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The Muskmelon (Cucumis melo L.), which includes several crops of great economic importance worldwide, belongs to the Cucurbitaceae family, and it is well recognized for culinary and medicinal purposes. The high fruit consumption produces a large quantity of waste materials, such as peels and seeds that are still rich in molecules like polyphenols, carotenoids, and other biologically active components that possess a positive influence on human health and wellness. A sustainable development in agro-food and agro-industry sectors could come through the reutilization and valorization of these wastes, which in turn, could result in reducing their environmental impact. The current study provides a biochemical characterization of cantaloupe by-products, peels and seeds, through evaluating total polyphenols, ortho-diphenols, flavonoids, and tannins content. Furthermore, the antioxidant activity was assessed in order to understand potential benefits as natural antioxidants. Overall, the peel extract revealed the highest radical's scavenging and reducing activities, moreover, it showed higher polyphenolic content than seed extract as revealed by both cromatographic and spectrophotometric analyses. The results of the present study indicate that the melon residues are a good source of natural phytochemicals useful for many purposes, such as ingredients for nutraceutic, cosmetic, or pharmaceutical industries, development of functional ingredients and new foods, and production of fertilizers and animal feed.
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Characterization of Polyphenolic Compounds in
Cantaloupe Melon By-Products
Filomena Monica Vella 1, Domenico Cautela 2and Bruna Laratta 1, *
1Consiglio Nazionale delle Ricerche (CNR), Istituto di Ricerca sugli Ecosistemi Terrestri (IRET),
via P. Castellino, 111-80131 Napoli, Italy;
2Stazione Sperimentale per le Industrie delle Essenze e dei derivati dagli Agrumi (SSEA), Azienda Speciale
della Camera di Commercio di Reggio Calabria, via T. Campanella, 12-89125 Reggio Calabria, Italy;
*Correspondence:; Tel.: +39-081-6132329
Received: 2 April 2019; Accepted: 1 June 2019; Published: 6 June 2019
The Muskmelon (Cucumis melo L.), which includes several crops of great economic
importance worldwide, belongs to the Cucurbitaceae family, and it is well recognized for culinary
and medicinal purposes. The high fruit consumption produces a large quantity of waste materials,
such as peels and seeds that are still rich in molecules like polyphenols, carotenoids, and other
biologically active components that possess a positive influence on human health and wellness. A
sustainable development in agro-food and agro-industry sectors could come through the reutilization
and valorization of these wastes, which in turn, could result in reducing their environmental impact.
The current study provides a biochemical characterization of cantaloupe by-products, peels and seeds,
through evaluating total polyphenols, ortho-diphenols, flavonoids, and tannins content. Furthermore,
the antioxidant activity was assessed in order to understand potential benefits as natural antioxidants.
Overall, the peel extract revealed the highest radical’s scavenging and reducing activities, moreover,
it showed higher polyphenolic content than seed extract as revealed by both cromatographic and
spectrophotometric analyses. The results of the present study indicate that the melon residues are a
good source of natural phytochemicals useful for many purposes, such as ingredients for nutraceutic,
cosmetic, or pharmaceutical industries, development of functional ingredients and new foods, and
production of fertilizers and animal feed.
Keywords: Cucumis melo; polyphenols; flavonoids; antioxidants; by-products; waste valorization
1. Introduction
The Cucurbitaceae family covers several species of great economic importance, including
muskmelon (Cucumis melo L.), which is largely cultivated and consumed in Europe. Muskmelon
encircles a wealth of varietal types, such as smooth-skinned varieties like Honeydew, Crenshaw, and
Casaba (C. melo var. inodorous), rough-skinned varieties like Cantaloupe, Persian melon, and Santa
Claus or Christmas melon (C. melo var. reticulatus), and varieties used when they are immature as
vegetables like Barattiere, Carosello, and Armenian Cucumber (C. melo var. flexuosus). The Cantaloupe
melon is well recognized by its net-like slightly ribbed, gray-to-green or light brown skin. It is one
of the most consumed melons worldwide thanks to its sweetness, juicy taste, pleasing flavor, and
nutritional value [
]. In 2016, about 1.9 million tons of melon were harvested in the Mediterranean
area, with Spain, Italy, and France representing the main European producers, accounting for 35%,
34%, and 13% overall yield, respectively [
]. In Italy, Cantaloupe is the most cultivated variety. Its
name is supposed to derive from Italian “Cantalupo in Sabina”, which was formerly a papal county
seat near Rome [4].
Foods 2019,8, 196; doi:10.3390/foods8060196
Foods 2019,8, 196 2 of 10
Cantaloupe is an excellent source of vitamin A, vitamin C, and microelements such as potassium
and magnesium [
]. In recent years, it has been shown to possess useful medicinal properties
such as analgesic, anti-inflammatory, antioxidant, antiulcer, anticancer, antimicrobial, diuretic, and
antidiabetic properties [
]. Furthermore, it showed a hepato-protective eect, activity against
hypothyroidism and immune-modulator action [6].
Ever-increasing demand for healthy food has stimulated the manufacturing sectors to search for
new natural sources of nutritional and healthful components to be employed as food additives or
supplements, with high nutritional value [
]. As a consequence, the European Union has encouraged
the exploitation of fruit by-products for their use as a source of nutritionally and therapeutically
functional ingredients to utilize for dietary intake, and as active ingredients in pharmaceuticals and
cosmetic industries [10,11].
During fresh consumption and industrial processing of melons (juices, compotes, and salads),
large quantities of peels and seeds are produced, and are considered waste. The complete utilization
of these by-products could minimize the litter volume, so reducing the environmental impact and
the economic costs associated to their disposal. Peels and seeds, in fact, are potential sources of
phytochemicals, such as polyphenols, carotenoids, flavonoids, and other bioactive compounds with
potential health-promoting eects [
]. Among them, polyphenol compounds show antioxidant
activity, delaying or inhibiting the oxidation of lipids and other molecules, thus playing an important
role in defending cells against free radical damage, a very important way of preventing diseases like
cancer and cardiovascular disorders [1215].
Studies related to melon peels and seeds are scarce; data concerning their whole biochemical
characterization are insucient. Recently, Mallek-Ayadi et al. [
] studied only the phenolic composition
and functional properties of peels, concluding that this by-product could be considered as a rich source
of carbohydrates, proteins, calcium, potassium, and polyphenols. Fundo et al. [
] characterized the
edible and the waste parts of cantaloupe melon, only considering the bioactive compounds showing
antioxidant activity. These studies suggested that the valorization of cantaloupe by-products should
be encouraged because they are important sources of healthy compounds for food, cosmetics, and
nutraceutical products.
On this basis, this research aims to examine the peels and seeds from cantaloupe melon, evaluating
total polyphenol, ortho-diphenol, flavonoid, and tannin contents. At the best of our knowledge,
this is the first time that such a comprehensive investigation, by means of spectrophotometric,
chromatographic and
in vitro
assays, is achieved on both extracts from seeds and peels, in order to
explore their potential attitude as natural sources of antioxidants.
2. Materials and Methods
2.1. Reagents and Standards
Sodium carbonate, Folin–Ciocalteu reagent, sodium nitrite, sodium molybdate, aluminum
chloride 6-hydrate, 2,2-diphenyl-1-picrylhydrazyl (DPPH), sodium acetate, iron(III) chloride 6-hydrate,
2,4,6-tripyridyl-s-triazine (TPTZ), bovin serum albumin (BSA), standards phenolic acids (gallic,
caeic, chlorogenic, syringic, ferulic, and ellagic acids), flavonoids (rutin, quercetin, kaempferol and
isorhamnetin) and the HPLC-grade solvents were purchased from Sigma Chemical Co. (St. Louis,
MO, USA). Sodium hydroxide, hydrochloric acid and ethanol were obtained from Carlo Erba Reagents
(Milan, Italy).
2.2. Extraction of Bioactive Compounds
Three “Prescott” varieties of cantaloupe melons (Cucumis melo L. var. reticulatus) were purchased
in a local market at commercial ripening stage. Peels were manually removed with a knife and seeds
were separated too. Peels and seeds were oven-dried at 37
C, until constant weight. Randomly chosen
samples were utilized for analyses. Both samples were milled with a food mixer (Moulinex, Italy) and
Foods 2019,8, 196 3 of 10
kept at
C until extractions were performed. For bioactive compounds recovery, 200 mg of fine
powder of cantaloupe peels and seeds were extracted with 10 mL of 95% ethanol (ratio 1:50 w/v) for
6 h at 50
C in a closed vessel using an ultrasonic bath. The extracts were recovered by centrifugation
at 13,000
gfor 10 min at 4
C, and dried using a rotary evaporator (IKA RV8, IKA-Werke GmbH &
Co, Staufen, Germany).
2.3. Total Polyphenols Content
Total polyphenols were spectrophotometrically determined according to the Folin–Ciocalteu
method [
]. In brief, 150
L of extracts were mixed with 750
L of Folin–Ciocalteu reagent and 600
of 7.5% (w/v) Na
. After incubation, the absorbance was read at 765 nm (UV-Vis spectrophotometer,
model DMS-200, Varian, Leini, Italy). Total phenolic amount was calculated by a six point calibration
curve obtained with dierent quantities of gallic acid standard solution ranging from 1.5 to 10
(y =0.0768 x; R
=0.9909) and the results were expressed as mg of gallic acid equivalents (GAE) per g
of extract.
2.4. Ortho-Diphenols Content
Ortho-diphenols content was evaluated by Arnow assay [
]. Briefly, 400
L of extracts were
mixed with 400
L of 0.5 M HCl, 400
L of 1.45 M NaNO
—0.4 M Na
and 400
L of 1 M NaOH.
The absorbance was recorded at 500 nm and ortho-diphenols were determined by a calibration curve
obtained using caeic acid as standard. The ortho-diphenolic content was determined by a calibration
curve obtained using a caeic acid standard solution ranging from 5 to 50
g (y =0.0152 x; R
and the results were expressed as mg of caeic acid equivalents (CAE) per g of extract.
2.5. Flavonoid Content
Flavonoid content in the extracts was determined according to the colorimetric method based on
the formation of flavonoid-aluminum compounds [
]. In the assay, extracts were mixed with distilled
water and NaNO
. After 5 min, AlCl
O were added and the reaction was stopped by adding
1 M NaOH and distilled water. The absorbance was read at 510 nm and (+)-catechin was used to create
the standard curve. (+)-Catechin, from 5 to 100
g was used to create the calibration curve (y =0.009 x;
R2=0.9940) and the results were expressed as mg of catechin equivalents (CE) per g of extract.
2.6. Tannins Content
Total tannins were assessed as reported by Vella et al. [
] incubating extracts with BSA at 30
C for
1 h. The supernatant, representing the non-tannin fraction, was collected by centrifugation at 13,000
for 10 min at 4
C and was analyzed using the Folin-Ciocalteu method. Tannins were determined
by dierence from the amounts of the polyphenols determined before and after BSA precipitation.
Tannins were expressed as mg of gallic acid equivalents (GAE) per g of extract.
2.7. In Vitro Antioxidant Activity
The antioxidant activity of cantaloupe peels and seed extracts were evaluated by means of
in vitro
biochemical assays: The Ferric Reducing Antioxidant Power (FRAP) and the DPPH
(2,2-diphenyl-1-picrylhydrazyl) radical-scavenging activity.
As reported by Benzie and Strain [
], freshly prepared FRAP reagent were added to the extracts.
The absorbance was recorded after 4 min at 593 nm. The antioxidant activity of samples was calculated
from a calibration curve with L-ascorbic acid ranging from 0.5 to 5
g (y =0.1662 x; R
=0.9918) and
the results were expressed as mg of ascorbic acid equivalents (AAE) per g of extract.
The free radical scavenging activity (RSA) of the extracts was assessed according to the procedure
of Blois [
]. In brief, dierent concentrations of peels and seeds extracts were mixed with DPPH
methanolic solution. The absorbance reduction at 517 nm of the DPPH was determined continuously.
The RSA was calculated as a percentage of DPPH discoloration, using the following equation:
Foods 2019,8, 196 4 of 10
ADPPH #100, (1)
where A
is the absorbance of the solution when the extract was added and A
is the absorbance
of the DPPH solution. The EC
value was obtained from the graph of %RSA against the extract
concentrations in mg/mL.
2.8. Cromatographic Analyses
High performance liquid chromatography-photodiode-array-mass spectrometry (HPLC-PDA-ESI-
MS/MS) analyses were performed using a Surveyor LC pump, a Surveyor autosampler, coupled with a
photodiode array detector (PDA) Surveyor and a LCQ Advantage ion trap mass spectrometer (Thermo
Finnigan, Waltham, MA, USA) equipped with Xcalibur 3.1 software (Thermo Fisher Scientific, Waltham,
A volume of 5
L was employed for the analysis on a Supelco Spherisorb
ODS2 HPLC Column
4.6 mm), and the column was thermostatically controlled at 35
C. The elution was conducted,
as already reported [
], by employing 0.3% acetic acid solution (solvent A) and acetonitrile (solvent B).
A gradient elution was performed as following: the initial solvent was 90% A and 10% B; the gradient
elution was changed from 10% to 20% B in a linear mode for 15 min; this composition was maintained
at isocratic flow for 10 min; the solvent B reached 50% in 10 min and from 50 to 90% B in 10 min.
Elution was performed at a flow rate of 0.5 mL/min with a splitting system of 2:8 to the MS
detector (100
L/min) and PDA detector (400
L/min). Analyses were performed with an electrospray
ionization (ESI) interface in the negative mode. The optimization of the instrumental parameters for
bioactive compounds was performed by continuous infusion (FIA)-ESI MS/MS analyses. Parameters
for analysis were set using negative and positive ion modes, with spectra acquired over a mass range
from m/z50 to 1100. The ionization conditions were optimized, and the parameters used were as
follows: capillary temperature, 210
C; capillary voltage,
10.0 V; tube lens oset,
50.0 V; sheath gas
flow rate, 60.00 arbitrary units; auxiliary gas flow rate, 20.00 arbitrary units; spray voltage, 4.50 kV;
and scan range of m/z150–1200. In the MS/MS experiments, normalized collision energy of 35.0%
was applied.
PDA data were recorded with 200–600 nm range, and HPLC/UV chromatograms were acquired at
three dierent wavelengths (226, 284 and 369 nm) according to the absorption maxima of analyzed
compounds. Figure 3 shows the 284 nm absorption data for all compounds. For the quantitative analysis
of phenolic compounds, a calibration curve was obtained by the injection of dierent concentrations of
each standard. Peak identification of phenolic compounds was performed according to their retention
time, UV-Vis and mass spectra.
For the quantification of phenolic compounds by HPLC-UV, a calibration curve was obtained
through injection of dierent concentrations of standard mixture, blending aliquots of dierent stock
individual standards into a 10 mL glass volumetric flask. The standard solutions were prepared in
methanol in the range of 0.0025–0.045 mg/mL. The reproducibility of the detector response at each
concentration level was evaluated by a triplicate injection of standard mix and expressed as percentage
of relative standard deviations (RSD%). The RSDs were expected to be less than 2%. The limits of
detection (LOD) were established at a signal to noise ratio (S/N) of 3. The limits of quantification (LOQ)
were established at a signal to noise ratio (S/N) of 10. LOD and LOQ were experimentally verified by
the nine injections of reference compounds in LOQ concentrations.
2.9. Statistical Analysis
All samples were analyzed in triplicates and the results were expressed as mean
deviation (SD). Means, SD, calibration curves and linear regression analyses (R
) were determined
using Microsoft Excel 2013 (Microsoft Corporation, Redmond, WA, USA).
Foods 2019,8, 196 5 of 10
3. Results and Discussion
The phenolic composition and functional activity of melon residues, peels and seeds, were
studied in order to explore their beneficial properties in sight of potential industrial applications.
In this contribution, a biochemical characterization was obtained through the evaluation of total
polyphenols, ortho-diphenols, flavonoids, tannins, and antioxidants by means of photometric assays
and by HPLC profiling.
In Figures 1and 2polyphenol, ortho-diphenol, flavonoid, and tannin contents in cantaloupe peels
and seeds, respectively, are reported.
Figure 1. Polyphenol, ortho-diphenol, flavonoid, and tannin contents in cantaloupe peels.
Figure 2. Polyphenol, ortho-diphenol, flavonoid, and tannin contents in cantaloupe seeds.
In peels, the polyphenol content was 25.48
1.44 mg GAE/g, which is 6- and 8-fold higher than
that reported by Isamil et al. [
] and Mallek-Ayadi et al. [
], respectively. This gap could be attributed
to several factors, including cultivar, degree of ripening, and environmental elements, such as climatic
conditions and geographical origin [
]. Conversely, cantaloupe seeds content of polyphenols
was 1.50
0.02 mg GAE/g, and this result matches with the range reported in literature data [
Polyphenols are commonly found in both edible and non-edible plant parts, being essential compounds
for their growth and reproduction pathways. They also play an important role in modulating the
Foods 2019,8, 196 6 of 10
defense response against insects, pathogens, and microorganisms. Moreover, they take an active part
in determining color, flavor, taste, and appearance of fruits. Among phenolics, ortho-diphenols are
recognized as the most important in relation to their antioxidant activity, since they are able to improve
radical stability by forming an intra-molecular hydrogen bond between the hydrogen and phenoxyl
radicals. As reported in Figures 1and 2,ortho-diphenols content was 17.86
1.43 and 0.92
0.04 mg
CAE/g in peels and seeds, respectively. To the best of our knowledge, data on ortho-diphenols have
never been reported in cantaloupe until now.
Considering flavonoids, they are the most common and widely distributed group of plant
phenolics, being very eective antioxidants [
]. Cantaloupe peels showed the highest flavonoid
content of 15.19
1.88 mg CE/g, meanwhile seeds had 0.74
0.03 mg CE/g, as shown in Figures 1
and 2, respectively. In addition, these components scored higher content values, as well for the total
phenolic compounds, than those reported in the literature [
]. Moreover, similarly to polyphenols,
flavonoid content has many sources of variation such as genotype, fruit ripening, plant phenotypic
state and pedoclimatic conditions [4,19,22].
Tannins have been considered health-promoting components of plants, since possessing
anti-carcinogenic and anti-mutagenic potentials, as well as antimicrobial, antioxidant and antiradical
properties [
]. In the present study, tannins content was higher in peels than in seeds, displaying
1.44 and 0.92
0.03 mg GAE/g, respectively. The literature reports many studies comparing
polyphenolic and flavonoid contents of dierent parts of cantaloupe [
] but tannins were
never assessed.
As the phenolic compounds are known to protect cellular components against free radicals, the
antioxidant properties of cantaloupe peels and seed extracts were estimated by means of the FRAP
assay and by the DPPH radical scavenging activity, whose results are shown in Table 1. As reported by
Benzie and Strain [
], the FRAP assay measures the reduction of a ferric 2,4,6-tripyridyl-s-triazine
complex (Fe
-TPTZ) to the ferrous form (Fe
-TPTZ) in the presence of an antioxidant compound.
The antioxidant ability, measured by the FRAP assay, indicated a higher value in peels as compared to
seeds, with values of 12.27 ±1.22 mg AAE/g and 0.31 ±0.02 mg AAE/g, respectively.
Table 1. Antioxidants content and activity in cantaloupe peels and seeds.
Antioxidant Power (mg AAE/g) * EC50 (mg/mL) **
Peels 12.27 ±1.22 6.65
Seed 0.31 ±0.02 55.03
* The antioxidant power was measured by FRAP assay; ** EC50 was calculated by DPPH assay.
The scavenging activity was studied by means of the DPPH assay, based on the evaluation of the
reduction of the DPPH radical to hydrazine as a consequence of the antiradical activity of the extracts.
Similarly to the results of the FRAP assay, scavenging activity in the peels extracts was stronger since
the EC
after 15 min was 6.65 mg/mL, while seed extracts showed a value of 55.03 mg/mL, thus
indicating a lower antioxidant activity of this latter cantaloupe by-product. These results were in
agreeance with literature data: in particular, the cantaloupe peels extract in our experiment proved
to be 1.4 fold more active when compared to the results published by Isamil et al. [
]. Conversely,
seed extract showed an activity that was half than that observed and reported by Isamil et al. [
]. The
results of the DPPH assay suggest that extracts are capable of scavenging free radicals via electron or
hydrogen-donating mechanisms. Moreover, DPPH activity of these cantaloupe by-products showed
similar behavior with the polyphenols, ortho-diphenols, flavonoids, and tannins content, thus indicating
that radical scavenging activity of cantaloupe peels and seeds extracts is related to the amount of
phenolic compounds.
Nowadays, synthetic antioxidants are widely used as additives in food, pharmaceuticals, and
cosmetics, but their uses have been questioned because of their possible toxic or carcinogenic activities
due to some components formed during their degradation occurring in industrial processing [
Foods 2019,8, 196 7 of 10
Therefore, the application of natural plant-based substances may be a suitable alternatives to replace
artificial molecules, not only because of their safety, but also since they protect food, feed, and
derivatives from the deleterious eects of natural oxidation.
The two extracts from melon peels and seed were also analyzed by HPLC to evaluate the real
composition of the phenolic profiles (Figure 3).
Figure 3.
HPLC chromatograms of melon peel and seed extracts, monitored at 284 nm. (
) Standard
mixture of bioactive compounds. (
) Melon peels ethanolic extract. (
) Melon seeds ethanolic extract.
Gallic acid (Gal), Chlorogenic acid (Clo), Caeic acid (Caf), Syringic acid (Sir), Rutin (Rut), Ferulic acid
(Fer), Ellagic acid (Ell), Quercetin (Que), Kaempferol (Kae), Isorhamnetin (Iso).
Foods 2019,8, 196 8 of 10
Phenolic acids and flavonoids were quantified according to HPLC-PDA data recorded at 284 nm,
where gallic acid (2.45
0.08 mg/g), ellagic acid (0.57
0.01 mg/g), and kaempferol (0.32
0.03 mg/g)
were the main bioactive compounds found in the peels extract (Table 2; Figure 3B). In seed extract, the
richest phytochemicals were ferulic acid (1.51
0.02 mg/g), followed by kaempferol (
0.54 ±0.02 mg/g
and gallic acid (0.07
0.02 mg/g), as reported in Table 2and in Figure 3C. Peak identification of phenolic
compounds was performed according to their retention time, UV-Vis and mass spectra (Table 2).
Table 2. Bio-active contents in melon peel and seed extracts (UV-Vis, HPLC and MS data).
Bioactive Compound Retention
Time (min)
Parent Ion
Peel Extract
Seed Extract
(mg/g) λ(max)
Gallic acid (Gal) 7.39 169.0 125.1 2.45 ±0.08 0.07 ±0.02 272
Chlorogenic acid (Clo)
14.62 353.0 191.1 0.08 ±0.03 0.03 ±0.01 243,328
Caeic acid (Caf) 17.52 179.0 135.1 <LOD <LOD 287,324
Syringic acid (Sir) 18.33 198.1 153.1 <LOD <LOD 276
Rutin (Rut) 26.15 609.0 299.9 0.06 ±0.01 nd 258,356
Ferulic acid (Fer) 27.58 193.0 176.9 0.09 ±0.01 1.51 ±0.02 287,312
Ellagic acid (Ell) 29.86 301.3 229.0 0.57 ±0.01 nd 254,364
Quercetin (Que) 38.61 301.0 150.9 0.02 ±0.01 nd 255,372
Kaempferol (Kae) 39.96 285.0 185.0 0.32 ±0.03 0.54 ±0.02 266,366
Isorhamnetin (Iso) 40.51 315.0 286.0 <LOD <LOD 268,342
LOD =limit of detection S/N: 3 (n=9) LOD =0.02 µg/mL.
Gallic acid, ellagic acid and kaempferol have been reported to have antiviral, anti-mutagenic,
anticancer, antioxidant and cytotoxic eects [
]. Ferulic acid is a ubiquitous natural phenolic
compound in seeds; it exhibits a wide variety of biological activities such as antioxidant,
anti-inflammatory, antimicrobial, antiallergic, hepatoprotective, anticarcinogenic, antithrombotic,
antiviral and vasodilatory actions, increase sperm viability, metal chelation, modulation of enzyme
activity, activation of transcriptional factor [
]. Peel and seed HPLC profiles showed some dierences
from what was reported by Mallek-Ayadi et al. [
] and Zeb [
]. We suppose that these dierences
might be due to variation relating to dierent cultivar, environmental conditions during plant growth
and fruiting, plant phenotypic state, and possibly due to extraction conditions too [4,19,22].
Altogether, HPLC analysis confirms a higher level of phenolic acids and flavonoids in melon
peel than in seed extract. The diverse tissue distribution of bioactive compounds may be attributed to
dierent metabolic roles and networks active in peels and seeds due to their dierent roles in plant
architecture and physiology. Furthermore, it is important to underline that in this study ethanol was
used for chemical extraction of peels and seeds and, since it is a GRAS (Generally Recognized As Safe)
solvent, it can be utilized safely for bioactive compound recovery, to be used in the food industry.
4. Conclusions
Normally, the non-edible parts of the melon (seeds and peels) are discarded during production
processes, reaching approximately 8 to 20 million tons of waste per year worldwide [
]. The
extracts of melon exhibit valuable functional and nutraceutical properties, in the light of all the data,
spectrophotometry, HPLC profiling and biological activity, obtained in the course of the present study.
With the aim of developing new nutraceuticals, such as supplements, dietary and nutritional
products, these cantaloupe by-products seem to be very promising, opening up new perspectives
for their use, mainly due to the solubility in water and the stability of their extracts. Therefore, the
melon extracts could be used in the production of functional waters, greatly demanded by markets
and consumers all over the world, or in food and cosmetic products. Indeed, it has been observed
that these by-products act against the oxidation process, thus suggesting their possible future uses
as natural colorants and antioxidants in yogurt, biscuits, cupcakes, jellies, sweets and bread, and
in anti-wrinkle creams, soaps and bathroom foams, as reported in the literature [
]. Moreover, in
this study the reduction to a minimum of the waste volumes and the possibility of developing new
Foods 2019,8, 196 9 of 10
products, with the recovery of biomolecules with high added value, may contribute to the sustainable
management of waste biomasses that otherwise imply environmental and economic costs.
Author Contributions:
Conceptualization, B.L.; formal analysis, F.M.V., D.C. and B.L.; investigation, F.M.V. and
D.C.; writing—original draft, F.M.V. and B.L.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflict of interest.
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2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
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... Bioactive compounds, total polyphenols, ortho-diphenols, and flavonoids were extracted using 2 g of melon juice, as previously reported by Vella et al. [15] and were tested in triplicate. ...
... Flavonoids content was determined according to colorimetric method based on the formation of flavonoid-aluminum compounds, modified according to Vella et al. [15]. In the assay, amount of juice was mixed with distilled water and NaNO 2 (5% w/v) up to 1 mL. ...
... Total tannins were assessed as reported by Vella et al. [15] incubating samples with BSA at 30 °C for 1 h. The supernatant, representing the non-tannin fraction, was collected by centrifugation at 4 °C and was analyzed using Folin-Ciocalteu method. ...
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Foods and beverages are nutrient-rich systems prone to a rapid development of microorganisms that hamper their long-period storage. Particularly, yeasts are strong fermenters of fresh and processed fruits and vegetables; hence, they are often accountable for their spoilage and production of off-flavor. This work provides a quick and easy tool to recognize and count the spoilage of juices with ergosterol as distinctive biomarker of molds and yeasts. Melon juice was reconstituted at natural physical–chemical parameters according to legislation, and Saccharomyces cerevisiae was selected as yeast to contaminate the juice. Chemical and enzyme tests were performed on the fresh juice to ensure its authentic properties. Ergosterol was then evaluated using a spectrophotometric method that was proven against the official plate count test. The study showed linear and consistent results and, therefore, the ergosterol molecule may be indicated for testing molds and yeasts in contaminated beverages, replacing the common and time-consuming analysis.
... Therefore, as a source of compounds in food and health products, the value of muskmelon peel and seed has attracted attention and reuse has been encouraged. The rational utilization of flesh, peel, and seed resources of muskmelon fruit is of great significance for the sustainable development of related agricultural food and industrial sectors (Vella et al. 2019). ...
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Cadmium is toxic to plants. The accumulation of cadmium in edible plants such as muskmelon may affect the safe production of crops and result in human health problem. Thus effective measures are urgently needed for soil remediation. This work aims to investigate the effects of nano-ferric oxide and biochar alone or mixture on muskmelon under cadmium stress. The results of growth and physiological indexes showed that compared with the application of cadmium alone, the composite treatment (biochar and nano-ferric oxide) decreased malondialdehyde content by 59.12% and ascorbate peroxidase activity increased by 276.6%. Their addition can increase the stress resistance of plants. The results of soil analysis and cadmium content determination in plants showed that the composite treatment was beneficial to reduce the cadmium content in various parts of muskmelon. In the presence of high concentration of cadmium, the Target Hazard Quotient value of peel and flesh of muskmelon in the composite treatment was less than 1, which means the edible risk was greatly reduced. Furthermore, the addition of composite treatment increased the content of effective components; the contents of polyphenols, flavonoids, and saponins in the flesh of the compound treatment were increased by 99.73%, 143.07%, and 18.78% compared with the cadmium treatment. The results provide a technical reference for the further application of biochar combined with nano-ferric oxide in the field of soil heavy metal remediation, and provide a theoretical basis for further research on reducing the toxicity of cadmium to plants and improving the edible quality of crops. Graphical Abstract
... As shown in Table 2, many EPs in F&Veg wastes have better antioxidant properties. For example, the EC50 of fruit Cantaloupe Melon peel against DPPH radicals was 6.65 mg/mL [56]. The antioxidant capacity of vegetable red pepper and cucumber wastes was also high, with 2.34 ± 0.14 mmol Trolox/100 g DW in the ABTS test and 7.00 ± 0.51 mmol Fe 2+ /100 g DW in the FRAP test, respectively [99]. ...
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Non-extractable phenolic compounds (NEPs), or bound phenolic compounds, represent a crucial component of polyphenols. They are an essential fraction that remains in the residual matrix after the extraction of extractable phenolic compounds (EPs), making them a valuable resource for numerous applications. These compounds encompass a diverse range of phenolic compounds, ranging from low molecular weight phenolic to high polymeric polyphenols attached to other macro molecules, e.g., cell walls and proteins. Their status as natural, green antioxidants have been well established, with numerous studies showcasing their anti-inflammatory, anti-aging, anti-cancer, and hypoglycemic activities. These properties make them a highly desirable alternative to synthetic antioxidants. Fruit and vegetable (F&Veg) wastes, e.g., peels, pomace, and seeds, generated during the harvest, transport, and processing of F&Vegs, are abundant in NEPs and EPs. This review delves into the various types, contents, structures, and antioxidant activities of NEPs and EPs in F&Veg wastes. The relationship between the structure of these compounds and their antioxidant activity is explored in detail, highlighting the importance of structure-activity relationships in the field of natural antioxidants. Their potential applications ranging from functional food and beverage products to nutraceutical and cosmetic products. A glimpse into their bright future as a valuable resource for a greener, healthier, and more sustainable future, and calling for researchers, industrialists, and policymakers to explore their full potential, are elaborated.
... Furthermore, the collected genotypes must be characterized to obtain character information for each. For example, the melon characterization was aimed at obtaining genetic similarity from a collection of melon population (Vella et al. 2019;Esteras et al. 2020;Merheb et al. 2020;Wibowo et al. 2020;Salamah et al. 2021). After collecting several genotypes, it is necessary to select the genotypes that can be used as parents to produce high-quality new varieties that meet the community's needs (Ewing et al. 2019;Zaidi et al. 2019). ...
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Saputra HE, Syukur M, Suwarno WB, Sobir. 2022. Diversity and similarity of melon (Cucumis melo L.) groups and determination of distinguishing morphological characters. Biodiversitas 23: 6254-6261. Characterization is an important activity for the study of genotype diversity and similarity. The study was aiming at obtaining information about the diversity and similarity of melon groups and to determine morphological characters as differentiators between melon groups. The genotypes tested were IPB240, IPB283, IPBM21, IPBM23, IPBME5, IPBMETA9, UME20, UME38, UME39, UME90, UME91, UME98, UME99, UME100, UME101. Characterization was based on UPOV and IPGRI guidelines for qualitative and quantitative characters. Two qualitative characters showed no variation in all tested genotypes, namely sex expression (EK) and secondary skin color outside the groove (WKSDA). Qualitative characters that have high diversity were groove color (WA), maximum width between grooves (LMAA), groove color intensity (IWA), and flower stalk thickness (KTBN). The UME98 genotype had the most different color appearance from the other genotypes on the heatmap. The color and depth of fruit grooves are distinguishing characteristics of all genotypes. There were genotype differences in the inodorus and reticulatus types. Unlike the IPBMETA9 genotype, UME100, UME101, and UME38 formed the same clusters with the characteristics of the makuwa group. Melon group makuwa had different characteristics with the inodorus and reticulatus groups. The distinguishing characters for the makuwa type were groove depth, ratio length to diameter, the diameter of hermaphrodite flower stalks, fruit diameter, and fruit skin thickness. Melon groups in the inodorus and reticulatus groups had high similarities, making it difficult to find specific characters in all melon genotypes observed.
... The major concern, according to Vella et al. (2019), is that after consumption or industrial processing, excessive amounts of peels and seeds are generated, which usually receive inadequate disposal. ...
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The objective of this work was to apply a diffusive model to describe the drying of melon peels and use them to analyze the process for various operating conditions. For this, a numerical solution was developed considering shrinkage and diffusivity as a function of the local moisture content. This solution was obtained considering a boundary condition of the third kind. In the present work, drying of melon peels was carried out in an oven (with and without osmotic pretreatment) at temperatures of 60 and 70°C. The osmotic pretreatments were carried out in binary solutions (sucrose and distilled water) with 20 °Brix at a ratio of 1:3 (g/g) (peel to solution). According to the statistical indicators obtained, the model proposed adequately fitted to the experimental data, providing values for the chi‐square and the coefficient of determination of 7.682 × 10−4 to 2.356 × 10−3 and .99953–.99982, respectively. Both pretreatment and temperature influenced the drying parameters of the process.
... Hence, the valorization of this entire vegetable is extremely important because it can reduce waste, as well as its environmental impact and the economic costs associated with its disposal. Besides, it can also be a source of active compounds for cosmetics, and pharmaceutical products [17,32]. Citrullus lanatus has a potential use in the treatment of diabetes mellitus being investigated in vivo with obese and diabetic-induced rats. ...
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Since ancient times, plants have been an extensive reservoir of bioactive compounds with therapeutic interest for new drug development and clinical application. Cucurbitacins are a compelling example of these drug leads, primarily present in the plant kingdom, especially in the Cucurbitaceae family. However, these natural compounds are also known in several genera within other plant families. Beyond the Cucurbitaceae family, they are also present in other plant families, as well as in some fungi and one shell-less marine mollusc. Despite the natural abundance of cucurbitacins in different natural species, their obtaining and isolation is limited, as a result, an increase in their chemical synthesis has been developed by researchers. Data on cucurbitacins and their anticancer activities were collected from databases such as PubMed/MedLine, TRIP database, Web of Science, Google Scholar, and ScienceDirect and the information was arranged sequentially for a better understanding of the antitumor potential. The results of the studies showed that cucurbitacins have significant biological activities, such as anti-inflammatory, antioxidant, antimalarial, antimicrobial, hepatoprotective and antitumor potential. In conclusion, there are several studies, both in vitro and in vivo reporting this important anticancer/chemopreventive potential; hence a comprehensive review on this topic is recommended for future clinical research.
... The primary nutritional components found in watermelon and muskmelon fruits include amino acids, ascorbic acid, β-carotene, carbohydrates, fatty acids, flavonoids, minerals, potassium, sugars, vitamins, and a number of bioactive compounds [2,[5][6][7][8]. They also possess beneficial medicinal properties such as analgesic, anticancer, anti-inflammatory, antimicrobial, antioxidant, antiulcer, and hepatoprotective properties [9,10]. More interestingly, the watermelon fruit is a great natural source of lycopene and also principally contains about 93% water [2]. ...
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Fruit rot of cucurbits caused by several pathogenic fungi has become an important postharvest disease worldwide. In 2022, fruit rot on watermelon (Citrullus lanatus) and muskmelon (Cucumis melo) was observed during the postharvest storage phase in the Chiang Mai and Phitsanulok Provinces of northern Thailand. These diseases can lead to significant economic losses. This present study was conducted to isolate the causal agent of fungi in lesions of fruit rot. A total of four fungal isolates were obtained, of which two isolates (SDBR-CMU422 and SDBR-CMU423) were obtained from rot lesions of watermelons, while the remaining isolates (SDBR-CMU424 and SDBR-CMU425) were obtained from rot lesions of muskmelons. All fungal isolates were identified using both morphological characteristics and molecular analyses. Morphologically, all isolated fungal isolates were classified into the genus Fusarium. Multi-gene phylogenetic analyses of a combination of the translation elongation factor 1-alpha (tef-1), calmodulin (cam), and RNA polymerase second largest subunit (rpb2) genes reveled that four fungal isolates belonged to the Fusarium incarnatum–equiseti species complex and were distinct from all other known species. Thus, we have described them as two new species, namely F. citrullicola (SDBR-CMU422 and SDBR-CMU423) and F. melonis (SDBR-CMU424 and SDBR-CMU425). A full description, illustrations, and a phylogenetic tree indicating the position of both new species have been provided. Moreover, pathogenicity tests were subsequently performed and the results showed that F. citrullicola and F. melonis caused symptoms of fruit rot on inoculated watermelon and muskmelon fruits, respectively. Notably, this outcome was indicative of the symptoms that appeared during the postharvest storage phase. To our knowledge, two new pathogenic fungi, F. citrullicola and F. melonis, are new causal agents of watermelon and muskmelon fruit rot, respectively. Importantly, these findings provide valuable information for the development of effective strategies for the monitoring and prevention of these diseases.
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Visando promover um mapeamento dos trabalhos relacionados à produção e aplicação de antioxidantes naturais em cosméticos, utilizaram-se os bancos de dados Periódicos, Pub Med e Scielo, de forma a avaliar o panorama do estágio atual no desenvolvimento científico e tecnológico nesta área. A pesquisa demonstrou a liderança da China na produção científica voltada ao tema, sendo a maioria dos trabalhos publicados na revista Molecules no ano de 2020. A partir do estudo nas diversas bases, é notável que o número de artigos publicados relacionados à área investigada ainda é limitado, demonstrando a necessidade de mais estudos e investigações para ampliação do aporte tecnológico acerca de tal conteúdo
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Plants are rich in phytochemicals and they use them for their basic processes including growth and development. Besides playing pivotal roles in the plants, phytochemicals also have different biological activities such as antiviral, antitumour, anti-inflammatory and antimicrobial activity. Many of the plant-based compounds have shown health-promoting activities. Medicinal plants are still used in various countries for primary health-care purposes due to their bioactivities. Scientists have tried to isolate the active compounds from the plants which have medicinal properties during the nineteenth and twentieth centuries. Secondary metabolites including alkaloid, saponins, lignans and terpenes are produced through numerous biosynthetic pathways, including shikimate, malonyl-CoA, mevalonate and pentose phosphate pathways. Among the angiosperms, it has been reported that Amaranthaceae, Apiaceae, Cucurbitaceae, Lamiaceae, Lauraceae, Poaceae, Rutaceae and Solanaceae are the major plant families rich in phytochemicals. Due to their huge medicinal importance, researchers are now attempting to obtain plant-derived bioactive compounds in higher amounts for their usage in nutraceuticals and medicinal industries. This book chapter includes information about phytochemical extraction, biosynthesis and their biological activities in some important plant families including Amaranthaceae, Apiaceae, Cucurbitaceae, Lamiaceae and Lauraceae.
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Food waste utilization is a strategy to reduce residues and add value to new products. Fruits, particularly their residues, are associated with a decreased risk of cancer; this may be attributed to the presence of phytochemical constituents, such as polyphenols. Melon is a fruit consumed worldwide, especially in tropical countries. The high consumption of melon is accompanied by large amounts of waste generated from its processing, including waste from barks, peels and seeds. These data are significant, especially in the current scenario of sustainable development, with the proposal to reduce waste in industries and foodservice sectors. This review summarizes the current state of knowledge regarding melon residues (Cucumis melo L.) and their role in health promotion and biotechnology applications. Discussion of the potentialities of the melon and its application for value aggregation are encouraged, based on its nutritional properties, antioxidant capacity, antiproliferative effect and its potential for substrate to solid state fermentation. Melon wastes, such as seeds and peel, are of interest thanks to their bioactive compounds that makes them a good alternative for valorization of fruit processing by-products.
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Although it is known that fruit products are rich sources of natural bioactive compounds, information on the nutritional value of their waste parts is scarce. The objective was to characterize the edible (juice and pulp) and waste (peel and seeds) parts of Cantaloupe melon (Cucumis melon L. var. reticulatus) in terms of some physicochemical characteristics, bioactive compounds and total antioxidant activity. Juice, pulp, peel and seeds represent 42, 23, 25 and 7% of total weight, respectively. Juice and pulp presented identical profiles in terms of physicochemical characteristics, bioactive compounds and antioxidant activity. They contributed to the majority of the overall content of carotenoids (80%) and vitamin C (84%) in Cantaloupe. Peel and seeds had the highest concentrations of potassium, being seeds the richest portion (7.08 ± 0.16 mg/g). Seeds had also the significantly highest total phenolics concentration (229.13 ± 20.92 µg/g), antioxidant activity (653.67 ± 169.20 µg/g), and soluble solids content (11.79 ± 0.90 °Brix). Peel stood out by the presence of chlorophylls. Since waste parts of Cantaloupe melon represent around 32% of total weight, their valorization is a challenge and strategies to improve ways of re-using them should be developed.
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Phenolic composition of different extracts of honeydew melon seeds and their antioxidant activity was determined for the first time. Phenolic compounds were identified using a reversed phase high performance liquid chromatography with diode array detection (HPLC-DAD) method. Results showed the identification of five phenolic compounds in water extract namely gallic acid and its derivative, hydroxybenzoic acid and catechin derivatives and caffeic acid. There were nine phenolic compounds identified in methanol–water extract, which are caffeic acid, two vanillic acid derivatives, ellagitanins, quercetin-3-rutinoside, derivatives of syringic acid and ellagic acid. The amounts of gallic acid, caffeic acid and catechin were higher among all phenolic compounds. Total phenolic compounds and radical scavenging activity were higher in water and methanol–water extract than their corresponding methanol extracts. In conclusion, melon seeds are a good source of natural antioxidants with significant biological functions and may serve as food ingredients and as fortifying material for maintaining shelf life.
Proanthocyanidins (syn condensed tannins) are complex flavonoid polymers naturally present in cereals, legume seeds and particularly abundant in some fruits and fruit juices. They share some common structural features—phenolic nature and high molecular weight—with phenolic polymers found in black tea and red wine (called here tannin‐like compounds). The polymeric nature of proanthocyanidins makes their analysis and estimation in food difficult. For this reason, little is known about their consumption, although they likely contribute a large part of the daily polyphenol intake. They also share common physicochemical properties: they form stable complexes with metal ions and with proteins and are, like other polyphenols, good reducing agents. Many of their biological effects of nutritional interest derive from these properties. As metal ion chelators, they influence the bioavailability of several minerals. The nutritional significance of the non‐specific complexation of proteins is less clear. As reducing agents, they may participate in the prevention of cancers, both of the digestive tract and inner organs. They may also protect LDLs against oxidation and inhibit platelet aggregation and therefore prevent cardiovascular diseases. In vitro , animal and human studies on the prevention of these chronic diseases are reviewed with particular attention to wine and tea polyphenols. The lack of data on their bioavailability and the paucity of human studies are emphasised. © 2000 Society of Chemical Industry
Quantitative data for hydroxybenzoic acids (naturally occurring and permitted additives) and their conjugates in foods and beverages are summarised. Tea, rosaceous fruits, red wines and potatoes are important sources for which more comprehensive compositional data are required. Their absorption, metabolism, toxicological evaluation and possible biological significance are discussed. There are insufficient data to properly define the dietary burdens, but it would seem that ellagic acid and gallic acid from natural sources may dominate in many cases, although the intake of added benzoic acid may be of a similar magnitude. It is pointed out that an additional, previously overlooked and possibly significant burden, particularly of benzoic acid itself, might arise as a result of the gut flora metabolism of larger‐mass dietary phenols. © 2000 Society of Chemical Industry
Phenolics in Food and Nutraceuticals is the first single-source compendium of essential information concerning food phenolics. This unique book reports the classification and nomenclature of phenolics, their occurrence in food and nutraceuticals, chemistry and applications, and nutritional and health effects. In addition, it describes antioxidant activity of phenolics in food and nutraceuticals as well as methods for analysis and quantification. Each chapter concludes with an extensive bibliography for further reading. Food scientists, nutritionists, chemists, biochemists, and health professionals will find this book valuable.
The underutilised forest and industrial biomass of Castanea sativa (Mill.) is generally discarded during post-harvest and food processing, with high impact on environmental quality. The searching on alternative sources of natural antioxidants from low-cost supplies, by methods involving environment-friendly techniques, has become a major goal of numerous researches in recent times. The aim of the present study was the set-up of a biomolecules extraction procedure from chestnut leaves, burs and shells and the assessing of their potential antioxidant activity. Boiling water was the best extraction solvent referring to polyphenols from chestnut shells and burs, whereas the most efficient for leaves resulted 60% ethanol at room temperature. Greatest polyphenol contents were 90.35, 60.01 and 17.68 mg gallic acid equivalents g⁻¹ in leaves, burs and shells, respectively. Moreover, flavonoids, tannins and antioxidant activity were assessed on the best extract obtained from each chestnut by-product.
The aim of this work is to investigate the phytochemical composition and functional properties of the melon peels, considered as a by-product. Melon peels (maazoun cultivar) are rich in nutritional ingredients such as carbohydrates (69.77%) and ash (3.67%). They contain significant amounts of total dietary fibers (41.69%) and antioxidants as polyphenols and flavonoids (332 mg/100g extract and 95.46 mg/100g extract, respectively). The identification and the quantification of the phenolic compounds of melon peels were performed by high performance liquid chromatography apparatus. The obtained results indicate that hydroxybenzoic acids and flavones constitute their main phenolic classes. 3-Hydroxybenzoic acid is the major phenolic compound in the melon peels by 33.45 mg/100g, followed by apigenin-7-glycoside (29.34 mg/100g). Determination of the functional properties (water and oil retention capacities) and color shows that melon peels have properties that may be useful in industrial applications.
Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases is emerging. Bioavailability differs greatly from one polyphenol to another, so that the most abundant polyphenols in our diet are not necessarily those leading to the highest concentrations of active metabolites in target tissues. Mean values for the maximal plasma concentration, the time to reach the maximal plasma concentration, the area under the plasma concentration-time curve, the elimination half-life, and the relative urinary excretion were calculated for 18 major polyphenols. We used data from 97 studies that investigated the kinetics and extent of polyphenol absorption among adults, after ingestion of a single dose of polyphenol provided as pure compound, plant extract, or whole food/beverage. The metabolites present in blood, resulting from digestive and hepatic activity, usually differ from the native compounds. The nature of the known metabolites is described when data are available. The plasma concentrations of total metabolites ranged from 0 to 4 mumol/L with an intake of 50 mg aglycone equivalents, and the relative urinary excretion ranged from 0.3% to 43% of the ingested dose, depending on the polyphenol. Gallic acid and isoflavones are the most well-absorbed polyphenols, followed by catechins, flavanones, and quercetin glucosides, but with different kinetics. The least well-absorbed polyphenols are the proanthocyanidins, the galloylated tea catechins, and the anthocyanins. Data are still too limited for assessment of hydroxycinnamic acids and other polyphenols. These data may be useful for the design and interpretation of intervention studies investigating the health effects of polyphenols.