ENDOSYMBIONTS: A CONTINUING SOURCE OF CYTOTOXIC METABOLITE TAXOL.

Taxol? (generic name: paclitaxel) is a naturally occurring diterpenoid cytotoxic metabolite. Approved by FDA, this drug has been widely used for the treatment of various kinds of cancers. Plants belonging to Taxus sp. are the primary natural source of Taxol?. In 1960 it was isolated from bark of the Pacific yew tree (Taxus brevifolia) for the first time. However, due to the environmental constraints and to protect the yew trees, alternatives to the use of trees were sought. Microbiologists screened the novel fungus capable of producing Taxol?-precisely two decades back. This was followed by a plethora of investigations on other endophytes possessing similar biosynthetic potential. Till date, highest level of Taxol? has been synthesized after 7 days of incubation period from Cladosporium sp. F3 isolated from Iranian yew (Taxus baccata) producing paclitaxel at 139.2 mg/kg. However, industrial-scale of Taxol? production using fungal endophytes, although ostensibly capable, has not happened at a practical level yet. This review examines the potential for production of Taxol? from fungi. The biology of Taxol? synthesis in fungi and different methods which may improve Taxol? yield is also discussed. Significance of the study: Endophytic fungi have ability to synthesize diverse classes of secondary metabolites originally from plants, one such classical example being paclitaxel. Better understanding and exploration of host-endophyte lifestyle will provide considerable knowledge that can be utilized to increase and improve production of desired pharmaceutical or industrial product by employing biotechnological manipulations. Therefore, our present dependency on medicinal plants for paclitaxel production can be minimized with the help of this endophytic fungus derived end product.