In Vitro Evaluation of Virucidal Effect of Polysaccharides Extracted and Purified from Arthrospira platensis and Dunaliella salina on Human Adenovirus Type 5 in A549 Cells.

Polysaccharides derived from cyanobacteria and microalgae have attracted increasing interest as natural virucidal agents. Among them, polysaccharides from the cyanobacterium Arthrospira platensis (A. platensis), and the green microalgae Dunaliella salina (D. salina) have shown virucidal activities, mainly against enveloped viruses, while evidence on non-enveloped viruses is still limited. In this study, the virucidal activity of purified polysaccharides extracted from A. platensis (APPs) and from D. salina (DSPs) was evaluated in vitro against human adenovirus type 5 (HAdV5), a non-enveloped pathogenic virus with high persistence in the environment and resistance to disinfection. The in vitro assays were carried out at concentrations previously verified as non-toxic by morphological evaluation of A549 cells after 24 and 48 h of incubation, testing two viral loads, namely, 103 and 104 tissue culture infectious dose 50% per milliliter (TCID50/mL). For APPs, a possible time-dependent effect was also assessed at different contact times (15, 30 and 60 min). DSPs showed a limited virucidal effect related to the starting viral concentration, while APPs induced a consistent viral reduction (up to 98.8%) at both viral concentrations. The virucidal effect of APPs occurred rapidly and was not significantly influenced by contact time, thus suggesting that prolonged exposure is not a determining factor for polysaccharide virucidal activity. These findings demonstrate the virucidal activity of APPs against a highly resistant non-enveloped virus and provide preliminary in vitro evidence of their potential application as natural virucidal agents, particularly for environmental disinfection purposes. Further investigations are warranted to elucidate the underlying mechanisms of action and to optimize their practical use.