Antihyperglycemic and Insulin Secretagogue Activities of Abrus precatorius Leaf Extract

Study on the potential hypoglycemic flavonoids in Abrus precatorius leaves: purification process, quality profile and activity mechanisms by transcriptomics and network pharmacology

The aim of the study was to investigate the relationship between flavonoids in Abrus precatorius leaves (APL) and their hypoglycaemic effects, which have not been studied before. An efficient purification process, transcriptomics and network pharmacology analysis were applied for the first time. High-performance liquid chromatography (HPLC) was used to determine the content of total flavonoids. The results showed that D101 resin was most suitable for purification of flavonoids of APL, which could increase its purity from 25.2% to 85.2% and achieve a recovery rate of 86.9%. The analysis of transcriptomics and network pharmacology revealed that flavonoids of APL could play a hypoglycaemic role by regulating 31 targets through AGE-RAGE and other signal pathways. Flavonoids of APL could exert hydroglycaemic effects by inhibiting AGEs, α-glucosidase and DPPH. This study provides a solid basis for hypoglycaemic product development and in-depth research of flavonoids in APL.

Abrus precatorius Leaf Extract Reverses Alloxan/Nicotinamide-Induced Diabetes Mellitus in Rats through Hormonal (Insulin, GLP-1, and Glucagon) and Enzymatic (α-Amylase/α-Glucosidase) Modulation

BACKGROUND

Abrus precatorius is used in folk medicine across Afro-Asian regions of the world. Earlier, glucose lowering and pancreato-protective effects of Abrus precatorius leaf extract (APLE) was confirmed experimentally in STZ/nicotinamide-induced diabetic rats; however, the underlying mechanism of antidiabetic effect and pancreato-protection remained unknown.

OBJECTIVE

This study elucidated antidiabetic mechanisms and pancreato-protective effects of APLE in diabetic rats.

MATERIALS AND METHODS

APLE was prepared by ethanol/Soxhlet extraction method. Total phenols and flavonoids were quantified calorimetrically after initial phytochemical screening. Diabetes mellitus (DM) was established in adult Sprague-Dawley rats (weighing 120-180 g) of both sexes by daily sequential injection of nicotinamide (48 mg/kg; ip) and Alloxan (120 mg/kg; ip) over a period of 7 days. Except control rats which had fasting blood glucose (FBG) of 4.60 mmol/L, rats having stable FBG (16-21 mmol/L) 7 days post-nicotinamide/Alloxan injection were considered diabetic and were randomly reassigned to one of the following groups (model, APLE (100, 200, and 400 mg/kg, respectively; po) and metformin (300 mg/kg; po)) and treated daily for 18 days. Bodyweight and FBG were measured every 72 hours for 18 days. On day 18, rats were sacrificed under deep anesthesia; organs (kidney, liver, pancreas, and spleen) were isolated and weighed. Blood was collected for estimation of serum insulin, glucagon, and GLP-1 using a rat-specific ELISA kit. The pancreas was processed, sectioned, and H&E-stained for histological examination. Effect of APLE on enzymatic activity of alpha (α)-amylase and α-glucosidase was assessed. Antioxidant and free radical scavenging properties of APLE were assessed using standard methods.

RESULTS

APLE dose-dependently decreased the initial FBG by 68.67%, 31.07%, and 4.39% compared to model (4.34%) and metformin (43.63%). APLE (100 mg/kg) treatment restored weight loss relative to model. APLE increased serum insulin and GLP-1 but decreased serum glucagon relative to model. APLE increased both the number and median crosssectional area (×106 μm2) of pancreatic islets compared to that of model. APLE produced concentration-dependent inhibition of α-amylase and α-glucosidase relative to acarbose. APLE concentration dependently scavenged DPPH and nitric oxide (NO) radicals and demonstrated increased ferric reducing antioxidant capacity (FRAC) relative to standards.

CONCLUSION

Antidiabetic effect of APLE is mediated through modulation of insulin and GLP-1 inversely with glucagon, noncompetitive inhibition of α-amylase and α-glucosidase, free radical scavenging, and recovery of damaged/necro-apoptosized pancreatic β-cells.

Isoflavanquinones from Abrus precatorius roots with their antiproliferative and anti-inflammatory effects

Phytochemical studies on the root of Abrus precatorius Linn. (Fabaceae), leads towards the identification of four undescribed (abruquinones M, N, O, and P), and seven known abruquinones, (abruquinones A, E, B, F, I, D, and G). Spectroscopic analyses (1D, and 2D NMR, HRESI-MS) were used in elucidating structures of the all compounds. Evaluation of anticancer activities of the isolated isoflavanquinones revealed that abruquinones M, and N showed cytotoxicity against oral CAL-27 (IC₅₀ values 6.48 and 5.26 μM, respectively), and colon (Caco-₂) cell lines (IC₅₀ values 15.79 and 10.33 μM, respectively). Abruquinone M also inhibited the growth of lung cancer cells (NCI-H460) with IC₅₀ of 31.33 μM. The isolated isoflavanquiones also showed potent anti-inflammatory potential through phagocyte oxidative burst and pro-inflammatory cytokine TNF-α inhibition in vitro. These findings suggest isoflavanquinones from A. precatorius roots as candidates for further research in cancer treatment.

Glucose lowering and pancreato-protective effects of Abrus Precatorius (L.) leaf extract in normoglycemic and STZ/Nicotinamide - Induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Abrus precatorius (L.) leaves are used as folk medicine by the local communities in the western region of Ghana to treat diabetes mellitus; however, this health claim remains unverified scientifically.

OBJECTIVE

The study investigated glucose lowering and pancreato-protective effects of Abrus precatorius leaf extract (APLE) in normoglycemic and STZ/nicotinamide (NIC)-induced diabetic rats.

METHOD

after preparation of APLE, it was subjected to phytochemical screening, proximate composition and elemental assessments by using standard methods. Oral glucose tolerance test (OGTT) and maltose, lactose and sucrose oral challenge were assessed in normoglycemic rats post-APLE. Morphological characteristics of glucose response curve (time of glucose peak and shape of glucose response curve) were determined. Subsequently, diabetes mellitus was experimentally established in normoglycaemic adult Sprague-Dawley rats (weighing 150-250 g) of both sexes by sequential injection of Streptozotocin (STZ, 60 mg/kg ip)-reconstituted in sodium citrate buffer and NIC (110 mg/kg ip)-reconstituted in normal saline (1:1 v/v) for 16 weeks. Except control rats (normal saline 5 ml/kg ip; baseline fasting blood glucose [FBG] of 6.48 mmol/L), rats having FBG (stable at 11.1 mmol/L or ≥ 250 mg/dL) 3 days post-STZ/NIC injection were randomly re-assigned to one of the following groups: model (STZ/NIC-induced diabetic rats), APLE (100, 200 and 400 mg/kg respectively po) and metformin (300 mg/kg po) and treated daily for 28 days. Bodyweight and FBG were measured on weekly basis. FBG was measured by using standard glucometers. On day 28, rats were sacrificed under chloroform anesthesia, blood collected via cardiac puncture; kidney, liver and pancreas surgically harvested. While the pancreas was processed, sectioned and H&E-stained for histological examination, fresh kidney and liver were homogenized for assessment of total anti-oxidant capacity. Median cross-sectional area of pancreatic islets of Langerhans was determined for each group by using Amscope.

RESULTS

Cumulatively, APLE (100, 200 and 400 mg/kg respectively) dose-dependently decreased the initial FBG by 55.22, 76.15 and 77.77% respectively compared to model (-1.04%) and metformin (72.29%) groups. APLE treatment recovered damaged pancreatic β-cells and also increased median cross-sectional area (x10⁶ μm²) of pancreatic islets compared to that of model group. APLE significantly (P < 0.05) increased total anti-oxidant capacity (5.21 ± 0.02 AscAE μg/mL) of plasma, kidney and liver compared to model (4.06 ± 0.04 AscAE μg/mL) and metformin (4.87 ± 0.03 AscAE μg/mL) groups.

CONCLUSION

APLE has demonstrated glucose lowering and pancreato-protective effects in rats and arrested the characteristic loss in bodyweight associated with diabetes mellitus. This finding preliminarily confirms folk use of APLE as an anti-diabetic herbal medicine, whiles providing a rationale for further translational studies on APLE.

Antihyperglycemic Activity of the Leaves from Annona cherimola Miller and Rutin on Alloxan-induced Diabetic Rats

Background:

Annona cherimola, known as “chirimoya” has been reported in Mexican traditional medicine for the treatment of diabetes.

Objective:

The aims of the present study were to validate and assess the traditional use of A. cherimola as an antidiabetic agent.

Materials and Methods:

The ethanol extract from A. cherimola (300 mg/kg, EEAc), subsequent fractions (100 mg/kg), and rutin (30 mg/kg) were studied on alloxan-induced type 2 diabetic (AITD) and normoglycemic rats. In addition, oral glucose tolerance test (OGTT) and oral sucrose tolerance test (OSTT) were performed in normoglycemic rats. Molecular docking technique was used to conduct the computational study.

Results:

Bioassay-guided fractionation of EEAc afforded as major antihyperglycemic compound, rutin. EEAc attenuated postprandial hyperglycemia in acute test using AITD rats (331.5 mg/dL) carrying the glycemic levels to 149.2 mg/dL. Rutin after 2 h, attenuated postprandial hyperglycemia in an acute assay using AITD rats such as EEAc, with maximum effect (150.0 mg/dL) being seen at 4 h. The antihyperglycemic activities of EEAc and rutin were comparable with acarbose (151.3 mg/dL). In the subchronic assay on AITD rats, the EEAc and rutin showed a reduction of the blood glucose levels since the 1^st week of treatment, reaching levels similar to normoglycemic state (116.9 mg/kg) that stayed constant for the rest of the assay. OGTT and OSTT showed that EEAc and rutin significantly lowered blood glucose levels in normoglycemic rats at 2 h after a glucose or sucrose load such as acarbose. Computational molecular docking showed that rutin interacted with four amino acids residues in the enzyme α-glucosidase.

Conclusion:

The results suggest that rutin an α-glucosidase inhibitor was responsible in part of the antihyperglycemic activity of A. cherimola. Its in vivo antihyperglycemic activity is in good agreement with the traditional use of A. cherimola for the treatment of diabetes.

SUMMARY

The ethanol extract from Annona cherimola (300 mg/kg, EEAc), subsequent fractions (100 mg/kg) and rutin (30 mg/kg) were studied on alloxan-induced type 2 diabetic (AITD) and normoglycemic rats. The results suggest that rutin; an α-glucosidase inhibitor was responsible in part of the antihyperglycemic activity of A. cherimola. Its in vivo antihyperglycemic activity is in good agreement with the traditional use of A. cherimola for the treatment of diabetes.

Abbreviations Used: EEAc: The ethanol extract from Annona cherimola, AITD: Alloxan-induced type 2 diabetic rats, OGTT: Oral glucose tolerance test, OSTT: Oral sucrose tolerance test, DM: Diabetes mellitus