(2021) 45:115
Ajilore et al. Bull Natl Res Cent
https://doi.org/10.1186/s42269-021-00574-2
Bulletin of the National
Research Centre
Open Access
RESEARCH
Tetracarpidium conophorum seed extract
reduces intestinal absorption, and increases
cellular trapping of glucose
Bamidele Stephen Ajilore1, Olubukola Sinbad Olorunnisola2*
and Abiodun Olusoji Owoade2
Abstract
Background: Tetracarpidium conophorum is one of the numerous folklore medicinal plants for managing diabetes
but the mode of action and bioactive compounds responsible for the antihyperglycemic property are missing in literatures. This study aimed at investigating the possible modes of its antihyperglycemic action using both in-vitro and
ex-vivo methods. Powdered Tetracarpidium conophorum seed (TECOSE) was extracted with methanol using standard
extraction procedure. Gas chromatography- Mass spectrometry (GCMS) analysis of the extract, and its effects on
tissue glucose uptake, α-amylase, α-glucosidase and glucokinase enzymes were assessed using standard laboratory
procedures.
Results: Seven heterocyclic compounds were identified by GCMS of which one is structurally related to sulphonylurea. TECOSE strongly inhibited α-glucosidase (IC50 = 1.90 mg/ml) but partially inhibited α-amylase (IC50 = 7.20 mg/ml)
activities. Also, glucokinase activity and tissue glucose uptakes were significantly (p < 0.05) increased by TECOSE.
Conclusions: The results obtained deduced that antihyperglycemic action of TECOSE could be due to modulation of
postprandial hyperglycaemia through inhibition of intestinal α-glucosidase, increasing glucokinase activity, improving
peripheral glucose uptake by mimicking sulfonylurea action.
Keywords: Tetracarpidium conophorum seed, Mode of action, α-Amylase, α-Glucosidase, Glucokinase
Background
Traditional medicine is gaining more acceptability for treatment of chronic ailments in several countries. In Africa,
many patients rely on traditional medicine because of the
high cost of the synthetic drugs. The reasons for increasing
use of plants in the management of diabetes are efficacious,
safety-less side effects, less expensive and easy availability
of plants. Even metformin, the mainstay drug used in the
treatment of type 2 diabetes, is derived from guanidines
which were obtained from Galegine officinalis (Newman
and Cragg 2012). The region of Africa has the highest
*Correspondence: osolorunnisola@lautech.edu.ng
2
Department of Biochemistry, Faculty of Basic Medical Sciences, College
of Health Sciences, Ladoke Akintola University of Technology, Ogbomoso,
Nigeria
Full list of author information is available at the end of the article
percentage of undiagnosed diabetes cases reaching 66.7%,
the highest proportion of diabetes mellitus related mortality and the lowest health expenditure spent on diabetes
(Federation 2015). Due to adverse impact of the economic
burden of diabetes, financial constraints and increased side
effects of the conventional drugs, there is continuing advocacy to treat those with the disease with more affordable
and accessible medicinal plant with little or no side effects.
Several medicinal plants have been reported to possess
antidiabetic activities (Tripathi and Chandra 2010) including the study plant. Tetracarpidium conophorum (African
walnut) leaf, root and nut have been recently reported to
possess antihyperglycemic activity (Ogbonna et al. 2013;
Onwuli et al. 2014; Ajilore and Adesokan 2018; Ayeni and
Nuhu 2018). Chemical compounds and mode of action
responsible for antidiabetic and other therapeutic health
benefits attributed to the plant are missing in literatures
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Ajilore et al. Bull Natl Res Cent
(2021) 45:115
(Tiwari et al. 2011). Therefore, this study was aimed at
identifying the bioactive compounds present in T. conophorum seed and assessing its biochemical effects on tissue
glucose uptakes, α-amylase, α-glucosidase and glucokinase
activities with a view to investigating its possible mode of
action.
Methods
Reagents and chemicals
Methanol, concentrated H2SO4, acetic anhydride, ammonia solution, hydrochloric acid, citric acid, sodium citrate, streptozotocin, tris, EDTA, ATP, trichloroacetic acid,
sodium chloride, sodium hydroxide, sodium hypochlorite,
mono-potassium phosphate, di-potassium phosphate,
ethanol, sodium carbonate, sodium acetate, acetic acid,
tri-chloro acetic acid, ammonium molybdate, amino naphtol sulfonic acid, sodium bisulfate, sodium sulfite, ascorbic
acid, dimethyl sulfoxide, sucrose, glucose, maltose, 3,5-dintrosalicylic acid, potassium chloride, magnessium chloride,
calcium chloride, dodium bicarbonate, HumulinR and metformin were obtained from Sigma Chemical Company, St.
Lious, Mo, U.S.A., and British Drug House (BDH) chemical Ltd., Poole, England. The diagnostic kits were obtained
from Randox Laboratories Ltd., Crumlin, Co. Antrim, UK.
All reagents and chemicals used were of analytical grade.
Collection and preparation of Tetracarpidium conophorum
seed
Tetracarpidium conophorum seeds were purchased from
a local market in Osogbo, Osun State, Nigeria. The plant
was identified and authenticated by Mr. G.A. Ademoriyo at
Ife Herbarium, Department of Botany, Obafemi Awolowo
University, Ile-Ife, Nigeria, where specimen copy was
deposited. The herbarium identification number was
17,713. The shells were removed, and the seeds shade dried
for 4 weeks. The T. conophorum seeds were pulverized and
weighed into the sample container.
Extraction of Tetracarpidium conophorum seed
Dried powder of T. conophorum seed (500 g) was subjected
to cold maceration with frequent agitation in 5 L of 100%
methanol for 72 h at room temperature (Ajilore and Adesokan 2018; Asare and Oseni 2012; Santos et al. 2018). The
filtrate was concentrated using standard procedure. Methanolic extract of T. conophorum was stored in the fridge
until used.
GC–MS analysis of Tetracarpidium conophorum seed
extract
GC–MS was utilized to identify compounds in the methanol extract of the plant seed according to the method
described by Santos et al. (2018).
Page 2 of 10
Extraction and determination of the α‑amylase activity
α-Amylase was extracted from sorghum grains according to the method described by Adewale et al. (2006)
and the activity was determined spectrophotometrically at 540 nm according to the dinitro salicylic acid
(DNSA) procedure of Bernfeld (1955). One unit of
enzyme activity is defined as the amount of the enzyme
that produces 1 μmol maltose /min under the assay
conditions. Activity was calculated using enzyme activity extinction coefficient of 0.354 cm2/mM.
Estimation of α‑amylase inhibitory activity
of Tetracarpidium conophorum seed
α-amylase inhibitory activity of T. conophorum seed
extract was estimated using DNSA method as follows:
Procedure
Test (µl) Control (µl) Blank (µl)
Extract (1.25–10.00 mg/ml)
250
–
–
1% starch solution
500
500
–
1% NaCl
250
250
250
Phosphate buffer (0.02 M, pH 7)
Pre-incubate for 5 min at 37 °C
250
250
250
α-Amylase solution
Incubate again for 15 min at 37 °C
200
250
–
2 M NaOH
Boil for 1 min
200
200
–
Add DNSA solution
500
500
–
The assay mixtures were incubated again for 2 min
and cooled. The OD was read @ 540 nm against blank.
Calculation:
% Inhibition = (OD control – OD test)/OD control × 100.
Concentrations of extracts resulting in 50% inhibition
of enzyme activity (IC50) were determined.
Mode of α‑amylase inhibition
The mode of inhibition of α-amylase by T. conophorum
seed extract was determined according to the method
described by Ali et al. (2006). The amount of reducing
sugar released was determined spectrophotometrically at 540 nm against blank. Concentration of maltose released from starch solution was calculated from
the absorbance using maltose standard curve and converted to reaction velocities. The type of inhibition in
the presence and absence of the extract on α-amylase
activity was determined by analysis of the Michaelis–
Menten kinetics plot.
Ajilore et al. Bull Natl Res Cent
(2021) 45:115
Page 3 of 10
α‑Glucosidase inhibitory assay
The effect of the plant extract on α-glucosidase activity
was determined according to the method described by
Dahlqvist (1964). The amount of glucose liberated was
measured by RANDOX commercial glucose kit.
% Inhibition Rate = (Amount of glucose produced
by + ve control) – (Amount of glucose produced by
addition of extract) / (Amount of glucose produced
by + ve control) × 100.
Concentrations of extracts resulting in 50% inhibition
of enzyme activity (IC50) were determined.
following overnight lysis at 4 °C. The supernatant collected was used as enzyme extract immediately.
Assay for glucokinase enzyme activity
The effects of T. conophorum seed extract (TECOSE)
on glucokinase activity was measured by estimating the
amounts of glucose consumed and glucose-6-phosphate
produced during phosphorylation of glucose in glucokinase assay mixture as follows:
Procedure
Negative
control
(µl)
Positive
control
(µl)
TECOSE (µl)
TECOSE (5–10 mg/ml)
–
–
100
Glucokinase extract
–
100
100
Glucose (100 mM and 50 mM)
100
100
100
4 mM ATP
–
100
100
7.5 mM MgCl2
–
100
100
Mode of α‑glucosidase inhibition
The mode of inhibition of α-glucosidase by T. conophorum seed extract was determined according to the
method described by Ali et al. (2006). The amount of
glucose liberated in the presence and absence of extract
was measured by RANDOX commercial glucose kit.
The amount of reducing sugars released was converted
to reaction velocity. The type of inhibition in the presence and absence of the extract on α-glucosidase
activity was determined by analysis of the Michaelis–
Menten kinetics plot.
Preparation and extraction of glucokinase eenzyme
An albino rat was fasted for 24 h after which the basal
blood glucose level was determined by glucose oxidase
method. The study was conducted according to the
institutional guidelines and conforms to national guidelines for animal usage in research. The rat was subjected to monitored glucose tolerance test (as shown in
the table below) following administration of 0.3 g/kg,
50% dextrose intra-peritoneal glucose load given over
one minute.
Duration (Min)
0
Blood sugar
(mmol/L)
2.89
5
6.67
10
11.11
15
25.00
20
33.33
25
35.33
30
33.06
The rat was sacrificed after 30 min and liver immediately harvested and homogenized (tissue: buffer = 1: 10)
in glucokinase buffer containing 150 mM KCl, 50 mM
Tris–HCl (pH 7.6), 4 mM EDTA, 4 mM Dithiothreitol
and 7.5 mM MgCl2 (Zhang et al. 2009). The homogenate was centrifuged at 3,000 rpm for 10 min at 4 °C
The assay mixture was incubated for 10 min at 30 °C.
Glucokinase activity was calculated as mU/mg protein in
the presence and absence of TECOSE as the difference
between 100 and 0.5 mM glucose. Glucose concentration
was determined using RANDOX commercial glucose kit
while the amount of glucose-6-phosphate was measured
using modified Fiske and Subbarow (1925) method by
addition of ascorbic acid into the assay mixture to stabilize the phosphate ester. Protein in the liver extract was
measured using RANDOX total protein kit.
Determination of glucose uptake in muscle and diaphragm
Tissue glucose uptake was determined according to the
method described by Chattopadhyay (1992). Five groups,
with each group containing five test tubes (n = 5) for each
of the tissue, were considered as follows:
Group 1: Perfusion solution only (negative control).
Group 2: Perfusion solution + tissue (muscle or diaphragm).
Group 3: Perfusion solution + tissue (muscle or diaphragm) + extract.
Group 4: Perfusion solution + tissue (muscle or diaphragm) + metformin.
Group 5: Perfusion solution + tissue (muscle or diaphragm) + insulin.
Glucose concentration was determined using RANDOX
commercial glucose kit.
Amount of glucose uptake by tissue = Amount of
glucose in perfusate of negative control – Amount of
glucose left in perfusate in other treatment groups.
Ajilore et al. Bull Natl Res Cent
(2021) 45:115
Page 4 of 10
Statistical analysis
Results
Data obtained were analyzed using One Way Analysis of
Variance (SPSS version 20.0). Levene statistic was used
for tests of homogeneity of variance. Tukey’s test was
used for multiple comparisons and homogenous subsets.
A p-value of less than 0.05 was considered statistically
significant.
Gas chromatography mass spectrometry (GCMS) analysis
of Tetracarpidium conophorum seed extract
Seven aromatic compounds were identified by GCMS
analysis of T. conophorum seed extract (Table 1 and
Fig. 1).
Table 1 GCMS analysis of Tetracarpidium conophorum seed extract
Peak no.
Retention
time (min)
Identified compounds
Other names
Molecular formula
Molecular
weight (g/
mol)
1
8.333
Bicyclo [4.2.0] Octa-1,3,5-triene
Benzocyclobutene
C8H14
110.2
2
36.420
Naphthalene, 1,2,3,4-tetrahydro-2- phenyl
Phenyl Tetralin
C16H16
208.3
3
36.858
Benzene, 1,1′-(1,2-cyclobutanediyl) bis-, trans
Trans-1,2-Diphenylcyclobutane
C16H16
208.3
4
42.262
Benzene, 1,1′-(3-methyl-1-propene-1,3,-diyl) bis
1-Butene, 1,3-diphenyl
C16H16
208.3
5
43.357
Benzene, 1,1′-(1,3-butadienylidene) bis
1,1-Diphenyl-buta-1,3-diene
C16H14
206.3
Thiocarbamic acid, N,N-dimethyl, S-1,3-diphenyl2-butenyl ester
S-[(E)-1,3-Diphenylbut-2-enyl]
N,N-dimethylcarbamothioate
C19H21NOS
311.4
C22H20S
316.5
6
43.563
43.632
7
43.745
Benzene, 1,1′-[2-methyl-2-(phenyl thio) cyclopropylidene] bis
Fig. 1 GCMS analysis of Tetracarpidium conophorum seed extract. a showed spectral analysis of the methanol extract of T. conophorum seed while b
showed structures of the identified heterocyclic compounds in the extract
Ajilore et al. Bull Natl Res Cent
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Page 5 of 10
Fig. 2 Glucose standard curve
Fig. 4 Rate of maltose released from starch by α-amylase in the
presence and absence of TECOSE
Fig. 3 Percentage inhibition of α-amylase by Tetracarpidium
conophorum seed
α‑Amylase and α‑glucosidase activities
1 unit of α-amylase and α-glucosidase activity is defined
as the amount of the enzyme required to liberate 1 mM
(0.18 mg equivalence) of reducing sugar from starch and
sucrose respectively under assay conditions. From the
regression equation of the glucose standard curve (Fig. 2)
using:
Enzyme activity (U/ml) =
E × Vf
t × ×Vs × d
α-amylase activity was 0.54 U/ml while α-Glucosidase
activity was 1.17 U/ml.
Inhibitory effects of Tetracarpidium conophorum seed
extract (TECOSE) on α‑amylase activity
The concentration of the extract that inhibited 50% of
α-amylase activity (IC50) was 7.20 mg/ml (Fig. 3). Maximum velocity (Vmax A) in the presence of TECOSE
was 0.096 mmol/L/min and Vmax A/2 was approximately 0.048 mmol/L/min. Vmax B (in the absence of
Fig. 5 Percentage inhibition of α-glucosidase by Tetracarpidium
conophorum seed
TECOSE) was 0.120 mmol/L/min and Vmax B/2 was
approximately 0.060 mmol/L/min. V max decreased by
the presence of TECOSE while Km (affinity) remained
the same. Km was 0.400 mg/ml (Fig. 4).
Inhibitory effects of Tetracarpidium conophorum seed
extract on α‑glucosidae activity
The concentration of the extract that inhibited 50% of
α-glucosidse activity (IC50) was 1.90 mg/ml (Fig. 5).
Maximum velocity (Vmax A) in the presence of
TECOSE was 0.086 mmol/L/min and Vmax A/2 was
approximately 0.043 mmol/L/min. Vmax B (in the
absence of TECOSE) was 0.106 mmol/L/min and Vmax
B/2 was approximately 0.053 mmol/L/min. V max was
decreased by the presence of TECOSE while Km (affinity) remained the same. Km was 0.400 mg/ml (Fig. 6).
Ajilore et al. Bull Natl Res Cent
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Page 6 of 10
Table 2 Amount of glucose consumed and glucokinase activity
in the presence of Tetracarpidium conophorum seed extract
TECOSE
concentration
(mg/ml)
Unused
glucose
(mmol/L)
5.0
17.31 ± 0.03d
13.94 ± 0.03a
3.29 ± 0.01a
c
b
5.05 ± 0.08b
bc
5.25 ± 0.16bc
bc
5.34 ± 0.00bc
bc
5.45 ± 0.32bc
bc
5.50 ± 0.01bc
c
5.77 ± 0.50c
d
6.55 ± 0.23d
10.0
15.0
20.0
25.0
30.0
35.0
40.0
Fig. 6 Rate of glucose released from sucrose by α-glucosidase in the
presence and absence of TECOSE
Effects of Tetracarpidium conophorum seed extract
on glucokinase activity
Amount of glucose in the assay medium (negative
control) was 31.24 mmol/L. Amount of glucose left in
the assay medium following addition of glucokinase
enzyme extract (positive control) was 30.14 mmol/L.
Therefore, amount of glucose consumed by glucokinase
in the absence of TECOSE, was 1.10 mmol/L (19.8 mg/
dl). Concentration of total protein in liver extract was
7.62 ± 0.87 g/dl (7620 mg/dl).
Glucokinase activity (1 unit) was defined as the
amount of protein (glucokinase) used in consumption of 1 mM (0.18 mg equivalence) of glucose, or
1 mM of glucose-6-phosphate produced per minute at
30 °C under the specified conditions. Therefore, estimated glucokinase activity in the absence of TECOSE
was estimated to be 6.3 × 10–3 U/ml/mg protein. At
increasing concentrations of TECOSE, the amounts
of glucose consumed, glucose-6-phoshate produced
and corresponding glucokinase activities were significantly (p < 0.05) increased in a dose-dependent manner
(Tables 2 and 3). Glucokinase activity using the amount
of glucose consumed was higher than that of glucose6-phoshate produced at all concentrations of TECOSE.
Also, glucokinase activity was significantly (p < 0.05)
higher in the presence of TECOSE than in the absence
of TECOSE (Fig. 7).
Consumed
Glucose
(mmol/L)
9.87 ± 0.31
Glucokinase
activity (U/ml/mg
protein) × 10–2
21.37 ± 0.31
bc
9.35 ± 1.10
bc
8.64 ± 0.00
bc
8.16 ± 1.36
bc
7.96 ± 0.02
b
6.82 ± 2.13
22.23 ± 0.66
22.60 ± 0.00
23.08 ± 1.36
23.28 ± 0.02
24.42 ± 2.13
a
3.53 ± 0.94
27.71 ± 0.94
45.0
3.36 ± 0.64a
27.89 ± 0.64d
6.59 ± 0.15d
50.0
2.86 ± 0.03a
28.39 ± 0.03d
6.71 ± 0.01d
Values are expressed as mean ± SD (n = 3). Means with different Tukey
superscripts along the column are statistically significant at p < 0.05
metformin > insulin > TECOSE by muscle while it is
metformin > TECOSE > insulin by diaphragm.
Discussion
Tetracarpidium conophorum (African walnut) was
recently reported to possess antihyperglycemic property
(Ajilore and Adesokan 2018; Ayeni and Nuhu 2018) but
the chemical compounds or mode of action responsible for this therapeutic benefit are missing in literatures.
The present study identified the bioactive compounds
present in methanol extract of T. conophorum seed and
investigated its biochemical effects on tissue glucose
uptakes, α-amylase, α-glucosidase and glucokinase activities. α-glucosidase has been recognized as a therapeutic
Table 3 Amount of glucose-6-phosphate produced and
glucokinase activity following incubation with Tetracarpidium
conophorum seed extract
TECOSE
concentration
(mg/ml)
Glucose‑6‑phosphate
produced (mg/dl)
Glucokinase activity (U/
ml/mg protein) × 10–5
5.0
0.59 ± 0.01a
7.68 ± 0.07a
b
7.94 ± 0.07b
c
8.86 ± 0.07c
c
8.99 ± 0.07c
d
9.39 ± 0.07d
de
9.58 ± 0.00de
ef
9.65 ± 0.07ef
efg
9.78 ± 0.07efg
0.75 ± 0.00
fg
9.84 ± 0.00 fg
0.76 ± 0.01
g
9.97 ± 0.13 g
10.0
15.0
20.0
25.0
30.0
Glucose uptake by muscle and diaphragm in the control
and treatment groups
35.0
Figures 8 and 9 showed the percentage glucose uptake
by muscle and diaphragm respectively. The significant (p < 0.05) glucose uptake was in the order of
45.0
40.0
50.0
0.61 ± 0.01
0.68 ± 0.01
0.69 ± 0.01
0.72 ± 0.01
0.73 ± 0.00
0.74 ± 0.01
0.75 ± 0.01
Values are expressed as mean ± SD (n = 3). Means with different Tukey
superscripts along the column are statistically significant at p < 0.05
Ajilore et al. Bull Natl Res Cent
(2021) 45:115
Fig. 7 Mode of glucokinase activity with and without incubation
with Tetracarpidium conophorum seed extract
Fig. 8 Percentage glucose uptake by muscle in the control and
treatment groups. Values are expressed as mean ± SD (n = 5). Bars
with different Tukey superscripts are statistically significant at p < 0.05
target for the modulation of postprandial hyperglycemia,
which is the earliest metabolic abnormality that occurs
in type I diabetes (Kim et al. 2005; Thilagam et al. 2013).
Therefore, an effective treatment option for type I diabetes is to inhibit the activity of intestinal α -glucosidase
and pancreatic α-amylase enzymes. We observed in the
present study that T. conophorum seed extract strongly
inhibited α-glucosidase activity but demonstrated partial
inhibition on α-amylase. Although α-glucosidase isolated
from yeast is extensively used as a screening material for
α-glucosidase inhibition, but the results did not always
agree with those obtained in mammals (Thilagam et al.
2013). This was the reason rat small intestine homogenate was used as α-glucosidase solution in this study
Page 7 of 10
Fig. 9 Percentage glucose uptake by diaphragm in the control and
treatment groups. Values are expressed as mean ± SD (n = 5). Bars
with different Tukey superscripts are statistically significant at p < 0.05
because we speculated that it would better reflect the invivo state.
Glucokinase catalyzes the transfer of phosphate from
ATP to glucose to generate glucose 6-phosphate (Polonsky and Williams 2016). Liver glucokinase is rate limiting
for the phosphorylation rate of glucose and is an important determinant of glucose tolerance in vivo (Stefanovski
et al. 2012). The widely reported glucokinase assay in literatures is by measuring indirectly NADH/NADPH generated when Glucose-6-phosphate dehydrogenase and
NAD/NADP are added into the assay mixture. The basis
for this indirect assay of glucokinase, a glycolytic enzyme,
using activity of glucose-6-phosphate dehydrogenase,
an enzyme of another carbohydrate metabolic pathway
(Hexose monophosphate shunt), is controversial and
not mentioned in these literatures. In the present study,
we measured glucokinase activity directly using both
the amounts of glucose consumed and phosphate ester
(glucose-6-phosphate) produced during phosphorylation
of glucose by modifying previous methods (Zhang et al.
2009; Stefanovski et al. 2012). We observed that both the
amounts of glucose consumed, and phosphate ester produced when T. conophorum seed extract was incubated
in media containing glucokinase enzyme were significantly higher than in absence of the plant extract.
Glucose uptake by tissue plays an important role in
determining glycemia. Facilitated glucose transport is
essential for the maintenance of body glucose homeostasis in response to acute perturbations in blood glucose
(Bryant et al. 2002; Merry and McConell 2009). Effects of
treatments with T. conophorum seed extract, metformin
and insulin on tissue glucose uptake were comparatively studied using isolated tissues (skeletal muscle and
diaphragm) from normal rats. The percentage glucose
uptake was significantly increased following treatments
Ajilore et al. Bull Natl Res Cent
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Page 8 of 10
Fig. 10 Proposed mode of antihyperglycemic action of Tetracapidium conophorum seed extract
with metformin, T. conophorum seed extract and insulin. Insulin is known to stimulate uptake of glucose in fat
and muscle tissues by recruiting so-called insulin-mediated glucose transporters (GLUT4) from an intracellular
location to the plasma membrane (Fischer et al. 1995).
Likewise, metformin is also known to increase insulinmediated glucose uptake by improving insulin sensitivity (Iozzo et al. 2003). Mimicking these two conventional
antidiabetic drugs or increasing glucokinase activity
could be responsible for increased glucose uptake demonstrated by the study plant.
Beneficial effects of many plant extracts have been
linked to their bioactive compounds. Seven aromatic
compounds were identified from the plant seed extract.
Some of the biological activities previously reported
for some of the identified compounds are their uses in
the management of heart-related chest pain, heart failure, depression, HIV and melanoma (Yancy et al. 2016;
Aladeokin and Umukoro 2011; Kitamura et al. 2012;
Bata et al. 2015; Turan-Zitouni et al. 2018). Though the
biological activity for Thiocarbamic acid, N,N-dimethyl,
S-1,3-diphenyl-2-butenyl ester is not found in literatures
at present, but urea based compounds are known to be
derivatives of carbarmic acid (Serban 2019). Sulfonylurea,
a widely used antidiabetic drug, has structural relationship with Thiocarbamic acid, N,N-dimethyl, S-1,3-diphenyl-2-butenyl ester. Sulfonylurea is a sulfonyl-carbamic
acid ester. Some heterocyclic- sulfonyl-carbamic acid
esters have been patented in US as future antidiabetics (Hitzel et al. 1982). The N′,N′-di-phenyl- (as found
in Thiocarbamic acid, N,N-dimethyl, S-1,3-diphenyl2-butenyl ester), and others like N′-acetyl-, N′-nitro-,
N′-cyclohexyl- could substitute the phenyl ring of sulfonylurea and could be bonded to the central S-aryl group
of sulfonylurea directly or via bridge member –CH2–,
–NH–, or –O–. The invention further relates that the
processes of manufacture of these sulfonylureas are characterized in that -carbamic acid esters, -thiocarbamic
acid esters, -ureas, -semicarbazides or -semicarbazones,
which are substituted into the 4-position by the group are
reacted with amine R1-NH2 or its salts or sulfonamides
in the pharmaceutical preparation of these sulphonylureas for the treatment of diabetes (Hitzel et al. 1982).
Conclusions
The results obtained from this study concluded that the
possible mode of action responsible for antihyperglycemic property of Tetracarpidium conophorum seed could
be due to:
(a) Modulation of postprandial hyperglycemia through
inhibition of intestinal α-glucosidase (with partial
inhibition of α-amylase);
(b) Activation of glucokinase and thereby improving
peripheral glucose uptake and cellular trapping;
Ajilore et al. Bull Natl Res Cent
(2021) 45:115
(c) Mimicking sulfonylurea action, a known oral antidiabetic agent (Fig. 10).
Abbreviations
ATP: Adenosine triphosphate; DNSA: Dinitro salicylic acid; EDTA: Ethylenediaminetetraacetic acid; GCMS: Gas chromatography mass spectrometry; HCl:
Hydrochloric acid; H2SO4: Sulphuric acid; IC50: 50% Inhibitory capacity; MgCl:
Magnesium chloride; NAD: Nicotinamide adenine di-nucleotide; NADH:
Nicotinamide adenine di-nucleotide hydrogen; NADP: Nicotinamide adenine
di-nucleotide phosphate; NADPH: Nicotinamide adenine di-nucleotide phosphate hydrogen; OD: Optical density; Vmax: Maximum velocity.
Acknowledgements
We acknowledge the authors whose publications were used in the preparation of this manuscript.
Authors’ contributions
All the authors conceived and designed the study. ABS conducted the
research, provided research materials and collected the data. OOS and OAO
organized the data. ABS and OOS analysed and interpreted the data. ABS
wrote initial and final draft of the manuscript while OOS and OAO provided
logistic supports. All authors have read and approved the manuscript.
Availability of data and materials
The datasets used and/or analysed during the current study are available from
the corresponding author on reasonable request.
Declaration
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
All authors declare no conflict of interest.
Author details
1
Department of Medical Biochemistry, Faculty of Basic Medical Sciences, College of Health Sciences, Osun State University, Osogbo, Nigeria. 2 Department
of Biochemistry, Faculty of Basic Medical Sciences, College of Health Sciences,
Ladoke Akintola University of Technology, Ogbomoso, Nigeria.
Received: 19 April 2021 Accepted: 8 June 2021
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