Endophytic fungi have currently been acknowledged as the most promising source of bioactive compounds for drug discovery, and considerable progress has been made in exploring their diversity, species richness, and bioprospecting. Fungal endophytes from unique environmental settings offer a pool of potentially useful medicinal entities. Owing to the constant stresses imposed on macroalgae by marine environments, it is believed that algae and their associated endophytic symbionts represent a good source of structurally diverse bioactive secondary metabolites. Despite the proven significance of active metabolites of algal endophytes, little have been exploited. This review highlights the latest discoveries in algicolous endophytic research, with particular focus on the bioactive metabolites from algal endophytes. Compounds are classified according to their reported biological activities, like anticancer, antibacterial, antifungal, and antioxidant properties. Present experimental evidence suggests that a majority of the bioactive metabolites were reported from Phaeophyceae followed by Rhodophyceae and Chlorophyceae. An intensive search for newer and more effective bioactive metabolites has generated a treasure trove of publications, and this review partially covers the literature published up to 2016.
Diversity studies of endophytic assemblages are emerging challenges, which unveil novel phenotypes producing interesting chemical entities and a better understanding of their ecological significance. In the present investigation, we selected an extremely complex and unique environment supporting unexplored endophytes, ‘Macroalgae of Kerala coast, India’. Unlike terrestrial flora and mangroves, reports displaying endophytic assemblages of marine flora remain limited, especially from India. The main goal of this study was to expose hidden endophytic fungi from macroalgae and examination of their bioactive potential. An ecological investigation of four red, four green and three brown algae resulted in 133 fungal taxa with 29 distinct morphospecies. Aspergillus and Penicillium were found to be the dominant genera. Penicillium chrysogenum was the sole fungi that contributed 11% of the entire endophytic community. Antimicrobial activity against various aquaculture/human pathogens revealed that around 59% of endophytes inhibited at least one of the pathogens screened. The maximum number of isolates (37%) inhibited Escherichia coli tailed by Aspergillus fumigatus (27%). Antimicrobial profile of fungal endophytes endorses them as a potential source of bioactive molecules that can be explored to find a solution for drug resistance in microbial pathogens.
Utilization of renewable marine resources for the biosynthesis of metal nanoparticles is an innovative area in the current nanotechnology research. The present article reports a simple environmentally benign method for the synthesis of silver nanoparticles using aqueous extract of marine brown seaweed Padina Tetrastromatica, which act as both the reducing and stabilising agent. The formation, morphology and crystalline nature of the synthesised silver nanoparticles were determined using UVVisible Spectroscopy, Transmission electron microscopy, Selected area electron diffraction and X-ray diffraction techniques. The surface plasmon resonance peak at 424 nm in the UV-Visible spectrum confirmed the formation of silver nanoparticles. The biosynthesised silver nanoparticles were almost spherical with an average size of 15 nm. Crystalline nature of silver nanoparticles is evident from the characteristic peaks in the X-ray diffraction pattern, bright circular spots in the selected area electron diffraction pattern and clear lattice fringes in the High resolution Transmission electron microscopy images. Fourier transform infrared spectroscopic analysis revealed the presence of functional bio active metabolites in seaweed extract which is responsible for the formation and efficient stabilization of the nanoparticles. The biosynthesised silver nanoparticles show excellent antimicrobial activity against Escherichia coli and Aeromonas hydrophila. They also show very good catalytic activity for the reduction of methylene blue in the presence of NaBH4 in aqueous medium. Thus the green synthesised nanoparticles are expected to be a promising candidate for the application in diverse fields.
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