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Spasmogenic and spasmolytic activity of rind of Punica granatum Linn
© The Author(s). 2017
Received: 11 February 2016
Accepted: 31 January 2017
Published: 7 February 2017
Rind of Punica granatum is traditionally used in treatment of abdominal cramps and various GIT disorders. So far spasmolytic activity of rind of Punica granatum has been reported using in vitro model. However, its mode of action is not explored yet. Therefore, the current work describes the possible mode of action for spasmolytic activity of methanolic extract of rind of Punica granatum (Pg. Cr). Acute toxicity study is also performed to determine its safe dose range.
Rind of Punica granatum was subjected to shade drying. Shade dried materials were pulverized using conventional grinder. Grinded materials were macerated in commercial grade methanol. The extract of rind of P. granatum was concentrated using a rotary evaporator. Rabbits’ jejunal preparations were mounted in organ bath containing 10 ml Tyrode’s solution, constantly aerated with carbogen gas. Pg. Cr was tested on spontaneous rabbits’ jejunal preparations in concentrations 0.01, 0.03, 0.1, 0.3, 1.0, 3.0, 5.0 and 10.0 mg/ml. Pg. Cr was also tested on KCl (80 mM)-induced contractions in rabbits’ jejunal preparations. Since we observed spasmogenic activity for the first time, hence we also determined the effects of Pg. Cr in presence of atropine (0.03 μM). Pg. Cr was also tested in presence of 0.03 μM of loratadine HCl. Pg. Cr was also tested on barium chloride induced contractions. Calcium Concentration Response Curves (CCRCs) were constructed in the absence and presence of test samples of Pg. Cr in decalcified tissues to explore its possible mode of action. Acute toxicity screening was also performed to determine its safe dose range.
Phytochemical screening revealed the presence of saponins, tannins, carbohydrates, proteins, flavonoids, saponins and steroids. However, Pg. Cr tested negative for alkaloids and triterpenoids. Pg. Cr was safe up to 100 mg/kg with its LD50 = 1305 mg/kg. Its respective EC50, in the absence and presence of atropine, were 9.7 ± 0.3 and 3.12 ± 0.45 mg/ml. In the presence of 0.02 and 0.08 μM of loratadine HCl, respective EC50 were 5.6 ± 0.4 and 2.8 ± 0.15 mg/ml. EC50 for relaxant effects on KCl-induced contractions was 8.6 ± 1 mg/ml. In the presence of 0.3 mg/ml of Pg. Cr, a right shift was observed with EC50 (log [Ca++]M) = -1.8 ± 0.09 vs. control EC50 -2.6 ± 0.01. Similarly, EC50 for verapamil (0.1 μM) was −2.4 ± 0.011vs. control EC50= -2.4 ± 0.01. The right shift of P. granatum resembled the right shift of verapamil suggesting for inhibition of voltage gated calcium channels.
P. granatum is safe up to 100 mg/kg. In low concentrations, P. granatum produced spasmogenic activity possibly through involvement of cholinergic and histaminergic receptors. The spasmolytic action may follow inhibition of the voltage gated calcium channels.
Herbal medicine contributes to revenue of 2.5 $US in countries like Japan, China, Pakistan, Sri Lanka and Thailand [1, 2]. In general perspective, medicines of plant origin are considered relatively safe . Plant kingdom is a rich source of bioactive molecules. For example morphine, strychnine, cinchonine, quinine and caffeine were first derived from plants . With the passage of time, chemists started synthesis of these molecules in laboratories. Cocaine was synthesized by Schiff in laboratory . According to a report of WHO, more than 50% of the world population depend on household remedies. Pharmacopoeia of the United States describes various phyto-medicines that are also used in Europe . This strengthen the practice of complementary and alternative medicine for the maintenance of health in developing countries .
P. granatum is a plant that is referenced in Holy Quran by name. It belongs to the order of Myrtales and family of Lythraceace. More than 500 cultivators throughout the world cultivate P. granatum . It is abundantly available in Himalayan regions and Kashmir. It grows at an altitude of 1000–2000 m in Northern built (South Waziristan, Khyber Pakhtun Khwa, Dir, Kurram, Chitral and Baluchistan) of Pakistan. It is used as medicine to treat obesity, arthritis and ischemia of brains . More, P. granatum has anti-oxidant, anticancer and anti-inflammatory activities .
Resistant strains of Bacteria like Staphylococcus aureus, Streptococcus epidermidis, Lactobacillus acidophilus and E.coli have shown excellent sensitivity to Punica granatum . It is also used for treatment of erectile dysfunctions . Beside oral antiseptic, it is also used to treat periodontitis and dental carries . P. granatum has anti-diabetic activity . P. granatum is also used in treatment of skin infections and injuries, where its role may be attributed to its antioxidant effect [9, 10, 12]. Reported phytochemicals of P. granatum are anthocyanins, ascorbic acid, caffeic acid, catechin, Epigallocatechingallate (EGCG), quercetin, sterols, punicic acid, ellagic acid, phenolic punicalagins and flavonoids . The juice of the seeds is rich in anthocyanins, ascorbic acid, EGCG and iron. The seed oil has 95% punicic acid, ellagic acid and sterols . The leaves are rich in tannins (punicalin and punicafolin) and flavones glycosides, which include apigenin and luteolin . The extract of leaves of P. granatum is used as eye washer, as astringent for diarrhea and dysentery . The rind (peel) is rich in phenolic punicalagins, EGCG, quercetin, rutin, flavones, flavonols, flavonones, anthocyanidins gallic acid and other fatty acids . There are reports that extract of dried rind (peel) of P. granatum is traditionally used in stomach ache and colitis. In Indian traditional system of medicine, P. granatum is used as an astringent, anthelmintic, diuretic and cardio tonic . As peels of P. granatum is used in treatment of in gut spasms, therefore, the current work is an attempt to explore its rationale on scientific ground. More, there are studies that warrant for search of possible rationale for use of P. granatum in gut disorders to elucidate its mode of action . Hence, we designed the current model to elucidate possible mode of action for spasmolytic activity of rind of P. granatum.
Collection, identification and preparation of the test materials
Fruits of P. granatum were purchased from the Board Bazar of Peshawar, Khyber Pakhtunkhawa. Professor Dr. Jehandar Shah identified the plant. A voucher specimen no. Pg-01 was submitted to the herbarium of Hakim Abdul Jalil Herbal Research Center, Khyber Medical University, Peshawar. Their fleshy seeds were removed. Its rind was collected and subjected to shade drying. We targeted the rind as it is locally used in the treatment of gastric disorders and diarrhea . It is called “anarsawe” in Pashtoo. The dried rind (1.5 kg) was powdered using a conventional grinder. The powdered materials were then soaked in commercial grade methanol (80%) for 5 days. After 5 days, the materials were filtered. The process was repeated thrice. The filtrates were combined and concentrated under vacuum using a rotary evaporator till a brownish semisolid extract, free of solvent (20 g), was obtained. The extract was refrigerated for further pharmacological screenings.
Preliminary phytochemical screenings
Acute toxicity study
Acute toxicity testing was performed using mice model. In first phase, Pg. Cr was administered in test doses of 10, 100 and 1000 mg/kg (i.p) to group 1, group 2 and group 3 respectively. Each group had six mice. In second phase, 3 more groups, having 6 six mice each, were treated with respective test doses of 1250, 1500 and 1750 mg/kg (i.p). Death toll was noted in each group. Per cent lethality was plotted against respective test doses. LD50 was calculated [17, 18].
Drugs, chemicals, animals and ethical approval
All chemicals were of analytical grade. Acetylcholine was purchased from Poole England. Rest of the chemicals was of E. Merck grade, Germany. Double distilled water was used in the experiments. All solutions were prepared on the same day of experiments. For acute toxicity study, Pg. Cr was re-dissolved in water for injection (B.P.). Rabbits of either sex (average weight = 2.2 ± 0.24 kg) were purchased from the local market. Rabbits were housed in the animal house of Institute of Basic Medical Sciences, Khyber Medical University, Peshawar. Ethics Board of the Khyber Medical University in its 3rd meeting under agenda item no. 5 approved the study protocols on dated 8th April 2013. The protocols complied with international standards for dealing experimental animals for Scientific Procedures.
Effects on Isolated rabbits’ jejunal preparations
On spontaneous rabbits’ jejunal preparations
Rabbits were subjected to cervical dislocation. Their abdomens were opened. Their jejunums were removed and maintained in Petri dishes containing Tyrode’s solution, constantly aerated with Carbogen gas (95% oxygen/5% carbon dioxide). Portions of about 1.5 cm length of rabbits’ jejunal preparations were mounted in tissue organ baths. The tissues were stabilized in normal Tyrode’s solution for about 30 min. Following stabilization, Pg. Cr was tested on isolated rabbits’ jejunal preparations in concentrations 0.01, 0.03, 0.1, 0.3, 1.0, 3.0, 5.0 and 10.0 mg/ml [19–24]. Changes in isometric tension were recorded using force transducers (model MLT0201) coupled with bridge amplifiers FE221 connected to PowerLab 26/T (ADInstruments, Sydney, Australia). Data was recorded using Lab Chart 7 software (ADInstruments, Sydney, Australia). Intestinal responses were plotted as % of control.
On spontaneous rabbits’ jejunal preparations in the presence of cholinergic antagonists (atropine) and histamine antagonist (loratadine)
Since Pg. Cr produced spasmogenic response in isolated rabbits’ jejunal preparations contrary to the study published by Qnais et al. . Hence, we tried to explain the possible mode of spasmogenic action. As intestine is richly supplied with cholinergic and histaminergic receptors, therefore, we tried Pg. Cr in similar concentrations 0.01, 0.03, 0.1, 0.3, 1.0, 3.0, 5.0 and 10.0 mg/ml in presence of cholinergic antagonist atropine (0. 03 μM) following an incubation period of 20-25 min . Pg. Cr was also tested in similar concentrations in presence of histamine H1 receptor antagonist loratadine HCl (0.02 and 0.08 μM) following an incubation period of 30 min. Intestinal responses were recorded using Lab Chart 7 Software.
Effects of Pg. Cr on KCl-induced contractions
As Pg. Cr showed relaxant effect in higher concentrations, hence we tried to determine its possible mode of relaxation. We tried Pg. Cr on KCl (80 mM) induced contractions. Briefly describing, small portions of the rabbits’ jejunal preparations were mounted in the organ baths. After stabilization, sustained contractions were produced by 80 mM KCl (final bath solution’s strength). Pg. Cr was applied in similar concentrations 0.01, 0.03, 0.1, 0.3, 1.0, 3.0, 5.0, 10.0 mg/ml. Intestinal responses were recorded .
Effect of Pg. Cr on barium chloride induced contractions
Sustained contractions in the rabbits’ jejunal preparations were produced by barium chloride (1.0 μM). Pg. Cr was added in similar concentrations 0.01, 0.03, 0.1, 0.3, 1.0, 3.0, 5.0, 10.0 mg/ml in cumulative manner. Effects were recorded .
Effects of verapamil of spontaneous and KCl-induced contractions
Rabbits’ jejunal preparations were mounted in tissue organ bath. After stabilizing the tissues for 30 min, verapamil (concentration range of 0.003–3 μM) was tested on spontaneous and KCl (80 mM)-induced contractions. Effects of test samples are compared with effects of verapamil as standard calcium channel blocker.
Effects of Pg. Cr on voltage gated calcium channels
As Pg. Cr produced a spasmolytic response; hence we constructed calcium chloride curves to study its effects possibly through voltage gated channels as relaxant effects on high molar (>60 mM) KCl induced contractions usually, but not necessarily, imply to follow inhibition of voltage gated calcium channels. Hence, for confirmation, we compared the effects of Pg. Cr on calcium channels with the control Calcium Concentration Response Curves (CCRCs) using verapamil a standard calcium channel blocker.
For construction of CCRCs, the tissues were decalcified with the Potassium Normal Tyrode’s Solution (containing EDTA 0.03 g), followed by Potassium Rich Tyrode’s solution (containing K: 3.72 g and EDTA: 0.37 g). Once decalcified, known strengths of calcium were added and constructed the CCRCs. Curves were constructed in range of - 4 to - 1.6 log [Ca++] M.
In other series of experiments, tissues were stabilized in Tyrode’s solution for 30 min. The tissues were decalcified as described above. Pg. Cr was applied in different concentrations with an incubation period of one hour. CCRCs were reconstructed again in range of - 4 to - 1.6 log [Ca++] M. The process was repeated 4 times. The CCRCs for Pg. Cr were compared with its respective control. Similarly, control curves in presence of 0.1 μM and 0.3 μM of verapamil were also constructed. The CCRCs for verapamil were compared with its respective control curves [19, 21].
All data extracted from Lab Chart of Power Lab was plotted for each replicate using Graph Pad Prism 7. The response of tissues was plotted as % of its respective control. Data was analyzed at 95% CI, P ≤ 0.05 using ANOVA.
Results and discussion
Phytochemical screening revealed the presence of tannins, carbohydrates, proteins, flavonoids, saponins and steroids. However, Pg. Cr tested negative for alkaloids and triterpenoids. Test for the presence of saponins was strongly positive.
Results of acute toxicity of Punica granatum in mice
Dose (mg/kg body weight, (i.p)) (n = 6 in each group)
Group1 (10 mg)
Group 2 (100 mg)
Group 3 (1000 mg)
Group 1 (1250 mg)
Group 2 (1500 mg)
Group 3 (1750 mg)
Hence, care must be taken while using its rind as traditional medicine. Its dose should not be more than 100 mg/kg as it carries risks of acute toxicity.
Our findings suggest that rind of Punica granatum has spasmogenic as well as spasmolytic activity. Spasmogenic activity may follow the involvement of histaminergic and cholinergic receptors. However, spasmolytic activity may follow the inhibition of voltage gated calcium channels. The possibility of other mechanisms cannot be ruled out.
The authors thank Professor Dr. Jehandar Shah for identifying the plant. The authors want to thank the Higher Education Commission of Pakistan for providing research grant no: 20–1723/R&D/10 for establishment of pharmacology laboratory at IBMS, KMU.
The authors want to thank the Higher Education Commission of Pakistan for providing research grant no: 20–1723/R&D/10 for establishment of Pharmacology laboratory at IBMS, KMU.
Availability of data and materials
All data generated or analyzed during this study are included in this. Published article. More, original graph tracings are available on request.
NA: Supervision of the pharmacological tests and preparation of the manuscript. AJ: Performed the pharmacological tests (M. Phil & PhD Scholar). SWAS: interpretation of some laboratory data. IS: manuscript revision. GA: performed pharmacological screenings. All authors approved the manuscript.
The authors declare that they have no competing interests.
Consent for publication
Ethics approval and consent to participate
Approval was obtained from the Ethics Board of the Khyber Medical University, Peshawar, Pakistan.
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