© The Authors, 2024, Published by the Universidad del Zulia*Corresponding author: stingfox03@gmail.com
Keywords:
Kinetics
Peleg's equation
Aqueous extract
Mathematical model
Kinetic study of solid-liquid extraction of caeine in Ilex guayusa Loes
Estudio cinético de la extracción sólido-líquido de cafeína en Ilex guayusa Loes
Estudo cinético da extração sólido-líquido de cafeína em Ilex guayusa Loes
Sting Brayan Luna-Fox
*
Jhoeel Hernán Uvidia-Armijo
Jannys Lizeth Rivera-Barreto
Rev. Fac. Agron. (LUZ). 2024, 41(3): e244128
ISSN 2477-9407
DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v41.n3.08
Food technology
Associate editor: Dra. Gretty R. Ettiene Rojas
University of Zulia, Faculty of Agronomy
Bolivarian Republic of Venezuela.
Departamento de Ciencias de la Tierra, Universidad Estatal
Amazónica, Pastaza, Ecuador.
Received: 13-06-2024
Accepted: 25-07-2024
Published: 16-08-2024
Abstract
The kinetic study of the solid-liquid extraction of caeine in
Ilex guayusa Loes addresses a critical stage in the isolation of
alkaloids such as caeine. Solid-liquid extraction, a widely used
technique, plays a fundamental role in obtaining these compounds.
The study aimed to evaluate the applicability of the Peleg equation
to model the solid-liquid extraction of caeine in Ilex guayusa
Loes leaves. Caeine content was determined by UV-visible
absorption spectroscopy. Extraction kinetics were estimated using
the two-parameter Peleg’s equation. The correspondence between
the experimental results and those predicted by the model was
established by calculating Pearson’s correlation. The results
indicated signicant extraction temperature and time eects on
caeine content, with concentrations ranging from 0.24 to 1.52
g.100 g
-1
at dierent extraction temperatures (30, 40, and 50 °C).
The Peleg equation eectively modeled caeine extraction kinetics,
with high Pearson correlation coecients (0.96895 to 0.99685)
conrming its suitability for predicting caeine concentration.
These results highlight the importance of understanding extraction
kinetics to optimize caeine extraction processes, oering valuable
insights for industries using Ilex guayusa Loes extracts.
This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.
Rev. Fac. Agron. (LUZ). 2024, 41(3): e244128 July-September. ISSN 2477-9407.
2-6 |
Resumen
El estudio cinético de la extracción sólido-líquido de cafeína
en Ilex guayusa Loes aborda una etapa crítica en el aislamiento
de alcaloides como la cafeína. La extracción sólido-líquido, una
técnica ampliamente utilizada, desempeña un papel fundamental en
la obtención de estos compuestos. El estudio tuvo como objetivo
evaluar la aplicabilidad de la ecuación de Peleg para modelar la
extracción sólido-líquido de cafeína en hojas de Ilex guayusa Loes.
El contenido de cafeína se determinó por espectroscopía de absorción
UV-visible. La cinética de extracción se estimó utilizando la ecuación
de Peleg de dos parámetros. La correspondencia de los resultados
experimentales y los predichos por el modelo se estableció mediante
el cálculo de correlación de Pearson. Los resultados indicaron efectos
signicativos de la temperatura y el tiempo de extracción en el
contenido de cafeína, con concentraciones que variaron desde 0,24
hasta 1,52 g.100 g
-1
a diferentes temperaturas de extracción (30, 40
y 50 °C). La ecuación de Peleg modeló ecazmente la cinética de
extracción de cafeína, con altos coecientes de correlación de Pearson
(0,96895 a 0,99685) que conrmaron su idoneidad para predecir la
concentración de cafeína. Estos resultados resaltan la importancia de
comprender la cinética de extracción para optimizar los procesos de
extracción de cafeína, ofreciendo ideas valiosas para las industrias
que utilizan extractos de Ilex guayusa Loes.
Palabras clave: cinética, ecuación de Peleg, extracto acuoso, modelo
matemático.
Resumo
O estudo cinético da extracção sólido-líquido da cafeína em Ilex
guayusa Loes aborda uma etapa crítica no isolamento de alcalóides
como a cafeína. A extração sólido-líquido, técnica muito utilizada,
desempenha um papel fundamental na obtenção destes compostos. O
estudo teve como objetivo avaliar a aplicabilidade da equação de Peleg
para modelar a extração sólido-líquido de cafeína em folhas de Ilex
guayusa Loes. O teor de cafeína foi determinado por espectroscopia
de absorção UV-visível. A cinética de extração foi estimada através
da equação de Peleg de dois parâmetros. A correspondência entre os
resultados experimentais e os previstos pelo modelo foi estabelecida
pelo cálculo da correlação de Pearson. Os resultados indicaram
efeitos signicativos da temperatura e do tempo de extração no teor
de cafeína, com concentrações que variaram entre 0,24 a 1,52 g.100
g
-1
a diferentes temperaturas de extração (30, 40 e 50 °C). A equação
de Peleg modelou ecazmente a cinética de extração de cafeína, com
elevados coecientes de correlação de Pearson (0,96895 a 0,99685)
conrmando a sua adequação para prever a concentração de cafeína.
Estes resultados realçam a importância de compreender a cinética de
extração para otimizar os processos de extração de cafeína, oferecendo
informações valiosas para as indústrias que utilizam extratos de Ilex
guayusa Loes.
Palavras-chave: cinética, equação de Peleg, extrato aquoso, modelo
matemático.
Introduction
Caeine, a methylxanthine naturally present in several plants, has
been the subject of extensive research due to its stimulant eects on
the human central nervous system (Mahoney et al., 2019). Among
these plants, Ilex guayusa Loes, a shrubby species in the family
Aquifoliaceae, has emerged as a promising source of caeine,
especially in the Amazon of South America (Kelebek et al., 2024).
The solid-liquid extraction of caeine in I. guayusa represents a
fascinating and relevant eld of study in the current scientic context.
The extraction of bioactive compounds represents a fundamental
step in the isolation and identication of alkaloids such as caeine
(Rajput, 2022), and there is no single method that guarantees its
eciency. Among the most commonly used extraction techniques
for alkaloid isolation is solid-liquid extraction (Vandeponseele et
al., 2021), which plays a key role in obtaining these compounds. To
describe the mechanism underlying this process, Fick’s second law of
diusion is commonly employed, oering an in-depth understanding
of the matter transfer processes involved (Li et al., 2020; Hashim et
al., 2023).
Recent research has reported the caeine content in I. guayusa
(Paladines-Santacruz et al., 2021; Carvalho et al., 2021). However,
bibliographic data on the extraction kinetics of the solid-liquid
process are scarce. This lack of specic information highlights the
need to develop mathematical models that facilitate the simulation,
design, and control of extraction processes, thus contributing to the
ecient use of resources such as energy, time, and solvent.
On the other hand, mathematical models have an important role
in describing sorption processes, such as dehydration (Korniyenko
and Ladieva, 2021) and rehydration of food products (Tepe, 2024).
Among these models, the non-exponential Peleg model (Lalji et al.,
2022), which consists of two parameters, has proven to be particularly
useful. Given the similarity between extraction kinetics and sorption,
the study aimed to evaluate the applicability of Peleg's equation to
model the solid-liquid extraction of caeine in the leaves of Ilex
guayusa Loes.
Materials and methods
Experiment location and sample preparation
This study was carried out at the Bromatology Laboratory of the
Amazonian State University, located at km 2 ½ on the road to Tena,
in the canton and province of Pastaza, with an altitude of 940 meters
above sea level, 00° 59 ́-1” latitude and 77° 49 ́0” west longitude.
The leaves of
I. guayusa were purchased in the market of the city
of Puyo, Pastaza-Ecuador, at coordinates 1.4837° S 78.0026° W.
The leaves were washed with deionized water and then dried under
shade at room temperature. Subsequently, they were placed in a stove
(Memmert brand, SFE700 model) at 40 °C for 72 h, and the humidity
present in the leaves was calculated by mass dierence (Yu et al.,
2022). The result was used to express the initial mass of the leaves
based on the dry matter. The plant material was crushed in a mill
(KitchenAid brand, BCG111OB model), with a nominal frequency of
60 Hz. They were then sieved to obtain particles smaller than 0.5 mm.
Preparation of the extracts
For the solid-liquid extraction of caeine, the ultrasound-
assisted extraction technique (UAE) was performed using Wisd.23
equipment, WUC-DO6H model according to the procedure described
by Peñael-Bonilla et al. (2023). In each experiment, 5 ± 0.1 g of
ground I. guayusa was weighed into round-bottom asks, and 100
mL of distilled water was added. Each extraction was performed
in triplicate at 30, 40, and 50 °C for periods ranging from 10 to 90
minutes, with 5 intervals for each temperature. The obtained extracts
were ltered using Whatman No. 4 lter paper and the caeine
analyses were carried out immediately.
A = 0.006C + 0.0011
1
(
)
=
1
+
2
1
()
=
1
+
2
1
1
1
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Luna-Fox et al. Rev. Fac. Agron. (LUZ). 2024 41(3): e244128
3-6 |
Quantication of caeine
The determination of caeine was made according to Luna-Fox
et al. (2023). Prior to quantication, a liquid-liquid extraction was
carried out, using chloroform as an extraction solvent. For this, each
aqueous extract was placed in a separating funnel, alkalized with 1
mL of sodium hydroxide (0.1 M), and the caeine was extracted with
two portions of chloroform of 15 mL each. The chloroformic extracts
were joined in an Erlenmeyer and placed in a water bath for complete
evaporation. The caeine was then dissolved with 50 mL of hot
distilled water (60-90 °C), then cooled and transferred to a 100 mL
volumetric ask, and the volume was completed with distilled water.
From the previous solution, 5 mL was taken and transferred to a 25
mL volumetric ask, then 1 mL of hydrochloric acid (0.01 M) was
added and measured with distilled water. Finally, the absorbance of the
sample was read at 275 nm in a visible ultraviolet spectrophotometer
(Perkin Elmer brand). The concentration of caeine was determined
by a calibration curve according to equation (1), prepared with
nine concentrations (1, 2, 3, 5, 10, 12, 16, 20, and 25 mg.mL
-1
) and
R
2
=0.9991. The results were expressed in grams per 100 grams of dry
matter (g.100 g
-1
ms).
(1)
Where, C: concentration of caeine in the sample (mg.mL
-1
) and
A: absorbance of the sample.
Solid-liquid extraction kinetics
Since there is a similarity between the caeine vs. time extraction
curves and the humidity vs. time sorption curves, solid-liquid caeine
extraction in I. guayusa can be described by the model proposed by
Peleg (1988). This equation can be written as follows:
where C(t) indicates the concentration of caeine in relation to
time (g.100 g
-1
), t denotes the extraction time (min), indicates the
initial concentration of caeine in (g.100 g
-1
), is Peleg’s velocity
constant (min·100 g.g
-1
) and is Peleg’s capacity constant (100 g.g
-1
).
Since the initial concentration of caeine was zero, equation (3)
is represented as follows:
The values of the constants were obtained by plotting the
linearized equation, according to:
(4)
Where k
1
: represents the intercept and k
2
is the slope of the line.
Statistical analysis
The data obtained were processed using the Origin 2021 program
(Orji et al., 2022). An analysis of variance (ANOVA) was performed
with the F-test to determine how temperature and extraction time
aected caeine concentration. The validity of Peleg’s model was
evaluated by comparing the experimental results with the predicted
values, using Pearson’s correlation coecient according to equation
(5).
Where:
and are respectively the results of each experiment and
those obtained by Peleg’s model.
and are the averages of the values and respectively.
Results and discussion
Factors that aected caeine extraction
ANOVA indicated that both temperature and extraction time were
statistically signicant (p<0.05) on caeine content, with p values
of 0.0001 for temperature and time. On the other hand, the lack of
adjustment did not show statistical signicance (p>0.05), which
is good because the experimental data are intended to t the Peleg
model.
Figure 1 shows that temperature and extraction time had a
proportional behavior for caeine extraction, i.e., an increase
in temperature and extraction time led to an increase in caeine
concentration. Extractions performed at 30 °C, 40 °C, and 50 °C
indicated a caeine concentration between 0.24 and 1.03 g.100 g
-1
,
0.37 and 1.27 g.100 g
-1,
and 0.64 and 1.52 g.100
g
-1
, respectively.
The caeine present in dried leaves of I. guayusa has been
reported by dierent authors. In the research carried out by Cadena-
Carrera, caeine values of 2.27 % were obtained in aqueous extracts
using supercritical uids. On the other hand, Santana et al. (2018)
reported caeine concentrations of 2.98-3.02 % analyzed by high-
eciency liquid chromatography. These results are superior to those
obtained in this study. The variation in caeine concentration in
I. guayusa can be due to dierent factors. According to Rai et al.
(2021), the concentration of bioactive compounds can vary depending
on the age of the plant. Toscano et al. (2019) have indicated that
climatic conditions are a determining factor when collecting plant
samples since the concentration of secondary metabolites can change
signicantly. Jha and Sit (2022) showed that the content of chemical
compounds in plant samples can vary depending on the extraction
method used, likewise, the type of solvent can signicantly inuence
the extraction.
Temperature and extraction time were signicant factors with a
positive eect on caeine extraction, this result is in agreement with
what is indicated by Luna-Fox et al. (2023) when demonstrating that
() =
+
1
+
2
∙
1
(
)
=
1
+
2
1
()
=
1
+
2
1
=
(
) (
)
(
)
2
(
)
2
1
1
1
1
1
1
1
Figure 1. Caeine extraction curves at 30°C, 40°C and 50°C.
(5)
(2)
(3)
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4-6 |
the concentration of caeine increased with increasing extraction
time and temperature. The eect of temperature can be explained
by the kinetic energy of caeine molecules increasing at higher
temperatures, which facilitates their release and dissolution in the
solvent (Schaefer et al., 2020). This phenomenon aligns with the law
of mass action, in which an increase in temperature favors the reaction
toward product equilibrium. On the other hand, by prolonging the
contact time between the I. guayusa leaves and the solvent, further
extraction of caeine and other bioactive compounds present in the
leaves is allowed. This extra time allows the solvent to penetrate
the structure of the leaves, facilitating the release of caeine more
eectively.
It is important to highlight that the interaction between
temperature and extraction time can have synergistic eects on
the nal concentration of caeine obtained. For example, a higher
temperature can initially accelerate the extraction rate (Bitwell et al.,
2023), while a long extraction time allows this process to reach an
optimal balance, thus maximizing the amount of caeine extracted
from the leaves of I. guayusa.
Solid-liquid extraction kinetics of caeine
The caeine concentrations obtained experimentally were
adapted to Peleg’s equation (3). The values of the constants for
caeine extracted at 30, 40, and 50 °C were calculated by plotting
(gure 2) the values vs t, according to Peleg’s linearized equation (4).
The results of the constants are presented in table 1. The
mathematical models generated were the following:
Figure 2. Calculation of the constants k
1
and k
2
in extractions made at 30°C (A), 40°C (B) and 50°C (C).
C(t)
30°C
=
t
38.2797 + 0.5728t
1
C
(t)
40°C
=
t
23
.1509
+ 0.5434t
1
C
(t
)
50°C
=
t
13.7422
+ 0
.5126t
1
A B
C
The coecients of determination (R
2
) in the equations presented
in gure 2 for the calculation of the constants k
1
and k
2
were high
with values located at 0.97933, 0.96567, and 0.97209 in the
extractions carried out at 30, 40, and 50 °C respectively. These results
demonstrated a good relationship between the variables involved.
On the other hand, the Peleg velocity constants (k
1
) and the Peleg
capacity constants decreased with increasing time and temperature.
These results coincide with those reported by Segovia-Gómez et al.
(2013) and Bucić-Kojić et al. (2007).
Correlation between experimental caeine data and those
predicted by Peleg’s model
The experimental values of caeine and those estimated by the
Peleg models were compared and are indicated in table 2 and gure 3.
The Pearson coecients indicated in Figure 3 varied between
0.96895 and 0.99685. These results close to the unity indicate
that Peleg’s model has a good t for the experimental data. A high
correlation coecient shows that the values predicted by the model
are in close agreement with the experimental values, suggesting that
mathematical models are suitable to represent the behavior of the
experimental data obtained in this study.
The successful adaptation of the experimental values to the Peleg
equation for predicting the concentration of caeine in leaves of I.
guayusa has important implications because it conrms the suitability
of the Peleg model to represent the relationship between the relevant
variables in this particular context. This validation is essential, as
it provides a reliable tool to predict the concentration of caeine
in leaves of I. guayusa, which can be crucial for the energy drink
industry.
Conclusions
Temperature and extraction time were determining factors in
obtaining caeine from Ilex guayusa leaves. The Peleg equation
proved to be adequate for modeling the solid-liquid extraction
kinetics of caeine under the studied conditions. The results of this
study could contribute to the simulation and optimization of caeine
extraction kinetics in dried leaves of I. guayusa.
Literature cited
Bitwell, C., Indra, S. Sen, Luke, C., & Kakoma, M. K. (2023). A review of
modern and conventional extraction techniques and their applications for
extracting phytochemicals from plants. Scientic African, 19, 1–7. Doi.
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Bucić-Kojić, A., Planinić, M., Tomas, S., Bilić, M., & Velić, D. (2007). Study
of solid-liquid extraction kinetics of total polyphenols from grape seeds.
Table 1. Peleg constants (k
1
and k
2
) for solid-liquid extraction of
caeine and coecients of determination.
Temperature
(°C)
K
1
(min.100 g.g
-1
)
K
2
(100 g.g
-1
)
R
2
30 38.2797 0.5728 0.97933
40 23.1509 0.5434 0.96567
50 13.7422 0.5126 0.97209
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Luna-Fox et al. Rev. Fac. Agron. (LUZ). 2024 41(3): e244128
5-6 |
Time
(min)
Experimental
(30°C)
Predicted
(30°C)
Experimental
(40°C)
Predicted
(40°C)
Experimental
(50°C)
Predicted
(50°C)
10 0.24 0.23 0.37 0.35 0.64 0.53
15 0.33 0.32 0.50 0.48 0.74 0.70
20 0.39 0.40 0.61 0.59 0.85 0.83
25 0.47 0.48 0.68 0.68 0.95 0.94
30 0.53 0.54 0.74 0.76 0.99 1.03
35 0.59 0.60 0.81 0.83 1.08 1.10
40 0.64 0.65 0.87 0.89 1.15 1.17
45 0.69 0.70 0.91 0.95 1.23 1.22
50 0.74 0.75 0.98 0.99 1.24 1.27
55 0.78 0.79 1.02 1.04 1.29 1.31
60 0.82 0.83 1.09 1.08 1.32 1.35
65 0.85 0.86 1.09 1.11 1.38 1.38
70 0.87 0.89 1.15 1.14 1.44 1.41
75 0.91 0.92 1.19 1.17 1.46 1.44
80 0.96 0.95 1.22 1.20 1.49 1.46
85 1.01 0.98 1.24 1.23 1.51 1.48
90 1.03 1.00 1.27 1.25 1.52 1.50
Table 2. Comparison between the experimental values and those predicted by the Peleg model, expressed in g.100 g
-1
.
A B C
Figure 3. Experimental and predicted values of caeine obtained at 30 °C (A), 40 °C (B) and 50 °C (C).
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Rev. Fac. Agron. (LUZ). 2024, 41(3): e244128 July-September. ISSN 2477-9407.
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