PHYTOTHERAPY RESEARCH Phytother. Res. 13, 445–447 (1999) SHORT COMMUNICATION Effect of the Crude Extract of Cestrum parqui on Carrageenin-induced Rat Paw Oedema and Aggregation of Human Blood Platelets Darakhshanda Shehnaz,1* Faiza Hamid,1 Fehmida T. Baqai2 and Viqar Uddin Ahmad2 1 Pharmacology Division, International Centre for Chemical Sciences, H.E.J. Research Institute of Chemistry, University of Karachi, Karachi - 75270, Pakistan 2 Chemistry Division, International Centre for Chemical Sciences, H.E.J. Research Institute of Chemistry, University of Karachi, Karachi - 75270, Pakistan An extract of Cestrum parqui aerial parts in methanol:water (1:1) showed inhibition of carrageenin-induced oedema. The aggregation of human blood platelets induced by adenosine diphosphate and platelet activating factor was also inhibited (IC50s were 3 and 2 mg/mL, respectively). On the contrary, the extract did not inhibit arachidonic acid-mediated platelet aggregation. Copyright # 1999 John Wiley & Sons, Ltd. Keywords: Cestrum parqui; oedema; platelet aggregation; ADP; PAF. INTRODUCTION in the rotary evaporator and the concentrate was freezedried to the powdered form. The plant Cestrum parqui L’Herit belongs to the family Solanaceae. It is commonly known as willow-leaved Jessamine. The leaves contain parquine, a bitter toxic alkaloid that resembles atropine and strychnine in activity (Sastri, 1950). Cestrum parqui, known as a sudorific, is used in the treatment of fever and for skin diseases such as allergies, herpes and impetigo (Montes and Wilkomirksy, 1985 in Backhouse et al., 1996). However, with regard to the pharmacological activities, nothing has been reported in the literature except for an antiinflammatory action in the guinea-pig (Backhouse et al., 1996). The current work was carried out to investigate the effect of the methanolic extract of its leaves on carrageenininduced rat paw oedema and aggregation of human blood platelets. Antiinflammatory activity. The method of carrageenininduced rat paw oedema, first described by Winter et al. (1962) was employed. Male Sprague-Dawley rats, weighing 120–150 g, were used for this study. The aqueous suspensions of the crude extracts were given to the animals orally. The control animals were treated with water in the same manner. In the right hind paw of the animals, 0.05 mL of 1% carrageenin solution was injected. The volume of the paw was measured by a plethysmometer at 0, 0.5, 1, 2, 3, 4, 5 h after carrageenin injection. Oedema was estimated as the increase in volume over the 0 min value. Plant extract. The aerial parts were extracted with methanol:water (1:1). The crude extract was concentrated Platelet aggregation. Blood was drawn from normal healthy volunteers who had not taken any medicine for at least 15 days. It was then collected in a tube containing 3.8% sodium citrate (1 mL/10 mL of the blood). Plateletrich plasma (PRP) was obtained by centrifugation at 1200 rpm for 15 min at 4 °C. After removing the PRP, the remaining blood was centrifuged at 3000 rpm for 5 min in order to obtain the platelet poor plasma (PPP). Platelet aggregation was carried out by the method initially described by Born (1962). The volume of PRP in the cuvette was 400 mL and it was kept at 37 °C with constant stirring. The crude extract was added 1 min prior to the addition of ADP, PAF or AA. Then the aggregation was measured by an aggregometer on the principle that the absorption of light by plasma decreases as the aggregation of the platelets is increased. The aggregation was recorded for 4 min after addition of stimuli. * Correspondence to: D. Shehnaz, Pharmacology Division, International Centre for Chemical Sciences, H.E.J. Research Institue of Chemistry, University of Karachi, Karachi - 75270, Pakistan. Statistical analysis. The comparison between control and extract-treated groups was performed by Student’s ttest. MATERIAL AND METHODS All chemicals, reagents and solvents used in the experiments were purchased from Sigma Chemical Company, Research Biochemical Inc (RBI) or Merck. The animals used were rats of the Sprague-Dawley strain that were from the colony inbred for several years in the Animal House of H.E.J. Research Institute of Karachi. CCC 0951–418X/99/050445–03 $17.50 Copyright # 1999 John Wiley & Sons, Ltd. Received 21 July 1998 Accepted 4 November 1998 446 D. SHEHNAZ ET AL. Figure 1. Effect of Cestrum parqui (Cp-50) extract on carrageenin-induced rat paw oedema. The extract (1 and 3 g/kg weight) was administered orally to rats. The rats in the control group were left untreated. After half an hour, carrageenin (0.05 mL of 1% solution) was injected in the right hind paw. The volume of the paw was measured with a plethysmometer at 0, 0.5, 1, 2, 3, 4 and 5 h after the injection. The values represent an average (SEM) of ®ve observations each obtained from a separate rat. The reduction of oedema in the treated rats was statistically signi®cant as analysed by the Student's t-test, *p < 0.025, **p < 0.01, ***p < 0.005. RESULTS AND DISCUSSION The extract produced inhibition of the carrageenininduced rat paw oedema that was statistically significant (Fig. 1). Apparently, the two doses suppressed the oedema equipotently, however, the statistical analysis showed that the effect produced by 3 g/kg weight was significant while that caused by 1 g/kg weight was insignificant. The ADP-induced platelet aggregation was also inhibited by the extract in a concentration-dependent manner (Fig. 2). The IC50 value was estimated to be 3 mg/mL. Similarly, PAF-induced platelet aggregation was blocked with an IC50 of 2 mg/mL and almost 88% inhibition was observed with 5 mg/mL of the extract (Fig. 2). In contrast, the extract did not exhibit any effect on aggregation elicited by AA (Fig. 2). Therefore, it implies that the antiinflammatory activity of the extract did not implicate the inhibition of the cyclooxygenase pathway. The non-steroidal antiinflammatory drugs, such as aspirin, are known to exert their effect through the Figure 2. Effect of Cestrum parqui extract (Cp-50) on platelet aggregation induced by ADP, PAF or AA. The submaximal response of platelets to the stimulants was considered as 100% (control) and employed for studying the effect of the extract which was added to the reaction mixture 1 min prior to the addition of stimulant. Subsequently, the response was recorded for 4 min. Each value represents a mean (SEM) of ®ve experiments conducted on blood samples from ®ve different individuals. inhibition of cyclooxygenase (Vane, 1971). Also, AA is believed to cause platelet aggregation through its enzymatic conversion into endoperoxides and thromboxanes (Hamberg et al., 1975; Svensson et al., 1976). Clearly, the results indicate that the extract-mediated inhibition was selective for the PAF- and ADP-induced platelet aggregation. Since the possibility of AA release in the pathways triggered by ADP and PAF cannot be excluded, one of the possibilities is that the extract inhibited a site upstream of AA metabolism. The involvement of PAF in acute inflammation, asthma and systemic anaphylaxis has been reported (reviewed by Chao and Olson, 1993). As the most chemotactic factor for blood cells, PAF is also known to release inflammatory cytokines (Braquet et al., 1989). Thus it could be suggested that the extract inhibited the inflammation by blocking the chemotactic effect of PAF. In conclusion, the results explain the usefulness of Cestrum parqui in inflammatory conditions.The activitydirected fractionation of this plant extract needs to be continued. REFERENCES Backhouse, N., Delporte, C., and Negrete, R. et al. (1996). Antiin¯ammatory and anti-pyretic activities of Cuscuta chilensis, Cestrum parqui and Psoralea glandulosa. Int. J. Pharmacog. 34, 53±57. Born, G. V. R. (1962). Aggregation of blood platelets by adenosine diphosphate (ADP) and its reversal. Nature 194, 927±929. Braquet, P., Paubert-Braquet, M., Koltai, M., Bourgain, R., Bussolino, F., and Hosford, D. (1989). Is there a case for Copyright # 1999 John Wiley & Sons, Ltd. PAF antagonists in the treatment of ischemic states? Trends Pharmacol. Sci. 10, 23±45. Chao, W., and Olson, M. S. (1993). Platelet-activating factor: receptors and signal transduction. Biochem. J. 292, 617± 629. Hamberg, M., Svensson, J., and Samuelsson, B. (1975). Thromboxanes. 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