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    Pharmacodynamic Interaction between Cyamopsis tetragonoloba (Cluster Beans) and Acarbose: An in vitro and in vivo Study

    Ruchika Mourya1★, Manivannan Elangovan1, Hamendra Singh Parmar2, Rajesh Sharma1★ Corresponding author

    1. 1School of Pharmacy, Devi Ahilya Vishwavidyalaya, Takshashila Parisar, Khandwa Road (Ring Road), Indore, Madhya Pradesh, INDIA.
    2. 2School of Biotechnology, Devi Ahilya Vishwavidyalaya, Takshashila Parisar, Khandwa Road, Indore, Madhya Pradesh, INDIA.

    CORRESPONDENCE

    Ruchika Mourya

    Mrs. Ruchika Mourya School of Pharmacy, Devi Ahilya Vishwavidyalaya, Takshashila Parisar, Khandwa Road (Ring Road), Indore-452001, Madhya Pradesh, INDIA.

    mouryaruchika98@gmail.com

    Received: 13-06-2026; Revised: 27-08-2026; Accepted: 09-10-2026.

    Volume 18, Issue 1 · pp. 191–199 · PUBLISHED Jan-Mar 2026 · DOI: 10.5530/pres.20262368

    View on Pharmacogn. Res. original site ↗

    ABSTRACT

    Aim To investigate pharmacodynamic interaction of Cyamopsis tetragonoloba (Cluster beans or guar beans) with acarbose on type-2 antidiabetic targets α-glucosidase and α-amylase. Background The simultaneous use of herbal and ayurvedic medicines along with allopathic medicines is a common practice in India, without knowing their interactions. In particular, diabetic patients often use a combination of herbal, ayurvedic, and allopathic medications to achieve better results. Cyamopsis tetragonoloba (also known as cluster beans or guar beans), a popular vegetable in India, is thought to provide potential advantages for diabetes patients. Therefore, it was thought worthwhile to investigate pharmacodynamic interaction of Cyamopsis tetragonoloba (Cluster beans or guar beans) with a type-2 antidiabetic drug acarbose. Materials and Methods In the current study, an aqueous and ethanol extract of Cyamopsis tetragonoloba was prepared and tested for antidiabetic activity in vitro and in vivo in combination with acarbose. At first, the Cyamopsis tetragonoloba extracts have been tested for their ability to adsorb glucose and inhibit α-amylase and α-glucosidase. Then, an oral glucose tolerance test, acute and subacute study for Cyamopsis tetragonoloba extracts and acarbose was conducted on male albino Wister rats. Results The present results demonstrate the co-administration of aqueous extract and ethanol extract with acarbose have shown statistically significant reduction in blood glucose level in streptozotocin induced male diabetic rats. The aqueous extract with acarbose was more effective for postprandial hyperglycemia compares to ethanol extract with acarbose and acarbose. The additive pharmacological effect on blood glucose level has been observed after the co administration of extract of C. tetragonoloba with acarbose in streptozotocin induced male diabetic rats. Conclusion To summarise, the interaction of herbal and pharmaceutical medicines is a critical to both patients and health care practitioners. It is necessary to continue research on potential risks and benefits associated with the combination of C. tetragonoloba and Acarbose on pharmacokinetic aspects. Such data is crucial for the formulation of future clinical guidelines to improve health-care outcomes in diabetes.

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    INTRODUCTION

    Diabetes Mellitus (DM) is a chronic metabolic disorder characterised by hyperglycemia due to the failure of pancreatic cells to produce sufficient or efficient insulin.[1] The raise in blood glucose level resulted by DM causes physical harm as well as multiple organ damage and tissue failure.[2] Pancreatic beta cell malfunction is a significant cause of type 2 diabetes, and it is linked to insulin resistance and insufficiency. The insulin-regulated glucose transporter GLUT-4 receptor, present in muscle and adipose tissue, may lead to insulin resistance by increasing glucose uptake to these tissues.[3] Endoplasmic reticulum stress reduces insulin sensitivity in DM, and enhanced glucose metabolism can cause an increase in mitochondrial Reactive Oxygen Species (ROS) generation.[4] Overproduction of ROS destroys beta cells, impairing cellular activity and resulting in cell death in numerous organs and blood vessels, eventually leading to insulin deficit.[5] Furthermore, elevated levels of ROS activate inflammatory pathways, with catastrophic effects.[6] The complications of DM are divided into two categories: microvascular complications, which affect the microvascular network of blood vessels in the kidney, eyes, and nerves, diabetic retinopathy, which causes retinal rupture due to high blood glucose, and diabetic neuropathy, which damages peripheral nerves associated with lower limbs and leads to diabetic foot ulceration.[7–9] The Macrovascular complications involve high blood glucose levels affecting arteries and large blood vessels, leading to the development of cardiovascular disease in diabetic patients.[8]

    Currently available treatment for type 2 DM includes insulin secretagogues, biguanides, insulin sensitizers, alpha glucosidase inhibitors, incretin mimetics, amylin antagonists, and SGLT2 inhibitors.[10–12] Among these treatments, Acarbose is an α-glucosidase inhibitor that declines the enzymatic activity of α-glucosidase.[13] The α-glucosidase enzyme presents in the brush border of the small intestine, and acarbose binds reversibly or competitively to the oligosaccharide binding of the α-glucosidase enzyme.[14] The acarbose inhibits the α-glucosidase enzyme, delays the digestion of carbohydrates in the small intestine, and inhibits the absorption of glucose from the brush border of the small intestine. This results in a low level of glucose reaching the blood. The diabetic patients living in India often use a combination of herbal, ayurvedic, and allopathic medications to achieve better results. The simultaneous use of herbal and ayurvedic medicines along with allopathic medicines is a common practice in India, without knowing their interactions. Furthermore, many people assume that herbal remedies are natural and thus safe to use.[15] Cyamopsis tetragonoloba (also known as cluster beans or guar beans), a popular vegetable in India, is thought to provide potential advantages for diabetes patients.[16, 17] Cluster bean is gaining attention as functional food due to its high nutritional profile, including high levels of protein, fiber, carbohydrates, oil, moisture, polyphenols, tannins, and phytic acid.[18–20] Cluster bean seeds, rich in fatty acids like linoleic, palmitic, and oleic acids, are used by diabetes patients due to their tannins, flavonoids, and coumarins.[20] Cluster beans have been shown to have antioxidant, antidiabetic, antibacterial, and cytotoxic properties.[18–21] Antioxidant molecules in C. tetragonoloba can help diabetics improve their insulin sensitivity and glucose homeostasis.[22] Therefore, it was thought worthwhile to investigate the pharmacodynamic interaction of C. tetragonoloba with an α-glucosidase inhibitor-based antidiabetic drug known as Acarbose.

    MATERIALS AND METHODS

    Collection of Cyamopsis tetragonoloba (cluster beans) beans

    Ten kilogrammes of cluster beans were bought from the local market in Indore, Madhya Pradesh, India and their identity was verified by Dr. G.P. Choudhary, Associate Professor of Pharmacognosy, School of Pharmacy, Devi Ahilya Vishwavidyalaya, Indore-452001, M.P., India. C. tetragonoloba beans were dried in a shed and ground into a fine powder with an electric grinder.

    Animals and experimental approval

    Thirty-five male Wistar rats weighing between 260–300 g were obtained from the Central Animal House, Devi Ahilya Vishwavidyalaya, Indore. The animals were segregated into different groups and kept in separate cages with natural light and dark cycles in an air-conditioned room (25±1ºC) with consistent humidity levels of 55±5%. The experimental protocol was approved by the Institutional Animal Ethical Committee (IAEC approval No. 779/CPCSEA/IACE/2022/005).

    Chemical and reagents

    Acarbose Extra Pure 95% was purchased from Sisco Research Laboratories Pvt. Ltd., D-88/2, TTC Industrial Area, Navi Mumbai, Maharashtra, India. α-glucosidase, 4-nitrophenyl-β-D-Glucopyranoside (pNPG), and α-amylase were purchased from Sigma-Aldrich and Titans Biotech Limited, Bhiwadi, Rajasthan, respectively. The glucose test kit (GOD-POD method) was obtained from Robonik (India) Pvt. Ltd., Plot No. 3 and 4, MIDC, Morivali, Ambernath (W), India. Streptozotocin (Sigma-Aldrich) was received as a gift sample from the School of Biotechnology, Devi Ahilya Vishwavidyalaya, Indore.

    Extraction of crude plant extract

    The Soxhlet equipment was utilised to prepare the ethanol extract by a hot continuous extraction procedure.[23] The dried C. tetragonoloba beans were kept in the extractor and ethanol was used as solvent. The extraction was done at 78ºC for 3 hr. To remove moisture from the extract, the liquid was filtered through anhydrous sodium sulphate. The ethanol extract of C. tetragonoloba was dried and concentrated with a rotatory vacuum evaporator.[24] However, the aqueous extract was prepared by maceration method (24 hr) followed by decoction method.[25]

    Determination of glucose adsorption capacity

    Separately, 0.25 g of ethanol and 0.25 g of aqueous extracts of C. tetragonoloba were added to 25 ml of glucose solutions of different concentrations (5, 10, 20, 50, and 100 mMol). The individual mixture was stirred well, then incubated in a shaker water bath at 37ºC for 6 hr, then centrifuged for 15 mins at 3000 rpm. The GOD-POD kit was used to measure the final glucose level in the supernatant in order to calculate the glucose adsorption capacity (mMol g-1).[26, 27] All measurements were taken in triplicate, and the results are shown in Table 1. Glucose bound was calculated as follows:

    G1: glucose concentration of original solution, G6: glucose concentration after 6 hr (mMol L-1), V: volume of sample (L), W: weight of sample (g).

    Table 1: Experimental design for acute and sub-acute study.
    GroupTreatment
    Group 1: ControlWater and feed ad libitum.
    Group 2: Diabetic controlWater and feed ad libitum,
    Group 3: Acarbose treated diabetic rats5 mg/kg body weight per day of acarbose for 21 days.
    Group 4: Indian cluster bean treated diabetic rats250 mg/Kg body weight per day of aqueous extract of Indian cluster bean for 21 days.
    Group 5: Indian cluster bean treated diabetic rats250 mg/Kg body weight per day of ethanol extract of Indian cluster bean for 21 days.
    Group 6: Indian cluster bean and acarbose treated diabetic rats5 mg/kg and 250 mg/kg body weight per day of acarbose and aqueous extract of Indian cluster bean respectively for 21 days.
    Group 7: Indian cluster bean and acarbose treated diabetic rats5 mg/kg and 250 mg/kg body weight per day of acarbose and ethanol extract of Indian cluster bean respectively for 21 days.

    α-amylase inhibitory activity

    The solutions of different concentrations (ranging from 100 µg mL-1 to 1,000 µg mL-1) of acarbose, ethanol and aqueous extracts were prepared in distilled water. Then, 50 μl solution of acarbose and extracts of different strengths were added to 50 μL of α-amylase solution, separately. The phosphate buffer was used as a blank and acarbose as control. The mixture was incubated at 37ºC for 10 min, followed by the addition of 50 μL of soluble starch (1%, W/V), and again incubated at 37ºC for 15 min. Then, 1 M HCl (2 μL) was added to the above mixture to stop the enzymatic reaction. At last, 10 μL of iodine reagent was added. The color change was noted, and the absorbance was recorded at 630 nm with the help of a microplate reader.[28]

    α-glucosidase inhibitory activity

    The solutions of different concentrations (ranging from 100 µg mL-1 to 1,000 µg mL-1) of ethanol and aqueous extracts were prepared in distilled water. Then 2U/mL of α-glucosidase enzyme was added to 20 µL of extract solutions. The mixtures were incubated at 37ºC for 5 min. followed by addition of 20 µL of 1 mM p-nitrophenyl glucopyranoside prepared in 50 mM of phosphate buffer (pH 6.8). These mixtures were incubated at 37ºC for 20 min. Tat last, 50 µL of 1 mM sodium carbonate was added. The α-glucosidase activity was determined by recording absorbance at 405 nm.[29] The α-glucosidase inhibitory activity was calculated using the formula:

    Where AC +: Absorbance of enzyme in solvent, AC -, absorbance of solvent only, AS: absorbance of test sample enzyme a, AB: absorbance of test sample only.

    Oral glucose tolerance test

    Oral glucose tolerance tests for non-diabetic normal rats were performed.[30] Twenty normal rats were randomly divided into four groups and each group contained five male rats. The rats were allowed to fast overnight. Group-1 (control) was treated with normal saline; Group-2 was treated with acarbose at a dose of 5 mg kg-1; Group-3 was treated with an ethanol extract of C. tetragonoloba at a dose of 250 mg kg-1 and Group-4 was treated with an ethanol extract (250 mg kg-1) with acarbose (5 mg kg-1). After 30 min of extract administration, all the groups were administered glucose orally at 2 mg kg-1 of body weight of rats. The blood glucose level was measured at 0 (just prior to glucose administration), 30, 60, 90, and 120 min. after glucose loading by glucometer.

    Induction of diabetes in rats

    Type 2 diabetes was induced in male Wistar rats by a single intraperitoneal (i.p.) injection of Streptozotocin (STZ) dissolved in a citrate buffer; pH 4.5 (60 mg kg-1 of body weight) and nicotinamide in normal saline was administered (110 mg kg-1 of body weight) after 15 min. The control group was given a vehicle citrate buffer and normal saline. Hyperglycemia was confirmed by higher fasting glucose levels measured 72 hr following STZ or vehicle injections. Rats with fasting glucose levels of more than 126 mg dL-1 were considered diabetic.[31]

    Effect of extract on blood glucose level (acute and sub-acute study)

    The thirty-five male rats were randomly divided into seven groups, each consisting of five male rats. The treatment for all animal groups is described in Table 2. The blood glucose level was measured at 0, 1, 2 and 3 hr after the treatment for the acute test, and at 0, 1, 7, 14, and 21 days after the treatment for the subacute test.

    Table 2: Glucose adsorptive capacity of ethanol extract of C. tetragonoloba.
    Concentration (mM)Glucose adsorptive capacity of ethanol extract (mM g-1)Glucose adsorptive capacity of aqueous extract (mM g-1)
    50.0920.066
    100.1450.101
    200.2640.211
    501.30.623
    1002.6921.2

    RESULTS

    Effect of extracts of C. tetragonoloba on glucose adsorption

    The adsorptive capacity of the aqueous extract was found to be the maximum at 2.692 mMol/g at 100 mM glucose, while the lowest was 0.092 mMol/g at 5 mM glucose. The ethanol extract results demonstrated that the adsorptive capacity was highest at 1.2 mMol/g at 100 mM glucose and lowest at 0.066 mMol/g at 5 mM glucose. The results of the ethanol extract and aqueous extract mean are significantly different (p<0.05).

    Effect of C. tetragonoloba on α- amylase and α- glucosidase enzymatic activity

    The α-amylase enzyme has been found to be inhibited by aqueous extract (Table 3). At lower concentrations of the aqueous extract, 5.9±0.20% inhibition was observed, but at higher concentrations, 44.09±0.05% inhibition was recorded. Similarly, the percentage inhibition of lower and higher concentrations of ethanol extract were found to be 3.68±0.08% and 22.98±0.11%, respectively (Table 4). The percent inhibition of alpha-glucosidase enzyme was highest (35.8±0.06%) and lowest (7.4±0.01%) at concentrations of ethanol extract of 1000 μg mL-1 and 100 μg mL-1, respectively. The concentrations of aqueous extract at 1000 μg mL-1 and 100 μg mL-1 showed the highest (40.3±0.13%) and lowest (8.2±0.15%) percent inhibition of the alpha-glucosidase enzyme. Aqueous extract has inhibited the α-amylase enzyme and the α-glucosidase enzyme with 5.3 mg/mL and 5.81 mg/mL IC50 values, respectively.

    Table 3: Inhibition of α-amylase enzyme by ethanol extract and aqueous extract of C. tetragonoloba.
    Concentration (μg mL-1)% Inhibition by ethanol extract% Inhibition by aqueous extract
    1003.6±0.085.9±0.20
    30008.06±0.1211.96±0.1
    50011.81±0.0721.1±0.26
    70016.96±0.0935.514±0.18
    100022.98±0.1144.09±0.05
    Table 4: Percent inhibition of α- glucosidase enzyme by ethanol extract and aqueous extract of C. tetragonoloba.
    Concentration (μg mL-1)% Inhibition by ethanol extract% Inhibition by aqueous extract
    1007.4±0.118.2±0.15
    30019.77±0.0620.6±0.05
    50028.73±0.0932.9±0.11
    70033.95±0.1436.04±0.01
    100035.8±0.0640.3±0.13

    On contrast, the IC50 value 110 mg/mL and 6.5 mg/mL has been observed by ethanol extract for inhibition of α-amylase and α-glucosidase enzymes, respectively. We have investigated the in vitro amylase and glucosidase inhibitory activity for the aqueous and ethanol extracts of C. tetragonoloba. The aqueous extract of C. tetragonoloba has inhibited the α-amylase enzyme and the α-glucosidase enzyme with IC50 values of 5.3 mg/mL and 5.81 mg/mL, respectively. A higher concentration will be required for potent inhibitory activity of the α-amylase enzyme and the α-glucosidase enzyme. On contrast, the IC50 values of 110 mg/mL and 6.5 mg/mL have been observed by ethanol extract for inhibition of α-amylase and α-glucosidase enzymes, respectively.

    Oral glucose tolerance test

    A normal rat model was chosen for the oral glucose tolerance test. The glucose level observed were 120.20±1.77 mg/dL and 104.80±2.72 mg/dL after 180 min of glucose loading by aqueous extract and aqueous extract with acarbose, respectively.

    The glucose levels measured with ethanol extract and ethanol extract with acarbose after 180 min of glucose loading were 143.40±1.91 mg/dL and 123.80±1.82 mg/dL, respectively. The blood glucose level declined by 2.76% after 90 min and 16.36% after 120 min in the aqueous extract with the acarbose-treated group with respect to the acarbose-treated group. The aqueous extract has a lower 4.09% blood glucose level than the acarbose. The acarbose has a lower blood glucose level than ethanol extract with acarbose. The results of the OGTT are listed in Tables 5 and 6. The results of the oral glucose tolerance test have revealed that the aqueous extract with acarbose had a greater blood glucose lowering effect, shown in Figures 1 and 2. The effect of acarbose and aqueous extract with acarbose was found to be similar in normal rats after 2 hr of glucose loading. The ethanol extract with acarbose has a significantly lower blood glucose-lowering effect as compared to the aqueous extract with acarbose. The ethanol extract lowers the blood glucose level because of the phenolic contents that are soluble in ethanol.

    Figure 1: Effect of aqueous extract of C. tetragonoloba on oral glucose tolerance in normal rats.
    Figure 2: Effect of ethanolic extract of C. tetragonoloba on oral glucose tolerance in normal rats.
    Table 5: Effect of aqueous extract of C. tetragonoloba on oral glucose tolerance in normal rats.
    Group0 min30 min60 min90 min180 min
    Group-1 (Control)99±1.94136±1.98183±1.45165±1.70147±2.034
    Group-2 (Acarbose)99.6±2.21128.20±2.24142.40±2.01132.80±1.98125.20±1.65
    Group-3 (Aqueous extract)99.80±3.59141.40±4.36166.20±4.78149.20±3.05120.20±1.77
    Group-4 (Aqueous extract+acarbose)99.56±3.24133±3.39152±3.44128.80±2.03104.80±2.72
    Table 6: Effect of ethanol extract of C. tetragonoloba on oral glucose tolerance in normal rats.
    Group0 min30 min60 min90 min120 min
    Group-1 (Control)99±1.94146±1.98183±1.45165±1.70137±2.034
    Group-2(Acarbose)99.6±2.21128.20±2.235142.40±2.01132.80±1.98125.20±1.65
    Group-3 (Ethanol extract)99±3.01165.4±1.46185.8±1.39157.2±0.96143.40±1.91
    Group-4 (Ethanol extract+acarbose)101.60±3.54158.20±2.39176.60±1.12143.00±1.30123.80±1.82

    Acute and sub-acute study

    The glucose levels of 214.60±7.99 mg/dL and 199.20±4.70 mg/dL were observed after 3 hr of the administration of ethanol extract and ethanol extract with acarbose in streptozotocin-induced diabetic rats. The reduction of glucose by ethanol extract and aqueous extract was significantly different (p<0.05) between the diabetic control group and the normal control group. The glucose levels of 169.60±5.53 mg/dL and 126.00±3.78 mg/dL were measured after 3 hr of the administration of aqueous extract and aqueous extract with acarbose in streptozotocin-induced diabetic rats, illustrated in Figure 3. The reduction of glucose by ethanol extract and aqueous extract with acarbose was significantly different (p<0.05) between the diabetic control group and the normal control group. The blood glucose level of diabetic male rats is listed in Table 7. The 14th day of administration has shown the glucose effect of C. tetragonoloba extract, and the 7th day has shown a decrease in blood glucose due to the co-delivery of acarbose with both extracts. On the 14th day of concurrent administration of an aqueous extract with acarbose and an ethanol extract with acarbose, the blood glucose levels were measured at 179.60±17.22 mg/dL and 214.20±21.20 mg/dL, respectively. The blood glucose levels of diabetic control group 501±34.92 mg/dL were lowered to 240.8±9.1 mg/dL and 179.60±17.22 mg/dL by the administration of the ethanol and aqueous extracts of C. tetragonoloba, respectively (Table 8). The difference in mean was found to be significant (p<0.05) and shown in the Figure 4.

    Figure 3: Effect of aqueous and ethanolic extracts of C. tetragonoloba on sub-acute study in diabetic rats.
    Figure 4: Results of acute study after treatment of extracts of C. Tetragonoloba.
    Table 7: Effect of aqueous and ethanol extracts of C. tetragonoloba on acute study in diabetic rats.
    Blood Glucose Level
    Blood Sample Time (h)
    0123
    Group 1106.00±2.85134.00±5.93127.60±1.32114.80±1.24
    Group 2531.20±39.47537.20±38.23528.00±37.22522.00±42.92
    Group 3342.40±9.54294.80±12.75238.40±13.44184.00±7.77
    Group 4366.20±8.15308.20±6.12233.00±8.82214.60±7.99
    Group 5361.60±9.26285.40±8.30223.80±6.71199.20±4.70
    Group 6358.80±5.77275.00±9.44224.80±8.25169.60±5.53
    Group 7349.60±15.62243.00±12.66173.20±22.23126.00±3.78
    Table 8: Effect of aqueous and ethanol extracts of C. tetragonoloba on sub-acute study in diabetic rats.
    Sample time (days)
    Day 0Day 1Day 7Day 14Day 21
    Group-1124.60±2.27146±3.91131.8±9.41124.80±1.24125.8±0.66
    Group-2462.60±33.82475±39.22464.20±44.75471.20±27.28501±34.92
    Group-3479±36.91451.60±41.1415.80±47.89345.60±34.30215.60±15.91
    Group-4442±10.53467±9.92444.2±3.76360±10.0240.8±9.1
    Group-5467.60±40.58471.20±60.54439.60±59.77304.40±48.49214.20±21.20
    Group-6479.60±29.09422.2±28.70284.60±32.35232±21.49179.60±17.22
    Group-7466±46.67452±45.03273.40±45.88224.80±27.9165±128.76

    DISCUSSION

    This study comprehensively evaluates the efficacy of aqueous and ethanol extracts of C. tetragonoloba (guar) in adsorbing glucose, inhibiting key carbohydrate-digesting enzymes, and managing blood glucose levels in both normal and diabetic rat models. The findings underscore the superior performance of the aqueous extract across multiple parameters, attributed largely to its high fiber content and the presence of bioactive compounds. The glucose adsorptive capacity of the extracts indicates their potential to reduce glucose absorption in the small intestine, thus mitigating postprandial hyperglycemia. The study found that the aqueous extract of C. tetragonoloba exhibited a maximum adsorptive capacity of 2.692 mMol/g at 100 mM glucose, significantly higher than the ethanol extract's capacity of 1.2 mMol/g at the same concentration.

    Even at lower glucose concentrations (5 mM), the aqueous extract maintained a higher adsorptive capacity (0.092 mMol/g) compared to the ethanol extract (0.066 mMol/g). This superior adsorptive capacity of the aqueous extract is primarily due to its rich content of water-soluble fibers, such as galactomannan. These fibers form a viscous gel in the digestive tract, which can trap glucose molecules and slow their absorption. This mechanism reduces the postprandial spike in blood glucose levels, making the aqueous extract particularly effective for managing diabetes.32 The significant difference in adsorptive capacity (p<0.05) between the aqueous and ethanol extracts underscores the importance of fiber content and solubility in determining the efficacy of glucose adsorption. Inhibiting α-amylase and α-glucosidase enzymes is crucial for managing postprandial hyperglycemia, as these enzymes break down complex carbohydrates into glucose. The study revealed that the aqueous extract demonstrated a higher inhibition of α-amylase, with a maximum inhibition of 44.09±0.05% at higher concentrations, compared to 22.98±0.11% by the ethanol extract. Similarly, for α-glucosidase inhibition, the aqueous extract showed higher efficacy, with 40.3±0.13% inhibition at 1000 μg/mL compared to 35.8±0.06% by the ethanol extract. The IC50 values, which represent the concentration required to inhibit 50% of enzyme activity, further support these findings. The aqueous extract had lower IC50 values for both α-amylase (5.3 mg/mL) and α-glucosidase (5.81 mg/mL), compared to the ethanol extract (110 mg/mL for α-amylase and 6.5 mg/mL for α-glucosidase). These results suggest that the aqueous extract is more potent in inhibiting these enzymes, likely due to its higher content of water-soluble fibers and bioactive compounds such as phenolic acids and flavonoids. Phenolic compounds, including p-coumaric acid, gallic acid, kaempferol, quercetin, and ferulic acid, present in the extracts, are known to inhibit carbohydrate metabolism enzymes. Gallic acid, in particular, is a strong inhibitor of disaccharidases such as maltase, trehalase, and lactase, but its main inhibitory action is on α-amylase.[33, 34] The higher efficacy of the aqueous extract in enzyme inhibition may be due to the higher solubility and bioavailability of these phenolic compounds in an aqueous medium. The OGTT results in normal rats demonstrated that the aqueous extract, both alone and in combination with acarbose, significantly lowered blood glucose levels more effectively than the ethanol extract. After 180 min of glucose loading, the aqueous extract with acarbose resulted in a blood glucose level of 104.80±2.72 mg/dL, compared to 123.80±1.82 mg/dL for the ethanol extract with acarbose. This indicates a synergistic effect between the aqueous extract and acarbose, enhancing the glucose-lowering effect. The aqueous extract alone also showed a greater reduction in blood glucose levels (120.20±1.77 mg/dL) compared to the ethanol extract (143.40±1.91 mg/dL) after 180 min. These findings suggest that the aqueous extract has a more potent postprandial glucose-lowering effect, likely due to its higher fiber content and the presence of bioactive compounds that inhibit carbohydrate-digesting enzymes. In streptozotocin-induced diabetic rats, both extracts significantly reduced blood glucose levels, but the aqueous extract was more effective. After 3 hr of administration, the aqueous extract with acarbose reduced glucose levels to 126.00±3.78 mg/dL, compared to 199.20±4.70 mg/dL for the ethanol extract with acarbose. Aqueous extract with acarbose had a potent postprandial glucose-lowering effect and was observed in acute treatment. The aqueous extract with acarbose reduced blood glucose levels after 2 and 3 hr in a diabetic rat model. The ethanol extract of C. tetragonoloba has also shown a blood glucose-lowering effect. That effect was less compared to the acarbose and aqueous extracts with acarbose. The results of acute treatment have shown that the aqueous extract of C. tetragonoloba with acarbose may be used to treat postprandial hyperglycemia. The sub-acute study has shown that the after the administration of aqueous extract and ethanol extract reduces the blood glucose level after the 14th day. The co- administration of acarbose with aqueous and ethanol extract had reduced the blood glucose level from 7th day. The highest lowering effect of blood glucose level was observed at 21th day of treatment by aqueous extract with acarbose. The co-administration of aqueous extract with acarbose have shown additive effect against the hyperglycemia may be because of Gaur gum. It is a viscous galactomannan extract from the endosperm of C. tetragonoloba seeds. Guar gum has demonstrated hypoglycemic activity. Guar gum is a polysaccharide, that forms gel when mixed with water. It increases the viscosity of the stomach and small intestine, which reduces the movement and absorption of glucose. This effect delays the gastric emptying.[35, 36] The 20% gaur gum reduced 52% of the glucose level in rats after 28 days of treatment; the effect was significantly higher than that of the control drug, glibenclamide (2 mg/kg). The gaur gum reduces the cholesterol, triglycerides, and LDL-C levels in diabetic rats.[37] Guar gum increases the effect of insulin in diabetic patients. Guar gum increases insulin sensitivity and decreases lipid content in the blood via a delay in gastric emptying and a slow absorption of glucose. The glucose utilization in adipose tissue was observed after the treatment of guar gum.[38]

    The in vivo study results suggest that the co-administration of aqueous extract with acarbose may be used to reduce postprandial hyperglycemia. The results of the in vitro study corroborate those of the in vivo study. The results of glucose adsorption capacity of aqueous extract support the additive effect of aqueous extract with acarbose on streptozotocin-induced diabetic rats.

    CONCLUSION

    The present results demonstrate the co-administration of aqueous extract and ethanol extract with acarbose have shown statistically significant reduction in blood glucose level in streptozotocin induced male diabetic rats. The aqueous extract with acarbose was more effective for postprandial hyperglycemia compares to ethanol extract with acarbose and acarbose. The additive pharmacological effect on blood glucose level has been observed after the co administration of extract of C. tetragonoloba with acarbose in streptozotocin induced male diabetic rats. However, it is vital to understand the pharmacodynamic interactions yielding therapeutic benefits as a result of synergistic action. To summarise, the interaction of herbal and pharmaceutical medicines is a critical to both patients and health care practitioners. It is necessary to continue research on potential risks and benefits associated with the combination of C. tetragonoloba and Acarbose on pharmacokinetic aspects. Such data is crucial for the formulation of future clinical guidelines to improve health-care outcomes in diabetes.

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    Mourya, R., Elangovan, M., Parmar, H. S., & Sharma, R. (2026). Pharmacodynamic Interaction between Cyamopsis tetragonoloba (Cluster Beans) and Acarbose: An in vitro and in vivo Study. Pharmacognosy Research, 18(1), 191–199. https://doi.org/10.5530/pres.20262368