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Melatonin Profile during Rice (Oryza Sativa) Production

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Rice (Oryza sativa) is the foremost cereal crop in Southeast Asia. It serves as staple food, thus has a major contribution to the calorie intake. In addition, rice contains melatonin which is beneficial for human health. It is, therefore, essential to retain this compound by appropriate rice production processes. Melatonin profile during rice production was monitored for three varieties (IR64, umbul-umbul and pandan wangi) from conventional farming and four varieties (batang lembang, pandan wangi, black and red rice) from organic farming. The effect of polishing degree on melatonin content in rice was also evaluated. Melatonin level decreased throughout rice production and then remained steady at roughly 25-40% in final product. The most influential factor was polishing which led to melatonin losses of up to 50%. The results for organically cultivated varieties were similar. However, melatonin in black rice appeared to be persistent in the matrix during rice production.
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Melatonin Profile during Rice (Oryza Sativa)
Production
Widiastuti Setyaningsih
Department of Analytical Chemistry, Faculty of Science, University of Cádiz, Puerto Real, Spain
Department of Food and Agricultural Product Technology, Gadjah Mada University, Yogyakarta, Indonesia
Email: widiastuti.setyaningsih@uca.es
Nikmatul Hidayah1, Irfan Estiono Saputro2, Miguel Palma Lovillo3, and Carmelo García Barroso3
1 Indonesian Center of Agricultural Postharvest Research and Development, Bogor, Indonesia
2 Department of Analytical Chemistry, Faculty of Chemistry, University of Barcelona, Barcelona, Spain
3 Department of Analytical Chemistry, Faculty of Science, University of Cádiz, Puerto Real, Spain
Email: nikmatul.hidayah@litbang.deptan.go.id, iestiosa7@alumnes.ub.edu, miguel.palma@uca.es,
carmelo.garcia@uca.es
AbstractRice (Oryza sativa) is the foremost cereal crop in
Southeast Asia. It serves as staple food, thus has a major
contribution to the calorie intake. In addition, rice contains
melatonin which is beneficial for human health. It is,
therefore, essential to retain this compound by appropriate
rice production processes. Melatonin profile during rice
production was monitored for three varieties (IR64, umbul-
umbul and pandan wangi) from conventional farming and
four varieties (batang lembang, pandan wangi, black and red
rice) from organic farming. The effect of polishing degree on
melatonin content in rice was also evaluated. Melatonin
level decreased throughout rice production and then
remained steady at roughly 25-40% in final product. The
most influential factor was polishing which led to melatonin
losses of up to 50%. The results for organically cultivated
varieties were similar. However, melatonin in black rice
appeared to be persistent in the matrix during rice
production.
Index Termsmelatonin, rice, organic rice, polishing degree
I. INTRODUCTION
Melatonin, also known chemically as N-acetyl-5-
methoxytriptamine, is an indoleamine that is synthesized
from the essential amino acid L-tryptophan. It has a
number of important activities that include neurohormone
and chronobiotic actions in biological systems. There is
good evidence that melatonin provides effective
treatments for cardiovascular diseases [1], sleep disorders
and headache [2].
Melatonin is a naturally occurring compound that is
found in humans, animals, plants and microbes. The
presence of melatonin in plants has been identified in a
range of species including rice [3].
Rice (Oryza sativa) is a major staple food and is
pivotal for Southeast Asian livelihoods. Therefore, rice is
exceptionally important for the nutrition of large numbers
Manuscript received February 13, 2014; revised May 22, 2014.
of the population in Southeast Asia. Within this region,
rice dominates not only food security but also national
economies. Rice production has increased since 1925 in
some countries of Southeast Asia, particularly in
Indonesia. It has been domesticated in Indonesia from the
time of approximately 2300 B.C., thereby giving rise to a
number of rice varieties.
Around 7,000 rice varieties (or lines) have been
recognized and being suitable for diverse areas of
Indonesia. Furthermore, hundreds of improved varieties
have been developed and introduced into society since
1940. Nevertheless, merely 10 to 20 varieties are widely
cultivated by Indonesian farmers [4]. These cultivated
rice varieties are high-yielding types, mainly IR-64, and
local varieties such as umbul-umbul, batang lembang,
pandan wangi (aromatic rice), black and red rice
(pigmented rice). The nutritional properties of rice
including melatonin differ in specific classified rice
varieties [5].
In addition to the rice variety in question, changes in
the chemical composition of rice can also occur in the
post-harvest treatment and rice processing. Nutritional
losses can occur in the field, principally during processes
such as improper drying or milling [6].
It has been demonstrated that changes occur in the
major compounds during processing and one would also
expect changes in the minor compounds i.e. melatonin.
Nonetheless, research into the melatonin profile for
different cultivation systems, post-harvest treatments and
rice production processes has not been carried out to date.
The aim of the study described here was to assess
melatonin levels throughout the rice production processes.
The results from this study could help rice producers to
ensure that maximum melatonin levels are present in the
final rice product, which in turn would lead to some
important health benefits from rice intake.
II. MATERIALS AND METHODS
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of Advanced Agricultural Technologies Vol. 1, No. 1, June 2014
©2014 Engineering and Technology Publishing
doi: 10.12720/joaat.1.1.60-64
A. Materials and Chemicals
HPLC-grade methanol, acetic acid and ethyl acetate
were purchased from Merck (Darmstadt, Germany).
Melatonin standard, M-5250, was obtained from Sigma-
Aldrich (St. Louis, MO, USA). Water was purified with a
Milli-Q purification system (Millipore, Billerica, MA,
USA).
B. Rice Samples
Three varieties of Indonesian rice produced using
conventional farming systems were obtained randomly
from various smallholder rice mills in the Central Java
area (umbul-umbul, pandan wangi and IR64). Samples
were taken from different lines of rice production to
represent each step of the production process, i.e.,
threshing (rough rice), drying (dried rice), hulling (whole
grain rice), and polishing (polished rice).
A sample of the rice variety pandan wangi was then
collected per degree of polishing (70%, 80%, 90% and
100% bran removal) based on the Indonesian National
Standard SNI 6128:2008 [7]. Four varieties of Indonesian
organic rice were obtained from CV. Green Health
Agriculture (batang lembang, black rice, red rice and
pandan wangi). The samples were stored in vacuum
packaging.
C. Sample Preparation
A rice sample (20 g) was placed in a plastic cylinder
and rice grains were milled with an Ultraturrax
homogenizer (IKA® T25 Digital, Germany) for 10 min
prior to extraction. The milling process was stopped
every 1 min to avoid excessive heating of the sample. The
fine grain was then homogenized by stirring and then
stored in a closed, labelled bottle.
D. Extraction Technique
Melatonin extraction was performed in a Dionex ASE
200 extractor (Dionex, Sunnyvale, CA, USA) equipped
with incorporating stainless steel extraction cells (11 mL
volume) and collection vials (60 mL capacity). A
cellulose filter (Dionex) was inserted at the outlet end of
the extraction cell.
An accurately weighed sample of rice powder (2.5 g)
and washed sea sand was loaded into the extraction cell.
The Pressurized Liquid Extraction (PLE) conditions were
70% (v/v) EtOAc, static time of 5 min in 2 cycles at 200
ºC under a pressure of 200 atm, flushing 50% and purge
for 60 s. The resulting extract was dried under vacuum on
a rotary evaporator. The residue was reconstituted with
methanol and adjusted to a final volume of 10.0 mL. The
liquid was then passed through a 0.45 µm nylon filter
prior to injection on the HPLC-FD system.
E. Determination of Melatonin
High performance liquid chromatography (HPLC)
analyses were carried out on an Alliance HPLC 2695
system, controlled by an Empower Pro 2002 data station
(Waters, Milford, MA) and coupled with a fluorescence
detector (Waters 474 Fluorescence Detector). A reverse
phase RP-18 Lichrospher Column (LiChroCART 250 × 4
(5 µm)) from Merck was used. A gradient elution
program was used with two mobile phases: A (2% acetic
acid and 5% methanol in water) and B (2% acetic acid
and 88% methanol in water). The mobile phase was
filtered through a 0.45 µm membrane filter (Millipore)
and was degassed for 15 min prior to use. The applied
gradient was as follows: (time, solvent B): 0 min, 0%; 5
min, 35%; 12 min, 40%; 15 min, 40%; 20 min, 45%; 25
min, 50%. The flow rate was fixed at 0.5 mL min-1. The
established conditions for fluorescence detector were as
follows: excitation wavelength was set at 290 nm,
emission wavelength was set at 330 nm, sensitivity was
set at gain 1000, attenuation was fixed at 16, and
injection volume was set to 10 µL.
F. Performance of the Method
The analytical procedure for the chromatographic
method for melatonin determination was carried out
according to the recommendations of ICH Guideline Q2
(R1) [8] and suggestions in ISO 17025 [9]. Linearity,
range, precision, detection and quantification limits of the
method were established. Linearity was assessed in order
to express the ability of the method to obtain test results
that are directly proportional to the concentration of
melatonin in two different ranges. Appropriate dilution
from a stock solution of melatonin was carried out to give
concentrations ranging from 0.75 to 15 µg L-1 and 15 to
750 µg L-1. Gnumeric 1.12.9 was used to generate the
regression analysis. Calibration curves were obtained
from this regression analysis and the melatonin in the
extracts was quantified. The standard deviation (σ)
obtained for the response and the slope (a) from the
regression were then used to calculate the limit of
detection (LOD) and limit of quantification (LOQ). The
precision of the method was evaluated by studying
repeatability (intra-day) and intermediate precision
(extra-day). Precision was expressed as Coefficient of
Variance (CV) of retention time (RT) and peak height.
The analytical properties for the chromatographic method
for the determination of melatonin are listed in Table I.
G. Data Analysis
The experimental results in single- and two-factor
experiments were analysed using Gnumeric. The
Analysis of Variance (ANOVA) and Least Significant
Difference (LSD) test were used to determine the
significant differences (p < 0.05) between the means.
TABLE I. ANALYTICAL CHARACTERISTICS FOR THE DETERMINATION OF MELATONIN
Concentration
range
(mg L-1)
Observations
(n)
Linear equation
R2
LOD
LOQ
Intra-day, CV (%)
n = 10
RT
Height
RT
Height
0.75 to 15
11
Y = 587.82X + 1722.99
0.982
1.7
5.2
0.99
0.93
1.23
2.05
15 to 750
14
Y = 614.22X + 1472.11
0.999
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III. RESULT AND DISCUSSION
A. Rice Production Processes
The main objective of industrial rice production is the
transformation of rough rice (paddy) into polished rice. A
number of production processes are necessary to provide
a good quality grain for the consumer.
Three different rice varieties from conventional
cultivation were used in this study. In addition to being
considered as aromatic rice, together with umbul-umbul,
pandan wangi represents the local rice varieties of
Indonesia. IR64 is a rice variety that was developed in a
major advance in rice production as it provided higher
yield potential, greater yield stability and more efficient
management practices.
Melatonin was determined in the samples taken at
different production processes. The levels of melatonin
remaining after treatments i.e. threshing (rough rice),
drying (dried rice), hulling (whole grain rice), and
polishing (polished rice) during rice production are
demonstrated in Fig. 1. Subsequently, in order to study
the effect of rice production processes and rice varieties
on the level of melatonin, a two-factor ANOVA has been
used (p.0.05). ANOVA revealed that the processing steps
in rice production and the varieties of rice both have
significant effects on the level of melatonin in rice and
therefore LSDs for these factors were also estimated (Fig.
2).
Figure 1. Melatonin levels in different rice varieties during rice
production by conventional farming.
Figure 2. LSD analysis for rice production processes and rice variety.
Bars followed by the same letter are indicated as not being significantly
different (p = 0.05)
The level of melatonin for the three difference rice
varieties decreased gradually during the course of
processing throughout rice production, particularly after
hulling (decreased around 30-50%). Nonetheless, a
substantial decreasing in melatonin level by around 30%
was also observed for umbul-umbul and IR64 due to
drying process. The stability of melatonin is known to be
adversely affected by light and heat. Similar results were
obtained by Murch et al., who conducted research into
melatonin levels in feverfew leaves (Tanacetum
parthenium) and found that the levels of melatonin
reduced by about 30% after drying the fresh leaves in an
oven [10].
The levels of melatonin in final rice products after a set
of milling processes remained as high as 55 to 65%. This
is a reasonable content of melatonin bearing in mind that
husk and bran removal have taken place during these
processes. The bran consists of pericarp, which is known
as a source of protein as it has three fibrous layers of
protein. To the best of present knowledge, nitrogen-
containing compounds, specially the amino acid
tryptophan, are essential for the biosynthesis of melatonin
in plants. Furthermore, the presence of melatonin in seeds
was related to the protection of the germs to oxidative
stress experienced by the pericarp of the grain [11].
Hence, the removal of this part of the grain may reduce
the concentration of melatonin in the product.
Different rice varieties showed differences in
melatonin losses due to the production processes. Drying
was found to be an insignificant process in terms of its
effect on melatonin content for the aromatic local variety
Pandan wangi, whereas polishing was insignificant for
the high-yielding variety IR64. These differences in the
melatonin stability and loss for different rice varieties
during the drying and polishing processes can be best
explained by considering the initial level of melatonin
that is naturally present in rice grains and the possible
distribution of melatonin in the seed.
Allameh and Alizadeh confirmed that rice cultivars
and drying days after harvesting had significant effects
(p<0.01) on head rice yield. The results of this study
demonstrated that the strength of varieties against applied
stresses is different and is related to both genetics and
grain physical properties [12]. Additionally, the thickness
of grain contributes to rice breakage as stress is applied
on the rice kernel due to moisture transfer between the
grain and environment. Grains of freshly harvested paddy
with a lower thickness have higher average moisture
contents than the thicker ones [13].
Pandan Wangi is characterized by a round-shaped
grain and it is a relatively thick grain with a lower
moisture content than other rice varieties, e.g., IR64 (long
thin grain). As a result, a shorter drying treatment is
required to meet the standard drying process (< 14% of
moisture content in rice product) and consequently
melatonin degradation during the drying step can be
suppressed for this rice variety.
B. Organic Farming
Consumers are inclined to pick healthier food
produced from a cultivation system where the use of
a
bc
c
ab
a
ab
b
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©2014 Engineering and Technology Publishing
chemical pesticides, weed killers and fertilizers,
genetically modified organisms, antibiotics and growth
hormones is avoided. As a result, the most important
developments in rice cultivation systems have concerned
an increased awareness of organic farming.
The effect of rice production by organic farming on the
melatonin content of rice is shown in Fig. 3. Comparison
of the melatonin levels of rough rice (paddy) and finished
rice products shows that the melatonin content decreased,
especially in milled rice (batang lembang and pandan
wangi). In pigmented rice, particularly black rice, the
melatonin level was maintained in the final product due
to the absence of a husk and bran removal process.
Figure 3. Melatonin levels in organic rice samples.
Hence, rice production from both organic and
conventional farming produced similar results and
milling was the most significant process in rice
production in terms of the loss of melatonin.
C. Polishing Degree
It can be seen in Fig. 4 that an increase in bran removal
leads to a gradual decrease in the melatonin content in
rice. The melatonin levels present after different
polishing degrees of 70%, 80%, 90% and 100% were of
28.8 μg Kg-1, 23.8 μg Kg-1, 20.9 μg Kg-1 and 16.3 μg Kg-1,
respectively. The significance level between polishing
degree and melatonin retention was assessed by single-
factor ANOVA (p.0.05).
Figure 4. LSD analysis for different polishing degrees. Bars followed
by the same letter indicate that parameters are not significantly different
(p = 0.05)
Result from data analysis indicated that the polishing
degree has a significant effect on the melatonin level in
rice. A post-hoc test by means of LSD was then
considered in order to review the significances between
treatments in the polishing process. LSD showed that the
percentage retention of melatonin differs significantly for
every 10% unit difference in the polishing degree.
In summary, the level of melatonin decreased by as
much as 9 to 16% when the polishing degree was
increased. This result seems to be associated with the
removal of bran in the polishing process as this
component must contain a certain amount of melatonin.
IV. CONCLUSION
Melatonin profiles throughout the rice production
process were studied. Differences in rice production
processes and rice varieties have significant effects on the
melatonin level in semi-finished and finished rice.
In addition to samples from conventional rice farming,
the effect of processing steps during rice production on
melatonin levels from organic rice farming was also
studied. Similar results were obtained for each farming
approach, showing that the changes in melatonin levels
are due to the application of rice production processes.
The milling process involves hulling and polishing and
it is considered to be a major factor that affects the
retention of melatonin in rice. The degree of polishing
was also investigated and the results indicated that the
bran removal process decreased the melatonin content in
the rice product. Hence, it is recommended that the rice
production processes are carefully controlled in order to
attain a high level of melatonin in rice products by
efficient drying and the optimum degree of milling. The
level of melatonin in pigmented black rice was
successfully retained in the final product as the husk and
bran removal processes were omitted.
The study reported here provides opportunities to
develop advanced techniques in rice processing. Bearing
in mind the importance of rice science and technology, it
is envisaged that this work will significantly support
further studies to improve rice production techniques in
the coming decades.
ACKNOWLEDGMENT
The authors acknowledge the support of CV. Green
Health Agriculture, Indonesia, in providing the organic
semi-finished and finished rice products.
W. S. thanks the CIMB Foundation for a Ph.D.
studentship through the CIMB Regional Scholarships.
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“Development of online reference of indonesian rice variety,” in
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[5] W. Setyaningsih, M. Palma, and C. G. Barroso, “A new
microwave-assisted extraction method for melatonin
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[6] B. O. Juliano, Rice in Human Nutrition, Rome, Italy: FAO Food
and Nutrition, 1993, ch.5, pp. 85-100.
[7] Rice, SNI (Indonesian National Standard) 6128-2008.
[8] Validation of Analytical Procedures, ICH Topic Q2 (R1)-2006.
[9] General Requirements for the Competence of Testing and
Calibration Laboratories, ISO standard 17025-2005.
[10] S. J. Murch, C. B. Simmons, and P. K. Saxena, “Melatonin in
feverfew and other medicinal plants,” vol. 350, pp. 1598-1599,
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review-analysis of melatonin in foods,” Journal of Food
Composition and Analysis, vol. 22, pp. 177-183, May 2009.
[12] A. Allameh and M. R. Alizadeh, “Evaluating rice losses in
delayed rough rice drying, International Journal of
Agronomy&Plant Production, vol. 4, pp. 799-804, 2013.
[13] J. I. Wadsworth, J. Matthews, and J. J. Spadaro, “Moisture content
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1982.
Widiastuti Setyaningsih was born in Klaten,
Indonesia on July 21, 1984. She graduated
magna cum laude from Gadjah Mada
University (UGM) with a Bachelor of Food
Technology. She received her M.Sc. from
Gdansk University of Technology (GUT) in
Poland, University of Barcelona (UB) and
University of Cadiz (UCA) in Spain under the
frame of European Master in Quality in
Analytical Laboratories (EMQAL).
She is a LECTURER at the Department of
Food and Agricultural Product Technology, Faculty of Agricultural
Technology, UGM, Indonesia. Presently, she is pursuing her doctoral
studies in field of food analytical chemistry at the Department of
Analytical Chemistry, Faculty of Sciences, UCA, Spain. She held an
undergraduate scholarship from UGM for the period 2004 to 2005, an
Erasmus Mundus Scholarship from European Union Commission
(Education, Audiovisual and Culture Executive Agency-EACEA)
during the period 2010-2011, a MAEC-AECID scholarship (Agencia
Española de Cooperación Internacional para el Desarrollo) from the
Ministry of Spain for 2011-2012, and a Ph.D. studentship from the
CIMB Foundation from 2012 to date. Her research is focused on
analytical method development and validation for bio-active compounds
in food samples.
Nikmatul Hidayah was born in Magelang,
Indonesia in February 1982. She graduated
from Gadjah Mada University (UGM) with a
bachelor of Food Technology. At present, she
is a RESEARCHER at Indonesian Center of
Agricultural Postharvest Research &
Development, Bogor, Indonesia. Her research
is focused on postharvest handling and
processing of agricultural product such as enzymatic processing of rice
and modification of flour based on local agricultural product in
Indonesia.
Irfan Estiono Saputro was born in Jakarta,
Indonesia on 25 April 1984. His desire to
pursue a career in science was reinforced after
opting for Food Quality Assurance as his
major at Bogor Agricultural University (IPB),
Indonesia. In order to advance his knowledge
in food analytical chemistry, he is currently
pursuing a European Master in Quality in
Analytical Laboratories (EMQAL) at the
University of Barcelona (Spain).
Professor Miguel Palma Lovillo was born in
Olvera, Spain on January 14, 1968. He
obtained his degree in Chemistry at the
University of Cádiz (UCA) and later obtained
his Ph.D. in Science at the same University in
1995.
He is PROFESSOR of Analytical Chemistry
at the Faculty of Sciences, UCA, Spain. He
was visiting scientist at the Department of
Pharma-ceutical Sciences at the Southern
School of Pharmacy in Mercer University,
Atlanta, GA, USA and also at the Department of Chemistry, at Virginia
Tech, Blacksburg, VA, USA.
Professor Palma received the Premio Extraordinario de Doctorado (the
Highest Distinction at PhD level) at the Faculty of Sciences (UCA) and
the Premio Extraordinario de Licenciatura “Octavio Comes”
(Distinction at Bachelor degree). His research interests include food
analytical methods, food science, functional foods and bioactive
compounds in foods.
Professor Carmelo García Barroso was born
in Arcos, Spain on December 9, 1955. He
obtained his degree in Chemistry at the
University of Cádiz (UCA) and then his Ph.D.
in Sciences at the same University in 1985.
He is PROFESSOR of Analytical Chemistry at
Faculty of Sciences, UCA, Spain. His research
is focus on food and wine science and food
analytical methods.
Professor García co-founded the Spanish
Society for Wine Research (GIENOL) and
was elected President of this Society in 1999. He is responsible for the
postgraduate program in Agrifood Sciences, a common teaching
program between UCA and the University of Cordoba (Spain) since
2006. In 2001 he became Chairman of the Andalusian Center for Wine
Research, a research center at UCA sponsored by the local Andalusian
Government.
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Journal
of Advanced Agricultural Technologies Vol. 1, No. 1, June 2014
©2014 Engineering and Technology Publishing
... Hence, rice is extremely important, not only to satisfy hunger but also to provide nutrients for the population of Indonesia. Several health-benefited substances have been identified in rice and these include melatonin (Setyaningsih et al., 2014). Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine that is synthesized from the essential amino acid L-tryptophan. ...
... The whole grain (brown) rice, as well as pigmented (red and black) varieties contain higher levels of melatonin than the polished (white) grain. The level of melatonin in these unpolished rice grains is maintained in the final product because there is no bran removal process (Setyaningsih et al., 2014;Setyaningsih et al., 2016). Henceforth, consumption of whole grain (brown, red, and black) rice has additional functional benefit. ...
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Rice, especially the pigmented varieties, contains a higher level of melatonin (N-acetyl-5- methoxytryptamine), which is used in treatment for sleeping disorders and for improving mood. It has potent antioxidant properties, anti-obesity, and anti-inflammatory, thus potential as the basis for functional food development. The purpose of the study was to examine how the various rice attributes and demographic characteristics affect the willingness to pay of Indonesian consumers on functional rice. Multi-Factor Categorical Design (MFCD) and Balanced Incomplete Block Design (BIBD) have been used to study multiple non-quantitative factors, including different rice varieties and health benefits information on the label (x1, 3 levels: white rice, brown rice-label, and red rice-label), price (x2, 2 levels: low and high), and rice producers (x3, 3 levels: international brand, established national brand, and new national brand). Data collection was administered through an online questionnaire survey to 204 respondents, living in four major Indonesian islands: Java, Bali, Sumatra, and the Moluccas. The results showed that despite the health benefits of the melatonin contained in the whole brown and red rice, Indonesian consumers still preferred conventional white rice over the aforementioned rice varieties. Price was recognized as the main attribute affecting the selection of functional rice, whilst rice producers gave less impact on willingness to pay. The results indicated that cultural value, consumers’ knowledge of melatonin, consumers’ health status, and consumers’ income were the sources of heterogeneity in consumers’ willingness to pay for functional rice.
... We also determined the levels of melatonin and tryptophan in rice and corn extracts. Previously, there was a study revealing the level of melatonin content in black rice at 140 μg/kg (Manchester et al. 2000;Hernandez-Ruiz & Arnao 2008;Setyaningsih et al. 2014). Our results demonstrated that the highest levels of melatonin content were detected in black rice extracts from ethanol fraction at 396.38 μg/kg. ...
... The levels of melatonin in the two rice varieties decreased gradually during the course of processing throughout rice production, particularly after a set of milling processes, and only 30-40% of the original melatonin remained in the final samples. These data are consistent with previously reported results [16]. ...
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An analytical ultrasound-assisted extraction (UAE) technique has been optimized and validated for the extraction of melatonin from rice grains. A Box–Behnken design in conjunction with a response surface methodology based on six factors and three levels was used to evaluate the effects of the studied factors prior to optimizing the UAE conditions. The significant (p < 0.05) response surface models with high coefficients of determination were fitted to the experimental data. Solvent composition and extraction temperature were found to have very significant effects on the response value (p < 0.005). The optimal UAE conditions were as follows: extraction time of 10 min, ultrasound amplitude of 30%, cycle of 0.2 s−1, extraction temperature of 40 °C, 50% methanol in water as the extraction solvent at pH 3.5 and a solvent/solid ratio 2.5:1. The method validation ensured right values for linearity, LOD, LOQ, precision and recovery. Furthermore, the method was successfully applied in the analysis of a number of rice samples throughout the rice production process. Hence, it was demonstrated that this particular UAE method is an interesting tool for the determination of melatonin in rice grain samples.
... As well as phenolic compounds, the presence of melatonin [N-acetyl-3-(2-aminoethyl)-5-methoxyindole] in rice grain has been identified in a wide range of varieties [8]. However, both the level and composition of these compounds in different varieties of rice grains may diverge in phenolics and melatonin concentrations. ...
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Cultivated rice (Oryza sativa) is a global cereal crop in Southeast Asia. It serves as staple food, thus has a major contribution to the calorie intake. Furthermore, a number of antioxidant substances have been identified in rice including phenolic compounds and melatonin. The concentration and composition of these antioxidant compounds were studied on glutinous and nonglutinous grains for both pigmented and non-pigmented rice varieties. Additionally, several medium-amylose rice grains of three Indonesian varieties (IR64, umbul-umbul and pandan wangi) were also evaluated. Finding indicates that the composition of phenolic compounds are noticeably different between glutinous and nonglutinous rice grains. The level of both melatonin and total phenolics in non-glutinous rice was higher than its glutinous variety. Hence, higher amylose content exhibits relatively higher amount of antioxidant compounds
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Melatonin provides a number of benefits for human health. The study reported here concerns the optimization, validation, and application of analytical pressurized liquid extraction and high-performance liquid chromatography coupled to a fluorescence detector for the determination of melatonin in rice grains. The factors that are most likely to affect the extraction efficiency were optimized with a 2IV7–2 fractional factorial design. The optimum extraction conditions were achieved by applying 70% EtOAc in MeOH at 200 °C and 200 atm for a static time of 5 min in two cycles with 50% flushing and a 60 s purge to extract a 2.5 g rice sample. The method validation ensured excellent linearity, limit of detection, limit of quantification, precision, and recovery. Furthermore, the method was applied to various rice products composed of polished, whole grain, aromatic, black, black glutinous, red, and parboiled rice. All kinds of pigmented rice grains showed high levels of melatonin (>100 μg kg –1), and the highest levels were found in red rice.
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Rice (Oryza sativa) is an important food crop of Indonesia. It was cultivated over an area of 11.786 thousand hectares with average paddy yield of 4.62 ton per hectare during the year 2006. With continuous increase in population, the demand of rice is also growing; confirming that task of increasing rice production to all related components. Many factors contribute to the yields. Among others are seed quality and suitable varieties. The strategies for increasing yield are including supply of quality seed of varieties with high yield potential. Hundreds of improved varieties have been developed and introduced to the society. Those improved varieties usually are developed with specific purpose (criteria), such as certain pest resistance, certain taste (aromatic rice), certain grain shape, etc. However, due to ineffective information sharing and dissemination system, adoption of the improved varieties for specific location and preference is often become problematic. This paper discussed about a work being carried out for developing an online reference system for rice cultivation with special emphasis on rice variety. The system consists of database of improved rice varieties and its characteristics, application program for identifying the recommended rice variety for certain location and preference, and application program for estimating harvest time and yield based on transplanting time input. Location indicates agro-ecological aspect of rice cultivation such as soil characteristics, altitude, rain intensity as well as irrigation method while preference is dealing with expectation of the system users on several rice characteristics. Heat units (degree-days) concept is used for estimating the harvest time and potential yield. The system is developed by using VB.Net. It is intended to be used by researchers, consultants, field extension officers, and or practitioners in exploring the available rice variety and rice variety selection for cultivation.
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Rough rice drying plays an important role in post-harvest practices. Excessive losses can be avoided if drying had conducted properly. Head rice yield (HRY) is a commonly accepted standard for measuring rice milling quality. After harvesting, in major rice producing regions of Iran, there would be delayed rough rice drying and milling due to great deals of produced paddy and low capacity of rice milling plants. This research aimed to investigate the effect of various drying dates on milling recovery head rice yield. The experiments were conducted on five different dates of 0, 15, 30, 60, and 90 days after harvesting and two long grain cultivars of Hashemi (local) and Khazar (improved). The results revealed that cultivars and drying dates had significant (p<0.01) effects on head rice yield. Head rice yield for Hashemi had a decreasing trend under delayed drying dates whereas there was not such a circumstance for Khazar. The highest head rice yield (58.78%) obtained when Hashemi dried immediately after harvesting but for Khazar (57.44%), when it was dried by the most delay.
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This editorial refers to "Cardiovascular effects of melatonin receptor agonists". The hormone melatonin is synthesized primarily in the pineal gland, retina, several peripheral tissues and organs. In the circulation, the concentration of melatonin follows a circadian rhythm, with high levels at night providing timing cues to target tissues endowed with melatonin receptors. Based on the data available, the last 18 years indicate that melatonin influences multiple factors of the cardiovascular function. Multiple evidences reveal that the rhythmicity of melatonin has a crucial role in a variety of cardiovascular pathophysiological processes including anti-inflammatory, antioxidant, anti-hypertensive and possibly as an antilipidemic function. Melatonin receptors receive and transduce melatonin's message to influence daily and seasonal rhythms of physiology. The melatonin message is translated through the interaction between the melatonin receptors (MT1 and MT2) and its coupling to G proteins, which are potential therapeutic targets in disorders ranging from insomnia, circadian sleep disorders, depression and cardiovascular diseases. Based on the data available, melatonin seems to have cardioprotective properties via its direct free radical scavenger activity. Melatonin efficiently interacts with several reactive oxygen species (receptor-independent actions). Collectively, these protective actions of melatonin may have potential clinical applicability for individuals with cardiovascular disease.
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A large number of individuals suffer from migraine headaches. Several theories attempt to explain migraine etiology. One such theory holds that since environmental stimuli are well known to trigger migraine headaches, the pineal gland may be involved in migraine etiology. Specifically, a pineal gland irregularity may be the physical origin of migraine headaches, with subsequent physiological changes being secondary. Research has found the pineal hormone melatonin is low in migraine patients. Additionally, several studies found administering melatonin to migraine sufferers relieved pain and decreased headache recurrence in some cases. It has been suggested melatonin may play an important therapeutic role in the treatment of migraines and other types of headaches, particularly those related to delayed sleep phase syndrome. Current research supports the hypothesis that migraines are a response to a pineal circadian irregularity in which the administration of melatonin normalizes this circadian cycle; i.e., melatonin may play a role in resynchronizing biological rhythms to lifestyle and subsequently relieve migraines and other forms of headaches. In addition, research testing the administration of melatonin found it safe in migraine sufferers, with few or no side effects. However, a larger, randomized control trial is needed to definitively determine if administration of melatonin to migraine patients is effective.
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A new microwave-assisted extraction (MAE) method has been developed for the extraction of melatonin from rice grains. The stability of melatonin under MAE conditions was studied in order to define the working range. The studied analytical conditions for the MAE were temperature (125−175 °C), microwave power (500−1000 W), time (5−15 min), solvent (10−90% EtOAc in MeOH), and ratio of solvent to sample (10:1–20:1). Extraction variables were optimized by Response Surface Methodology (RSM). Extraction temperature was found to have a highly significant effect on the response value (p < 0.0001) and the solvent and quadratic of time also had significant effects (p < 0.1). The optimized MAE conditions were as follows: extraction temperature 195 °C, microwave power 1000 W, extraction time 20 min, solvent 100% MeOH, and ratio of solvent to sample 10:1. The developed method showed high precision (in terms of CV: 4.97% for repeatability and 4.34% for intermediate precision). Finally, the new method was applied to real samples in order to investigate the presence of melatonin in a wide variety of rice grains.
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Melatonin (N-acetyl-5-methoxytriptamine), a neurohormone produced by the pineal gland, has recently been reported in foods, mainly of plant origin. Literature concerning the biological properties is extensive. However, little is known about melatonin presence in foods or the analytical methods suitable for assay in food matrices and the potential influence of dietetic intake on human health. The aim of this work is to review current knowledge and available data of dietary intake of melatonin as it has been proposed as a new bioactive food component. There are gaps in the knowledge and insufficiently standardised methods for its analysis. Advantages and disadvantages of analytical methods to assess melatonin in different food matrixes are discussed, as well as the effect of dietetic melatonin.