Abstract
Zanthoxylum oxyphyllum Edgew. is a medicinal plant widely been used by the local tribal communities of Assam as an alternative source of medicine for the treatment of various diseases. In the present study, endophytic fungi associated with Z. oxyphyllum were undertaken with an aim to investigate the isolates for their antimicrobial potential. The endophytic fungi were recovered using four different media, namely, Malt Extract Agar (MEA) media, Potato Dextrose Agar (PDA) media, Water Agar (WA) media and media amended with the Plant Extract (PEA) from samples collected from three sites. Altogether, 18 isolates of endophytic fungi were isolated from 150 surface sterilized and healthy leaf fragments. Colletotrichum was found to be dominant endophytic genus with 7 different species. Other isolated endophytic fungal genera were Fusarium, Curvularia, Aspergillus, Corynespora and isolates belonging non-sporulating fungi categorised as Mycelia Sterilia. The endophytic fungi were determined for antimicrobial activity against selected clinically significant human pathogenic test organisms. Ethyl acetate crude extracts of all endophytic fungi exhibited antimicrobial activity by inhibiting a minimum of one of the four test pathogens. Amongst the isolates, crude extracts obtained from Fusarium sp. and five Colletotrichum spp. showed wide-spectrum antimicrobial activity against all the test organisms. The study indicated that Z. oxyphyllum harbours a wide range of endophytes capable of producing secondary metabolites with antimicrobial properties. Further detailed investigation of their bioactive metabolites might lead to discovery of compounds with potential therapeutic applications as a new source of medicine.
Highlights
Plants known to possess medicinal values have been used in traditional folk medicine by ethnic tribal communities all over the world including India
The highest recovery of endophytes was obtained in Potato Dextrose Agar (PDA) media (21.33%), followed by Plant Extract (PEA) (10%), Malt Extract Agar (MEA) (9.33%) and the least were in Water Agar (WA) media (8.67%)
The total colonizing frequency (CF%) of endophytic fungi in healthy leaf tissues of Z. oxyphyllum was found to be 49.33% out of which isolates belonging to the genus Colletotrichum showed the highest colonization frequency (25.34%), followed by non-sporulating isolates categorised as morphotypes of Mycelia sterilia (12.66%) and the genus Curvularia (6.67%) (Table 2)
Summary
Plants known to possess medicinal values have been used in traditional folk medicine by ethnic tribal communities all over the world including India. They are potential sources of drugs since long back and recently used for the development of modern and commercial medicines. There are increased reports of resistance developed by most of the pathogenic microorganisms against already available commercial drugs [1] This has become a serious concern for the health services around the world. Endophytic microorganisms, especially fungi inhabiting medicinal plants have the ability of synthesizing bioactive secondary metabolites analogous to those produced by their respective host plants [5]. Plants growing in regions with high biodiversity having medicinal properties and used in traditional medicine has been reported to be a significant area for exploration of new bioactive strains of endophytic
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