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Research Article
In Vitro Inhibitory and Proliferative Cellular Effects of Different
Extracts of Struthanthus quercicola: A Preliminary Study
Luz Eugenia Alc´
antara-Quintana,
1
Carely Arjona-Ruiz,
2
Denisse de Loera,
2
Rub´
ıGamboa-Le ´
on,
3
and Yolanda Ter´
an-Figueroa
4
1
CONACYT Chair Attached to Coordination for Innovation and Application of Science and Technology (Ciacyt),
Autonomous University of San Luis Potosi, Av. Sierra Leona 550, Lomas de San Luis, CP 78210. San Luis Potos´ı, Mexico
2
Photochemistry and Synthesis Laboratory, Faculty of Chemical Sciences, Autonomous University of San Luis Potos´
ı,
Av. Dr. Manuel Nava 6 Zona Universitaria, CP 78210, Mexico
3
Academic Coordination Southern Huasteca Region, Autonomous University of San Luis Potosi,
Km. 5 Carretera Tamazunchale-San Mart´
ın, CP 79960. Tamazunchale, Mexico
4
Laboratory of Microbiology, Parasitology and Food Toxicology, Faculty of Nursing and Nutrition,
Autonomous University of San Luis Potosi, Av. Niño Artillero 130, Zona Universitaria, CP 78240. San Luis Potos´
ı, Mexico
Correspondence should be addressed to Yolanda Ter´
an-Figueroa; yolandat@uaslp.mx
Received 10 September 2021; Accepted 25 February 2022; Published 13 April 2022
Academic Editor: Jos´
eRoberto Santin
Copyright ©2022 Luz Eugenia Alc´
antara-Quintana et al. is is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
Struthanthus quercicola, a hemiparasitic plant known as “seca palo,” is used by Nahuatl traditional healers against diabetes,
wounds, and rashes. We aimed to investigate the effects of different S. quercicola extracts, which were selected based on their
traditional use in Tamazunchale, San Luis Potos´
ı, on the cell viability and antioxidant activity in HeLa cell cultures. S. quercicola
growing on Guazuma ulmifolia and Citrus sp. hosts was collected, and methanolic and ethanolic extracts as well as decoctions,
infusions, and microwave-assisted extracts were obtained. e terpenoid, alkaloid, flavonoid, saponin, and tannin contents of each
extract were evaluated qualitatively and quantitatively. e effects of different extracts on the viability of cervical adenocarcinoma
(HeLa) cells were tested using an MTT assay. e differences in the total flavonoid and phenolic contents and free-radical
scavenging activity in relation to the host and the extract were also determined. In assessments of the effects of the extracts on cell
viability, eight organic extracts (4 from G. quercicola grown on Host 1 and 4 from G. quercicola grown on Host 2) were shown to
decrease cell viability significantly in comparison with the control. However, the extract obtained by percolation (PMeOH) caused
a significant increase in cell viability (p<0.05), especially with the plant grown on Host 1. e microwave aqueous and methanolic
extracts of the plants grown on both hosts showed a significant increase in the percentage of apoptosis (p<005). In conclusion,
different extracts of Struthanthus quercicola showed variable effects on cell viability and apoptosis. Isolation of the molecule or
molecules with inhibitory and proliferative effects on cells should be conducted to evaluate their possible use as
antineoplastic agents.
1. Introduction
Humans have long used natural products, especially plants,
for medical purposes and relied on these products to provide
leads for drug discovery and development. A number of
approved therapeutic agents show a natural product rela-
tionship since 21% of synthetic drugs are natural product
mimics and 4% contain a pharmacophore from a natural
product; additionally, 4% of approved drugs are unaltered
natural products, 21% are derived from a natural product,
and 1% are botanical drugs containing a defined mixture
recognized as a drug entity by the U.S. FDA [1, 2].
Huasteca Potosina is a region of San Luis Potos´
ı where
traditional medicine is used to treat several illnesses. Alonso-
Castro et al. identified 73 plant species used against several
ailments such as diabetes, cough, epilepsy, arthritis, diarrhea,
Hindawi
Evidence-Based Complementary and Alternative Medicine
Volume 2022, Article ID 9679739, 9 pages
https://doi.org/10.1155/2022/9679739
stomachache, vomiting, heart attack, body pain, and rash in
Aquismon [3]. Some studies have also reported the anti-
proliferative, cytotoxic, and antitumor effects of Mexican
plants, indicating their potential usefulness for cancer
treatment [4–9].
Struthanthus Mart. species, also named mistletoe, are
herbaceous plants that are scandent, dioecious, epiphytic,
and foliated. e stems are cylindrical or quadrangular, and
the inflorescences are spikes or racemes of three. e fruit is
oval orange, red, or blue, and the seeds have bright green
embryos and copious endosperms. ese mistletoes are also
known as “injertos” or “seca palo”. ey are hemiparasitic
plants (Loranthaceae) abundant in Mexico and could affect
significant extensions of trees, reducing the production of
cones and seeds and diminishing the diameter, height, and
volume. e endophytic system invades the host vascular
system and shoots regeneration from new endophyte buds
[10]. is plant is native to Costa Rica, El Salvador, Gua-
temala, Honduras, Mexico Central, Mexico Northeast,
Mexico Southeast, Mexico Southwest, Nicaragua, and
Panama [11].
Struthanthus quercicola, known as seca palo, is used by
Nahuatl traditional healers against diabetes, wounds, and
rash. e administration is like infusion or decoction, which
are prepared according to the recommendation of tradi-
tional healers (three 15 cm rods of the whole plant are boiled
in 1 L of water for 20 min and are drunk throughout the day).
is mistletoe (Loranthaceae) uses other plants as hosts and
is classified as a hemiparasite. Traditional healers use plants
growing on Guazuma ulmifolia and Citrus sp. Jim´
enez-
Estrada et al. [12] reported the antiproliferative activity of
Struthanthus palmeri on RAW 264.7 and L929 cell lines.
Considering its traditional use and that it has been re-
ported to have an effect against cancer, the aim of this study
was to investigate which type of antioxidants is present in
different extracts of S. quercicola and the effect of these
extracts on the cell viability in cervical cancer HeLa cell
cultures.
2. Materials and Methods
2.1. Plant Material. e plants were selected based on their
traditional use with the assistance of traditional healers
(Martina Chaires from Aquism´
on, Teenek Region, and
Santos Santiago Cruz and Eustolia Suviri from Tam-
azunchale, Nahuatl Region, both of which are regions in the
state of San Luis Potosi, Mexico). Plants growing on Gua-
zuma ulmifolia were collected in La Garita, Tambaque,
Aquism´
on (−99.042778, 21.681111), and plants growing on
Citrus sp. were collected in Enramaditas, Tamazunchale
(−98.808056, 21.202500) in January 2016. e plants were
taxonomically identified by the taxonomist Jos´
e Garc´
ıa P´
erez
at the Herbal “Isidro Palacios,” Desert Areas Research In-
stitute, Autonomous University of San Luis Potos´
ı, and a
voucher of classification was assigned (Table 1).
2.2. Extract Preparation. e whole plant was dried at
room temperature and protected from dust and sunlight.
e dried material was ground using a manual mill
(Estrella®). Five grams of each plant were macerated
separately at room temperature using methanol and
ethanol. Decoctions were obtained by boiling 5 g of plant
material in 50 mL of distilled water for 20 min. Infusions
were prepared by placing 1 g of the plant material in 50 mL
of boiling water for 20 min. Microwave-assisted extraction
was performed in a Mars 6 microwave reactor (CEM)
using methanol and 5 g of the plant material with the
following parameters: radiofrequency power, 350 W;
temperature-time ramp, 10 min with a final temperature
of 50°C (356 °F) held for 20 min. All extracts were filtered,
the organic solvents were evaporated to dryness under
reduced pressure, and the extracts were stored at −4°C in
amber glass vials until analysis. Table 2 lists the extract
codes and yields.
2.3. Phytochemical Screening
2.3.1. Test for Sterols and Terpenoids (Liebermann–Burchard
test). 10 mg of the extract was dissolved in 2 mL of chlo-
roform, after which 2 drops of acetic anhydride and con-
centrated sulfuric acid were carefully added. A reddish-
brown color at the interface indicated the presence of sterols
and terpenoids [13].
2.3.2. Test for Alkaloids (Dragendorff Test).
Approximately 10 mg of the extract was warmed with 2%
sulfuric acid for 2 min and then filtered. A few drops of
Dragendorff’s reagent were added, and an orange precipitate
indicated the presence of alkaloids [14].
2.3.3. Tests for Flavonoids
Shinoda Test. 10 mg of the extract was dissolved in 1 mL of
methanol, a chip of magnesium metal was added, and a few
drops of 0.5 N HCl were added. e presence of a pink
magenta color indicated the presence of flavonoids [15].
Constantinesco Test. ree drops of 10% sodium acetate
solution were added to 1 mL of the extract, followed by the
addition of 3 drops of aluminum chloride 2.5%; the for-
mation of a yellow color indicated the presence of flavonoids
[16].
Table 1: Taxonomic classification of Struthanthus quercicola.
Kingdom Plantae
Phylum Magnoliophyta
Class Magnoliopsida
Order Santalales
Family Loranthaceae
Genus Struthanthus
Species Struthanthus quercicola (Schltdl. & Cham.) Blume
Common name Seca palo
Voucher 56,112 collected from Citrus sp.
56,113 collected from Guazuma ulmifolia
2Evidence-Based Complementary and Alternative Medicine
2.3.4. Test for Saponins (Frothing Test). Samples were mixed
with 5 mL of water in a test tube, warmed, and shaken
vigorously. e formation of a stable foam indicated the
presence of saponins [17].
2.3.5. Test for Tannins (Folin–Ciocalteu Test). Five drops of
Folin reagent and two drops of sodium carbonate 7.5% were
added to the extract. e green color indicates the presence
of phenols, light blue indicates moderate presence of phe-
nols, and intense blue indicates the abundance of phenols
[16].
2.4. Total Phenolic Content of the Extracts. e total phenolic
content of the aqueous and organic extracts was determined
by using the Folin–Ciocalteu reagent with the microplate
method, as reported by Bobo-Garc´
ıa et al. [18]. In this
method, 100 μL of the Folin–Ciocalteu reagent (1 : 4 diluted)
was added to 20 μL of the diluted plant extract (1 mg/mL)
and shaken for 60 s in a 96-well microplate. e mixture was
left for 240 s, after which 75 μL of sodium carbonate solution
(100g/L) was added, and the mixture was shaken and left for
2 h at room temperature. e absorbance at 750 nm was
measured using a spectrophotometer (Synergy H
Y20003642T; BioTek). An ethanol solution was used as a
blank. e phenolic content was calculated as gallic acid
equivalent by comparison with a calibration curve of gallic
acid standard solutions (10–100 μg/mL) and was expressed
as mg gallic acid equivalent per gram of dry extract. Samples
were analyzed in triplicate. Y�0.1072 + 0.1307, R
2
�0.9985.
2.5. Total Flavonoid Content of the Extracts. e aqueous
extracts were used to determine the total flavonoid content
using an aluminum chloride colorimetric assay adapted to a
microplate method [16]. e plant extract (100 μL, 1 mg/mL)
was mixed with 100 μL of AlCl
3
(2%) in a 96-well microplate.
e mixture was kept in a dark place at room temperature
for 10 min. e absorbance at 365 nm was measured using a
spectrophotometer (Synergy H Y20003642T; BioTek). An
ethanol solution was used as a blank. e flavonoid content
was calculated as quercetin equivalent by comparison with a
calibration curve of quercetin standard solutions (5–45 μg/
mL) and was expressed as mg quercetin equivalent per gram
of dry extract. Samples were analyzed in triplicate.
Y�0.0085x −0.1554, R
2
�0.9965.
2.6. Free-Radical Scavenging Activity. Antioxidant activity
was determined using the 2, 2-diphenyl-1-picryl-hydrazyl-
hydrate (DPPH) microplate method as reported by Bobo-
Garc´
ıa et al. [18], with slight modifications. Diluted plant
extract (100 μL) was mixed with 100 μL of DPPH solution
(0.4 mM) and shaken for 60 s in a 96-well microplate. e
mixture was kept in the dark at room temperature for
30 min. e absorbance at 517 nm was measured using a
spectrophotometer (Synergy H Y20003642T; BioTek). An
ethanol solution was used as a blank. DPPH free-radical
scavenging activity was calculated as Trolox equivalent by
comparison with a calibration curve of Trolox standard
solutions (4–28 μg/mL) and was expressed as mg Trolox
equivalent per gram of dry extract. Samples were analyzed in
triplicates. e DPPH radical scavenging assay was per-
formed using a microplate method as reported by Bobo-
Garc´
ıa et al. [18], with slight modifications. Briefly, 100 μL
DPPH radical solution (0.4 mM) was mixed with 100 μL of
various concentrations of the extract sample dissolved in
ethanol (4–30 μg/mL). e mixture was kept in the dark at
room temperature for 30 min. Absorbance was read at
517 nm using a spectrophotometer (Synergy H Y20003642T;
BioTek). Ethanol and Trolox solutions were used as the blank
and standard, respectively. e percentage inhibitory ac-
tivity was calculated using equation (1), where A0is the
absorbance of the control, and A1is the absorbance of each
sample extract. e half-maximal inhibitory concentration
(IC
50
) was obtained by fitting a nonlinear regression using a
four-parameter logistic function (equation (2)) and
expressed in µg/mL, where the parameter 10(x−LogC)is the
inflection point and the estimate of IC
50
.
Inhibition % �A0−A1
A0
×100,(1)
Y�D+(A−D)
1+10(x−LogC)B.(2)
2.7. Cell Line and Cell Culture. We used a HeLa cell line that
was obtained several years ago for human cervical adeno-
carcinoma (CCL-2™; ATCC). HeLa cells were maintained in
Dulbecco’s modified Eagle’s medium (DMEM D6429;
Sigma-Aldrich) supplemented with 10% (v/v) fetal bovine
serum (12103C; Merck-Millipore), 2 mM glutamine, 100 U/
Table 2: Extract yields of S. quercicola growing on G. ulmifolia and Citrus sp.
Guazuma ulmifolia Citrus sp.
Code Extract Solvent Host 1 Host 2
Weight (g) Yield (%) Weight (g) Yield (%)
Decoction Decoction Water 0.2472 5 0.6763 13
Infusion Infusion 0.8964 18 0.8092 16
MWaq Microwave 0.6226 12 0.5637 11
MWMeOH Methanol 0.7264 14 0.9736 19
MMeOH Maceration 0.6092 12 1.3762 27
PMeOH Percolation 100.00 15 33.00 16
MWaq, microwave water extract; MWMeOH, microwave water methanol extract; MMeOH, maceration methanol extract; PMeOH, percolation methanol
extract.
Evidence-Based Complementary and Alternative Medicine 3
mL penicillin, and 100 μg/mL streptomycin (P4083; Sigma-
Aldrich) at 37°C, 5% CO
2
in a humidified atmosphere. Cells
(5 ×10
4
cells/well) were cultivated in 96-well plates [19]. e
cells were observed, and images were acquired (magnifi-
cation, 20×) using an inverted microscope (Labomed TCM
400) and then separated by centrifugation at 600 ×g for
6 min. e supernatant was gently removed, and the cell
pellet was counted. ree replicates were used for each
treatment.
2.8. Exposure. e cells were treated with extracts (100, 50,
25, and 12.5 μg/mL) for 72 h.
2.9. Cell Viability Assay. After incubation for 72 h, 100 μL
(5.0 mg/mL) of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl
tetrazolium bromide (MTT, 11465007001; Roche) was
added to each well. After 4 h, the formazan product was
dissolved in dimethyl sulfoxide, and the absorbance at
570 nm was measured [20] using a microplate reader
(Multiskan; ermo Scientific). Nontreated cells and cells
treated with DMSO 0.01 μg/mL (D9170; Sigma-Aldrich)
were used as negative and positive controls, respectively. e
assays were performed in triplicate in three independent
experiments. e viability percentage was obtained by
considering the control as 100%.
2.10. Apoptosis Detection Assays. Apoptotic cells were
measured using an annexin V apoptosis kit according to the
manufacturer’s instructions (APOAF-20TST; Sigma-
Aldrich). Briefly, the cells were washed once with PBS 1X
and centrifuged at 13,000 rpm for 5 min. After that, they
were washed once in 1X binding buffer and resuspended in
1X staining buffer. en, 100 µL (approximately 5 ×10
5
cells)
was incubated with 10 µL of annexin V at room temperature
for 15 min in the dark. e absorbance at 570 nm was
measured using a microplate reader (Multiskan; ermo
Scientific). e assays were performed in triplicate in three
independent experiments. e apoptosis percentage was
obtained by using the control as 100%.
2.11. Statistical Analysis. For the analysis of variance, the
ANOVA parametric test was used, and significance was
assigned for a pvalue less than 0.05. GraphPad v.8.4 program
was used.
3. Results and Discussion
Table 3 shows the results of qualitative phytochemical tests of
the aqueous and organic extracts of S. quercicola harvested
from two different hosts. e analysis showed the presence of
alkaloids, flavonoids, and tannins. Saponins were present in the
aqueous extracts, except in infusion and decoction from Host 1.
e data indicated differences in the total flavonoid content
of the aqueous and organic extracts. Similar findings were
obtained in comparison of the data for extracts from different
hosts. As shown in Figure 1(a), the extracts from plants
growing on Citrus sp. (Host 2) showed higher total flavonoid
content than samples from plants growing on G. ulmifolia
(Host 1). On the other hand, in Figure 1(b), in evaluations
based on solvent polarity, since phenolic compounds were
polar molecules, extracts prepared using polar solvents, such as
water, methanol, and ethanol, were expected to have a higher
phenolic content. Extracts from S. quercicola growing on Host
2 contained higher phenolic compound content than extracts
from Host 1, regardless of the extraction method. For aqueous
extracts, microwave extraction was the best extraction method
for phenolic content, while percolation was the optimal method
for organic extraction.
e DPPH radical scavenging activity of the extracts is
shown in Figure 2, and Table 4 shows the inhibition activity
(IC
50
). e aqueous extracts showed higher activity than the
organic extracts, while the extracts from S. quercicola grown
on Host 2 exhibited greater antioxidant activity than those
from plants grown on Host 1. e extract with the highest
antioxidant activity was the aqueous extract from the plants
grown on Host 2.
Extract codes are defined in Table 2.
e effects of the six extracts (two aqueous and four
organic) from each plant were analyzed. In our analysis of
the cell viability in HeLa cell cultures, the eight organic
extracts (four each from G. quercicola grown on Host 1 and
Host 2) caused a significant decrease in cell viability in
comparison with the control. e maximum effect was
observed with the six extracts from plants grown on Host 1;
however, the organic extracts, specifically the percolation
extract (PMeOH), caused a significant increase in cell via-
bility (p<0.05), especially the 100 µg/mL extract from the
plant grown on Host 1 (Figure 3(a) and 3(c)).
To corroborate these findings, tests were conducted to
observe apoptosis in HeLa cell cultures grown in the
presence of the different extracts. e annexin V binding
Table 3: Qualitative phytochemical screening of extracts of S. quercicola growing on G. ulmifolia (Host 1) and Citrus sp. (Host 2).
Extract code∗Sterols Terpenoids Alkaloids Flavonoids Saponins Tannins
Host 1/Host 2
Decoction N/N N/N ∗/∗ ∗/∗N/∗ ∗/∗∗
Infusion N/N N/N ∗/∗ ∗∗/∗∗∗ N/∗ ∗∗/∗∗∗
MWaq N/N N/N ∗/∗ ∗∗/∗∗∗ ∗∗/∗∗∗ ∗∗/∗∗∗
MWMeOH ∗∗/∗∗∗ ∗∗/∗∗∗ N/∗∗ ∗∗/∗∗∗ N/N ∗∗/∗∗
MMeOH ∗∗/∗∗ ∗∗/∗∗ ∗∗/∗∗ ∗∗/∗∗ N/N ∗/∗∗
PMeOH ∗/∗N/N ∗∗/∗∗ ∗∗/∗∗∗ ∗∗/∗∗ ∗∗∗/∗∗∗
∗�little coloration/precipitation, ∗∗ �intermediate coloration/precipitation, ∗∗∗ �abundant coloration/precipitation; N �no reaction/precipitation. Extract
codes are defined in Table 2.
4Evidence-Based Complementary and Alternative Medicine
assay is an indicator of the early stages of apoptosis.
Translocation of phosphatidylserine (PS) from the inner face
of the plasma membrane to the cell surface was determined.
PS redistribution occurs earlier, and its externalization oc-
curs during apoptosis induced by a variety of stimuli. e
MWaq and MWMeOH extracts of the plants grown on both
hosts showed a significant increase in the percentage of
apoptosis (p<005), reflecting the findings for cell viability,
although the extracts from plants grown on Host 1 clearly
caused higher percentages of apoptosis.
e 100 µg/mL MMeOH extract of S. quercicola grown
on Host 1 caused a decrease in apoptosis and an increase in
cell viability (Figures 3(a) and 3(b)). In contrast, the PMeOH
extracts of the plants grown on both hosts caused an increase
in the percentage of apoptosis at 100, 50, and 12.5 µg/mL
(Figures 3(b) and 3(d)).
e documentation of traditional medicinal plants and
remedies is becoming increasingly important because of the
rapid loss of natural habitats [21]. Approximately 25% of the
drugs prescribed worldwide are from plants [22]. Traditional
medicine has a long history of use in Mexico. e document
written by Bernardino de Sahag´
un “Historia de las cosas de
la Nueva España” includes a description of the medicinal
plants used by the Aztecs before the arrival of the Spaniards
[23]. e different medicinal plants in Huasteca Potosina
and their uses have been described previously [3]. Despite
the current tendency to use plants with medicinal properties
to cure different diseases, the safety of their use remains to be
studied. In this regard, several properties have been at-
tributed to the genus Struthanthus [24–26].
In relation to the findings of the present study, some of
the extracts obtained from S. quercicola from two different
hosts showed notable effects on the viability of HeLa cells,
and the extracts that diminished cell viability did not have an
apoptotic effect and vice versa, except for the 100 and 50 µg/
mL MMeOH extracts, which caused an increase in cell vi-
ability with no effect on the percentage of apoptosis.
e qualitative phytochemical studies carried out between
the two decoctions showed that S. quercicola grown on Host 2
contains carbohydrates of sterols or triterpenes and greater
amounts of flavonoids and tannins; in addition, the quanti-
tative phytochemical analysis showed the same differences in
the amount of flavonoids and total phenols, which explains
why the antioxidant activity of the decoction of the plant grown
on Host 2 was greater than that grown on Host 1.
0
10
20
30
40
50
60
70
80
Decoction Infusion MWaq MWMeOH MMeOH PMeOH
mol Eq of quercetin/g of plant
Extracts
Host 1
Host 2
(a)
0
2
4
6
8
10
12
Decoction Infusion MWaq MWMeOH MMeOH PMeOH
mMolEq of Galic Acid/g of plant
Extracts
Host 1
Host 2
(b)
Figure 1: Total flavonoid (a) and phenolic (b) content of the aqueous and organic extracts of S. quercicola growing on G. ulmifolia (Host 1)
and Citrus sp. (Host 2). Extract codes are defined in Table 2.
120
100
80
60
40
20
0
Inhibition (%)
100
37
52
17
27
20
82
0.08
0.65
0.46 1.43
65 68
Decoction Infusion MWaq MWMeOH MMeOH PMeOH
Tro lox
Host 1
Host 2
Figure 2: Antioxidant capacity with DPPH radical inhibition of
Struthanthus quercicola extracts. Trolox served as the positive
control.
Table 4: S. quercicola extract free-radical scavenging activity.
Extract IC
50
(µg/mL) ±SD
Host 1 Host 2
Decoction 363 ±4 7 ±0.89
Infusion >500 69 ±0.45
MWaq 124 ±1.8 10 ±2.4
MWMeOH NA NA
PMeOH 149 ±0.31 55 ±1.4
MMeOH 221 ±5.2 149.5 ±3.45
Trolox 14 ±2
Evidence-Based Complementary and Alternative Medicine 5
Raffa et al. [27] have reported that flavonoids exhibit
topoisomerase inhibitory activity and affect different sig-
naling pathways such as AMP-activated protein kinase
(AMPK), so the activity observed with the decoction of the
plant grown on Host 2 could be attributed to the flavonoids
present in it and the lack of activity of the decoction of the
plant grown on Host 1 could be attributed to the absence of
these compounds in its phytochemical composition through
a saturable route. It is possible that the secondary metab-
olites that grant the inhibitory activity are different from
those that grant antioxidant activity; these differences could
also contribute to the differences in the antioxidant activity
of extracts from plants grown on the two hosts. e same
behavior could be seen among extracts obtained by mac-
eration, with both extracts showing an inhibiting effect on
viability, but the effect being significantly greater for the
extract from the plant grown on Host 1. Based on the results
obtained in the qualitative and quantitative analyses, the
effects on cell viability could also be attributed to flavonoids.
e results of this study suggest that the effects of the
extracts on cell viability and apoptosis in HeLa cells in
culture are related to the extraction method since the
microwave extracts showed reduced viability. Notably,
these effects were not linked to the nature of the solvent
(aqueous or organic) but were instead related to the
polarity of these solvents since extracts obtained by
3
2
1
0
Decoction
Infusion
MWaq
MWMeOH
MMeOH
PMeOH
Cell Viability (100%)
a
aaaa
b
bb
bb
c
c
cc
d
d
dd d
c
G. ulmifolia
Host 1
50 ug (ml)
Control
100 ug (ml)
25 ug (ml)
12.5 ug (ml)
(a)
80
60
40
20
0
Decoction
Infusion
MWaq
MWMeOH
MMeOH
PMeOH
Apoptotic effect (%)
d
d
d
d
c
c
b
b
b
b
b
a
a
a
a
a
50 ug (ml)
Control
100 ug (ml)
25 ug (ml)
12.5 ug (ml)
(b)
1.5
1.0
0.5
0.0
Decoction
Infusion
MWaq
MWMeOH
MMeOH
PMeOH
Cell Viability (100%)
a
a
c
cccc
d
d
ddeee
ef
ffff
Citrus sp.
Host 2
50 ug (ml)
Control
100 ug (ml)
25 ug (ml)
12.5 ug (ml)
(c)
80
60
40
20
0
Decoction
Infusion
MWaq
MWMeOH
MMeOH
PMeOH
Apoptotic effect (%)
a
a
a
a
a
b
b
b
b
b
c
cc
50 ug (ml)
Control
100 ug (ml)
25 ug (ml)
12.5 ug (ml)
(d)
Figure 3: Effects of the extracts of S. quercicola growing on G. ulmifolia and Citrus sp. on cell viability and apoptosis. (a) and (c) HeLa cell
viability. (b) and (d) Percentage apoptosis of HeLa cells. e cells were exposed to different concentrations of different extracts after 72 h of
culture. e average value obtained in three experiments in triplicate is presented. Bars represent standard deviation. e letters above the
bars indicate the extract and the concentration at which significance was observed. Extract codes are defined in Table 2.
6Evidence-Based Complementary and Alternative Medicine
methanolic percolation also had a negative effect on cell
viability (these are separated by affinity to the solvent, so
the metabolites extracted by methanol were polar, similar
to those found in aqueous extractions). e anti-
proliferative activity of these extracts could be attributed
not only to the flavonoids but also to the other poly-
phenols found in them since according to the quantitative
analysis all of them contain polyphenols to some extent.
Wang et al. [28] reported cytotoxic activity via apoptosis
in HeLa cells by polyphenols; therefore, it is likely that the
observed activity is attributed to these compounds.
Species of the genus Struthanthus exhibit various bio-
logical activities; for example, the hydroalcoholic extract of
S. vulgaris contains flavonoids, tannins, and saponins with
antimicrobial, antioxidant, and healing activities [29]. An-
other study reported the anti-inflammatory activity of ex-
tracts from this species but did not identify the secondary
metabolites responsible for this activity [30]. e antioxidant
and antiproliferative activities of the methanolic extract of
S. palmeri, which contains flavonoids to which biological
activity has been attributed, have also been investigated [12],
and the hydroalcoholic extract of S. venetus, which is rich in
polyphenols, has been reported to show antihypertensive
[31] and antiproliferative activities [32]. Table 5 shows a
summary of the classes of secondary metabolites identified
as responsible for the biological activities reported in the
species of the genus Struthanthus.
A previous study on the medicinal plants used in
Huasteca Potosina, Mexico, described the species Stru-
thanthus densiflorus. It has been traditionally used by people
in Aquism´
on, San Luis Potos´
ı, and Mexico for treating oral
wounds, diabetes, and rash [3]. Traditional medicine in-
cludes the use of plants for the treatment and prevention of
different types of cancer [33]. Plant-derived drugs of great
importance, such as taxol isolated from Taxus brevifolia
Nutt. (Taxaceae), have been used in the management of
breast, ovarian, and brain cancers [34].
In Mexico, different extracts of Cuphea aequipetala Cav.
(Lythraceae), known as the “cancer herb,” have been found
to show slight cytotoxicity in a cervical cancer cell line and
no cytotoxicity in nasopharyngeal carcinoma and colon
cancer [35]. In an evaluation of five species of plants used in
the state of Hidalgo, Mexico, to treat cancer, the crude
ethanolic extract of the leaves of Cupressus lusitanica
Klotzsch (Cupressaceae) showed cytotoxic effects in dif-
ferent cancer cell lines, and the cell death was shown to be
related to apoptosis [36].
To date, the effects of a series of plant compounds at the
molecular, cellular, or physiological level have not been
evaluated, even though these compounds have shown po-
tential in the treatment of conditions in humans [5]. In this
study, we performed cellular-level assessments in culture
and focused on cervical cancer. e effect of extracts of
S. quercicola on HeLa cells has not been reported, nor have
comparative studies been made from the same plant extracts
obtained by microwave extraction and from two different
hosts.
4. Conclusions
S. quercicola mainly contains metabolites such as alkaloids,
flavonoids, and tannins. e concentrations of these
metabolites vary depending on the host on which the plant
grows, and, thus, the effects on cell viability and apoptosis
also vary with the host plants. For aqueous extracts,
microwave extraction was the best method for phenolic
content, while percolation was the optimal method for
organic compounds. Extracts from the plant growing on
Host 2 contained higher phenolic compound content than
extracts from Host 1; however, the maximum effect on
HeLa cell viability was observed with the six extracts from
plants grown on Host 1. Studies on the isolation of the
molecule or molecules with inhibitory and proliferative
effects on cells should be conducted to evaluate their
possible use as antineoplastic agents in the treatment of
cervical cancer.
Data Availability
e data sets used and/or analyzed during the current study
are available from the Faculty of Nursing of Autonomous
University of San Luis Potos´
ı, the research department,
through the corresponding author on reasonable request.
Conflicts of Interest
e authors declare that there are no conflicts of interest
regarding the publication of this paper.
Table 5: Classes of secondary metabolites identified as responsible for the biological activities reported in the species of the genus
Struthanthus.
Species Biological activities Secondary metabolites Study Identified/Elucidate
S. vulgaris [20] Antioxidant, antimicrobial, anti-inflammatory wound
healing
Flavonoids, tannins,
saponins
In vitro
Identified
S. marginatus [24] Antiulcer Flavonoids
AntituberculousS. concinnus [24] Sterols, terpenoid
triterpenes Elucidate
S. palmeri [10] Antioxidant Flavonoids
IdentifiedAntiproliferative
S. venetus [22, 23] Polyphenols
In vivo
Antihipertensive
S. vulgaris [20] Antioxidant Flavonoids, tannins,
saponins Identified
Evidence-Based Complementary and Alternative Medicine 7
Acknowledgments
is work was supported by Consejo Nacional de Ciencia y
Tecnolog´
ıa (CONACYT), project PRONACE 172536.
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