DOI: 10.2478/s11686-014-0307-2 © W. Stefański Institute of Parasitology, PAS Acta Parasitologica, 2014, 59(4), 745–757; ISSN 1230-2821 A search for antiplasmodial metabolites among fungal endophytes of terrestrial and marine plants of southern India Naveen Kumar Kaushik 1 , Thokur Sreepathy Murali 2 *, Dinkar Sahal 1 and T.S. Suryanarayanan 3 1 Malaria Research Laboratory, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India; 2 Division of Biotechnology, School of Life Sciences, Manipal University, Manipal, Karnataka 576104, India; 3 Vivekananda Institute of Tropical Mycology (VINSTROM), Ramakrishna Mission Vidyapith, Chennai 600 004, India Abstract Eighty four different fungal endophytes isolated from sea grasses (5), marine algae (36) and leaves or barks of forest trees (43) were grown in vitro and the secondary metabolites secreted by them were harvested by immobilizing them on XAD beads. These metabolites were eluted with methanol and screened using SYBR Green I assay for their antiplasmodial activity against blood stage Plasmodium falciparum in human red blood cell culture. Our results revealed that fungal endophytes belonging to diverse genera elaborate antiplasmodial metabolites. A Fusarium sp. (580, IC 50 : 1.94 µg ml -1 ) endophytic in a marine alga and a Nigrospora sp. (151, IC 50 : 2.88 µg ml -1 ) endophytic in a tree species were subjected to antiplasmodial activity-guided re- versed phase high performance liquid chromatography separation. Purification led to potentiation as reflected in IC 50 values of 0.12 µg ml -1 and 0.15 µg ml -1 for two of the fractions obtained from 580. Our study adds further credence to the notion that fungal endophytes are a potential storehouse for a variety of novel secondary metabolites vested with different bioactivities including some that can stall the growth of the malaria parasite. Keywords Endophytes, antiplasmodial metabolites, Plasmodium falciparum, antimalarial compounds, marine-derived fungi *Corresponding author: murali.ts@manipal.edu Introduction Malaria poses a major health threat in developing countries and annually more than 200 million new malaria cases are re- ported (WHO 2011), emphasising the urgent need for new drugs against malaria. In India, its management is challenging due to the country’s huge population and large geographical area further compounded by rapid urbanisation (Shah et al. 2011) as well as the resistance developed by the malarial par- asite to most of the existing classes of antimalarial drugs (An- derson 2009). Although artemisinin, a sesquiterpene lactone of the Chinese herb Artemisia annua L., and its synthetic ana- logues are very effective in controlling drug-resistant malaria (White 2008), a recent report indicates the emergence of artemisinin-resistant malarial parasite strains in western Cam- bodia and western Thailand (Cheeseman et al. 2012). Such wide spectrum drug resistance and the possibility of the exis- tence of regional subpopulations of malarial parasites differ- ing in sensitivity to different classes of drugs necessitates continuing the search for novel antiplasmodial pharma- cophores for short- and long-term effective control of malaria (Anderson 2009). Natural products with antiplasmodial activ- ity appear to be superior to purely synthetic ones because (a) natural metabolites have better prospects of becoming drugs (Ortholand and Ganesan 2004) and (b) the genes coding for these metabolites can be cloned and overexpressed to obtain appreciable quantities of chemically complex metabolites like artemisinin at affordable costs (Westfall et al. 2012; Paddon et al. 2013). In this context, endophytes, an ecological group of fungi may be good sources of antiplasmodial metabolites. Endophytes are mostly ascomycetous fungi which reside inside living tissues of all major groups of plants without pro- ducing any visible disease symptoms. Endophytes of both land (Suryanarayanan et al. 2009; Weber 2009) and marine (Surya- narayanan et al. 2010; Aly et al. 2011) plants produce a vast array of secondary metabolites exhibiting diverse bioactivi- ties including antimicrobial, antifungal, free radical scaveng- ing, cytotoxic and anti-insect activities. Based on ex vivo inhibition of growth of Plasmodium falciparum in human red blood cell cultures, we report antiplasmodial activity (IC 50 : <10 mg/ml) in 19 of the 84 endophyte isolates screened by us. Although some antimalarial compounds have been reported Author’s copy