1. Introduction

The combat against diabetes mellitus must be made a matter of top priority by all due to the continual increase in the global prevalence of this social ill. Globally the prevalence was estimated to increase in year 2000 to 2010 from 14.2 million to 17.5 million in North America, 15.6 million to 22.5 million in South America, 26.5 million to 32.9 million in Europe, 9.4 million to 14.1 million in Africa, 84.5 million to 132.2 million in Asia and 1.0 million to 1.3 million in Australia giving a total global increase in prevalence from 151 million people in 2000 to 221 million people in 2010 ^[1]. This was projected to 324 million by 2025 ^[2] and 366 million 2030 ^[3]. In 2013, 382 million people had diabetes mellitus worldwide and this is expected to rise to 592 million by 2035 ^[4]. This shows clearly that the prevalence is increasing more than it was projected or expected hence, the need to overcome this disease cannot be over emphasized.

Spices are food adjunct commonly added to food to improve the sensory properties but many spices have been observed to exert medicinal effects. Some spices which have been reported to exert hypoglycemic effect both in laboratory animals and human subjects are: Fenugreek seeds (Trigonella foenumgraecum), garlic (Allium sativum), Onion (Allium cepa), turmeric (Curcuma longa), cumin seeds (Curminum cyminum), ginger (Zingiber officinale), mustard (Brassica nigra), curry leaves (Murraya koenigi) and coriander (Coriandum sativum) ^[5].

Ginger is a perennial plant with narrow, bright green, grass-like leaves. It is cultivated in the tropics for its edible rhizomes and has been found to be useful for both culinary and medicinal purposes ^{[6, 7]}. For culinary purposes ginger is suitable for all dishes both sweet (such as drinks, puddings, apple pie, cakes, breads, candies etc) and savory (such as soups, sauces, stews, savory puddings, grills, roasts, etc). Similarly, the medicinal uses of ginger are enormous. The spice had been reported to exert anti microbial, anti nausea ^[8], anti pyretic ^[9] analgesic, anti-inflammatory, hypoglycemic ^{[10, 11]} anti ulcer, antiemetic, ^[12] cardio tonic, anti-hypertensive ^[13], hypolipidemic ^[14], anti-platelet aggregation ^[15] effects in both laboratory animals and human subjects.

Several studies have reported the hypoglycemic effect of different forms of ginger in both animals and human subjects. Among the fairly recent reports are: Arablou et al., ^[16] used ginger powder in Type 2 diabetic patients; Mozaffari-Khosravi et al., ^[17] used ginger powder in diabetic patients; Son et al., ^[18] used 6-gingerol isolated from ginger in obese diabetic mice; Mahluji et al., ^[19] used ginger powder in diabetic patients; Sukalingam et al., ^[20] used 6-gingerol in STZ-induced diabetic rats; Abdulrazaq et al., ^[21] used aqueous ginger extract STZ-induced diabetic rats; while Jafri et al., ^[22] used aqueous extract in alloxan-induced diabetic rats. Very limited studies have reported the hypoglycemic effect of ginger juice while there is abject scarcity of scientific findings on hypoglycemic effect of cooked ginger extract. which is highly needed since the spice is mostly consumed in cooked forms in various cuisines. Hence, the objective of this study is to determine the hypoglycemic effect of raw and cooked ginger juice in normal and STZ-induced diabetic rats.

2. Materials and Method.

Fresh ginger rhizomes (Zingiber officinale Roscoe) w as purchased from Bodija market in Ibadan, Nigeria The raw extract was prepared according to the method used by Elshater et al., ^[23] with slight modification. Ginger rhizomes was washed, weighed, peeled, weighed and wet-milled using plate attrition mill (Amuda Plate mill, India). The smooth paste (without addition of water) was sieved using cheese cloth the raw extract was stored in plastic jars at 2C until use.

Cooked ginger was prepared by boiling the raw ginger extract for 1 hour on the medium burner of a 3-burner Haier Thermocool gas cooker, India. This was allowed to cool and stored in a plastic jar at 2C until use.

Male albino rats (70) of weight range 140-170 g were purchased from the Experimental Animals Unit of the Department of Veterinary Physiology, University of Ibadan, Ibadan, Nigeria. These were acclimatized for two weeks and were fed rats pellets and tap water ad libitum.. These were grouped according to weight in seven plastic cages with 10 rats in each group. The animals were treated in accordance with the study protocol as approved by the University of Ibadan/ University College Hospital Ethical Review Committee (Number- NHREC/05/01/2008a).

The seven groups of rats were designated thus: NT1S- normal control group, NT1R- normal rats given raw ginger extract (daily single oral dose-4 ml/kg body weight for 4 weeks), NT1Co- normal rats given cooked ginger extract, T1S- diabetic control group, T1R- diabetic rats given raw ginger extract, T1Co- diabetic rats given cooked ginger extract and T1D- diabetic rats given glibenclamide (5 mg/kg body weight), The control groups were given distilled water instead of ginger extract.

Diabetes was induced by intra peritoneal injection of streptozotocin (Sigma Aldrich, Germany) at 60 mg/kg body weight as used by Al-Amin et al, ^[14] and fasting blood glucose (FBG) was monitored until stable hyperglycemia was confirmed using the Glucometer.

Blood samples were taken from overnight fasted rats via the tail end before and after diabetes induction and at the end of the 2^nd and 4^th week of ginger extracts administration. The FBG was measured using ACCUCHEK Active Glucometer, Roche, Germany. The animals were sacrificed after experimentation by cervical dislocation.

Analysis of Variance was used to compare the groups of data while Least Significant Difference was used to compare mean values of one group and another (p< 0.05).

3. Results and Discussion

Raw and cooked ginger extracts reduced FBG in normal rats to 72.92 and 74.71% respectively at the end of 4 weeks extracts administration. This reduction observed at 2 weeks was similar to these, hence ginger consumption by normal rats may not reduced FBG beyond these values (Table 1) and may predispose the animals to undesired hypoglycemia since the long and short term consumption produced similar reduction effects.

Table 1. Effect of ginger extracts on FBG in normal and STZ-induced diabetic rats

Download as

PowerPoint Slide

Larger image(png format)

Tables index

Veiw figure

View current table in a new window

B FGB- FBG before the induction of diabetes.

S FBG- FBG after the induction of diabetes before extracts administration.

2 FBG- FBG at the end of 2 weeks ginger extracts administration

4 FBG- FBG at the end of 4 weeks ginger extracts administration.

There was no significant difference (p, 0.05) in the FBG values between all the groups before the induction of diabetes. After diabetes induction the values in the normal groups were similar and significantly different from that of the diabetic groups (p< 0.05). This shows clearly that intra peritoneal injection of streptozotocin at 60 mg/kg body weight increased the FBG by 334% as can be inferred from Table 1 which satisfied a diabetic state in the rat species (FBG≥ 170 mg/dl -).

Both extracts lowered FBG in normal and diabetic rats significantly (p<0.05) by 25 and 55% respectively but glibenclamide lowered it more (57%) in diabetic rats at the end of 2 weeks oral administration. The FBG was similar in the 2 different groups (normal and diabetic) that were given the extracts..

At 4 weeks extracts administration there was no significant difference (p<0.05) in FBG in normal control group and the diabetic groups that were given extracts and the anti diabetic drug. This shows that the ginger extracts were as effective as the drug in normalizing blood glucose in diabetic rats and this may also be the effect if applied to human subjects. This report differs from that of Elshater et al. ^[23] who reported a reduction in fasting blood glucose from 370 mg/dl in diabetic control group to 240 mg/dl in diabetic rats given raw ginger extract (4 ml/kg body weight) for 6 weeks in alloxan-induced diabetic rats while the FBG of the normal group was 120 mg/dl. The low effectiveness of the same dose of this extract may be as a result of variation in the drugs used for diabetes induction

More still it can be deduced that heat at cooking temperature did not de activate or affect the active hypoglycemic component in ginger (gingerol). There was no significant difference between the normal groups that were given the extracts at the end of 2^nd and 4th weeks hence it is possible that the FBG may not reduce lower than these values even at longer term consumption of the spice nevertheless more study is recommended in this area.

4. Conclusion and Recommendation

Ginger extracts, both raw and cooked, reduced fasting blood glucose to normal as effectively as the anti diabetic drug, glibenclamide, hence, the consumption of this spice in both raw (ginger drink) and cooked forms (stews, soups, sauces, sweet and savory puddings, grills, roasts etc) in different cuisines may be a very effective cheap and easy way of combating this disease globally towards the achievement of the 6^th Millennium Development Goal. The hypoglycemic component in ginger is heat labile and could withstand cooking temperature without losing its activity. More still the consumption of ginger by normal subjects may not predispose the body to hypoglycemia with increase in time of consumption because the fasting blood glucose remained constant after medium and long term consumption of the spice in rats. It is good a point to note here that ginger is safe for consumption by all and should be included in the diet management regimen for diabetics to improve their quality of life at very little cost.

Acknowledgment

We jointly appreciate the financial support of the Oyo State Scholarship Board under the leadership of the state governor, Senator Isiak Abiola Ajimobi, without which this study would not have had a timely commencement as well as the financial support of the management of the Institute of Agricultural Research and Training, Apata, Ibadan without which this research would not have had a timely completion.

References

[1]	Amos A., McCarty D. and Zimmet P. (1997). The rising global burden of diabetes and its complications: estimates and projections to the year 2010. Diabetic Med. ;14: S1-S85
	In article		CrossRef
[2]	Zimmet P., Shaw J and Albert K.G. (2003). Preventing Type 2 diabetes and the dysmetabolic syndrome in the real world: a realistic review. Diabet. Med.; 20: 693-702
	In article		CrossRef
[3]	Wild S., Roglic G., Green A., Sicree R and King H. (2004). Global prevalence of diabetes: Estimates for the year 2000 and projections for 2030. Diabetes Care; 27 (5): 1047-1053.
	In article		CrossRef
[4]	Guariguata L., Whiting D.R., Humbleton I., Beagley J.,Linnenkamp U and Shaw J.E. (2014). Global estimates of diabetes prevalence for 2013 and projections for 2035. Diabetes Research and Clinical Practice; 103 (2): 137-149.
	In article		CrossRef
[5]	Srinivasan K. (2005). Plant foods in the management of diabetes mellitus: Spices as beneficial anti diabetic food adjunct. International Journal of Food Science and Nutrition; 56 (6): 399-414.
	In article		CrossRef
[6]	Grant K.I. (2000). Ginger. Am. J. Health Sys. Pharm.; 57: 945-957.
	In article
[7]	Ursell A. (2000). The complete guide to healing foods: pp 112-114, Dorling Kindersley Ltd, London.
	In article
[8]	Portnoi G., Chng L.A., Karimi-Tabesh L., Koren G., Tan M.P. and Einarson A. (2003). Prospective comparative study of the safety and effectiveness of ginger for the treatment of nausea and vomiting in pregnancy. Am J. Obstet. Gynaecol.; 189: 1374-1377.
	In article		CrossRef
[9]	Suekawa M., Ishige A., Yuansa K., Sudo K., Aburada M. and Hosoya E. (1984). Pharmacological studies on ginger- Pharmacological actions of pungent constituents of 6-gingerol and 6-shogaol. J. Pharmacoblodyn; 7: 836-848.
	In article		CrossRef
[10]	Ojewole J.A.O. (2006). Analgesic, anti-inflammatory and hypoglycemic effects of ethanol extract of Zingiber officinale (Roscoe) rhizomes in mice and rats. Phytotherapy Research; 20: 764-772.
	In article		CrossRef
[11]	Young H.V., Luo Y.L., Chang H.Y., HaiehW.C. Liao J.C. and Peng W.C. (2005). Analgesic and anti-inflammatory activities of 6-gingerol. J. Ethnopharmacol.; 96: 207-210.
	In article		CrossRef
[12]	Mascolo N., Jain R.Jain S.C. and Capasso F. (1989). Ethno pharmacologic investigation of ginger (Zingiber officinale). J. Ethnopharmacol.; 27: 129-140.
	In article		CrossRef
[13]	Ghayur M.N. and Gilani A.H. (2005). Ginger lowers blood pressure through blockade of voltage-dependent calcium channels. J. Cardiosvasc. Pharmacol. 45: 74-80.
	In article		CrossRef
[14]	Al-Amin Z.M., Thomson M., Al-Qattan K.K., Peltonen-Shalaby R., and Ali M. (2006). Anti diabetic and hypoglycemic properties of ginger (Zingiber officinale) in streptozotocin-induced diabetic rats. British Journal of Nutrition; 96: 660-666.
	In article		CrossRef
[15]	Bordia A.,Verma S.K. and Srivastava K.C. (1997). Effect of ginger (Zingiber officinale Rosc.) and fenugreek (Trigonella foenumgraecum L.) on blood lipids, blood sugar and platelet aggregation in patients with coronary artery disease. Prostaglandins Leukotrienes and Essential fatty acids; 56 (5): 379-384.
	In article		CrossRef
[16]	Arablou T., Aryaeian N., Valizadeh M., Shariffi F., Hosseini A and Djalali M. (2014). The effect of ginger consumption on glycemic status, lipid profile and some inflammatory markers in patients with Type 2 diabetes mellitus. International Journal of Food Sciences and Nutrition; 65 (4): 515-520.
	In article		CrossRef
[17]	Mozaffari-Khosravi H., Talaei B., Jalali B-A., Najarzadeh A and Mozayan M.R. (2014). The effect of ginger powder supplementation on insulin resistance and glycemic indices in patients with Type 2 diabetes: A randomized double-blind placebo-controlled trial. Complementary Therapies in Medicine; 22 (1): 9-16.
	In article		CrossRef
[18]	Son M.J., Miura Y and Kazum Y. (2014). Mechanism of anti diabetic effect of gingerol in cultured cultured cells and obese diabetic model mice. Cytotechnology.
	In article		CrossRef
[19]	Mahluji S., Attari V.E., Mabassori M., Payahoo L., Ostadrahimi A and Golzari S.E.J. (2013). Effect of ginger (Zingiber officinale) on plasma glucose level, HbA1c and insulin sensitivity in type 2 diabetic patients. International Journal of Food Sciences and Nutrition; 64 (6): 682-686.
	In article		CrossRef
[20]	Sukalingam K., Ganesan K. and Gani S.B. (2013). Hypoglycemic effect of 6-gingerol, an active principle of ginger in streptozotocin-induced diabetic rats. Journal of Pharmacology and Toxicological Studies; 1 (2): 23-30.
	In article
[21]	Abdulrazaq N.B., Cho M.M., Win N.N., Zaman R. and Rahman M.T. (2012). Beneficial effects of ginger (Zingiber officinale) on carbohydrate metabolism in streptozotocin-induced diabetic rats. British Journal of Nutrition; 108 (7): 1194-1201.
	In article		CrossRef
[22]	Jafri S.A., Abass S. and Qasim M. (2011). Hypoglycemic effect of Ginger (Zingiber officinale) in alloxan-induced diabetic rats (Rattus norvagicus). Pakistan Veterinary Journal; 31 (2): 160-162.
	In article
[23]	Elshater A.A., Salman M.M.A and Moussa M.M.A. (2009) Effect of Ginger extract consumption on levels of blood glucose, lipid profile and kidney functions in alloxan-induced diabetic rats. Egypt Acad. J. Biol. Sci.; 2 (1): 153-162.
	In article