1Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 01 | Article 351486
Study of total antioxidant capacity of red raspberry (Rubus idaeous L.) shoots
JOURNAL VITAE
School of Pharmaceutical and
Food Sciences
ISSN 0121-4004 | ISSNe 2145-2660
University of Antioquia
Medellin, Colombia
Filliations
1Analytical Chemistry and Analytical
Toxicology Department, National
University of Pharmacy, Kharkiv,
Ukraine
2Pharmacognosy Department, National
University of Pharmacy, Kharkiv,
Ukraine
3Biochemistry Department, National
University of Pharmacy, Kharkiv,
Ukraine
4General Chemistry Department,
National University of Pharmacy,
Kharkiv, Ukraine
*Corresponding
Olexander Maslov,
alexmaslov392@gmail.com
Received: 08 October 2022
Accepted: 19 April 2023
Published: 22 April 2023
Study of total antioxidant capacity of red
raspberry (Rubus idaeous L.) shoots
Estudio de la capacidad antioxidante total de brotes de
frambuesa roja (Rubus idaeous L.)
Olexander Maslov1,* , Mykola Komisarenko2 , Mykola Golik1 , Sergii Kolisnyk1 ,
Oksana Tkachenko 3 , Iuliia Kolisnyk 4 , Sergii Baiurka 1 , Svetlana Karpushina 1 ,
Alexander Altukhov1
ABSTRACT
Background: Today, cardiovascular, oncological, and neurodegenerative diseases are the
main causes of death in the world, according to official World Health Organization (WHO)
statistics. Antioxidants are used to treat and prevent these diseases. In order to develop
optimal technology for obtaining drugs based on plant extracts with antioxidant action, it is
necessary to determine the total antioxidant capacity of raspberry shoots. Objectives: The
study aimed to determine the total antioxidant capacity of red raspberry shoots, study the
content of biologically active substances (BAS), and the antioxidant activity of red raspberry
shoot extracts obtained during subsequent exhaustive extraction. Methods: The number
of phenolic compounds, catechins, flavonoids, and hydroxycinnamic acids was determined
by a spectrophotometric analysis method, whereas organic acids were determined by the
alkalimetric method in red raspberry shoot extracts; the antioxidant activity of obtained
extracts was evaluated by potentiometric method. Results: The total antioxidant capacity of
red raspberry shoots was 164.12 mmol-equiv./m dry weight, the sum of the total content of
phenolic compounds was 24.40 mg gallic acid (GA)/mL, catechins – 21.36 mg epigallocatechin-
3-O-gallate (EGCG)/mL, flavonoids – 0.77 mg rutin (R)/mL, hydroxycinnamic acids derivatives
– 2.56 mg chlorogenic acid (ChA)/mL and organic acids – 1.88 mg citric acid (CA)/mL in red
raspberry shoot extracts obtained during subsequent exhaustive extraction. The analysis
showed that there is a very high positive correlation between antioxidant activity and total
phenolic compounds, catechin, flavonoid, hydroxycinnamic acids derivatives, and organic acids
content in red raspberry shoot extracts. Conclusions: Total red raspberry shoots’ antioxidant
capacity has been determined. The study results can be used to develop optimal technology for
obtaining drugs based on the extract of red raspberry shoots, which has an antioxidant effect.
Key words: Rubus idaeous L., Total Antioxidant capacity, Total Phenolic content, Total Organic
acids content, Correlation, Sequential Exhaustive extraction
REVIEW ARTICLE
Published 22 April 2023
Doi: https://doi.org/10.17533/udea.vitae.v30n1a351486
2Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 01 | Article 351486Olexander Maslov, Mykola Komisarenko, Mykola Golik, Sergii Kolisnyk, Oksana Tkachenko, Iuliia Kolisnyk, Sergii Baiurka, Svetlana Karpushina, Alexander Altukhov
1. INTRODUCTION
Nowadays we observe a great interest in antioxidants,
especially nature origin, due to the increasing level
of cancer, cardiovascular and metabolic diseases
[1]. Those diseases are associated with the growing
impact on humans of adverse environmental factors,
such as ultraviolet and electromagnetic radiation,
man-made pollution of the atmosphere with
radioactive and toxic compounds, the use of food
products with a high content of artificial chemical
agents (preservatives, thickeners, dyes, flavors, etc.),
leading to the formation of an excess amount of
free radicals in the body and oxidative damage to
organic macromolecules [2].
Oxidative stress causes an imbalance of the natural
antioxidant system, significantly increases the risk
of developing diabetes mellitus, atherosclerosis,
cancer, heart ischemia, and Alzheimer’s disease.
Therefore, it is recommended to regularly consume
certain foods and drinks, drugs, dietary supplements
with antioxidant activity to neutralize the harmful
effects of free radicals [3].
Raspberry (Rubus idaeus L.) is a shrub that belongs
to the Rosaceae family and widely grows in Ukraine,
Europe, Asian and America [4]. Raspberry fruit,
leaves, and shoots have been used for medicinal
purposes for centuries [5, 6]. The leaves and fruits
were traditionally used to treat gastrointestinal,
respiratory disorder and heart problems. Raspberry
shoots were used directly to treat sore throat, flu,
fever, and diabetes [7].
Red raspberry shoots contain catechins, ellagitannins,
flavanol derivatives, ellagic acid, phenolic, and
organic acids [8]. Ellagotannins are a group of
hydrolyzable tannins characteristic of the Rosaceae
family. Sanguine H-6 is the main ellagitannin found
in raspberry shoots [9]. Raspberry leaves have also
been found to contain ellagitannins, some catechins
and flavanols, and organic acids [10, 11]. In contrast
to the shoots and leaves of red raspberries, eleven
anthocyanins were found in the fruits [12, 13].
The antioxidant activity of raspberry fruit and leaves
have been established [5, 14]. However, much
less information is available on the antioxidant
activity and chemical composition of raspberry
shoots extracts. There is no reviews about the
determination total antioxidant capacit y of
raspberry shoots. The total antioxidant capacity
of raw materials needs to be studied and further
apply total antioxidant in developing drugs, dietary
supplements and cosmetologically products.
This study aimed to determine the total antioxidant
capacity and biologically active substances content
of red raspberry shoots extracts obtained by
subsequent exhaustive extraction.
RESUMEN
Contexto: Hoy en día, las enfermedades cardiovasculares, oncológicas y neurodegenerativas son las principales causas de
muerte en el mundo según estadísticas oficiales de la Organización Mundial de la Salud OMS. Los antioxidantes se utilizan
para tratar y prevenir estas enfermedades. Para desarrollar una tecnología óptima para la obtención de fármacos a base de
extractos de plantas con acción antioxidante, es necesario determinar la capacidad antioxidante total de los brotes de frambuesa.
Objetivos: El estudio tuvo como objetivo determinar la capacidad antioxidante total de los brotes de frambuesa roja, estudiar
el contenido de sustancias biológicamente activas (SBA) y la actividad antioxidante de los extractos de brotes de frambuesa
roja obtenidos mediante extracción exhaustiva. Métodos: La cantidad de compuestos fenólicos, catequinas, flavonoides y
ácidos hidroxicinámicos se determinó por método de análisis espectrofotométrico, mientras que los ácidos orgánicos por
método alcalimétrico en extractos de brotes de frambuesa roja; La actividad antioxidante de los extractos obtenidos se
evaluó por método potenciométrico. Resultados: La capacidad antioxidante total de los brotes de frambuesa roja fue de
164.12 mmol-equiv./m de peso seco, la suma del contenido total de compuestos fenólicos fue de 24.40 mg gálico ácido (GA)/
mL, catequinas – 21.36 mg epigalocatequina-3-O-galato (EGCG)/mL, flavonoides – 0.77 mg rutina (R)/mL, derivados de ácidos
hidroxicinámicos – 2.56 mg clorogénico ácido (ChA)/mL y ácidos orgánicos – 1.88 mg cítrico ácido (CA)/mL en extractos de
brotes de frambuesa roja obtenidos durante extracción exhaustiva. La correlación analizada mostró que existe una correlación
positiva entre la actividad antioxidante y el contenido de compuestos fenólicos totales, catequinas, flavonoides, derivados
de ácidos hidroxicinámicos y ácidos orgánicos en extractos de brotes de frambuesa roja. Conclusiones: Gracias a nuestros
resultados se ha determinado la capacidad antioxidante total de los brotes de frambuesa roja. Los resultados del estudio se
pueden utilizar para desarrollar una tecnología óptima para la obtención de fármacos basados en el extracto de brotes de
frambuesa roja, que tiene un efecto antioxidante.
Palabras clave: Rubus idaeous L., Capacidad antioxidante total, Contenido de fenoles totales, Contenido de ácidos orgánicos
totales, Correlación, Extracción exhaustiva secuencial
3Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 01 | Article 351486
Study of total antioxidant capacity of red raspberry (Rubus idaeous L.) shoots
2. MATERIALS AND METHODS
2.1 Plant material
The leafless second-year red raspberry shoots were
collected after the fruiting period near village of
Ternova, Kharkiv region, Ukraine in 2021.
2.2 Equipment and reagents
The pH meter HANNA 2550 (Germany) with a
combined platinum electrode EZDO 50 PO (Taiwan)
was used for potentiometric measurements.
Quantitative analysis of biologically active compounds
was carried out on UV-spectrophotometer UV – 1000
(China) with matched 1 cm quartz cells. The
weighing was performed using digital analytical
balance АN100 (AXIS, Poland) with d = 0.0001 g.
All solvents and other chemicals used in the study
were of analytical grade.
2.3 Extraction procedure
A 10.0 g of red raspberry shoots were ground to
1-2 mm in size. The extraction was carried out one
by one using distilled water, 20% ethanol, 40%
ethanol, 60% ethanol, and 96% ethanol at the ratio
raw material/solvent 1/20 (m/v) in a water bath at 80º
C with reflux for 1 hour. After cooling, the solutions
were filtrated and concentrated to 20 mL by a rotary
evaporator at 40 º C under a vacuum.
2.4 Quantitative analysis
2.0 mL of the extract was placed in a weighing bottle,
brought to a constant mass, evaporated in a water
bath, and dried from 100 to 105 ° C for 3 hours.
The weighing bottle was cooled in a desiccator at
room temperature for 30 min and weighed [16]. The
dry residue w, (%) in extract samples was calculated
according to equation 1:
100
(%) dry
a
m
w V
⋅
= (Eq.1)
where, mdry – mass of the dry residue after drying
an aliquot of the extract sample, g; Va – volume of
extract sample aliquot, mL.
The total content of phenolic compounds was
measured by the Folin-Ciocaltau assay, the
absorbance was measured at 760 nm [17]. The
phosphomolybdotungstic reagent is used as
standard in the assay. The calibration cur ve
(Y = 0.1055X + 0.1745 (R 2 =0.9951)) was plotted
with interval concentrations 1.0 – 5.0 μg/mL, the
calibration equation. The total phenolic compounds
content in extracts (X), expressed as GA was
calculated according to equation 2:
1000
( / ) x dilC K
X mg mL V
× ×
= (Eq.2)
where, Сx – concentration of gallic acid according
to the calibration curve, С×10-6, g/mL; V – extract
volume, mL; Kdil – coefficient of dilution, mL.
The vanillin reagent assay was applied to determine
the total catechins [18]; the absorbance was
measured at 505 nm. The calibration curve (Y =
0.0025X – 0.0851 (R 2 = 0.9951)) was plotted
with 100 – 400 μg/mL interval concentrations of
epigallocatechin-3-O-gallate (EGCG). The total
catechins content in extracts (X), expressed as EGCG
was calculated according to equation 3:
1000
( / ) x dilC K
X mg mL V
× ×
= (Eq.3)
where, Сx – concentration of epigallocatechin-3-O-
gallate according to calibration curve, С×10-6 g/mL;
V – volume of extract, mL; Kdil – coefficient of
dilution, mL.
The total flavonoids were determined using the
complex formation assay with AlCl3; the absorbance
was measured at 417 nm [19]. The concentration of
standard solution of rutin was 0.02 mg/mL. The total
flavonoids content in extracts (X), expressed as R,
was calculated according to equation 4:
1000
( / ) dil st
st
A K m
X mg mL A V
× × ×
= × (Eq.4)
where, A – absorbance of analyzed solution;
Ast – absorbance of standard solution of rutin;
V – volume of extract, mL; Kdil – coefficient of
dilution, mL, m st – mass of rutin, g.
The total hydroxycinnamic acids derivatives content
was measured by assay of complex formation with
NaNO2-Na2 MoO4, the absorbance was measured at
525 nm [20]. The total content of hydroxycinnamic
acids derivatives in extracts (X), expressed as
chlorogenic acid (ChA) was calculated according
to equation 5:
1000
( / ) 188
dilA K
X mg mL V
× ×
= × (Eq.5)
4Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 01 | Article 351486Olexander Maslov, Mykola Komisarenko, Mykola Golik, Sergii Kolisnyk, Oksana Tkachenko, Iuliia Kolisnyk, Sergii Baiurka, Svetlana Karpushina, Alexander Altukhov
where, A – absorbance of analyzed solution; 188
– specific adsorption coefficient of chlorogenic
acid; V – volume of extract, mL; Kdil – coefficient of
dilution, mL.
The total organic acids content was determined
by acid-base titration with the fixation endpoint by
potentiometric method [21]. The total content of
organic acids in extracts, expressed as citric acid
(CA) was calculated according to equation 6:
( ) 0.0032 1000
( / ) equiv x dilV V K K
X mg mL V
− × × × ×
= (Eq.6)
where, 0.0032 – the amount of citric acid, equivalent
to 1 mL of sodium hydroxide solution (0.05 mol/L),
g; Vequv. is the volume (mL) of sodium hydroxide
solution (0.05 mol/L), which was used for titration;
Vx – the volume (mL) of sodium hydroxide solution
(0.05 mol/L), which was spent for titration in a
blank experiment; V – volume of extract, mL; Kdil
– coefficient of dilution, mL.; K is the correction
coefficient for 0.05 mol/L sodium hydroxide solution.
2.5 Antioxidant activity assay
Antioxidant activity (AOA) of extracts was evaluated
by potentiometric method [22]. Antioxidant activity
was calculated according to equation 7 and
expressed as mmol-equiv./m dry res.
:
3 1
2
10
1
OX red
dil
C C m
AOA K m
α
α
− ×
= × × ×
+ (Eq.7)
where, α = Cox/Cred × 10(∆E – Eethanol)nF/2.3RT;
Сox – concentration of K 3 [Fe(CN) 6 ], mol/L; Cred
– concentration of K 3 [Fe(CN) 6 ], mol/L ; Еethanol –
0.0546·С% – 0.0091; С% – concentration of ethanol;
∆E – change of potential; F = 96485.33 C/mol –
Faraday constant; n = 1 – number of electrons in
electrode reaction; R = 8.314 J/molК – universal gas
constant; T – 298 K; Kdil– coefficient of dilution, mL.;
m1 – mass of dry residue; m2 – mass of dry residue
in 1.0 mL of extract.
2.6 Correlation analysis
Pearson’s (r) correlation coefficient was used to
analyze the correlation between antioxidant activity
(AOA) and the amount of phenolic, catechin,
flavonoid, hydroxycinnamic acids derivatives and
organic acids. The correlation coefficient to takes
a value in the range of -1 to +1. Correlation is very
high if it is within the range from 0.90 to 1.00;
from 0.70 to 0.90 is a high correlation; from 0.50
to 0.70 is a moderate correlation; from 0.30 to 0.50
is a low correlation; from 0.00 to 0.30 negligible
correlation [23].
2.7 Statistical analysis
Six samples were analyzed for all the experiments,
and all the assays were performed 5 times. The
results were expressed as mean values with
confidence intervals. MS EXCEL 7.0 and STATISTIKA
6.0 were used to execute the statistical analysis.
3. RESULTS
3.1 Determination the total content of phenolic
compounds
The aqueous extract had the most significant content
of phenolic compounds (13.90±0.29 mg/mL), while
other raspberry shoots extracts demonstrated a
much lower content of phenolic constituent (Table
1). The sum of the total phenolic compound content
of red raspberry shoots extracts was 24.40 mg/mL.
3.2 Determination the total content of catechins
The sum of total catechins content was 21.36 mg/mL.
The highest amount of catechins was observed
in the aqueous extract (12.50±0.25 mg/mL), followed
by the other ethanol extracts. According to the results,
the amount of catechins (87.54 %) was higher among
all phenolic compounds (3.16 % flavonoids, and 1.49
% hydroxycinnamic acids derivatives) (Table 1).
3.3 Determination the total content of flavonoids
The sum of total flavonoid content was 0.77 mg/mL.
The highest amount of flavonoids was observed
in the aqueous extract (0.40±0.01 mg/mL), followed
by the other ethanol extracts (Table 1).
3.4 Determi nat ion t he tot a l content of
hydroxycinnamic acids derivatives
The sum of total hydroxycinnamic acids derivatives
content was 2.56 mg/mL. The highest amount of
hydroxycinnamic acids derivatives was observed in
the aqueous extract (1.50±0.03 mg/mL), followed
by the other ethanol extracts (Table 1).
3.5 Determination the total content of organic
acids
The aqueous extract had the greatest content
of organic acids (1.10±0.03 mg/mL), while other
raspberry shoot extracts demonstrated a much
lower content of organic acids. The sum of total
organic acids content was 1.88 mg/mL (Table 1).
5Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 01 | Article 351486
Study of total antioxidant capacity of red raspberry (Rubus idaeous L.) shoots
3.6. Determination the total antioxidant activity
The total antioxidant capacity of raspberry shoots
was 164.12 mmol-equiv./m dry weight . The antioxidant
activity increases in the following extracts order: 96
and 80 % < 60 % extract < 40 % extract < 20 %
extract < aqueous (Table 1).
3.7 Correlation analysis
Pearson’s (r) coefficients between antioxidant
activity and phenolic compounds, catechins,
flavonoids, hydroxycinnamic acids derivatives, and
organic acids were 0.9898, 0.9860, 0.9723, 0.9851
and 0.9697, respectively (Table 2).
Table 1. The quantitative content of catechins, flavonoids, hydroxycinnamic acids derivatives, organic acids, and antioxidant activity,
calculated from the extraction of red raspberry shoots (1:20 ratio raw material/solvent)
Extractant Total phenolic
content, mg/mL
Total catechin
content, mg/mL
Total flavonoid
content, mg/mL
Total hydroxycinnamic acids
derivatives content, mg/mL
Total organic
acids, mg/mL
Antioxidant
activity, mmol-
equiv./mdry weight
distilled water 13.9±0.29 12.5±0.25 0.40±0.01 1.50±0.03 1.10±0.03 85.00±1.70
20% ethanol 5.8±0.12 5.0±0.10 0.20±0.01 0.60±0.01 0.40±0.01 37.60±0.75
40% ethanol 4.1±0.10 3.4±0.07 0.14±0.01 0.40±0.01 0.30±0.01 37.26±0.75
60% ethanol 0.4±0.01 0.3±0.01 0.02±0.003 0.04±0.003 0.03±0.003 3.11±0.06
80% ethanol 0.1±0.001 0.08±0.003 0.005±0.001 0.01±0.001 0.01±0.001 0.62±0.01
96% ethanol 0.1±0.001 0.08±0.001 0.005±0.001 0.01±0.001 0.01±0.001 0.62±0.01
The total content 24.40 21.36 0.77 2.56 1.88 164.12
Table 2. Pearson`s (r) correlation coefficient between antioxidant activity and biologically active compounds content in extracts of
red raspberry shoots
Total phenolic
content
Total catechin
content
Total flavonoid
content
Total hydroxycinnamic
acids derivatives content
Total organic
acids content
Antioxidant activity 0.9898 0.9860 0.9723 0.9851 0.9697
4. DISCUSSIONS
4.1 Description of sequential exhaustive extraction
In our previous research [23], we created and
described the approach of exhaustive sequential
extraction. This type of extraction is based on the
extraction of the same raw material with extractants
of different polarity for example, distilled water as
a more polar extractant and ethanol solutions of
different concentrations as a less polar extractant.
Consistent, exhaustive extraction allows you to
extract hydrophilic and lipophilic BAS completely.
In this case, the raw material was not dried after
extraction; therefore, the volume of the extractant
absorbed by the raw material was considered.
4.2 Determination the total content of phenolic
compounds
Raspberry shoots are a rich source of phenolic
compounds such as ellagitannins, catechins,
flavonols and phenolic acids derivatives. Ellagitannins
are a group of complex phenolic compounds found
in high concentrations in raspberry shoots. They
are represented by the derivatives of sanguiin and
lambertianin. Ellafitannins are metabolized in the
gut to form ellagic acid, which has been shown to
have anti-inflammatory and anticancer properties
[8]. The Folin-Ciocalteu method was applied to
evaluate the total amount of phenolic compounds.
The total phenolic compounds were expressed
as gallic acid. A recent study of Bobinatie R. et al.
[25], they have investigated 41 red raspberry leaves
cultivars. They found that the phenolic compounds
content varied in different samples from 1.0 to
6.0 mg/mL in ethanolic extract. Compared to our
results, in our study, the total amount of phenolic
compounds is higher from 4 to 24 times. In another
study, Pavlovic et al. reported 144.20 mg/mL in the
60% methanolic extract of red raspberry leaves [26].
Buricova et al. evaluated a total content of phenolic
compounds of 2.76 mg/mL aqueous extract of red
6Journal Vitae | https://revistas.udea.edu.co/index.php/vitae Volume 30 | Number 01 | Article 351486Olexander Maslov, Mykola Komisarenko, Mykola Golik, Sergii Kolisnyk, Oksana Tkachenko, Iuliia Kolisnyk, Sergii Baiurka, Svetlana Karpushina, Alexander Altukhov
raspberry leaves [27]. In our opinion, the difference
in the content of phenolic compounds, is associated
with different brewing times, leaves/extractant ratios
used, species, climate, and geographical position.
4.3 Determination the total content of catechins
The raspberry shoots presented a variety of catechins,
such as epigallocatechin-3-O-gallate, epicatechin,
catechin, and epigallocatechin. The catechin is the
main compound among catechins in the raspberry
shoots [28]. The vanillin reagent assay determined
the total catechins expressed in epigallocatechin-
3-O-gallate equivalent. In recent research by Durgo
K. et al. [9], the total catechins found were 0.17 mg/
mL in the aqueous extract of red raspberry leaves
in our research, we are reporting 21.36 mg/mL, 120
times higher than obtained by the authors. Luo et al.
reported a total catechin content of 0.10 mg/mL in
60% methanolic extract red raspberry leaves [29], and
we obtained 0.3 mg/mL in ethanol extract. The large
values difference may be because that raspberry
shoots contain more catechins than flavonol
derivatives. Catechins in the biometabolism of plant
shoots are responsible for the intensity of cell division
and protection. In contrast, flavonol derivatives have
a signal function and remarkable antioxidant effect
against reactive oxygen species.
4.4 Determination the total content of flavonoids
Flavonoids are a phytochemical widely distributed
in raspberries with various health benefits. Several
flavonols have been detected in the raspberry
shoot: rutin, quercetin-3-O-glucuronide, hyperoside,
myricetin and kaempferol [8]. The total flavonoids
were determined using complex formation with AlCl3
assay. The total flavonoid content was expressed in
rutin equivalent. Costa T. et al. [30], reported 12.92
mg/mL of flavonoids in 20% ethanolic extract of red
raspberry leaves. In contrast, we obtained a value
of 94 % lower (0.20 mg/mL). Pavlovic et al. reported
a total flavonoids content of 10.64 mg/mL in 60%
methanolic extract red raspberry leaves extract [26].
Comparing the content of flavonoids in extracts
obtained from the leaves and shoots of red raspberry,
we can conclude that flavonol derivatives dominate in
the leaves, then in the shoots. Therefore, our theory
mentioned above is approved.
4.5 Determi nat ion t he tot a l content of
hydroxycinnamic acids derivatives
Raspberries are a rich source of hydroxycinnamic
acids. The most abundant hydroxycinnamic acid
in raspberries is chlorogenica acid, a powerful
antioxidant associated with various health benefits.
Other hydroxycinnamic acids in raspberries
include: caffeic acid, p-coumaric acid, ferulic acid
and sinapic acid [9]. The total hydroxycinnamic
acids derivatives content was measured by assay
of complex formation with NaNO2-Na2 MoO 4 and
expressed in chlorogenic acid equivalent. Costa T.
et al. [30] reported 9.28 mg/mL hydroxycinnamic
acids derivatives in 20% ethanolic extract of red
raspberry leaves. in our case, the total amount
of hydroxycinnamic acids derivatives was 72.11%
lower. Yang et al. reported a total hydroxycinnamic
acids content of 8.24 mg/mL in distilled water
red raspberry leaves extract [31], meanwhile, we
obtained the total hydroxycinnamic acids – 2.56
mg/mL. We have observed that the concentration
of hydroxycinnamic acids in raspberry leaf extract
is higher than in the shoot extract. We believe that
this is related to the biometabolism of flavonoids.
According to the shikimate pathway, derivatives
of hydroxycinnamic acids serve as precursors to
flavonoids. As we have also demonstrated that the
concentration of flavonoids is higher in the leaf
extract than the shoot extract, it follows that the
content of hydroxycinnamic acids in the leaf extract
should also be higher.
4.6 Determination the total content of organic
acids
Some of the main organic acids in raspberry shoots
include malic acid, citric acid, quinic acid, and
oxalic acid and citric acid is considerably abundant
in raspberry shoots [32]. The total organic acids
content was determined by acid-base titration with
the fixation endpoint by potentiometric method.
The total organic acids were expressed in citric
acid. Mikulic-Petkovsek M. et al. [33] investigated
amount of organic acids in the aqueous extract
of red raspberry fruits by high-performance liquid
chromatography. This study revealed that the total
organic acids were 2.2 mg/mL In our research, the
sum of total organic acids was 14.54 % lower than
in the reported study.
4.7 Determination the antioxidant activity
The antioxidant activity values of investigated extracts
were estimated with the potentiometric method.
This method was chosen due to its high sensitivity,
rapid analysis procedure, and relatively low cost
of equipment and reagents [34]. However, certain
acceptance criteria are required to justify the choice
of extraction conditions,. According to the available
7Journal Vitae | https://revistas.udea.edu.co/index.php/vitaeVolume 30 | Number 01 | Article 351486
Study of total antioxidant capacity of red raspberry (Rubus idaeous L.) shoots
literature, the main acceptance criterion is obtaining
the maximum content of phenolic and extractive
compounds. We propose to use the total antioxidant
capacity of raw materials as an acceptance criterion
for choosing the optimal extraction conditions, for
several of reasons, firstly, the antioxidant activity
and the content of phenolic compounds have a high
positive correlation, secondly, the determination
of antioxidant activity requires less time than the
determination of the content BAS and extractive
compounds. The term “total antioxidant capacity
of raw materials” means the sum of the antioxidant
activity of all hydrophilic and lipophilic BAS contained
in the studied raw materials.
4.9 Correlation analysis
Luo et al. [29] reported a good correlation between
the antioxidant activity of red raspberry extract
and the amount of phenolic compounds. They
found correlation coefficients of 0.915 and 0.830
when evaluating antioxidant activity by ABTS
and DPPH assays, respectively. In our study, the
highest correlation coefficient value was between
antioxidant activity and the total content of phenolic
compounds (r = 0.9898). Therefore, phenolic
compounds influenced the antioxidant activity of
red raspberry leaf extract.
5. CONCLUSIONS
The total red raspberry shoots antioxidant activity
was determined. The BAS and antioxidant activity
analysis of red raspberry shoot extracts revealed
that the aqueous extrac t had a remarkable
content of phenolic compounds, catechins,
flavonoids, hydroxycinnamic acids, organic acids
and antioxidant activity. Moreover, the quantitative
analysis showed that catechins were the main
compounds among phenolic ones. Furthermore,
correlation analysis revealed a strong positive
linear relationship between antioxidant activity and
phenolic compounds. The study results can be used
to develop optimal technologies for obtaining drugs
based on the extract of red raspberry shoots, which
has an antioxidant effect.
Conflict of interests: the authors have no conflicts
of interests to declare.
Authors’ contributions: Mykola Golik, Sergii
Kolisnyk, Sergii Baiurka and Svetlana Karpushina
participated in the structuring of the study,
discussion of the results, and final writing of
the manuscript. Alexander Altukhov carried
out the experimental part and participated
in the discussion. Olexander Maslov, Mykola
Komisarenko, Oksana Tkachenko, and Iuliia
Kolisnyk participated in the conception of the
study, experimental phase, discussion of the
results, and final writing of the manuscript.
ACKNOWLEDGMENTS
This work was financial supported by National
University of Pharmacy, Kharkiv, Ukraine
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