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Abstract Purpose In this study, the optimization of extraction process parameters of caffeic acid content from Spirulina platensis is performed by supercritical green technology. Methods Especially, the optimization of supercritical carbon dioxide (SC-CO2) extraction parameters was carried out employing Box-Behnken design (BBD) and response surface methodology (RSM). Alongside, the three levels of extraction parameters i.e. extraction pressure, extraction time and temperature have been fixed. As a response, the caffeic acid content of the extracts was determined by HPLC. The statistical analysis (ANOVA) of developed mathematical models was used in the process. Results The extract exhibited the highest content of caffeic acid as 72.11 µg/g of dw at the optimized extraction conditions of 360.08 bar pressure for 57.13 min extraction time at 38.31 °C temperature. Simultaneously this extract exhibited the highest content of total phenolic content (76.87 µg GAE/g dw), reducing power (2278 µg BHT/g dw), FRAP value (4.19 mM FeSO4 equivalent/g dw) and IC50 for DPPH activity (89.28 µg/mL). Conclusion It has been also noted that supercritical fluid extract can significantly retard the growth of microorganisms in litchi beverage. Consequently, we can also predict that isolated SC-CO2 antioxidant containing fraction would have hopeful for foodstuff preservative.

Abstract Since the birth of Christ, in these 2019 years, the man on earth has never experienced a survival challenge from any acellular protist compared to SARS-CoV-2. No specific drugs yet been approved. The host immunity is the only alternative to prevent and or reduce the infection and mortality rate as well. Here, a novel mechanism of melanin mediated host immunity is proposed having potent biotechnological prospects in health care management of COVID-19. Vitamin D is known to enhance the rate of melanin synthesis; and this may concurrently regulate the expression of furin expression. In silico analyses have revealed that the intermediates of melanin are capable of binding strongly with the active site of furin protease. On the other hand, furin expression is negatively regulated via 1-α-hydroxylase (CYP27B1), that belongs to vitamin-D pathway and controls cellular calcium levels. Here, we have envisaged the availability of biological melanin and elucidated the bio-medical potential. Thus, we propose a possible synergistic application of melanin and the enzyme CYP27B1 (regulates vitamin D biosynthesis) as a novel strategy to prevent viral entry through the inactivation of furin protease and aid in boosting our immunity at the cellular and humoral levels.

Spirulina platensis derived organic nanodots (ND) may be used as an alternative of chemical food preservative that can increase shelf life of food and beverages. Microalgal nanodots were isolated by the supercritical carbon dioxide extraction (SCE) method. Then SCE extract was subjected to thin-layer chromatography (TLC) and fractions were screened by a well diffusion method to identify the active compound with strong antibacterial ability. A characteristic of ND is the emitting of red colour upon the absorbance of ultra-violet (UV) light. The isolated ND is active against both Gram-positive and Gram-negative bacteria that significantly avoid their auto-aggregation. The nanodots were characterized by using TEM, UV-VIS, FTIR and NMR spectroscopy. FTIR and NMR analysis revealed the presence of hydrogen-bonded hydroxyl and amide groups. In addition, ND is applied in litchi juice as a preservative to extend the shelf life. In general, our results revealed that the sensory quality i.e. colour, aroma and overall appearance were significantly affected by duration of storage. It proves that Spirulina platensis derived organic nanodots act as a strong food and beverage preservative.