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Macroalgae have evolved different strategies to mitigate the damaging effects of solar ultraviolet radiation (UVR), including accumulation of photoprotective compounds such as mycosporine-like amino acids (MAAs). MAAs are secondary metabolites, synthesized by a large variety of organisms including macroalgae, phytoplanktons, cyanobacteria, lichen, fungi and some marine animals. MAAs act as photoprotectants and antioxidants. In the present investigation, MAAs profile of methanolic extracts of two marine red algae Gelidium sp. and Ceramium sp., collected from their natural environment, was studied. High-performance liquid chromatography (HPLC) and UV-Vis spectrometry analyses were used to reveal different MAAs profile in the extracts obtained from these two red algae. The MAAs isolated by HPLC were identified as shinorine (λmax= 333.5 nm), porphyra-334 (λmax=332.3 nm) and palythine (λmax=317.9 nm) having retention times (RT) 1.26, 2.12 and 3.64 min, respectively, in the extract obtained from Gelidium sp. Similarly, shinorine (λmax=332.3 nm), porphyra-334 (λmax=333.5 nm) and palythinol (λmax=332.5 nm) with RT 1.27, 2.13 and 4.61 min, respectively, were identified in the extract obtained from Ceramium sp. This study revealed that Gelidium sp. and Ceramium sp. could serve as potential source for economical exploration of MAAs in pharmaceutical sciences.

Scytonemin acts as a natural photoprotectant against high-intensity solar photosynthetically active radiation and harmful ultraviolet radiation, which has been reported in several cyanobacteria, and gets accumulated in their extracellular polysaccharide sheath. UV-B radiation (280-315 nm) has detrimental effect on physiological and biochemical processes of living organisms. In this study, scytonemin was extracted from dried cyanobacterial mats collected from the bark of mango trees and was partially characterized using high-performance liquid chromatography and electrospray ionization-mass spectrometry (retention time: 1.7 min; UVλ max : 386 nm; [M + H] + m/z: 545.1). Thereafter, photoprotective capabilities of scytonemin against UV-B radiation in a non-sheathed cyanobacterium Nostoc sp. strain HKAR-2 were assessed followed by studying its role in the recovery process. We found that UV-B radiation inhibited growth, survival, Chl a content and total protein concentration and caused an increase in total carotenoid content. The activities of nitrogen-assimilating enzymes, glutamine synthetase and nitrate reductase, were also affected. In vivo nitrate reductase activity exhibited a stimulatory response, while in vivo glutamine synthetase activity was adversely inhibited after UV-B exposure. Scytonemin with different concentrations exhibited efficient photoprotective ability by nullifying the deleterious effects of UV-B and also enhanced the recovery process. UV-screening effects of scytonemin in terms of growth, pigmentation, survival and nitrogen metabolism enzymes in the cyanobacterial strain have been reported for the first time in the present study. Our results suggest that scytonemin aids in the better survival and adaptability of cyanobacteria in stressed habitats facing harsh environmental conditions.

COVID-19 has impacted the world economy in an unprecedented manner; the financial markets indicate the same. This spontaneous event landed most of the stock markets into extreme volatility. Large capital outflow and extreme rapid fall were seen among almost all the world financial markets. Though similar trend prevailed everywhere during this pandemic, the impact could not be accumulated in absolute terms. Using the data of five stock markets, the current study endeavored to draw an impact of COVID-19 on major stock exchanges. The study uses wavelet coherency analysis on one-year daily data from June 2019 to May 2020 of five stock markets: Bombay Stock Exchange (BSE), London Stock Exchange (LSE), NASDAQ, Tokyo Stock Exchange (Nikkei), and Shanghai Stock Exchange. It is observed that there are time-variation and scale-variation in co-movements between the studied markets. During the crisis, the co-movement concentrates on a short time scale, even for two days. These results have significant implications for international investors, which will help them in portfolio diversification with time elements. All the stock markets under study have indicated co-movement at different time scales and frequencies with varying cross-power levels. However, the concentration of co-movement is found the most between the UK and the US stock markets. It is the least between Japan and the UK. In BSE, co-movement at shorter time scales started late. NASDAQ is leading only in one case, i.e., Shanghai Stock Exchange. BSE is not leading any stock index. LSE is in the leading position in all four cases. It has also been observed that co-movement started to concentrate at a shorter time scale as soon as the impact of the crisis increased.

In the present investigation, biological crusts from the surface of eight historical monuments of Varanasi, India, were examined for the presence of scytonemin (a cyanobacterial photoprotective pigment) containing cyanobacterial species. Lyngbya sp. and Scytonema sp. were the dominant cyanobacteria present in all crust samples. The absorption spectroscopic data of chlorophyll, carotenoids and scytonemin showed that scytonemin was more abundant than the carotene and chlorophyll in all the crusts. Identification of these compounds was done using UV-Vis spectroscopy and High Performance Liquid Chromatography (HPLC) analysis. HPLC analysis revealed the presence of scytonemin in seven out of eight samples and peaks of scytonemin with retention time ranging from 1.4-1.9 min with corresponding absorbance maxima at 386, 300 and 252±2 nm. As per our knowledge this is the first report of its kind from monuments of Varanasi. From this study, it can be concluded that synthesis of photoprotective compounds like scytonemin and its derivatives counteract the damaging effects of solar radiation which enable cyanobacteria to colonize and inhabit almost all kinds of habitats, including extreme lithic habitats, such as rocks and walls of monuments which face prolonged high intensity solar radiation.