Antifilarial activity of diterpenoids from Taxodium distichum.

Vikas Kushwaha,Shiv K Verma,P Kalpana Murthy,Kirti Saxena,Neeraj Kumar,Deepali Katoch,Richa Verma,Brij Lal,Bikram Singh

doi:10.1186/s13071-016-1592-4

Vikas Kushwaha, Shiv K Verma + Show 7 more

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https://doi.org/10.1186/s13071-016-1592-4

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Abstract

BackgroundLymphatic filariasis caused by Wuchereria bancrofti, Brugia malayi and B. timori, is a debilitating disease with an adverse social and economic impact. The infection remains unabated in spite of treatment with existing antifilarial drugs diethylcarbamazine (DEC) and ivermectin which are chiefly microfilaricides. There is therefore, need for macrofilaricides, embryostatic agents and better microfilaricides. In the present study we explored the antifilarial potential of crude extract and its molecular fractions of the plant Taxodium distichum using in vitro assay systems and rodent models of B. malayi infection.MethodsEthanolic extract (A001) of aerial parts of T. distichum was solvent fractionated and sub-fractionated. Four molecules, 3-Acetoxylabda-8(20), 13-diene-15-oic acid (K001), Beta-sitosterol (K002), labda-8(20),13-diene-15-oic acid (K003) and Metasequoic acid A (K004) were isolated from the fractions and their structure determined by spectroscopic analysis. The extract, subfractions and molecules were evaluated for antifilarial activity against B. malayi by 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide (MTT) reduction and motility assays in vitro and in two animal models, Meriones unguiculatus and Mastomys coucha, harbouring B. malayi infection.ResultsA001 was effective in killing microfilariae (mf) and adult worms in vitro. The diterpenoid K003 produced 100 % reduction in motility of both mf and adult worms and > 80 % inhibition in MTT reduction potential of adult female worms. In B. malayi-M. unguiculatus model, A001 killed all the adult worms in > 80 % of infected animals. K003 was embryostatic (> 95 %) in this model. In the B. malayi-M. coucha model, K003 killed ~54 % of adult worms (macrofilaricidal activity) and rendered > 36 % female worms sterile; it also stopped any further rise in microfilaraemia after day 42 post-initiation of treatment.ConclusionEthanolic extract of aerial parts of the plant T. distichum possesses potent antifilarial activity and the active principle was localised to K003 which showed significant macrofilaricidal activity and late suppression of peripheral microfilaraemia and some embryostatic activity. These findings indicate that labdane diterpenoid molecule(s) may provide valuable leads for design and development of new macrofilaricidal agent(s). To the best of our knowledge, this is the first report on antifilarial efficacy of products from the plant T. distichum.

Highlights

Lymphatic filariasis caused by Wuchereria bancrofti, Brugia malayi and B. timori, is a debilitating disease with an adverse social and economic impact
Extraction, fractionation and isolation of molecules and their structure elucidation Aerial parts of the plant T. distichum were collected in February, 2010 from Palampur, Himachal Pradesh, India, by Dr Brij Lal (Biodiversity department of CSIR-Institute of Himalayan Bioresource Technology, Palampur, India)
In the present bioassay-guided fractionation of the ethanolic extract from the aerial parts of the conifer T. distichum, we found that the antifilarial activity was localised to labdane diterpenoids K003 and K004 of the subfractions SF2

Summary

Introduction

Lymphatic filariasis caused by Wuchereria bancrofti, Brugia malayi and B. timori, is a debilitating disease with an adverse social and economic impact. Current methods of controlling the transmission of the infection include administration of the microfilaricides diethylcarbamazine (DEC) and ivermectin either alone or in combination with an anthelmintic albendazole en masse to people living in areas endemic to the infection This Mass Drug Administration (MDA) strategy raised hopes for elimination of this disease, but the infection is unabated due to the technical limitations of MDA strategy [3]. There is a clear need to develop new antifilarial agent(s) that possess microfilaricidal activity but, most importantly, macrofilaricidal activity and if possible, adult worm sterilising activity as well In this direction our laboratories have been systematically screening a large number of plants to identify biologically active molecules against lymphatic filarial parasite [5,6,7,8,9,10,11]

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