Effect of isoflavone from Flemingia vestita (Fabaceae) on the Ca 2+ homeostasis in Raillietina echinobothrida , the cestode of domestic fowl Bidyadhar Das, Veena Tandon * , Nirmalendu Saha Department of Zoology, North Eastern Hill University, Shillong 793 022, India Received 22 July 2005; accepted 23 August 2005 Available online 29 September 2005 Abstract The alcoholic crude root-peel extract of Flemingia vestita and its major isoflavone, genistein, have been shown to have a vermifugal/ vermicidal effect by causing a flaccid paralysis accompanied by alterations in the structural architecture of the tegumental interface and metabolic activity in Raillietina echinobothrida , the cestode of domestic fowl. In the present study, the crude root-peel extract and pure genistein were tested in vitro with respect to Ca 2+ homeostasis and the occurrence of some metal ions was detected in the parasite. Live cestodes were incubated in pre- defined concentrations of the crude root-peel extract, genistein and praziquantel (as reference drug), till the paralysis time with simultaneous maintenance of respective controls. In the parasite tissue, a significant amount of Ca 2+ (¨400 Ag/g dry tissue wt) was found to be present besides magnesium, iron, zinc, lead and chromium, whilst manganese, cadmium and nickel were below the level of detection. The Ca 2+ concentration was decreased significantly by 39% – 49%, in the parasite tissue exposed to the test materials in comparison to the respective controls. There was also an increase in Ca 2+ efflux by 91% – 160% into the culture medium under similar treatments. The changes in Ca 2+ homeostasis may be related to the rapid muscular contraction and consequent paralysis in the parasite due to the anthelmintic stress caused by the phytochemicals of F. vestita . D 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Flemingia vestita ; Genistein; Anthelmintic; Raillietina echinobothrida; Ca 2+ homeostasis; Cestode; Parasite 1. Introduction In traditional medicine, the natives of Meghalaya conven- tionally use the edible root tuber of Flemingia vestita (Fabaceae) against intestinal helminths. The putative anthel- mintic isoflavones – genistein, formononetin, pseudobapti- genin and daidzein [1] – of the alcoholic crude root-peel extract of F. vestita have been shown to have vermifugal/ vermicidal effect against cestodes and trematodes [2]. These phytochemicals, genistein in particular, caused rapid muscular contraction followed by flaccid paralysis and alterations in the tegumental architecture (deformity, blebbing, vacuoliza- tion) in Raillietina echinobothrida , the cestode of domestic fowl [3]; these changes were also accompanied by alterations in the activities of several enzymes/metabolic processes in the parasite under the stress of the plant-derived components [4–8]. Praziquantel (PZQ) induced paralysis and tegumental disruption in Schistosoma mansoni [9,10]; these changes, having been led by a rapid, sustained muscular contraction [11], were attributed to disturbed Ca 2+ homeostasis [12,13]. Similar changes, induced by other drugs viz. calcium ionophore A-23187 and benzodiazepine Ro 11-3128, were also observed by Blair et al. [14] and Martin et al. [15]. Recent studies have shown that PZQ interacts with h subunit of voltage-gated Ca 2+ channel and responsible for changes in Ca 2+ homeostasis in S. mansoni [16–19]. Ca 2+ , which is stored in the calcareous corpuscles of many cestodes, especially in the metecestode stages, is intimately involved in both muscle contraction and many aspects of cell movement controlled by the cytoskeleton [20]. Enzymes like glycogen phosphorylase, glycogen synthase and protein kinases are also allosterically regulated by various modulators, for which Ca 2+ plays a key role [21,22]. In the quest to find the plausible mode of action of the putative anthelmintic active principles of F. vestita , it seemed desirable to ascertain whether or not the changes in Ca 2+ homeostasis are associated with the onset of paralytic state in the parasite, consequent to the exposure of the test phytochem- 1383-5769/$ - see front matter. D 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.parint.2005.08.002 * Corresponding author. Tel.: +91 364 272 2312; fax: +91 364 272 2301. E-mail address: tandonveena@hotmail.com (V. Tandon). Parasitology International 55 (2006) 17 – 21 www.elsevier.com/locate/parint