Journal of Animal Science, 2020, Vol. 98, No. 7, 1–6
doi:10.1093/jas/skaa203
Advance Access publication July 06, 2020
Received: 6 May 2020 and Accepted: 4 July 2020
Short Communication
SHORT COMMUNICATION
Jensen E. Cherewyk,† Sarah E. Parker,‡ Barry R. Blakley,|| and
Ahmad N. Al-Dissi$,1
Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5B4, ‡Centre for Applied Epidemiology, Large
Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada, S7N
5B4, ||Department of Veterinary Biomedical Sciences, Western College of Veterinary Medicine, University of Saskatchewan,
Saskatoon, SK, Canada, S7N 5B4, $Department of Veterinary Pathology, Western College of Veterinary Medicine, University of
Saskatchewan, Saskatoon, SK, Canada, S7N 5B4
†
Corresponding author: ahmad.aldissi@usask.ca
1
ORCiD numbers: 0000-0002-9250-0162 (J. E. Cherewyk).
Abstract
Ergot alkaloids are produced by the fungus Claviceps purpurea and their levels are carefully monitored in animal and human
diets due to their harmful effects and widespread contamination of cereal crops. Ergot alkaloids exist in two forms known
as the (R)- and (S)-epimers with only the former being monitored in diets in North America. The (S)-epimers of ergot
alkaloids are thought to be biologically inactive and, therefore, harmless. A major mechanism by which the (R)-epimers of
ergot alkaloids produce their toxic effect is through vasoconstriction. Therefore, the objective of this study was to examine
the vasoactivity potential (contractile response) of four (S)-epimers, namely ergocryptinine, ergocristinine, ergocorninine,
and ergotaminine utilizing an in vitro arterial tissue bath system. Bovine metatarsal arteries (n = 6, ergocryptinine and
ergocorninine; n = 6, ergocristinine and ergotaminine; n = 6 arteries/(S)-epimer, total n = 12) were collected from healthy
mixed-breed beef steers immediately after slaughter, cut into 3-mm arterial cross sections, and suspended in a tissue bath
with continuously oxygenated Krebs–Henseleit buffer. To assess the contractile response of each (S)-epimer, a cumulative
contractile dose–response curve was constructed by incubating arteries with increasing concentrations (1 × 10−11 to 1 × 10−6 M)
of that (S)-epimer. Contractile responses were recorded as grams of tension and were normalized to an initial contraction of
phenylephrine. Contrary to the widespread belief, all tested (S)-epimers were found vasoactive and produced a concentrationdependent arterial contractile response similar to what has been reported for the (R)-epimers. The arterial contractile
response to ergotaminine was strongest and was significantly greater than that of ergocryptinine and ergocristinine at the
highest concentration used (P ≤ 0.01). Our results indicate that the (S)-epimers are biologically active and are likely harmful
similar to the (R)-epimers. The levels of (S)-epimers should be carefully monitored in human and animal diets worldwide.
Key words: bovine, epimers, ergot alkaloids, metatarsal artery, vasoconstriction
Introduction
The fungus Claviceps purpurea produces ergot alkaloids that
invade cereal crops globally. In livestock feed, it is well established
that the presence of high concentrations of ergot alkaloids are
associated with clinical manifestations, including gangrene,
abortion, stillbirth, decreased birth weight, decreased immunity,
© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science.
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License
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1
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Assessment of the vasoactive effects of the
(S)-epimers of ergot alkaloids in vitro
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Journal of Animal Science, 2020, Vol. 98, No. 7
Abbreviations
EC50
GEE
PE
effective concentration giving halfmaximal response
generalized estimating equations
phenylephrine
Materials and Methods
No ethics approval was required. The primary investigator
(A.N.A) was required to submit a form to the University
Ethics Committee indicating only the number of animals to
be slaughtered. Animal slaughter was performed according to
slaughterhouse guidelines by slaughterhouse employees.
Animals and arteries
Dorsal metatarsal arteries were collected from healthy mixedbreed beef steers (n = 12) aged 15 to 20 mo immediately after
the slaughter at a local abattoir. One foot limb, with the hide
removed, was given to the researcher located in a separated
space within the abattoir approximately 7 min after animal
was euthanized (one foot limb collected per day). From each
foot limb, muscle, nerves, and tissues were removed to access a
Ergocristinine, ergocorninine, ergocryptine, and
ergotaminine cumulative concentration–response
For each experimental run, two of the four arterial cross sections,
from a 15-cm artery segment, would receive one (S)-epimer
and the other two would receive a different (S)-epimer. Values
for the contraction of each artery segment were based on the
average of duplicated arterial cross sections (two (S)-epimers and
two arterial cross sections/(S)-epimer). Twelve (n = 12) arteries
(artery segments) in total were used with six (n = 6) exposed
to ergocryptinine and ergocorninine, and the other six (n = 6)
exposed to ergocristinine and ergotaminine (n = 6 arteries/(S)epimer). After resting tension was restored, (S)-epimers were
added separately to each chamber in the tissue bath from
lowest concentration (1 × 10–11 M) to highest (1 × 10–6 M) for an
incubation period of 29 min, with one buffer replacement,
followed by a 2.5-min washout period and 1 min recovery before
the next (S)-epimer addition (Klotz and McDowell, 2017, with
slight modification). Preliminary investigation indicated that
the arteries do not relax after the (S)-epimers were removed
from the buffer within the tissue bath. The arteries continued
to increase in contractility several minutes after the (S)-epimers
were washed out. This is consistent with a previous study with
(R)-epimers (Pesqueira et al., 2014). In comparison, when PE was
washed out from the buffer solution, the contraction abated
almost immediately. A maximal response was not achieved in a
9- or 14-min incubation period, which had been used in previous
validated assays (Klotz et al., 2006; Klotz and McDowell, 2017);
therefore, a longer incubation period for each (S)-epimer was
employed to ensure contraction was not overlooked. After the last
concentration, PE (1 × 10–4 M) was added again to ensure viability
of all arterial cross sections. Arterial cross sections exposed
to PE at the conclusion of an experimental run had similar
contractile responses to the first PE additions. Stock solutions
of ergocristinine (Romer Labs, Vancouver, BC), ergocorninine
(Romer Labs, Vancouver, BC), ergotaminine (U.S. Pharmacopeia,
Rockville, MD) were prepared in 100% methanol (Fisher Scientific,
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and decreased fertility in multiple animal species (Klotz, 2015a).
These effects are mainly related to the vasoconstrictive effects
of ergot alkaloids, through structural similarity to biological
amines binding to their receptor, on multiple arterial and venous
vascular beds impacting the blood supply to multiple organs.
Over 90 ergot alkaloids have been isolated, which are
separated into two main categories, including amide derivatives
of lysergic acid and small peptides (ergopeptines), based on
chemical structure (Liu and Jia, 2017). Small peptide ergot
alkaloids exist in two conformational forms known as the (R)epimers and the (S)-epimers. The two forms are in equilibrium
with the transformation of (R)-epimers to their respective (S)epimers being complex and dependent on several factors,
including temperature, pH, and solvent for experimental use. The
transformation passes through an intermediate conformation.
The (R)-epimers contain the suffix “ine” whereas the (S)-epimers
contain the suffix “inine” (Krska and Crews, 2008).
Both forms have been shown to have different chemical,
physical, and biological properties (Smith and Shappell, 2002). It
is currently thought, under normal physiological conditions, that
the (R)-epimers exert biological effects, whereas the (S)-epimers
are inactive (Smith and Shappell, 2002; Klotz, 2015b; Guo et al.,
2016; Kudupoje et al., 2018). Original reports from the 1970s to
1980s are often cited in current publications stating inactiveness
(Stadler and Stürmer, 1970; Pierri et al., 1982).
The bioactivity, in terms of vasoactivity, of (R)-epimers is
commonly assessed using an in vitro tissue bath system where
the contractile response of dissected arteries is monitored after
incubation with increasing concentrations of a particular (R)epimer (Klotz et al., 2010;Foote et al., 2011; Klotz and McDowell,
2017). Specifically, cattle arteries (Oliver et al., 1993, Klotz et al.,
2010, Foote et al., 2011), such as the dorsal metatarsal artery
(Oliver et al., 1993; Yonipam, 2018), have been utilized. It is
hypothesized, based on a similar chemical structure, that the
(S)-epimers of ergot alkaloids will cause arterial contraction
similar to (R)-epimers. Therefore, the objective of this study was
to examine the vasoactivity potential (contractile response) of
bovine metatarsal arteries after incubation with one of four (S)epimers, including ergocryptinine, ergocristinine, ergocorninine,
and ergotaminine using an in vitro tissue bath system.
15-cm segment of the dorsal metatarsal artery that was located
directly next to the bone. Once the segment was carefully
removed using surgical scissors and a scalpel, it was placed in a
small container with a lid containing modified Krebs–Henseleit
oxygenated buffer, (95% oxygen/5% carbon dioxide mixture;
pH = 7.4; composition in g/2 liters deionized water: 13.68 NaCl,
0.7 KCL, 0.28 MgSO4, 0.32 KH2PO4, 3.6 NaHCO3, 1.8 glucose, and
CaCl2, made in house) and on ice for transport to the laboratory
(Klotz and McDowell, 2017). Upon arrival to the laboratory,
excess fat and connective tissue were removed from each artery
segment (Klotz and Barnes, 2014), which were sliced into 3-mm
arterial cross sections (Klotz and McDowell, 2017). Four arterial
cross sections were suspended horizontally in a four-chamber
(one arterial cross section per chamber) tissue bath (Radnoti
[159906], Monrovia, CA, USA) containing 15 mL of continuously
oxygenated (95% oxygen/5% carbon dioxide) modified Krebs–
Henseleit buffer, same as above, at 37 °C. Arterial cross sections
were then allowed to equilibrate for 1 h with a resting tension
of 2 g, with buffer solution replacement every 15 min (Foote
et al., 2011; Yonipam, 2018). Arterial cross sections were then
exposed to an alpha-adrenergic agonist, phenylephrine (PE) (1 ×
10–4 M, Fisher Scientific, Fair Lawn, NJ), to verify viability and
to provide contraction information to normalize experimental
contractions. Arterial cross sections were then washed every
15 min with incubation buffer to restore resting tension with 4
to 6 replacements made.
Cherewyk et al. |
Fair Lawn, NJ), and ergocorninine prepared in 100% ethyl acetate
(Fisher Scientific, Fair Lawn, NJ) (Klotz et al., 2010) within the
manufacturer amber vials, all stored at −20 °C (Smith and
Shappell, 2002; Hafner et al., 2008). From the stock solutions,
dilutions were made to obtain the desired concentrations, the
day of the experimental run, while arterial cross sections were
equilibrating. Each concentration of the working standards was
made within a 1.5-mL microcentrifuge tube with a snap cap
(Labcon North America, Petaluma, CA) and stored in dark and on
ice within a coved styrofoam container until use. The volume of
solvent used for each concentration of (S)-epimer did not exceed
0.5% of the 15 mL buffer within the tissue bath.
Data collection and statistical analysis
Results
All four (S)-epimers caused a measurable contraction of bovine
dorsal metatarsal arteries at a concentration of 1 × 10–7 M. The
arterial contractile response increased at the next highest
concentration of 1 × 10–6 M (Figure 1). Of the four (S)-epimers, at
the highest concentration, ergotaminine generated the strongest
contraction of followed by ergocorninine, ergocristinine,
and ergocryptinine. This study demonstrated a statistically
significant interaction effect between (S)-epimer type and
concentration on the percent contractility (P < 0.001). Due to a
significant interaction, GEE analysis was performed separately
at each individual concentration to test whether a difference
in effect existed between (S)-epimers (P < 0.001 for each
concentration). Specifically, at 1 × 10−7 M, ergocryptinine resulted
in a lower percentile contraction to ergotaminine (P = 0.011). At
1 × 10–6 M, ergocryptinine and ergocristinine each resulted in
a significantly lower percentile contraction than ergotaminine
(P = 0.011 and P = 0.001, respectively) (Table 1). The arterial
contraction from each (S)-epimer/concentration combination
was different from zero (P < 0.05), with the exception of both
ergocryptinine and ergocorninine at 1 × 10−7 M. The addition
of PE at the conclusion of the experiment resulted in a large
increase in contraction similar to the first PE addition.
Discussion
The bovine metatarsal artery was selected due to
its peripheral location within the limb and potential
for clinical disease (lameness). The presence of a
contractile
response
of
bovine
metatarsal
arteries
exposed to increasing concentrations of (S)-epimers,
namely ergotaminine, ergocorninine, ergocristinine, and
ergocryptinine, illustrates vasoactivity and the potential
for vasoconstriction leading to toxic effects. The findings of
the present study demonstrate the biological activity of (S)epimers, which have been previously stated as inactive (Smith
and Shappell, 2002; Klotz, 2015b; Guo et al., 2016; Kudupoje
et al., 2018). Evidence from previous studies have implied that
the (S)-epimers may be toxic due to accumulation within cell
lysate (Mulac and Humpf, 2011; Mulac et al., 2013), although
stating that more research need to be completed, especially on
single epimers. It has been reported that (S)-epimers negatively
affected the blood–brain barrier (Mulac et al., 2012), which also
supports (S)-epimers having biological activity, due to not only
Figure 1. Contraction of bovine arteries from (S)-epimers. Mean contractile
response, % of first addition of PE, of bovine metatarsal arteries to increasing
concentrations of (S)-epimers, namely ergocryptinine, ergocristinine,
ergocorninine, and ergotaminine (n = 6, ergocryptinine and ergocorninine; n = 6,
ergocristinine and ergotaminine; n = 6 arteries/(S)-epimer, total n = 12). Error
bars are SD.
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Contractile responses of each arterial cross section exposed to PE
or tested (S)-epimers were recorded as grams of tension using
Biopac Student Lab PRO (professional version 3.7.1, Goleta, CA),
which was connected to the four-chamber tissue bath. At the
end of the 29-min incubation period of each (S)-epimer, grams of
tension were recorded and corrected to the baseline tension. The
baseline tension was calculated from average tension prior to the
demonstration of contraction (increased tension) to ensure that
the natural resting baseline tension of each arterial cross section
was not missed. These values were then normalized as a percent of
the first addition of PE (1 × 10–4 M) to compensate for the variability
of animals as well as artery size. These data were used as a source
for data analysis. All data were reported as mean ± SD, with
contractile response expressed as a percent of PE contraction for
each (S)-epimer. Data were plotted with nonlinear regression using
GraphPad Prism version 8.0.0 (GraphPad Software, San Diego, CA).
All analyses were performed using a commercial software
package (IBM SPSS Statistics for Windows, version 23, IBM Corp.,
Armonk, NY). Statistical tests evaluated if mean % contractile
response of PE for bovine arterial segments was affected by
the two variables, epimer ((S)-epimers of four alkaloids) and
concentration, when considered together. The (S)-epimers were
ergotaminine, ergocristinine, ergocorninine, and ergocryptinine;
n = 6, ergocryptinine and ergocorninine; n = 6, ergocristinine and
ergotaminine (n = 6 arteries/(S)-epimer, total of n = 12 arteries).
Data were included for each concentration where a contraction
was observed (1 × 10–7 and 1 × 10–6 M). Statistical analysis was
undertaken using generalized estimating equations (GEE) with
an identity link function, robust errors, and an unstructured
correlation matrix to account for repeated measures (segments
of the same artery measured at different concentrations and for
different (S)-epimers). GEE is able to correctly analyze results
from an unbalanced design with incomplete repeated measures
(each steer artery did not receive all (S)-epimers). Differences
were considered to be significant at P < 0.05. In the presence
of a significant interaction effect between (S)-epimer type and
concentration on the percent contractility, GEE analysis was
performed separately at each individual concentration to test
whether a difference in effect existed between (S)-epimers.
This was followed by multiple pairwise comparisons with a
sequential Sidak correction. To test if arterial contraction from
each (S)-epimer/concentration combination was different from
zero, an individual one-sample t-test was utilized.
3
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Journal of Animal Science, 2020, Vol. 98, No. 7
Table 1. Comparison of mean arterial contractile responses to increasing concentration of four (S)-epimers of ergot alkaloids, namely
ergotaminine, ergocorninine, ergocristinine, and ergocryptinine after normalization to PE at two concentrations where contraction was observed
Concentration (1 × 10x), M
Ergotaminine
Ergocorninine
Ergocristinine
Ergocryptinine
Contraction, g as % PE contraction,
Mean ± SD
−7
−6
−7
−6
−7
−6
−7
−6
3.90 ± 2.80a
17.39 ± 4.64c
1.64 ± 2.21a,b
10.85 ± 9.35c,d
2.24 ± 1.94a,b
7.98 ± 2.71d
0.49 ± 0.91b
7.69 ± 7.10d
Min.1
Max.2
1.04
10.06
−0.55
0.00
0.44
4.01
−0.02
−1.71
8.78
22.44
5.57
27.87
5.63
12.13
2.06
18.62
Minimum arterial contractile response, % contractile response of PE.
Maximum arterial contractile response, % contractile response of PE.
a–d
(S)-epimers demonstrating significant differences between contraction of bovine arteries are designated by different letters at 10−7 M (a,b)
and 10−6 M (c,d) (n = 6 arteries/(S)-epimer, total n = 12, GEE, multiple pairwise comparison with Sidak correction, P < 0.05).
1
accumulation but also perhaps receptor activation as seen in
the present study.
Few studies examined the contractile response of (R)-epimers
in bovine metatarsal arteries to provide published comparators
for the present study. In a previous study examining the
contractile response of (R)-epimers using a bovine ruminal
artery, the contractile response of ergotamine was first observed
at 10−6 M, while ergocornine and ergocryptine did not cause
contraction until the 10−5 M addition and only the highest dose of
ergocristine (10−4 M) elicited a contractile response (Foote et al.,
2011). Two other in vitro studies reported an arterial contractile
response for lysergamide and ergovaline using bovine metatarsal
and uterine arteries, respectively. Lysergamide first elicited a
contractile response at 10−7 M, while ergovaline resulted in slow
but sustained contractions over 2 h suggesting a high affinity to
the receptors (Dyer, 1993; Oliver et al., 1993). Comparing results
in the present study to previous investigations indicate that the
(S)-epimers may be more potent than their corresponding (R)epimers. The contractile response seen in the present study at
the two concentrations, 10−7 and 10−6 M, was visually similar to
graphed results provided for similar-sized arteries exposed to
(R)-epimers (Klotz et al., 2010; Klotz and McDowell, 2017). The
difference/similarity, however, could be related to the use of
various arterial segments and experimental differences in the
studies mentioned. It is anticipated that incubation with higher
concentrations of the (S)-epimers would generate similar higher
comparable contractile responses as demonstrated in other
studies using the corresponding (R)-epimers.
It is important to note that the current study was conducted
using only the lower end of the concentration range than what
is commonly used for the (R)-epimers studies (1 × 10−9 to 1 ×
10−4 M; Klotz and McDowell, 2017). The (S)-epimers are available
commercially from few sources and only in very limited
quantities (0.125 mg/vial). To achieve concentrations exceeding
1 × 10−6 M of an (S)-epimer within a single tissue bath was
practically unrealistic. Also, a measurement of potency such as
the effective concentration giving half-maximal response (EC50)
is commonly used in in vitro arterial tissue bath studies (Oliver
et al., 1993; Klotz et al., 2010). However, it was not appropriate
to include EC50 values in the present study because arterial
contraction was observed at only two concentrations. A reliable
EC50 value requires multiple data points to be useful. Kinetic
modeling would not have generated reliable results for this
descriptive study.
To the authors’ knowledge, no studies have been performed to
assess the contractile activity of the (S)-epimers or the contractile
response resulting from the transformation of (R)-epimers to
(S)-epimers. To assess the contractile response in vascular beds,
dissected arteries or veins must be maintained alive under
normal physiological conditions of pH (7.4), temperature (37 °C),
nutrients, and gas. Under these experimental conditions, it is
possible for the transformation between the (R) and (S)-epimers
to occur until an equilibrium is reached (Komarova and Tolkachev,
2001; Smith and Shappell, 2002). We, therefore, cannot rule out
the possibility that the contractile response seen in the present
study was, in part, due to the transformation of the (S)-epimer to
the (R)-epimer. However, this transformation was unlikely. The
reason being, the transformation of the (S) to (R)-epimer is not
favored and the (S)-epimer slightly dominates the equilibrium
(Andrae et al., 2014). The (S)-epimer would have to undergo a
more difficult rearrangement to switch to the intermediate and,
therefore, the (R)-epimer. This is also supported by examining
the transformation of a (R)- to (S)-epimer under physiological
conditions (Smith and Shappell, 2002). When an aqueous
solution was used to assess the epimerization of pure ergovaline
(R) at 37 °C (pH 7.5), equilibrium was reached after 11 h and
only 59.4% of ergovaline (R) remained. The transformation
between epimers has been observed at 75 min (Smith and
Shappell, 2002), which is longer than the time period used in
the present study. At the highest concentration used, for specific
(S)-epimers, there was observation of slight artery contraction
within 14 min of incubation and an increase in contraction at
the end of the 29-min incubation period. Analytical detection
of each form of epimer in the buffer solution may provide
evidence for which form is present and/or dominant. However,
the time and methods needed for testing will likely result in
an increase in epimer transformation. This will not accurately
reflect the conformational form of an epimer at the time of
artery contraction. Therefore, the time frame within the present
experiment, along with the likeliness of the transformation of
ergot alkaloids favoring the (S)-epimers within the conditions
used, pH 7.5 and 37 °C, it is strongly suggested that the (S)epimer administered to the buffer within the tissue bath did not
transform into the (R)-epimer. This supports that the S-epimers
were responsible for the arterial contraction observed.
The (R) and (S)-epimers of ergot alkaloids are found in
almost all food products derived from Claviceps-infested crops.
Along with animal feed, food products intended for human
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2
Cherewyk et al. |
Acknowledgments
We would like to thank I. Moshynskyy for assistance with
the aortic tissue bath machine, E. Doerksen for help with the
dissection technique of the bovine artery, and M. Friesen
for providing animal tissue. This study was funded by
financial support from The Saskatchewan Ministry of
Agriculture-Agriculture Development Fund (ADF) [ADF grant
number: 20180361]. The grant was received by A.N.A. We are
grateful for the financial support received from SaskMilk.
Conflict of interest statement
We declare no competing interests.
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consumption (including, but not limited to, baby formula, bread,
and pasta) may contain ergot (S)-epimers (Debegnach et al., 2019).
Studies often report that the “harmful” (R)-epimers convert to the
“inactive” (S)-epimers after food processing intended for human
consumption (Merkel et al., 2012). One study examined changes in
concentrations of six (R)- and (S)-epimers during the production
of rye bread (Bryła et al., 2019). The study reported that thermal
processing (or baking) caused the concentration of the (R)-epimers
to decrease but resulted in an increase of (S)-epimers. The study
concluded that baking contributes to the reduction of toxicity of
the final bread product. Similarly, a study examining the milling of
durum and the production of pasta reported comparable results
(Tittlemier et al., 2019). These studies emphasize the importance
of understanding specifically the biological effect of (S)-epimers
and the significance of the findings in the present study.
The (S)-epimers used in the present study are routinely
encountered in cereal crops in Western Canada (Tittlemier
et al., 2015). The mere presence of a contractile response after
incubating arteries with four different (S)-epimers indicates
that their presence in human diets and animal feed may be
significant and should be considered in analytical and food safety
assessments. Concentrations of (R)-epimers are monitored
in human and animal feed worldwide by regulatory agencies
in many countries, whereas (S)-epimers are not measured
or evaluated in human and animal feed standards in North
America (Coufal-Majewski et al., 2016). Since the (S)-epimers
are thought to be biologically inactive, their concentrations
in the feed are considered less important. Previously, studies
report that the quantification of (R)-epimers should consider
their epimerization toward (S)-epimers and, therefore, utilize
extraction solvents and conditions that decrease the chance
of epimerization (Smith and Shappell, 2002). However, because
these conditions are not easy to maintain in an experimental
setting and naturally contaminated feed contain (R)- and (S)epimers, it is important to quantify both (Guo et al., 2016). The
adverse manifestations such as ergotism seen in livestock, as a
result of contaminated feed consumption, are likely produced
by the combined action of the (R)- and (S)-epimers and not
exclusively the (R)-epimers.
In conclusion, this study reports the demonstration of
biological activity for four (S)-epimers of ergot alkaloids, namely
ergotaminine, ergocorninine, ergocristinine, and ergocryptinine,
through potential vasoconstriction as demonstrated by arterial
contraction, which were thought to be previously inactive.
Ergotaminine had the greatest contractile response compared
with the other (S)-epimers with each having different degrees of
contractility. This may be similar to that reported for (R)-epimers
(Klotz et al., 2010). Future work would include the comparison of
contractility between (R) vs. (S)-epimers. This will be beneficial
for understanding the potencies of each form. The mere presence
of a contractile response in bovine arteries stimulates future
discussion concerning the biological activity of (S)-epimers in
multiple settings, which may influence the direction of, and
development of, regulatory standards for ergot concentrations
relating to human and animal food safety worldwide.
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