishen, Mengcheng, and
Jianming (1999). Absorbance was read at 510 nm in a spectrophotometer (Spectrophotometer UV/VIS 6705 Jenway).
Results were expressed as mg of catechin equivalents per 100 g of sample (fresh fruit).
2.6 DPPH radical-scavenging assay
Antioxidant activity was determined using the DPPH radical scavenging method according to Brand-Williams,
Cuvelier, and Berset (1995). Absorbance was read at 515 nm in a spectrophotometer (Spectrophotometer UV/VIS 6705
Jenway). Results were expressed as percentage of inhibition of DPPH radical. It was calculated by the formula below:
% inhibition = Abs control – Abs sample / Abs control x 100
2.7 ABTS radical-scavenging assay
The ABTS method was performed according to Re et al. (1999). Sample absorbance was read at 734 nm by a
spectrophotometer (Spectrophotometer UV/VIS 6705 Jenway). Results were expressed as percentage of inhibition of
ABTS radical. It was calculated by the formula below:
% inhibition = Abs control – Abs sample / Abs control x 100
2.8 α-amylase inhibition assay
Inhibitory activity of α-amylase was performed according to Yu et al. (2011) with modifications. First 0.02 mL of αamylase from Bacillus licheniformis (40 unit/mL in distilled water) was incubated with 0.01 mL of fruit extracts at different
concentrations (0.1; 0.25; 0.5; 1.0; 2.5; 5.0; 10.0 mg/mL) for 15 min at 25 ºC. Then solution of soluble starch (1%) in
phosphate buffer pH 6.9 (0.5 mL) was added and it remained in a water bath at 37.5 ºC for 5 min. This reaction was stopped
by adding dinitrosalicylic (DNS) reagent (0.5 mL) (1% 3,5-dinitrosalicylic acid, 12% Na-K tartrate in 0.4 mol/L NaOH)
and it was incubated in a water bath at 100 ºC for 15 min. Acarbose was used as positive control (3.2 mg/L) (Jockovic et
al., 2013). The absorbance was read at 540 nm by a microplate reader (Spectramax 190 Molecular Devices) at room
temperature. The inhibition (%) was calculated by using the following formula:
% inhibition = Abs control – Abs sample / Abs control x 100
2.9 α-glucosidase inhibition assay
Intestinal α-glucosidase inhibitory activity was based on the method of Adisakwattana et al. (2012) with
modifications. First 25 mg of intestinal acetone powders from rat were homogenized in 0.75 mL of 0.9% sodium chloride.
Then 0.01 mL of this enzyme solution was incubated with 0.03 mL of maltose (86 mM) or with 0.04 mL of sucrose (400
mM). Further, an aliquot of 0.01 mL of each concentration of extracts (1; 2.5; 5.0; 10.0 mg/mL) and phosphate buffer pH
6.9 were added to give a final volume of 0.1mL. The reaction continued in a water bath at 37 ºC for 30 min (maltose) or
60 min (sucrose). The reaction stopped with 0.02 mL of 10% trichloroacetic acid. Acarbose was used as a positive control
(3.2 mg/L) (Jockovic et al., 2013). Absorbance was read at 510 nm by a microplate reader (Spectramax 190 Molecular
Devices) at room temperature. The inhibition (%) was calculated by using the following formula:
% inhibition = Abs control – Abs sample / Abs control x 100
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2.10 Statistical analysis
The results were expressed as mean values and standard error (SE). Data were analyzed using one-way analysis
of variance (ANOVA) followed by Tukey’s Test with P < 0.05. The statistical program used was GraphPad Prism® version
5.0. All analyses were performed in triplicate.
3. Results and Discussion
3.1 Phenolic content and antioxidant capacity
The total content of phenolic compounds and flavonoids and the antioxidant capacity of fruits analyzed in this study
are shown in Table 1.The total phenolic contents ranged from 181.48 to 541.15 mg of GAE/100 g fresh weight. Among
them, S. cumini had the highest phenolic compounds content followed by C. xanthocarpa and P. cattleianum (all accesses).
P. cattleianum accesses 44, 87 and bicudo, and S. cumini showed a higher flavonoid content. It can be said that all fruits
in the study belong to the groups of medium (100 to 500 mg of GAE/100g fresh weight) and high (> 500 mg of GAE/100g
fresh weight) phenolic compound content (Rufino et al., 2010).
Table 1.Total phenolics, total flavonoids and antioxidant capacities of metanolic extracts (80%) of the fruits from
Rio Grande do Sul, Brazil.
Antioxidant capacities
Total
Total
Fruits
Phenolics1
Flavonoids2
DPPH3
ABTS4
b
a
a
P. catteianum access 44
435,81
82,51
95,62
66,12a
b
a
a
P. catteianum access 87
439,33
85,37
93,95
65,18a
b
a
a
P. catteianum access bicudo
445,64
100,07
94,51
71,95a
b
b
a
C. xanthocarpa
495,86
52,61
95,13
55,32b
a
a
a
S. cumini
541,15
86,75
94,53
64,14a
c
c
c
E. uniflora access 156
293,48
12,65
67,10
21,78c
c
b
b
E. pyriformis access 3
399,01
43,67
87,20
25,99c
c
c
d
E. pyriformis access 4
181,48
14,35
40,78
18,32c
c
c
d
E. pyriformis access 11
240,25
20,50
47,02
21,37c
c
c
d
E. pyriformis access 15
211,93
21,84
41,60
24,13c
Date represents the mean of triplicate. Values in each column with distinct letters are significantly different (* P < 0.05)
using ANOVA and Tukey’s post hoc analysis.
1
Total phenolics compounds expressed in milligram gallic acid equivalente per 100 g of fresh weight (mg AGE/100 g fw).
2
Total flavonoids expressed in milligram of catechin equivalente per 100 g of fresh weight (mg CE/100 g fw).
3
Expressed in % of inhibition of DPPH radical.
4
Expressed in % of inhibition of ABTS radical.
Discrepant values for phenolics were found between our results and others studies. In a study of total phenolic
compounds of water extract of red and yellow P. cattleianum, values were found ranging from 632.56 to 581.02 mg of
GAE/100 g fresh weight and 402.68 to 528.30 mg of GAE/100 g fresh weight respectively (Medina et al., 2011). Another
study found lower values of phenolics for yellow P. catteianum in methanolic extract (80%) (103.10 mg of GAE/100 g
fresh weight) (Silva et al., 2014). Phenolic values found for E. pyriformis showed less variation in two studies. In the first
about 127 mg of GAE/100 g fresh weight (Rufino et al., 2009) were found and in the other about 115 mg of GAE/100 g
fresh weight (Silva et al., 2014).
These differences may be due to several factors such as humidity, type of soil, climate during the development phase
(Pepato et al., 2005; Djeridane et al., 2013), variations in maturity (Biegelmeyer et al., 2011), genetic differences and
postharvest storage conditions (Pinto et al., 2010). Furthermore, the plant extraction method (Crozier, Jaganath, & Clifford,
2009) and the method used to determine phenolics also have a great influence.
The Folin-Ciocalteu colorimetric method was widely used to determine phenolics but several non phenolic
compounds (ascorbic acid, some sugars, amino acids) having reducing power could impair their quantification (Georgé et
al., 2005). Moreover, phenolics may be in free and bound forms in plants but only free compounds can be extracted with
water or aqueous/organic solvent mixtures (Su et al., 2014).
P. cattleianum accesses 44, 87 and bicudo, and S. cumini had the highest antioxidant activities observed by the
percentage of inhibition of DPPH and ABTS radicals. The type of compound and its structure appear to be more closely
related to the antioxidant activity of fruit than the total amount of these compounds (Pinto et al., 2010). As seen in phenolic
compounds, inhibition values found in the literature varied. They are affected by the same factors. Furthermore, the results
are expressed in different ways, affecting the comparisons between the studies.
A study with yellow and red P. cattleianum (100% acetone extracts) found a radical DPPH inhibition ranging from
19.7% to 34.6% and from 35.3% to 45.3%, respectively (Medina et al., 2011). Another study with E. uniflora detected
about 35.5% of inhibition (Celli, Pereira-Netto, & Beta, 2011).
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3.2 Inhibitory activities against α-amylase and α-glucosidase
Currently available drugs for the control of hyperglycemia are effective. However, the search for alternatives that will
have less side effects is of great interest. Therefore this study assessed fruit extracts for their inhibitory potential in the
activity of α-amylase and α-glucosidase which are directly related to glucose absorption). Extracts of plants that are rich in
phenolic compounds are described as inhibiting both enzymes (Manaharan et al., 2012).
P. cattleianum access 44, S. cumini and E. pyriformis accesses 11 and 15 extracts significantly inhibited (P < 0.05)
α-amylase activity in vitro (Figure 1). P. cattleianum access 44 inhibited only at a concentration of 2.5 mg/mL (15.25 ±
5.02%). S. cumini inhibited at concentrations of 0.1 mg/mL (60.50 ± 1.37%); 0.25 mg/mL (49.46 ± 1.78%); 0.5 mg/mL
(48.41 ± 2.25%) and 1.0 mg/mL (13.16 ± 3.28%).
7
Acarbose
0.1 mg/mL
a
a
E. pyriformis access 15
0.25 mg/mL
0.5 mg/mL
a
1.0 mg/mL
2.5 mg/mL
E. pyriformis access 11
a
5.0 mg/mL
a
10.0 mg/mL
a
a
E. pyriformis access 4
E. pyriformis access 3
E. uniflora access 156
S. cumini
a
a
a
a b
C. xanthocarpa
P. cattleianum access bicudo
P. cattleianum access 87
a
P. cattleianum access 44
80
60
40
20
0
10
0
a
Acarbose
Control
% of inhibition of  -amylase activity
Fig. 1. α-amylase inhibitory activities of the fruits from Rio Grande do Sul, Brazil.
a
Indicate significantly difference (* P < 0.05) using ANOVA and Tukey’s post hoc analysis in relation of control (0% of
inhibition).
b
Indicate significantly difference (* P < 0.05) between different concentrations of the same group.
c
Date represents the mean of triplicate.
8
Extract of S. cumini was responsible for the highest percentage of inhibition of α-amylase activity at lower
concentrations (0.1 mg/mL). This same trend was observed in the other extracts.
The population traditionally used S. cumini as a hypoglycemiant agent (Trojan-Rodrigues et al., 2012). Barcia et al.
(2012) found that the main phenolic compounds from the fruit were epicatechin, gallic acid, caffeic acid, cyanidin-3glycoside, pelargonidin, condensed and hydrolysable tannins. The tannins can inhibit the activity of both α-amylase and αglucosidase through binding to the active site of the enzyme or some other secondary site (Souza et al., 2012).
Flores et al. (2013) consider that the concentration of tannins is directly related to the inhibitory activity of α-amylase.
A study showed that soluble and hydrolysable tannins of red fruits were able to inhibit α-amylase because, when they were
removed, inhibition stopped (McDougall et al., 2005). Furthermore, the possible presence of anthocyanins increases
inhibition promoted by these tannins (Grussu, Stewart, & McDougall, 2011).
Accesses 11 and 15 of E. pyriformis also inhibited the enzyme, however there was less inhibition (25 to 38%) as
observed in the study by Grussu et al. (2011) with yellow raspberry. The main phenolic compound found in E. pyriformis
was gallic acid and its derivatives such as HHDP-bis-hexoside (elagitannin) (Silva et al., 2014).
The results of a study that evaluated the inhibitory potential of six flavonoid groups in relation to the porcine
pancreatic α-amylase showed that myricetin (64%) was the compound that provided the greatest inhibition followed by
luteolin (61%) and quercetin (50%). From these results, a relationship was found between the number of hydroxyl groups
in B ring and enzyme inhibition in which compounds with more hydroxyl groups in B ring more strongly inhibited the
enzyme (Tadera et al., 2006).
The α-amylase inhibition was also attributed to the catechins. These were able to bind to the active site side chains,
resulting in a complex that prevents the substrate from binding (noncompetitive inhibition). The variation in catechin
structure can affect its power of inhibition. When adding the galloyl group, the compound formed is capable of exerting
powerful inhibition (Miao et al., 2014).
However, high inhibition of α-amylase was not very useful because of possible adverse effects such as abdominal
distention and discomfort due to the presence of undigested starch (Pinto et al., 2010) that could ferment in the colon
(Rubilar et al., 2011).
The results were difficult to discuss because of the variability of the methods used. The type of enzyme and substrate
chosen interfered in the results. It was observed that when using starch as substrate, epigallocatechin gallate and cyanidin
significantly inhibited the activity of α-amylase. However, these two compounds were capable of only weakly inhibiting
the same enzyme when using a synthetic substrate (p-nitrophenyl maltoheptaoside) (Tadera et al., 2006).
Maltose and sucrose were used as substrates for the evaluation of α-glucosidase activity. The choice was due to the
commercial enzyme used in the experiment that has multiple α-glucosidases with a greater prevalence of maltase and
sucrase.
P. cattleianum accesses 44 and 87 were capable of significantly inhibiting maltase activity (P < 0.05) and access 44
inhibited at concentrations of 2.5 mg/mL (35.43 ± 5.26%); 5.0 mg/mL (61.77 ± 3.39%) and 10.0 mg/mL (55.86 ± 1.61%).
Access 87 inhibited only at concentrations of 5.0 mg/mL (38.44 ± 6.28%) and 10.0 mg/mL (30.65 ± 11.33%) (Figure 2).
Accesses 44 and 87 were also responsible for sucrase inhibition at concentrations of 5.0 mg/mL and 10.0 mg/mL.
9
Acarbose
1.0 mg/mL
2.5 mg/mL
5.0 mg/mL
10.0 mg/mL
E. pyriformis access 15
E. pyriformis access 11
E. pyriformis access 4
E. pyriformis access 3
E. uniflora access 156
S. cumini
C. xanthocarpa
P. cattleianum access bicudo
a
a
P. cattleianum access 87
ab
ab
P. cattleianum access 44
a
a
Acarbose
Control
0
20
40
60
80
10
0
% of inhibition of -glucosidase activity
Fig. 2. α-glucosidase inhibitory activities of the fruits from Rio Grande do Sul, Brazil, using maltose substrate.
a
Indicate significantly difference (* P < 0.05) using ANOVA and Tukey’s post hoc analysis in relation of control (0% of
inhibition).
b
Indicate significantly difference (* P < 0.05) between different concentrations of the same group.
c
Date represents the mean of triplicate.
10
Inhibitions of 37.58 ± 3.75% and 36.70 ± 6.92% (access 44) and 18.45 ± 6.23% and 15.83 ± 6.83% (access 87) were
found (Figure 3).
Acarbose
1.0 mg/mL
2.5 mg/mL
5.0 mg/mL
10.0 mg/mL
E. pyriformis access 15
E. pyriformis access 11
E. pyriformis access 4
E. pyriformis access 3
E. uniflora access 156
S. cumini
C. xanthocarpa
P. cattleianum access bicudo
a
a
P. cattleianum access 87
a
a
P. cattleianum access 44
0
10
60
40
20
0
80
a
Acarbose
Control
% of inhibition of -glucosidase activity
Fig. 3. α-glucosidase inhibitory activities of the fruits from Rio Grande do Sul, Brazil, using sucrose substrate.
a
Indicate significantly difference (* P < 0.05) using ANOVA and Tukey’s post hoc analysis in relation of control (0% of
inhibition).
b
Date represents the mean of triplicate.
It was observed that only the highest concentrations of the extracts were able to inhibit maltase and sucrase, unlike
what was observed in the inhibition of α-amylase. P. cattleianum access 44 was able to inhibit the maltase activity of more
than 50%. A study with red fruits of P. cattleianum determined its major phenolic compounds finding cyanidin-3-glucoside,
malvidin-3-glucoside and cyanidin chloride (Dalla Nora et al., 2014).
Researchers evaluated the effect of phenolic compounds of Davidson’s plum, a native fruit of Australia, on the activity
of α-glucosidase and found a dose-dependent inhibition. Elagitannins were the main compounds found in this fruit,
followed by anthocyanins and flavonoids such as myricetin (Sakulnarmrat, Srzednicki, & Konczak, 2014). The
glycosylated anthocyanins could inhibit this enzyme competitively (Flores et al., 2013).
Red raspberry was able to inhibit α-glucosidase activity. Compounds which were found and responsible for this were
ellagic acid, cyanidin-diglucoside, pelargonidin-3-rutinoside and catechin (Zhang et al., 2010). In another study, rich
fraction raspberry anthocyanins were able to inhibit α-glucosidase (McDougall et al., 2005). However the activities of the
extracts containing anthocyanins and anthocyanidins may be impaired by freeze-drying and rehydration because of pigment
degradation (Flores et al., 2013).
Likewise for the α-amylase enzyme, enzymes of different origins showed different results. When assessing yeast
inhibition, α-glucosidase, cyanidin (99%), myricetin (94%) and genistein (93%) were the main inhibitors. When using rat
small bowel α-glucosidase, the main inhibitors were epigallocatechin gallate (32%), myricetin (29%) and quercetin (28%)
(Tadera et al., 2006).
11
Some features were very important for the inhibitory capacity of these compounds, such as hydroxylation at positions
3, 5 of B ring and 6 of A ring; and galloylation at position 3 of the C ring. On other hand, the hydrogenation of the double
bond and glycosylation of the hydroxyl group in C ring decrease this inhibitory capacity. However cyanidin glycosides
showed greater inhibition when compared with cyanidin. This may be due to the binding site and the type of sugar (Xiao
et al., 2013).
The extracts of P. cattleianum access bicudo, E. uniflora, E. pyriformis accesses 3 and 4 did not significantly inhibit
α-amylase and α-glucosidase activity in our study. Pinto et al. (2010), Djeridane et al. (2013) and Podsędek et al. (2014)
report that inhibition of the activity of both enzymes seems not to depend on total phenolic compounds but the
characteristics of the individual compounds such as concentration, structure and interaction between them (Grussu et al.,
2011; Podsędek et al., 2014). These characteristics can contribute to the stability, solubility, and binding ability of these
compounds to target enzymes (Podsędek et al., 2014).
4. Conclusions
Plant species evaluated in this study can be classified as fruits that have medium to high content of phenolic
compounds with high percentages of of DPPH radical inhibition. Furthermore, the methanol extracts of P. cattleianum
accesses 44 and 87, S. cumini and E. pyriformis accesses 11 and 15 were effective in inhibiting the activity of α-amylase
and / or α-glucosidase in vitro.
Some evidence suggests that polyphenols are involved in the prevention of chronic diseases, including T2DM. Thus,
the results described encourage further studies by determining the major compounds and evaluation of these in vitro and
in vivo to define those responsible for the reported activities. The characterization of substances that can modulate
postprandial hyperglycemia is very important in the prevention and / or treatment of T2DM.
5. Acknowledgement
This study was support by CNPq. We thank Embrapa Clima Temperado for the supply of fruits.
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