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Context: Almost one year after the onset of COVID-19 pandemic in Wuhan, China and still no specific therapy has emerged, counting millions of dead worldwide. The association of an uncontrolled SARS-CoV-2 replication and host-dependent mechanisms in COVID-19 pathogenesis suggest that any therapeutic strategy must combine antiviral drugs and adjuvant therapy to modulate the host’s responses. Owing to the multiplicity of mechanisms involved in COVID-19 pathogenic expressions, such as severe hypoxia, excessive inflammatory reaction and impaired immune response, an emerging therapeutic paradigm is the searching for agents acting as multifunctional drugs. Methylene blue (MB), the antique medication, seems to meet the above criterion. Aims: To summarize the probable beneficial effects of MB against COVID-19 supported by a discussion of the drug mechanisms of action counteracting the pathogenic mechanisms of the disease. Methods: PubMed, Google Scholar, and Scopus databases were used to collect the biomedical research on MB, and the discussed dataset finally included 150 published articles. Those COVID-19 pathogenic pathways possibly targeted by MB were critically appraised. Results: It was found that MB may act as multimodal agent by targeting simultaneously several pathogenic mechanisms of COVID-19 as hypoxic damage, hyper-inflammatory reaction and death signaling activation. It also may act as a virucidal agent by preventing virus-induced metabolic re-orientation. Its high safety profile, low cost, along with the mechanisms discussed herein might be essential criteria to test MB as an adjuvant therapy against COVID-19. Conclusions: Overall, this critical review provides theoretical grounds for MB clinical evaluation in the therapeutic management of SARS-CoV-2 infection.

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Disodium 5 '-inosinate (IMP) and disodium 5'-guanylate (GMP) are flavor enhancers that can be used as food additives.' Sodium salts of cytidine 5'-phosphate (CMP), and RNA Extractionfa) Batch Mode uridine 5'-phosphate (UMP) have important applications in the pharmaceutical industry. These 5'-ribonucleotides can be manufactured by enzymatic degradation of RNA, yeasts being the usual source of RNA.*The economic feasibility of such a process is related to the development of cheap methods to produce both RNA and the 5'-phosphodiesterase enzyme.Ribonucleic acid preparations are usually obtained from yeasts because the ratio RNA-DNA is the highest in these microorganisms. Moreover, the fermentation and recovery techniques for yeasts are well established. The extraction Solutions containing different concentrations of sodium hydroxide and sodium chloride and ammonia solutions were investigated as extraction agents (see Table I for the amounts). Batch experiments were carried out in a stirred tank of 100 mL working volume, employing 10 g (dry weight) of yeasts as raw material. The agitation speed was 320 rpm, and the flask was submerged in a constanttemperature bath at the d e s d temperature. After the extraction, the mixture was centrifuged and RNA was recovered from the supernatant liquid by precipitation.of RNA has been extensively reported by several procedures, especially at the laboratory level, to obtain highfbl Column Extraction A mixture of brewer's yeasts and celite was packed into a jacketted column (1.3 X 240 mm) in a dry state, and the extraction solution was pumped through the column. The extracted fraction was treated by precipitation to RNA. molecular-weight RNA. Thus, the well-known phenol method3 is extensively used, although it is obviously too complex and expensive to be used at industrial scale. On the other hand, alkali and salt solutions have been reported as extraction agents to obtain less pure crude RNA preparations more In this article, the effect of the last mentioned agents has RNA Precipitation been compared, and a methodology for RNA extraction and recovery has been developed in batch and semicontinuous modes. The raw material used was brewer's yeasts because of their low cost, but the methodology could be easily extended to other kinds of yeasts.In order to choose an appropriate method to recover RNA, three methodologies were tested: (1) ethanol precipitation (by adding one-half volume of ethanol, 1M NaCl); (2) precipitation by adjusting the pH of the extract to pH 2 MATERIALS AND METHODS

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