Online - 2455-3891 Vol 10, Issue 5, 2017 Print - 0974-2441 Research Article ELICITATION OF TRIGONELLINE, A HYPOGLYCEMIC AGENT IN FENUGREEK SPROUTS BY CALCIUM AND NITRIC OXIDE PRIMING GUPTA SK1, NANDA AK2, GHOSH R2, MANDAL P1* 1Department of Botany, Plant Physiology and Pharmacognosy Research Laboratory, University of North Bengal, Siliguri, West Bengal, India. 2Department of Chemistry, University of North Bengal, Siliguri, West Bengal, India. Email: [email protected] Received: 03 January 2016, Revised and Accepted: 09 February 2017 ABSTRACT Objective: This work was performed to evaluate the effect of priming with exogenous sources of calcium ion and nitric oxide on the antidiabetic activity and the alkaloid contents of fenugreek sprouts along with isolation and identification of trigonelline, a bioactive alkaloid responsible for hypoglycemic property of fenugreek. Methods: The fenugreek seeds were pre-treated with calcium chloride (CC), lanthanum chloride (LC) a calcium channel blocker; ethylene glycol-bis (2-aminoethylether) -N, N, N´, N tetra acetic acid (EG) a calcium chelator; sodium nitroprusside (SNP) and 2-(4-carboxyphenyl) -4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CP) a nitric oxide scavenger and germinated for 72 hrs. The sprout extracts were evaluated for their in vitro was isolated from fenugreek sprouts and identified by Infrared analysis and nuclear magnetic resonance (NMR) spectroscopy. antidiabetic potential by α-amylase and α-glucosidase inhibition along with their trigonelline content. Trigonelline Results: The results revealed that sprouts pre-treated with CC and SNP exhibited enhanced antidiabetic potential as well as alkaloid content over control; on the other hand, their action was reversed by their antagonists, EG, LC, and CP. The sprouts pre-treated with 2mM CC showed the best elicitation of alkaloid content and antidiabetic activity followed by SNP-20 mM. Conclusions: The study suggests probable involvement of the signaling molecules, calcium ion, and nitric oxide in pathways associated with biosynthesis of bioactive compounds responsible for hypoglycemic activity of fenugreek sprouts one of which being trigonelline. Keywords: Antidiabetic, Calcium, Fenugreek sprouts, Nitric oxide, Priming, Trigonelline, Nuclear magnetic resonance. © 2017 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4. 0/) DOI: http://dx.doi.org/10.22159/ajpcr.2017.v10i4.16910 INTRODUCTION exhibit adverse side effects after long term use [8-10]. To prevent or overcome the side effects of these synthetic drugs and also to create Plants are the basic source of knowledge of modern medicine. Almost other safer alternative drug choices, it has become essential to seek all the parts of a plant, namely leaves, flowers, fruits, bark, roots, stem, other inhibitors for further drug development. Thus, in recent years, and seeds are known to have various medicinal properties [1]. The several efforts have been made for increasing the availability of trend of using natural products has increased, and the active plant glucosidase inhibitors from natural sources [11,12]. extracts are frequently screened for new drug discoveries and for the presence of potential bioactive components [2,3]. Likewise, fenugreek besides having several pharmacological properties it is also reported to possess potent antidiabetic India with the highest number of people suffering from diabetic property both and system. Fenugreek is known disorders has been considered as the diabetic capital of the world in vitro in vivo to be a rich source of various bioactive components having a by the “International Journal of Diabetes in Developing Countries.” There is an alarming rise in diabetes patients in India; approximately different therapeutical property such as sapogenins, fenugreekine, 3.4 million deaths occur due to complication related to high blood nicotinic acid, phytic acid, and trigonelline [13,14]. Trigonelline is a sugar [4]. pyridine alkaloid known to be mostly found in Fabaceae members and is reported to be metabolically active as a hypocholesterolemic Diabetes mellitus is a serious metabolic disorder that leads to agent along with potential hypoglycemic effect [15-18]. Fenugreek hyperglycemic condition due to decreased insulin production has been successfully implemented as antidiabetic remedy for both or inefficient insulin utilization. It is usually characterized by types I and II diabetes [19]. Moreover, fenugreek has been reported hyperglycemia, lipoprotein abnormalities, high basal metabolic rate, to be enriched with wide spectrum of pharmacological and folkloric impairment in the activity of important enzymes, and oxidative stress significance [20]. which damages the pancreatic beta cells. It is the most common endocrine disorder which disrupts glucose homeostasis causing This study deals with the isolation and identification of trigonelline severe diabetic associated complications in major organs such as eye, by 1-D and 2-D nuclear magnetic resonance (NMR) from fenugreek blood vessels, and brain [5,6]. Multiple risk factors responsible for sprouts. Further, the elicitors of calcium and nitric oxide were applied the disease to occur include persistent stress and depression, obesity, for the enhancement in the alkaloid content of fenugreek sprouts environmental pollutants, and sedentary lifestyle [7]. along with the in vitro antidiabetic property. This study may provide an insight in the role of these signaling molecules in modulating the Some of the synthetic antidiabetic components such as metformin, biosynthesis of alkaloids, a potential hypoglycemic agent; in addition, acarbose, biguanides, and voglibose are found to be used clinically in the utility of 2-D NMR spectroscopy in identification of bioactive combination with another diet to control diabetes, but moreover, they compounds. Gupta et al. Asian J Pharm Clin Res, Vol 10, Issue 5, 2017, 120-125 METHODS required to inhibit 50% of AG activity under the assay conditions is defined as the concentration inhibition 50% (IC ) value. Priming and sprouting 50 The fenugreek seeds were surface sterilized with 0.1% sodium Total alkaloid estimation hypochlorite solution. After sterilization, the seeds were washed thrice The extract was gently heated, and methanol was evaporated on a with distilled water and subjected to priming with the solutions of rotary evaporator under vacuum at a temperature of 45°C to dryness. calcium chloride (CC), an exogenous source of calcium ion; a calcium The residue was dissolved in 2 N HCl and then filtered. 1 ml of this chelator: Ethylene glycol-bis (2-aminoethylether)-N,N,N´,N, tetra solution was transferred to a separation funnel and washed with 10 ml acetic acid (EG); a calcium channel blocker: Lanthanum chloride (LC); chloroform (3 times). The pH of this solution was adjusted to neutral sodium nitroprusside (SNP) as an exogenous source of nitric oxide and with 0.1 N NaOH. Then, 5 ml of Bromocresol Green solution and 5 ml 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide of phosphate buffer were added to this solution. The mixture was (CP), a nitric oxide scavenger. The priming agents applied in various shaken and the complex formed was extracted with 5 ml chloroform combinations are given in Table 1. For control set, seeds were primed by vigorous shaking. The extracts were collected in a 10 ml volumetric with normal water and kept in a rotary shaker along with the treated flask and diluted to the same volume with chloroform. The absorbance seeds. After priming for 24 hrs, the seeds were again washed thrice of the complex in chloroform was measured at 470 nm against with sterile water and kept in the seed germinator for germination for blank [23]. Similarly, trigonelline content was also estimated from the 72 hrs. purified extract. Determination of antidiabetic property by in vitro method Isolation of trigonelline Preparation of extract The extraction procedure was followed as suggested by Ahmed The fenugreek sprouts of three different stages: 24 hrs, 48 hrs, and et al. [24] with some modifications. The fenugreek sprouts of about 72 hrs were crushed in mortar-pestle and individually processed 100 g were homogenized in 10 M HCl solution and gently boiled through Soxhlet extraction apparatus with methanol for 8 hrs duration. for 2 hrs in an Erlenmeyer flask. Next, the mixture was filtered, and The refluxed samples were separated from the residues by filtering zinc dust was added to the mixture and kept on a magnetic stirrer through Whatman No. 1 filter paper, and the extract was concentrated for overnight. In next morning, the mixture was filtered again and to a uniform concentration of 1 g/ml using a vacuum rotary evaporator extracted with equal volume of dichloromethane (CH2Cl2). The CH2Cl2 at 50°C. The obtained methanolic extracts were further used for layer containing the alkaloid was separated and later evaporated. experimental analysis for determination of antidiabetic activity and The obtained extract after CH2Cl2 evaporation was reconstituted in total alkaloid estimation. methanol for further analysis. Inhibition of α-amylase (AA) enzyme activity Thin layer chromatography (TLC) The AA inhibition potential of the extract was estimated by standard The extract dissolved in methanol was applied manually on spectrophotometric method [21]. 0.5 ml of aqueous extract was reacted activated TLC plates, along with standard trigonelline. After