The overwhelming effects of climate change have become evident of late and will likely become more prominent over a longer timescale. The pivotal role of agriculture in human welfare makes climate change a key concern, as the stationary nature of plants subjects them to harsh climate conditions. Research has shown that the major abiotic stress factors, such as salinity, drought and extreme temperatures, contribute to a 70% loss in global productivity. Various approaches, such as cross-breeding genetic engineering, have been employed to enhance the tolerance of plants to changing environmental conditions. Likewise, one such emerging strategy is the utilization of the symbiotic association between endophytic fungi and host plants. Endophytic fungi are ubiquitously existing microorganisms that contribute positively to the host plant's fitness. Recent years have witnessed a growing trend in studies reporting mitigation of abiotic stresses using endophytic fungi in many plants. Though of this little is understood, it is concurred that the plant growth-promoting attributes of endophytic fungi aid plants during stressful circumstances. The present chapter discusses the recent advances in the enumeration of major abiotic stress conditions, namely, heavy metals, extreme temperatures, drought and salinity in different plants. In addition, the mechanism of endophyte action is also discussed briefly.
Xanthine oxidase is a key enzyme responsible for hyperuricemia, a pre-disposing factor for Gout and oxidative stress-related diseases. Only two clinically approved xanthine oxidase inhibitors Allopurinol and Febuxostat are currently used for treatment of hyperuricemia. However, owing to their side effects there is a need for new non-purine-based selective inhibitors of xanthine oxidase. In the process of exploring novel xanthine oxidase inhibitors and anti-oxidants, we screened the culture filtrate of 07 novel species of Muscodor, a sterile endophytic fungi isolated from Cinnamomum and Aegle marmelos. Chloroform extract of M. darjeelingensis exhibited the maximum xanthine oxidase inhibition in the qualitative and quantitative assays. The IC50 of chloroform extract of M. darjeelingensis was 0.54 µg/ml which was much lower to Allopurinol but higher when compared to Febuxostat. 88% reduction in uric acid production was recorded by M. darjeelingensis chloroform extract which was similar to allopurinol. The maximum anti-oxidant activity was exhibited by M. indica against the gallic acid standard in the DPPH-free radical assay. Anti-oxidant activity index of M. indica was 7.7, which was followed by M. kashayum with 5.4. M. darjeelingensis exhibited a moderate anti-oxidant activity with anti-oxidant activity index of 1.63 in the DPPH assay. The present study is the very first report of Muscodor species exhibiting xanthine oxidase inhibitory and anti-oxidant activity together. Chloroform extract of M. darjeelingensis and M. indica stand out as potential candidates for isolation and characterization of the xanthine oxidase inhibitor and anti-oxidant compound, respectively.
Xanthine oxidase, a key enzyme of purine metabolism, is considered to be a prime target for the treatment of hyperuricemia and oxidative stress related disorders. Allopurinol and febuxostat are two FDA approved xanthine oxidase inhibitors currently being used for management of chronic hyperuricemia. Plethora of natural sources has been explored in search of novel chemical templates for the development of antihyperuricemic drugs. Studies in past decade have shown the potential of endophytic fungi, which colonize the internal tissues of plants without any evident sign of their ubiquitous existence, as repository of novel chemical entities exhibiting antimicrobial, anti-oxidant, anti-inflammatory and anticancer potential. However, very scanty preliminary data is available of exploration of xanthine oxidase inhibitors from fungal endophytes. The present review summarizes the efficacy of xanthine oxidase as target for developing ant-gout agents and highlights the prospective of endophytic fungi as producers of xanthine oxidase inhibitors for the anti-hyperuricemic therapy regimen.
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