Antioxidant and α-Glucosidase Inhibitory Activity of Colored Grains in China

Abstract

Colored grains including red, purple, and black rice, purple corn, black barley, and black soybean contain anthocyanins. The present study was designed to (i) identify and quantify the individual anthocyanins and measure the total phenolic content (TPC), (ii) evaluate the antioxidant and alpha-glucosidase inhibitory activity, and (iii) correlate the TPC with total antioxidant activity and alpha-glucosidase inhibitory potency in these colored grains. The TPC was measured using a Folin-Ciocalteu assay, while the total antioxidant activity was determined by a method based on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity. Among all of the studied colored grains, black rice possessed the highest TPC, which was 86 times greater than that of red rice. In addition, black rice had the highest total anthocyanin contents and alpha-glucosidase inhibitory activity. A significant positive correlation of the antioxidant activity and alpha-glucosidase inhibitory activity with total anthocyanin content and TPC was observed in this study. It is concluded that black rice possesses the highest antioxidant activity and alpha-glucosidase inhibitory among all of the colored grains tested and can be further explored as a functional food.

Full text

pubs.acs.org/JAFC©XXXX American Chemical Society
J. Agric. Food Chem. XXXX, XXX, 000–000 A
DOI:10.1021/jf903234c
Antioxidant and r-Glucosidase Inhibitory Activity of Colored
Grains in China
Y
ANG
Y
AO
,
†
W
EI
S
ANG
,
†
M
ENGJIE
Z
HOU
,
‡
AND
G
UIXING
R
EN
*
,†
†
Institute of Crop Science, Chinese Academy of Agricultural Sciences, No. 80 South Xueyuan Road,
Haidian District, Beijing 100081, People’s Republic of China and
‡
Dong Zhimen Middle School, No. 2
North Shuncheng Street, Dong Cheng District, Beijing 100007, People’s Republic of China
Colored grains including red, purple, and black rice, purple corn, black barley, and black soybean
contain anthocyanins. The present study was designed to (i)identify and quantify the individual
anthocyanins and measure the total phenolic content (TPC),(ii)evaluate the antioxidant and
R-glucosidase inhibitory activity, and (iii)correlate the TPC with total antioxidant activity and
R-glucosidase inhibitory potency in these colored grains. The TPC was measured using a
Folin-Ciocalteu assay, while the total antioxidant activity was determined by a method based on
the 1,1-diphenyl-2-picrylhydrazyl (DPPH)radical-scavenging activity. Among all of the studied
colored grains, black rice possessed the highest TPC, which was 86 times greater than that of
red rice. In addition, black rice had the highest total anthocyanin contents and R-glucosidase
inhibitory activity. A significant positive correlation of the antioxidant activity and R-glucosidase
inhibitory activity with total anthocyanin content and TPC was observed in this study. It is concluded
that black rice possesses the highest antioxidant activity and R-glucosidase inhibitory among all of
the colored grains tested and can be further explored as a functional food.
KEYWORDS: Anthocyanins; antioxidant; R-glucosidase inhibitory
INTRODUCTION
Interest in glucosidase inhibitors is growing because it has
implication in the management of diabetes mellitus (DM). DM is
a serious metabolic disorder that affects approximately 4% of the
population worldwide and is expected to increase to 5.4% in
2025 (1). Grains and cereals are generally recommended for
diabetic patients to control their blood glucose level (2,3). Acting
as a key enzyme for carbohydrate digestion, intestinal R-gluco-
sidase is one of the glucosidases located at the epithelium of the
small intestine. R-Glucosidase has been recognized as a thera-
peutic target for modulation of postprandial hyperglycemia,
which is the earliest metabolic abnormality to occur in type-2
DM (4,5). The inhibition on intestinal R-glucosidases would
delay the digestion and absorption of carbohydrates and, conse-
quently, suppress the postprandial hyperglycemia (6).
Antioxidants refer to compounds possessing free-radical-
scavenging activity, transition-metal-chelating activity, and/or
singlet-oxygen-quenching capacity (7,8). Accumulated evidence
has suggested that diabetic patients are under oxidative stress,
with an imbalance between the free-radical-generating and radi-
cal-scavenging capacities. The increased free-radical production
and reduced antioxidant defense may partially mediate the
initiation and progression of diabetes-associated complications
(9,10). Colored grains are rich in pigments called anthocyanins.
Among these anthocyanins, cyanidin-3-glucoside has an antiox-
idant activity that is 3.5 times stronger than Trolox (vitamin E
analogue) (11). A structure-activity relationship study has re-
vealed that the antioxidant activity of anthocyanidins is depen-
dent upon positions of hydroxylation and glycosylation (11).
Despite some research on anthocyanins in some colored grains,
a systematic comparison on their relative abundance and anti-
oxidant and glucosidase-inhibiting activity is lacking. The present
study was therefore carried out to (i) identify and quantify the
individual anthocyanins and total phenolic content (TPC) in red,
purple, and black rice, purple corn, black barley, and black
soybean and (ii) assess their relative antioxidant and R-glucosi-
dase inhibitory activities.
MATERIALS AND METHODS
Materials.
Red, purple, and black rice, purple corn, and black barley
were provided by the Chinese National Genebank (Beijing, China).
Individual anthocyanin standards (cyanidin-3,5-diglucoside, cyanidin-3-
glucoside, cyanidin-3-arabinoside, delphindin-3-glucoside, malvidin-3-
glucoside, petunidin-3-glucoside, peonidin-3-arabinoside, peonidin-3-
glucoside, and peonidin-3-galactoside) (Figure 1)wereobtainedfrom
polyphenols (Sandnes, Norway). Standards of gallic acid, Trolox, 1,1-
diphenyl-2-picrylhydrazyl (DPPH) radical, Folin-Ciocalteu phenolic
reagent, and rat intestinal acetone powder were purchased from Sigma-
Aldrich (St. Louis, MO). Ethanol and trifluoroacetic acid (TFA) were
obtained from Beijing Chemical Reagent (Bejing, China).
Extraction.
All samples were dried at 40 °C, ground in a laboratory
mill, and passed through a 80-mesh screen sieve. Extractions were carried
out according to the method previously described, with slight modifica-
tions (12 ). Briefly, 10 g of samplewas extracted twice in 100 mL ofethanol
acidified with 1.0 N HCl (85:15, v/v) for 2 h at room temperature. After
*To whom correspondence should be addressed. Telephone: þ86-
10-6211-5596. Fax: þ86-10-6215-6596. E-mail: renguixing@caas.
net.cn.

BJ. Agric. Food Chem., Vol. XXX, No. XX, XXXX Yao et al.
vacuum filtration at 50 °C, the supernatants were combined and concen-
trated to
1
/
3
volume under a reduced pressure in a rotary evaporator. The
resultant extracts were then stored at 4 °Cuntilanalysis.
Determination of TPC.
TPC was measured using the Fo-
lin-Ciocalteu method described previously by Zhou et al. (13 )and
modified by Fang et al. (14). Briefly, 50 μL of the extract was mixed in
5 mL of distilled deionized water followed by the addition of 500 μLof
Folin-Ciocalteu reagent (1 M) and 500 μLofNa
2
CO
3
(20%, w/v). The
mixture was thoroughly mixed and allowed to stand for 60 min at room
temperature before the absorbance was measured at 765 nm (Bio-Rad
Smart Spec Plus spectrophotometer, Hercules, CA). Quantification was
performed with respect to the standard curve of gallic acid. The results
were expressed as milligrams of gallic acid equivalent (GAE) per 100 g of
dry weight (dw). All determinations were performed in triplicates.
Determination of Total Anthocyanins.
Quantification of anthocy-
nins was carried out as previously described by Giusti et al. (15). Samples
were dissolved in 0.025 M potassium chloride solution (pH 1.0) and
0.4 M sodium acetate buffer (pH 4.5), and the absorbance was measured
at 510 and 700 nm in a BioRad Smart Spec Plus spectrophotometer. Data
were expressed as milligrams of anthocyanins per 100 g of fresh weight of
seed powder using a molar extinction coefficient of 26 900, a molecular
weight of 449, and an absorbance of A=[(A
510
-A
700
)pH1.0-
(A
510
-A
700
)pH4.5].
High-Performance Liquid Chromatography (HPLC)Analysis of
Individual Anthocyanidins.
A HPLC system equipped with two Shi-
madzu LC-20Apumps, a Shimadzu LC-20 autosampler, a SPD-20A UV/
vis detector, and an Alltima C18 column (4.6 250 mm, Metachem
Technologies, Inc., Torrance, CA) was used. The wavelength of the UV
detector was set at 520 nm. The mobile phase was a mixture of solvent A
(HPLC water containing 0.1% TFA) and solvent B (acetonitrile contain-
ing 0.1% TFA). The elution started with 5% B with a linear gradient to
25% B in 38 min and then to 90% B from 38 to 55 min. The flow rate was
set at 1.0 mL/min, and the injection volume was 10 μL. Each anthocya-
nidin was quantified according to its calibration curve.
Evaluation of the Total Antioxidant Activity Using the DPPH
Method.
The DPPH radical-scavenging activity was determined using the
method reported by Yen and Chen (16 ). DPPH (100 μM) was dissolved in
96% ethanol. The extract was dissolved in ethanol in a ratio of 1:3. The
DPPH solution (1 mL) was mixed with 1 mL of the extract solution. The
mixture was shaken and allowed to stand at room temperature in the dark
for 10 min. The decrease in absorbance of the resulting solution was
monitored at 517 nm after 10 min. The results were corrected for dilution
and expressed in micromolar Trolox equivalents (TE) per 100 g of dw. All
determinations were performed in triplicates (n= 3).
Measurement of r-Glucosidase Inhibitory Activity.
The R-gluco-
sidase inhibitory activity was determined as described previously, with
some slight modification (17). R-Glucosidase (1 unit/mL) activity inhibi-
tion was assayed using 50 μL of extracts with varying concentrations
incubated with 100 μL of 0.1 M phosphate buffer (pH 7.0) in 96-well plates
at 37 °C for 10 min. After preincubation, 50 μLof5mMp-nitrophenyl-R-
D
-glucopyranoside solution in 0.1 M phosphate buffer (pH 7.0) was added
to each well at varying time intervals. The reaction mixtures were
incubated at 37 °C for 5 min. The absorbance readings were recorded
at 490 nm on a microplate reader before and after incubation (BioRad,
IMAX, Hercules, CA). The results were expressed as a percentage
of R-glucosidase inhibition and calculated according to the following
equation: percent inhibition = Abs
control
-Abs
extract
100/Abs
control
.
IC
50
is defined as the concentration of grain extracts required to inhibit
50% of the enzyme activity.
Statistical Analysis.
All values were expressed as mean (standard
deviation (SD). Data were analyzed using one-way analysis of variance
(ANOVA) followedby posthoc Dunnett’s ttest. Differences withp<0.05
were considered significant.
RESULTS AND DISCUSSION
Individual Anthocyanidins.
We used HPLC to quantify the
individual anthocyanins in these colored grains. Table 1 showed
Figure 1.
Chemical structures of anthocyanins in colored grains.

Article J. Agric. Food Chem., Vol. XXX, No. XX, XXXX C
the contents of individual anthocyanidins in red, purple, and black
rice, purple corn, black barley, black soybean, and black soybean
seed coat. Figure 2 showed typical HPLC chromatograms of
anthocyanin profiles in these colored grains. It was noticed that
red rice contained only cyaniding-3-glucoside, while purple and
black rice contained four types of anthocyanins, namely, cyanid-
ing-3-glucoside, delphindin-3-glucoside, petunidin-3-glucoside,
and peonidin-3-glucoside. Black barley had three species of antho-
cyanins, including cyanidin-3-glucoside, delphindin-3-glucoside,
and petunidin-3-glucoside, while black soybean coat contained
Table 1. Average Concentration of Antrocyanins in Red, Purple, and Black Rice, Purple Corn, Black Barley, Black Soybean, and Black Soybean Coat (mg/100 g)
a
red rice purple rice black rice purple corn black barley black soybean black soybean coat
cyanidin-3,5-diglucoside nd nd nd nd nd nd nd
cyanidin-3-glucoside 1.50 (0.13 148.83 (7.88 631.01 (13.08 20.18 (1.38 2.52 (0.71 21.29 (2.25 199.26 (5.49
cyanidin-3-arabinoside nd nd nd nd nd nd nd
delphindin-3-glucoside nd 8.38 (0.26 71.03 (1.06 nd 2.13 (0.22 41.35 (3.01 365.90 (11.20
malvidin-3-glucoside nd nd nd 7.48 (0.11 nd 1.26 (0.19 4.78 (0.23
petunidin-3-glucoside nd 20.16 (1.33 90.04 (4.15 nd 28.57 (1.64 7.21 (0.34 62.32 (5.26
peonidin-3-arabinoside nd nd nd 24.82 (1.76 nd nd nd
peonidin-3-glucoside nd 82.09 (5.13 362.87 (21.08 29.61 (2.89 nd 2.92(0.14 22.55 (0.98
peonidin-3-galactoside nd nd nd 2.67 (0.23 nd nd nd
a
nd = not detected. Data are expressed as mean (SD of triplicate samples.
Figure 2.
(A)HPLC chromatogram of anthocyanins standard. (B)HPLC chromatogram of anthocyanins from black rice. (C)HPLC chromatogram of
anthocyanins from purple corn. (D)HPLC chromatogram of anthocyanins from black barley. (E)HPLC chromatogram of anthocyanins from black soybean
coat. Peak 1, cyanidin-3,5-diglucoside; peak 2, delphindin-3-glucoside; peak 3, cyanidin-3-glucoside; peak 4, petunidin-3-glucoside; peak 5, cyanidin-
3-arabinoside; peak 6, peonidin-3-galactoside; peak 7, peonidin-3-glucoside; peak 8, malvidin-3-glucoside; peak 9, peonidin-3-arabinoside.

DJ. Agric. Food Chem., Vol. XXX, No. XX, XXXX Yao et al.
five species of anthocyanins, namely, cyanidin-3-glucoside, del-
phindin-3-glucoside, malvidin-3-glucoside, petunidin-3-glucoside,
and peonidin-3-glucoside.
TPC and Total Anthocyanins Content (TAC).
TPC measured
by the Folin-Ciocalteu method varied widely in colored
grains. Phenolic compounds are considered as the major
compounds that contribute to the total antioxidant activities
of the grains (18). In the present study, black rice, with an average
of 8.58 (0.56 g of GAE/100 g, was found to possess the highest
TPC among all of the studied colored grains and had GAE 86
times greater than that of red rice (0.10 (0.01 g of GAE/100 g).
Purple rice (4.62 g of GAE/100 g) also had a high level of
phenolics. Black soybean coat had an average of 5.26 g of
GAE/100 g, which was significantly higher than black soybean.
It is known that the phenolic compounds are mainly present in the
seed coats (19).
TAC varied significantly among black, purple, and red grains
(Table 2). Significant differences in the concentrations of TAC
were previously reported among black, brown, and red sor-
ghum (20 ), as well as among blue, pink, purple, and red rice (12).
In the present study, black rice had the highest TAC, followed by
black soybean coat and purple corn (Table 2). Astadi et al. (21)
reported a higher level of TAC in black soybean. At present, most
of the purple corn is used in ornamentation for its colorful
appearance and only a small amount is being used in making
naturally colored tortillas (12). In contrast, red rice had a very low
concentration of TAC, because only a small cyanidin-3-glucoside
peak was detected under the present conditions.
Antioxidant Activity.
The antioxidant activities of colored grain
extracts were evaluated by measuring their DPPH radical-scaven-
ging activities. All of the extracts exhibited strong antioxidant
activities (Table 2). Among the tested samples, black rice had
the greatest DPPH free-radical-scavenging capacity (73.47 μM
TE/g), whereas red rice had the least DPPH free-radical-scaven-
ging capacity (1.68 μM TE/g). In this research, the DPPH
scavenging activity of purple rice was higher than that in black
soybean seed coat. However, the levelsof TPC and TAC in purple
rice were lower than that in black soybean seed coat. Brown
et al. (20 ) once reported that anthocyanins contributed mainly to
total TPC and antioxidant activity. However, our results did not
support this claim. The possible reason is that anthocyanins
content in black soybean seed coat is perhaps to have a color
interference with the DPPH radical, leading to underestimation
of its antioxidant activity (21). Thus, the anthocyanins levels in
colored grains do not necessarily correspond to their DPPH
scavenging capacity (22).
r-Glucosidase Inhibition Activities.
To determine the R-gluco-
sidase inhibition ability of colored grains in vitro,wecalculated
the IC
50
values (Table 3). The black rice was the most active (IC
50
of 13.56 mg/mL), followed by the black soybean seed coat (IC
50
of 111.11 mg/mL). The IC
50
values in red rice, black barley, and
black soybean were all higher than 1000 μg. To explain, it is
known that certain polyphenols, such as anthocyanins, can
directly induce secretion of insulin from pancreatic cells in ex
vivo assays (23). Similar to acarbose, anthocyanin could act as a
competitive R-glucosidase inhibitor because of the structural
similarity between the normal substrate maltose and the glucosyl
group, which is β-linked to the anthocyanin (24).
Correlation of TPC and TAC with DPPH and r-Glucosidase
Inhibition Activities.
Correlation coefficients for TPC and TAC
with the DPPH assay and R-glucosidase inhibition activities were
shown in Table 4.Zhouetal.(13 )havedemonstratedahigh
correlation between the content of total phenolic compounds and
their antioxidant capacity. The results (Table 4) obtained in our
study showed that TPC and TAC significantly correlate with the
DPPH assay (p< 0.01). Except for red rice, black barley, and
black soybean, TPC and TAC positively correlate with R-gluco-
sidase inhibition activities. In conclusion, black rice appeared to
possess the most active antioxidant activity and R-glucosidase
inhibitory activity among all of the colored grains tested and
should be explored further as a functional food.
LITERATURE CITED
(1) Yao, Y.; Ren, G.; Wang, J. S.; Chen, F.; Wang, M. F. Antidiatbetic
of mung bean extracts in diabetic KK-A
y
mice. J. Agric. Food Chem.
2008,56, 8869–8873.
(2) Lee, S. H.; Chun, H. K.; Park, H. J.; Lee, Y. S. Supplementary effect
of the high dietary fiber rice on blood glucose in diabetic KK-A
y
mice. Korean J. Nutr. 2004,37, 75–80.
(3) Yao, Y.; Shan, F.; Bian, J. S.; Wang, J. S.; Chen, F.; Wang, M. F.;
Ren, G. D-chiro-Inositol-enriched tartary buckwheat bran extract
lowers the blood glucose level in KK-A
y
mice. J. Agric. Food Chem.
2008,56, 10027–10031.
(4) Krentz, A. J.; Bailey, C. J. Oral antidiabetic agents current role in
type 2 diabetes mellitus. Drugs 2005,65, 385–411.
(5) Lebovitz, H. E. Postprandial hyperglycemic state: Importance and
consequences. Diabetes Res. Clin. Pract. 1998,40, 27–28.
(6) Puls, W.; Keup, U.; Krause, H. P.; Thomas, G.; Hofmeister, F.
Glucosidase inhibition: A new approach to the treatment of diabetes,
obesity, and hyperlipoproteinaemia. Naturwissenschaften 1977,64,
536–537.
(7) Rice-Evans, C. A.; Miller, N. J.; Bolwell, P. G.; Bramley, P. M.;
Pridham, J. B. The relative antioxidant activities of plantderived
polyphenolic flavonoids. Free Radical Res. 1995,22, 375–283.
(8) Luiz, M.; Biasutti, A.; Garcia, N. A. Micellar effect on the scaven-
ging of singlet molecular oxygen by hydroxybenzenes. Redox Rep.
2002,7, 23–28.
Table 2. TPC, TAC, and Anti-DPPH Radical Activity of Red, Purple, and Black
Rice, Purple Corn, Black Barley, Black Soybean, and Black Soybean Coat
a
TPC TAC DPPH
red rice 0.10 (0.01 d 0.05 (0.01 f 1.63 (0.15 c
purple rice 4.62 (0.18 b 1.22 (0.08 c 30.92 (1.58 b
black rice 8.58 (0.56 a 3.83(0.04 a 73.47 (4.63 a
purple corn 1.11 (0.09 c 0.31 (0.01 d 1.68(0.19 c
black barley 0.46 (0.04 cd 0.27 (0.05 de 2.21 (0.37 c
black soybean 0.75 (0.06 cd 0.19 (0.02 e 4.59 (0.27 c
black soybean coat 5.26 (0.42 b 1.63 (0.03 b 13.94 (4.86 b
a
Data are expressed as mean (SD of triplicate samples. TPC was expressed
as grams of GAE/100 g. TAC was expressed as milligrams of anthocyanin/gram. The
anti-DPPH capacity was expressed as micromolar TE/gram. Values in the same
column sharing different letters are expressed as significantly different (p< 0.05).
Table 3. R-Glucosidase Inhibitory Activity of Red, Purple, and Black Rice,
Purple Corn, Black Barley, Black Soybean, and Black Soybean Coat
a
IC
50
red rice >1000
purple rice 475.14 (25.46
black rice 13.56 (1.2
purple corn 833.33 (56.31
black barley >1000
black soybean >1000
black soybean coat 111.11 (21.24
a
IC
50
was expressed as mg/mL.
Table 4. Correlation Coefficient of Total Phenolic Acids and Total Anthocya-
nins to DPPH and R-Glucosidase Inhibition Assays
DPPH R-glucosidase inhibition
TPC 0.916
a
-0.929
TAC 0.958
a
-0.856
a
Correlation is significant at p< 0.01 level (two-tailed).

Article J. Agric. Food Chem., Vol. XXX, No. XX, XXXX E
(9) Maritim, A. C.; Sanders, R. A.; Watkins, J. B. Effect of Rlipoic acid
on biomarkers of oxidative stress in streptozotoc in-induced diabetic
rats. J. Nutr. Biochem. 2003,14, 288–294.
(10) Jin, L.; Xue, H. Y.; Jin, L, J.; Li, S. Y.; Xu, Y. P. Antioxidant and
pancreas-protective effect of aucubin on rats with streptozotocin-
induced diabetes. Eur. J. Pharmacol. 2008,582, 162–167.
(11) Wang, H.; Cao, G.; Prior, R. Oxygen radical absorbing capacity of
anthocyanins. J. Agric. Food Chem. 1997,45, 304–309.
(12) Abdel-aal, E. M.; Young, J. H.; Rabalski, I. Anthocyanin composi-
tion in black, blue, pink, purple, and red cereal grains. J. Agric. Food
Chem. 2006,54, 4696–4704.
(13) Zhou, S.; Fang, Z.; L€
u, Y.; Chen, J.; Liu, D.; Ye, X. Phenolics and
antioxidant properties of bayberry (Myrica rubra Sieb. et Zucc.)
pomace. Food Chem. 2009,113, 394–399.
(14) Fang, Z.; Zhang, Y.; L€
u, Y.; Ma, G.; Chen, J.; Liu, D.; Ye, X.
Phenolic compounds and antioxidant capacities of bayberry juices.
Food Chem. 2009,113, 884–888.
(15) Giusti, M. M.; Rodriguez-Saona, L. K.; Wrolstad, R. E. Molar
absorptivity and color characteristics of acylated and non-acylated
pelargonidin-based anthocyanins. J. Agric. Food Chem. 1999,47,
4631–4637.
(16) Yen, G. C.; Chen, H. Y. Antioxidant activity of various tea extracts
in relation to their antimutagenicity. J. Agric. Food Chem. 1995,43,
27–32.
(17) Nishioka, T.; Wabata, J.; Aoyama, Y. Baicalein, R-glucosidase
inhibitor from Scutellaria baicalensis.J. Nat. Prod. 1998,61, 1413–
1415.
(18) Huang, W.; Xue, A.; Niu, H.; Jia, Z.; Wang, J. Optimised ultrasonic-
assisted extraction of flavonoids from Folium eucommiae and eva-
luation of antioxidant activity in multi-test systems in vitro. Food
Chem. 2009,114, 1147–1154.
(19) Madhujith, T.; Shahidi, F. Antioxidant potential of pea beans
(Phaseolus vulgaris L.). J. Food Sci. 2005,70, 85–90.
(20) Brown, C. R.; Culley, D.; Yang, C. P.; Durst, R.; Wrolstad, R.
Variation of anthocyanin and carotenoid contents and associated
antioxidant values in potato breeding lines. J. Am. Soc. Hortic. Sci.
2005,130, 174–180.
(21) Awika, J. M.; Rooney, L. W.; Waniska, R. D. Anthocyanins from
black sorghum and their antioxidant properties. Food Chem. 2004,
90, 293–301.
(22) Astadi, I. R.; Astuti, M.; Santoso, U.; Nugraheni, P. S. In vitro
antioxidant activity of anthocyanins of black soybean seed coat in
human low density lipoprotein (LDL). Food Chem. 2009,112, 659–
663.
(23) Jayaprakasam, B.; Vareed, S. K.; Olson, L. K.; Nair, M. G. Insulin
secretion by bioactive anthocyanins and anthocyanidins present in
fruits. J. Agric. Food Chem. 2005,53, 28–31.
(24) Gordon, J. M.; Derek, S. The inhibitory effects of berry polyphenols
on digestive enzymes. BioFactors 2005,23, 189–195.
Received for review September 13, 2009. Revised manuscript received
October 27, 2009. Accepted October 27, 2009. The present study was
supported by the Talent Fund (to G.R.)of the Chinese Academy of
Agricultural Sciences, the Institute Fund (2060302-2-09)from The
Ministry of Sciences and Technology, People’s Republic of China, and
Technology Promotion Fund from the Beijing Municipal Rural Affair
Committee (to Y.Y.).