Indian Journal of Pharmacology Medknow Publications on behalf of Indian Pharmacological Society ISSN: 0253-7613 EISSN: 1998-3751 Vol. 36, Num. 3, 2004, pp. 163-166

Indian Journal of Pharmacology, Vol. 36, No. 3, June, 2004, pp. 163-166

Research Paper

Cardiac stimulant activity of Ocimum basilicum Linn. extracts

Muralidharan A, Dhananjayan R

Department of Environmental Toxicology, Dr. ALM PG Institute of Basic Medical Sciences, Taramani, Chennai - 600 113
Correspondence Address:Department of Environmental Toxicology, Dr. ALM PG Institute of Basic Medical Sciences, Taramani, Chennai - 600 113 rdhananjayan@hotmail.com

Code Number: ph04055

ABSTRACT

INTRODUCTION

Ocimum basilicum Linn. (Labiatae), popularly known as "Sweet Basil" is used in both Ayurvedic and Unani systems of Medicine.[1] It is a small perennial, tropically growing shrub of Asian origin.[2] It has antipyretic, antiemetic, diuretic and cardiotonic[3] properties.

Despite continuing advances in understanding the basic pharmacology of cardiac glycosides, digitalis intoxication remains a common clinical problem. It necessitates research for new nature based drugs which increase cardiac muscle contractility with a broad therapeutic index. As a part of the screening for a suitable natural drug we have chosen Ocimum basilicum Linn. and evaluated its cardio active potential and its mechanism of action.

MATERIAL AND METHODS

Drugs
Adrenaline, digoxin, propranolol and nifedipine. (Sigma Chemical Co, St.Louis, MI, USA).

Animals
Frogs of Rana hexadactyla species maintained in the animal house and male Wistar albino rats (150 to 200 g) housed in cages at 270 ± 2°C on a 12 h light / dark cycle were used for the studies. The animals were fed with food and water ad libitum. The animals were maintained as per the norms of CPCSEA and the experiments were cleared by CPCSEA and the local ethics committee.

Frog heart in situ preparation
Frogs were pithed and the heart exposed. The inferior vena cava was cannulated for perfusing the heart with the frog′s Ringer solution.[4] (The composition of the frog Ringer solution in millimoles: NaCl-110; KCl-1.9; CaCl₂-1.1; NaHCO₃-2.4; NaH₂PO₄-0.06; Glucose-11.1). The basal cardiac contraction was recorded on a smoked kymographic drum after the administration of frog Ringer′s solution and gum-acacia (5%). The administration of gum acacia was done to see that it did not contribute to the effects of TAE. The drugs and extracts were administered through the cannula. The average basal heart rate and the contraction amplitude were 70 beats/min and 18 mm respectively. The effects obtained with the drugs and extracts were transposed to the respective percentage of the basal values. Graded dose-response was recorded for each extract (0.5, 1 and 1.5 mg) and the dose which caused the maximum effect was chosen as the experimental dose. The frog heart was washed with the Ringer solution after every administration of extracts and drugs till it was brought back to the normal state.

The frog heart was perfused with propranolol, a β-adrenergic blocker at 3 X 10^-5 M concentration in frog Ringer solution for 60 seconds followed by the administration of extracts and the recording were noted. Nifedipine, a calcium-channel blocker at 2.88 X 10^-5M concentration in frog Ringer solution was administered for 60 seconds followed by extracts and the recordings were noted.

Biochemical studies
Wistar albino rats were divided into 3 groups of 6 animals each. Group I received with 5% gum acacia suspension which served as control; Group II and Group III were treated with TAE and TAQ at a dose of 100 mg/kg (approximately 1/10 of the LD₅₀) body weight i.p. for 7 days. On the 8th day the animals were sacrificed and the blood and heart-tissue were collected and the serum was separated from the blood. The heart was washed in ice-cold saline and about 100 mg of tissue was weighed and homogenized in chilled 0.1 M Tris-HCl Buffer in Patter-Elvejhem teflon homogenizer. The serum and homogenized samples were assayed for clinical marker enzymes like CPK,[5] LDH[6] and transaminases AST and ALT.[7] Heart homogenate samples were also assayed for Na²⁺ K²⁺ATPase,[8] Ca²⁺ATPase [9] and Mg²⁺ATPase.[10]

Statistical analysis
The frog heart in situ experiment and biochemical parameters obtained were subjected to one-way ANOVA followed by Tukey′s multiple comparison test. P value < 0.05 was considered significant.

RESULTS

Total alcoholic extract (TAE) produced significant positive ionotropic and negative chronotropic actions similar to that of digoxin on frog heart. This cardiotonic action was not antagonized by propranolol [Table - 1]. Nifedipine pretreatment significantly reduced the cardiotonic activity of the extracts. There was a significant decrease in membranous Na²⁺ K²⁺ATPase, and Mg²⁺ATPase and an increase in Ca²⁺ATPase [Figure - 1]. Total aqueous extract produced a significant increase in the force of contraction as reflected by an increase in the amplitude and heart rate. Both propranolol and nifedipine antagonized the effect of the extract TAQ [Table - 1]. No significant change was observed in Na²⁺ K²⁺ATPase, Mg²⁺ATPase and Ca²⁺ATPase of the heart [Figure - 1].

Both the TAE and TAQ did not produce any significant changes in the levels of AST, ALT, LDH and CPK in heart and in serum samples when compared with the control animals [Table - 2].

DISCUSSION

Cardiac glycosides and catecholamines have been used as the main therapeutic drugs in the treatment of congestive cardiac failure.[11] However, the dangers of cardiac glycoside intoxication are well documented[12] and doubts have been expressed about their long-term effectiveness. The use of catecholamines is limited by their insufficient differentiation between positive ionotropic and chronotropic actions, their potential arrhythmogenic properties and tachyphylaxis due to receptor down-regulation.[11]

Total alcoholic extract elicited a powerful cardiotonic effect, which was characterized by positive ionotropic and negative chronotropic actions. This effect was not significantly blocked by propranolol whereas nifedipine, the calcium channel blocker antagonized the effect significantly.

The cardiac enzyme profile indicates that TAE exhibited cardiotonic like activity which manifested as a result of general decrease in the activity of Na²⁺ K²⁺ATPase, and Mg²⁺ATPase and an increase in Ca²⁺ATPase. This inhibition of Na²⁺ K²⁺ATPase is similar to the action of cardiac glycosides.[13] Cardiac glycosides are specific and unique inhibitors of Na²⁺ K²⁺ATPase at normal concentrations (10^-8 to 10^-9M).[14]

Na²⁺ K²⁺ATPase inhibition by cardiac glycosides leads ultimately to increase intracellular Ca²⁺concentrations through Na²⁺/ Ca²⁺exchange and an associated increase in slow inward Ca²⁺current[16] as well as in transient Ca²⁺current[15]. Ca²⁺induced Ca²⁺release is a general mechanism that most cells use to amplify Ca²⁺ signals.[16] In heart cells, this mechanism is operated between voltage-gated L-type calcium channels (LCCs) in the plasma membrane and calcium release channel, commonly known as ryanodine receptors in the sarcoplasmic reticulum.[17] Nifedipine is a LCC antagonist.[16] Since nifedipine, blocks the cardiotonic action of TAE significantly, the extract might have produced its action by opening the voltage sensitive slow Ca²⁺channel. In connection with the cardiotonic effects observed one could see a relationship that exists between the inhibitory levels of the activities of Mg²⁺ATPase and Na²⁺ K²⁺ATPase.[18] The significant rise in the level of activity of Ca²⁺ATPase might be due to the rise of cytosolic Ca²⁺.[19]

The total aqueous extract (TAQ) produced positive chronotropic and ionotropic effects similar to that of adrenaline by stimulating the β-adrenergic receptors.

REFERENCES

1.	Jain ML, Jain SR. Therapeutic utility of Ocimum basilicum Linn. VAR Album. Planta Med 1988;54:66-70.  Back to cited text no. 1
2.	Dhar AK. Sweet Basil: Ocimum basilicum- a review. Journal of Medicinal and Aromatic Plant Sciences 2002;24:738-55.   Back to cited text no. 2
3.	Warrier PK, Nambiar VPK, Ramankutty C. Indian Medicinal Plants. Orient Longman 1995;3:162-3.  Back to cited text no. 3
4.	Burn JH. Practical pharmacology blackwell. Scientific Publications; 1952. p. 1-7.  Back to cited text no. 4
5.	Okinaka S, Kumagi H, Ebashi S, Sugita H, Momoi H, Toyokura Y, et al. Serum creatine phosphokinase. Activity in progressive muscular dystrophy and neuromuscular diseases. Arch Neurol 1961;4:520-5.  Back to cited text no. 5
6.	King J. The dehydrogenases or oxidoreductases. Lactate dehydrogenase In: Practical Clinical Enzymology. London: Van Nostrand, D.Company Ltd; 1965.  Back to cited text no. 6
7.	King J. The Transferases -alanine and aspartate transaminases In: Practical Clinical Enzymology. London: Van Nostrand, D.Company Ltd; 1965.  Back to cited text no. 7
8.	Bonting SL. Sodium-potassium activated adenosine triphosphatase and cation transport In: Bittar EE, editor. Membrane and ion transport. London: Wiley-Interscience; 1970.  Back to cited text no. 8
9.	Hjerten S, Pan H. Purification and characterization of two forms of low affinity Ca2+ATPase from erythrocyte membranes. Biochem Biophys Acta 1983;728: 281-8.  Back to cited text no. 9  [PUBMED]
10.	Ohinishi T, Suzuki T, Suzuki Y, Ozawa K. Comparative study of plasma membrane Mg2+ATPase activities in normal, regenerating and malignant cells. Biochem Biophys Acta 1982;684:67-74.  Back to cited text no. 10
11.	Kitada Y, Narimatsu A, Suzuki R, Endoh M, Taira N. Does the positive ionotropic action of a novel cardiotonic agent, MCI-154, involve mechanisms other than cyclic AMP? J Pharmacol Exp Ther 1987;243:639-45.  Back to cited text no. 11  [PUBMED]
12.	Beller GA, Smith TW, Abelmann WH, Haber E, Hood WB Jr. Digitalis intoxication. A prospective clinical study with serum level correlations. N Engl J Med 1971;284:989-97.  Back to cited text no. 12  [PUBMED]
13.	Akera T, Brody TM. The role of Na+ K+ATPase in the ionotropic action of digitalis. Pharmacol Rev 1977;29:187-220.  Back to cited text no. 13  [PUBMED]
14.	Goto A, Yamada K, Yagi N, Yoshioka M, Sugimoto T. Physiology and pharmacology of endogenous digitalis-like factors. Pharmacol Rev 1992;44:377-99.  Back to cited text no. 14  [PUBMED]
15.	McGarry SJ, Williams AJ. Digoxin activates sarcoplasmic reticulum Ca2+ release channels: a possible role in cardiac ionotropy. Br J Pharmacol 1993;108: 1043-50.   Back to cited text no. 15  [PUBMED]
16.	Wang SQ, Song LS, Lakatta EG, Cheng H. Ca2+ signaling between single L-type Ca2+ channels and rynodine receptors in heart cells. Nature 2001;410:592-6.  Back to cited text no. 16  [PUBMED]  [FULLTEXT]
17.	Fabiato A. Time and calcium dependence of activation and inactivation of calcium-induced release of calcium from the sarcoplasmic reticulum of a skinned canine cardiac Purkinjee cell. J Gen Physiol 1985;85:247-89.  Back to cited text no. 17  [PUBMED]  [FULLTEXT]
18.	Chen CL, Sangiah S, Patterson E, Berlin KD, Garrison GL, Dunn W, et al. Effects of BRB-I-28, a novel antiarrhythmic agent, and its derivatives on cardiac Na+ K+ATPase, Mg2+ATPase activities and contractile force. Res Commu Chem Pathol Pharmacol 1992;78:3-16.  Back to cited text no. 18
19.	Kelly RA, Smith TW. Pharmacological treatment of Heart failure. In: Goodman, Gillman, editors. The pharmacological basis of therapeutics. 9th ed. McGraw-Hill; 1996. Chapter 34. p. 811.  Back to cited text no. 19

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