Anthelmintic efficacy of Flemingia vestita (Leguminoceae): Genistein-induced alterations in the activity of tegumental enzymes in the cestode, Raillietina echinobothrida

Abstract

The crude root-tuber peel extract of Flemingia vestita, an indigenous leguminous plant of Meghalaya, and its active chemical component, i.e. genistein, have shown paralyzing effects on soft-bodied helminth parasites of trematode and cestode groups. With a view to investigating the mode of action of the plant-derived component, its effect on the activity of tegumental enzymes of the parasite was studied. Acid phosphatase (AcPase), alkaline phosphatase (AlkPase), adenosine triphosphatase (ATPase) and 5′-nucleotidase (5′-Nu) are predominantly distributed in the tegument, subtegument, and somatic musculature. After exposure to the crude extract (50 mg/ml of the incubation medium) or genistein (0.5 mg/ml), a pronounced decline in the visible stain intensity was noticeable indicating very little or no activity in these sites. Quantitatively the activity of AcPase, AlkPase, ATPase and 5′-Nu was found to be suppressed by 97, 95, 88, and 57%, respectively, following genistein treatment. The reference drug, praziquantel (0.01 mg/ml) also caused a reduction in the enzymatic activities, somewhat at par with the genistein treatment. The results suggest that the tegumental enzymes of the parasite may be an important target of action for genistein, which appears to act transtegumentally.

Introduction

Flemingia vestita Benth and Hooker (Family Leguminoceae) is an indigenous medicinal plant of Meghalaya, north-east India, the tuberous roots of which are considered to have anthelmintic properties and hence eaten unpeeled by the natives as a popular cure against worm infections. In-vitro treatment of the adult trematodes namely, Fasciolopsis buski and Artyfechinostomum sufrartyfex, with the crude extract of the root-tuber peel of this plant induces paralysis and pronounced tegumental damage and disruption in the flukes [1]. While the crude extract of the root-tuber peel seems effective against trematode and cestode parasites, it did not show any effect on the viability of the nematode parasites [2]. The major active component of the root peel which has been identified as an isoflavone, genistein [3], induces paralysis and deformity in the tegument of the cestode, Raillietina echinobothrida [2]. The plant-derived components were also shown to cause alterations in the acetylcholinesterase activity of the parasite [4].

Activities of acid phosphatase (AcPase), alkaline phosphatase (AlkPase), adenosine triphosphatase (ATPase), and 5′-nucleotidase (5′-Nu) have been detected by biochemical and histochemical means in a number of helminth parasites wherein these enzymes are found in close association with the tegument, subtegument, somatic musculature, gut and cuticle 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. All the tegumental enzymes are believed to be involved in the digestive and/or absorptive function 16, 17, 18in cestodes. Some drugs alter the metabolism and inhibit the formation of mitochondrial energy and deprive the parasite of ATP 19, 20, 21. Isatin, hexachlorophene, praziquantel, luxabendazole and thiabendazole bring about a change in the activities of AcPase and AlkPase in cestodes 22, 23, such as Echinococcus multilocularis and Hymenolepis diminuta, and trematodes 6, 11, 24. However, aqueous crude extract of some medicinal plants namely, Butea monosperma, Embelia ribes and Roltleria tinctoria caused a reduction in both AcPase and AlkPase activity in Paramphistomum cervi in vitro [25].

In view of the functional significance of tegumental enzymes in digestion and/or absorption in cestodes, we studied the alterations, if any, in the AcPase, AlkPase, ATPase and 5′-Nu activities in R. echinobothrida following exposure in vitro of the root-tuber peel extract of F. vestita and its active component, genistein. Histochemical localization and biochemical quantification of the above-mentioned enzymatic activities form the basis of the present communication.