INTRODUCTION:

Diabetes is a metabolic diseases which is characterized by hyperglycemia results from impaired insulin metabolism. Persistent hyperglycemia associated with diabetes may result in the failure of different organs like the kidneys, eyes, nerves, blood vessels, and heart¹. Over the last thirty years the number of diabetic patients have been doubled worldwide. It is speculated that globally the number of diabetic patients will rise to 439 million by 2030, which represents 7.7% of the total adult². In reality, there is no limitation for using plant extract because of having their curative properties, plant extracts were found to be used for the treatment of chronic diseases like diabetes³.

Researcher postulated that the extract derived from whole parts of Derris scandens had antidiabetic activity⁴, we specifically and narrowly investigated whether only leaves of the plant exhibits hypoglycemic potency. At the same time we also investigated the hypoglycemic potency of the leaf extract of Thunbergia erecta as it was known that Thunbergia species have antidiabetic activity.

Derris scandens Benth. belongs to Leguminosae family, which is a woody vine like growing and climbing shrub abundantly found plains of southeast Asian countries like Thailand^5,6. Its Thai name is Tao-Wan-Priang which is a well-recognized Asian medicinal plant⁷. The plant is also found in Bangladesh in Teknaf of Cox’s Bazar district and Nijhum Dweep and is locally known as “Kalilata”^8,9. Stem of the plant has been used in the traditional medicine as antitussive, expectorant, antidysentery, diuretic, and for the treatment of cachexia¹⁰. Stem extracts have also been used in traditional medicine for the treatment of arthritis, muscular pain, and inflammation¹¹. D. scandens is also reported to have antihypertensive, antibacterial, anti-HIV and immunomodulatory activity⁴. Root of the plant contains rotenone, lonchocarpic acid those have potential insecticidal activity. Chemical constituents including coumarins, isoflavones, flavones, isoflavone glycosides and phenyl coumarins have been identified from D. scandens¹². A study reported to find meaningful antidiabetic action in hexane extract where it showed α- glucosidase inhibitory activity⁴.

Thunbergia erecta (Acanthaceae) (Syn: Meyenia erecta) is also known as King’s Mantle, Blue Bell, and Bush Clock Vine¹³. It is woody, straight shrub which has 2-2.5 m altitude. It contains flower that blooms throughout the year and has blue to purple color range¹⁴. Thunbergia is native to the tropical part of Madagascar, Australia, Africa, and South Asia. Leaves, roots and stems of Thunbergia species have the traditional history to be used for the treatment of inflammation and pyrexia¹³. Thunbergia species have been reported to show antibacterial effects against both gram positive and gram negative bacteria including Klebsiella pneumonia, Escherichia coli Staphylococcus aureus, Proteus mirabilis, Bacillus cereus, and Streptococcus pyogenes¹⁵. Thunbergia species also possess analgesic, antipyretic, anthelmintic, antidiabetic, cytotoxic, antioxidant, hepatoprotective^16,17, antitumor and antinociceptive activities¹⁸. Chemical ingredients separated from Thunbergia genus include alkaloids, glucosides, naphthalene, coumaroylmalic acid, iridoid glucosides, grandifloric acid, benzyl beta glucopyranoside, delphinidin, apigenin and phenolic compounds such as tannin, feruloylmalic, flavonoids, phenolic acids, rosmarinic acid^19,20. By considering the expenditure and longer time duration required by studies with diabetes induced animal model, authors decided to assess the hypoglycemic effect in mice with hyperglycemia (simulation of diabetic state) by loading glucose orally as a preliminary step for screening whether the plants have hypoglycemic effect. The current study was designed to evaluate the hypoglycemic activities of methanol extract of leaves of Derris scandens (MEDS) and methanol extract of leaves of Thunbergia erecta (METE) after oral administration in the mice model.

MATERIAL AND METHODS:

Extraction of plant parts:

Leaves of both Derris scandens and Thunbergia erecta were collected from Jahangir Nagar University Campus, Savar, Dhaka, Bangladesh in the month of April 2017. Identification of these plant parts was confirmed at the Bangladesh National Herbarium. ACCN of Derris scandens and Thunbergia erecta were 46542 and 45803 respectively those along with sample specimens of both were kept at herbarium for future reference.

After collection, the leaves of both plants were dried in the shade of sunlight for four days. Then dried leaves were crushed into a coarse powder using blender machine. About 450g and 750g of prepared powder of Derris scandens and Thunbergia erecta leaves respectively were macerated in methanol for 7 days. After filtration by cotton filter the filtrates were concentrated at 39°C with the aid of rotary evaporator. Air drying of the concentrated filtrates yielded to 30g and 25g methanol extract of Derris scandens and Thunbergia erecta respectively.

Animals:

Swiss albino mice of both sexes compatible for 20-25g of weight were selected for conducting in vivo hypoglycemic effect evaluation. Prior to one week the mice were purchased from ICDDR, B (International Centre for Diarrhoeal Disease Research, Bangladesh) and preserved in the laboratory keeping optimum ambience (temp. 25±2°C and humidity 55-60 %). Experimental animals were kept on 12 hrs dark-light cycle so that they could be used to with the experimental environment. Standard food supplied by ICDDR, B along with ample fresh water was allowed to take. Before 12 hrs of experiment, mice were kept under starvation and allowed only to have fresh water ad libitum. The Ethics Committee of Stamford University Bangladesh (SUB/IAEC/18.01) approved all experimental protocols.

Chemicals and drugs:

Following chemicals and drugs were used in the experiment: Reagent grade methanol (Merck, Germany), dimethyl sulfoxide (Merck, Germany), 2,2-diphenyl-1-picrylhydrazyl (Sigma-Aldrich, USA), glucose (Glaxo Smith Kline) and Glibenclamide (Square Pharmaceuticals).

Hypoglycemic effect evaluation:

In this study, a total eight groups of mice (n=5) were used and all mice were loaded by glucose to make the simulation as diabetic state. Groups were designated by Gr-1 to Gr-8 while Gr-1(control) was treated by vehicle, Gr-2(Std) was treated by glibenclamide. Rest six groups of mice were treated by three doses (100mg/Kg BW, 200mg/Kg BW and 400mg/Kg BW) of each plant extracts. Thus MEDS was subjected to Gr-3 to 4 and METE was given to Gr-5 to 8. All treatments were administered by oral route and all mice groups were allowed to take 2gm glucose/kg one hour after the completion of oral gavage of extracts, glibenclamide and 0.1% v/v DMSO in normal saline (vehicle). Blood sugar level after two hours of treatment was measured by glucometer which works following glucose oxidation method.

Percent of Blood sugar lowering was calculated following the formula given hereunder²¹.

Percent lowering of blood glucose level

= (1 – We/Wc) x 100,

Where We and Wc stand for the blood glucose concentration measured in glibenclamide or extracts administered mice and control mice respectively.

STATISTICAL ANALYSIS:

Statistical analysis of the hypoglycemic study involves the use of ANOVA followed by Dunnett’s post hoc test with IBM statistics data editor. Graphical presentation was executed by Graphpad prism 7 software.

RESULTS AND DISCUSSION:

Study indicated that the blood glucose level lowering capacity was dependent on the dose of test samples. At the dose of 200 mg/kg BW, MEDS and METE showed blood sugar 3.72 mmol/L and 3.78 mmol/L respectively whereas at the highest dose (400 mg/kg BW) MEDS and METE displayed 3.42 mmol/L and 2.88 mmol/L of blood glucose. Glibenclamide, used as standard, significantly decreased the blood glucose. Blood glucose level upon administration of extracts to the mice pretreated with glucose at 200 mg/kg BW and 400 mg/kg BW were statistically significant at the level of P ≤ 0.001 compared to control.

Table 1. Blood glucose lowering effect of methanol leaf extracts of Derris scandens and Thunbergia erecta.

Plants	Group	Dose	Blood glucose level (mmol/L)
	Gr-1 (Control)	10 ml/kg	4.86 ± 0.23
	Gr-2 (Glibenclamide)	10mg/kg	3.46^* ± 0.13
MEDS	Gr-3	100 mg/kg	4.46 ± 0.18
	Gr-4	200 mg/kg	3.72^* ± 0.04
	Gr-5	400 mg/kg	3.42^* ± 0.13
METE	Gr-6	100 mg/kg	4.68 ± 0.14
	Gr-7	200 mg/kg	3.78^* ± 0.29
	Gr-8	400 mg/kg	2.88^* ± 0.66

Values are shown as mean blood glucose level ± SEM and ^*indicates P ≤ 0.001; statistically significant when compared with hyperglycemic control animals.

Figure 1. represents percent blood glucose lowering potential of MEDS and METE at three different doses. Among all treatments METE at 400 mg/kg BW dose showed the highest glucose lowering capacity at the value of 40.74% while MEDS showed second highest hypoglycemic effect (29.62%) as well as glibenclamide reduced blood glucose level by 28.80% under the experimental condition. . doses 100, 200 and 400 mg/kg BW decreased blood glucose levels by 8.23, 23.45 and 29.62% respectively. METE decreased blood glucose levels by 3.70, 22.22 and 40.74% at doses 100, 200 and 400 mg/kg BW respectively. Percentage reduction of blood glucose levels achieved at 200 and 400 mg/kg BW were significant (P < 0.001) for both MEDS and METE. It is to be noted that percentage reduction of blood glucose levels for both MEDS and METE at doses 200 and 400 mg/kg BW was higher than that of the standard glibenclamide when administered at dose 10 mg/kg BW. Glibenclamide reduced blood glucose level by 28.80% under the experimental condition.

Fig 1: Percent reduction of glucose level of methanol extract of leaves of Derris scandens (MEDS) and methanol extract of leaves of Thunbergia erecta (METE)

Three flavonoids have been isolated from Derris scandens showed α-glucosidase inhibitory activity in rat model²². Isoflavones may also produce hypoglycemic effects in rat models²³. Coumarin, a phenolic compound has been reported to reduce blood glucose level in diabetic mice²⁴. Therefore it is quite possible that the isoflavones, coumarin or any other similar phytochemicals like phenyl coumarins, isoflavone glycosides present in Derris scandens may adopt mechanism to produce hypoglycemic effect.

Various types of alkaloids were found to be effective for the treatment of diabetes mellitus²⁵. Glucosides, like paeoniflorin and 8-debenzoylpaeoniflorin have also been reported to reduce blood sugar levels in mice with streptozotocin induced diabetes²⁶.Delphinidin contributed to increasing insulin secretion in INS-1 832/13 cells lines²⁷. These chemical compounds present in Thunbergia genus including Thunbergia erecta are likely to be associated with reduction in blood glucose level.

The hypoglycemic activity of several medicinal plants have already been established by a number of studies. From previous studies about the mechanism involved for reducing blood glucose level by these plants reduce several possible mechanisms were revealed. Among these, common mechanisms are stimulation of pancreatic β- cell to release insulin, inhibition of the hormones responsible for increasing blood glucose, improvement of the sensitivity or count of insulin receptors, retardation of glycogen discharge, acceleration of the use of glycogen by tissues or organs, scavenging free radical, defense in lipid peroxidation and rectification of other metabolic disorders, betterment of microcirculation in the body. Alkaloids, flavonoids, terpenes and phenolics are the classes of chemical compounds whose antidiabetic potency have already been confirmed by animal studies²⁸.

The similar phytochemicals present in the leaves of Derris scandens and Thunbergia erecta may be responsible for hypoglycemic effect by any of the underlying mechanisms.

CONCLUSION:

This study confirmed the hypoglycemic effects of leaves of these two medicinal plants. Consequently, leaves of Derris scandens and Thunbergia erecta may be effective in diabetes treatment. Before isolation of compound with hypoglycemic property, confirmation of underlying mechanism and declaration to use as antidiabetic agent by traditional healers it is suggested to evaluate the hypoglycemic effect of these plants’ leaves in diabetic animal (mouse or rat) model.

FUNDING:

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

CONFLICTS OF INTEREST:

The authors declare no conflict of interest.

REFERENCES:

1. American Diabetes Association. Diagnosis and classification of diabetes mellitus. Diabetes care. 2014, 37(Supplement 1): S81-90.

2. Chen L, Magliano DJ and Zimmet PZ. The worldwide epidemiology of type 2 diabetes mellitus—present and future perspectives. Nature reviews endocrinology. 2012, 8(4): 228.

3. Afifi FU, Al-Khalidi B and Khalil E. Studies on the in vivo hypoglycemic activities of two medicinal plants used in the treatment of diabetes in Jordanian traditional medicine following intranasal administration. Journal of ethnopharmacology. 2005; 100(3): 314-8.

4. Babu TH et. al. A new prenylated isoflavone from Derris scandens Benth. Journal of Asian natural products research. 2010; 12(7): 634-8.

5. Sriwanthana B and Chavalittumrong P. In vitro effect of Derris scandens on normal lymphocyte proliferation and its activities on natural killer cells in normals and HIV-1 infected patients. Journal of ethnopharmacology. 2001, 76(1): 125-9.

6. Ganapaty S, Josaphine JS and Thomas PS. Anti-inflammatory activity of Derris scandens. Journal of Natural Remedies. 2006, 6(1): 73-6.

7. Mahabusarakam W et. al. A benzil and isoflavone derivatives from Derris scandens Benth. Phytochemistry. 2004, 65(8): 1185-91.

8. Uddin MZ et. al. Diversity in angiosperm flora of Teknaf Wildlife Sanctuary, Bangladesh. Bangladesh Journal of Plant Taxonomy. 2013, 20(2).

9. Uddin MZ, Kibria MG and Hassan MA. Assessment of angiosperm plant diversity of Nijhum Dweep. Bangladesh. Journal of the Asiatic Society of Bangladesh, Science. 2015, 41(1): 19-52.

10. Sittiwet C and Puangpronpitag D. Antimicrobial properties of Derris scandens aqueous extract. Journal of Biological Sciences. 2009, 9: 607-11.

11. Hematulin A et. al. Ethanolic extract from Derris scandens Benth mediates radiosensitzation via two distinct modes of cell death in human colon cancer HT-29 cells. Asian Pacific Journal of Cancer Prevention. 2014, 15(4): 1871-7.

12. Sreelatha T et. al A new benzil derivative from Derris scandens: Structure-insecticidal activity study. Bioorganic & medicinal chemistry letters. 2010, 20(2): 549-53.

13. Manokari M and Shekhawat MS. Biosynthesis and characterization of zinc oxide nanoparticles using Thunbergia erecta (Benth.) T. Anders plant extracts. Archives of Agriculture and Environmental Science. 2017, 2(3): 148-51.

14. Kitajima EW, Rodrigues JC and Freitas-Astua J. An annotated list of ornamentals naturally found infected by Brevipalpus mite-transmitted viruses. Scientia Agricola. 2010; 67(3): 348-71.

15. Jeeva S et. al. Preliminary phytochemical and antibacterial studies on flowers of selected medicinal plants. International Journal of Medicinal and Aromatic Plants. 2011; 1(2): 107-14.

16. Oonsivilai R, Ferruzzi MG and Ningsanond S. Antioxidant activity and cytotoxicity of Rang Chuet (Thunbergia laurifolia Lindl.) extracts. Asian Journal of Food and Agro-Industry. 2008; 1(02): 116-28.

17. Wonkchalee O et. al. Anti-inflammatory, antioxidant and hepatoprotective effects of Thunbergia laurifolia Linn. On experimental opisthorchiasis. Parasitology research. 2012; 111(1): 353-9.

18. Jetawattana S et. al. Radical intermediate generation and cell cycle arrest by an aqueous extract of Thunbergia laurifolia Linn. In human breast cancer cells. Asian Pacific Journal of Cancer Prevention. 2015; 16(10): 4357-61.

19. Kanchanapoom T, Kasai R and Yamasaki K. Iridoid glucosides from Thunbergia laurifolia. Phytochemistry. 2002; 60(8): 769-71.

20. Areekul S et. al. Wild plant knowledge used in northern Thailand III. Bangkok: Amarin Printing and Publishing Public Company Limited. 2009.

21. Bhuiyan, M. M. R., Nahar, U. J. and Rahmatullah, M. Methanolic Extract of Spilanthes Calva Improves Glibenclamide-Induced Glucose Tolerance. 2016; 6(2): 60-67

22. Yin Z et. al. α-Glucosidase inhibitors isolated from medicinal plants. Food Science and Human Wellness. 2014; 3(3-4): 136-74.

23. Ojewole JA, Drewes SE and Khan F. Vasodilatory and hypoglycaemic effects of two pyrano-isoflavone extractives from Eriosema kraussianum NE Br. [Fabaceae] rootstock in experimental rat models. Phytochemistry. 2006; 67(6): 610-7.

24. Noipha K et. al. Carbazoles and coumarins from Clausena harmandiana stimulate glucose uptake in L6 myotubes. Diabetes research and clinical practice. 2010; 90(3): e67-71.

25. Patel MB and Mishra S. Hypoglycemic activity of alkaloidal fraction of Tinospora cordifolia. Phytomedicine. 2011; 18(12): 1045-52.

26. Hsu FL, Lai CW and Cheng JT. Antihyperglycemic effects of paeoniflorin and 8-debenzoylpaeoniflorin, glucosides from the root of Paeonia lactiflora. Planta medica. 1997; 63(04): 323-5.

27. Sancho RA and Pastore GM. Evaluation of the effects of anthocyanins in type 2 diabetes. Food Research International. 2012; 46(1): 378-86.

28. Jung M et. al. Antidiabetic agents from medicinal plants. Current medicinal chemistry. 2006; 13(10): 1203-18.

Received on 10.02.2019 Modified on 11.03.2019

Research J. Pharm. and Tech. 2019; 12(7):3467-3470.

DOI: 10.5958/0974-360X.2019.00587.0