Aqueous Extracts of Hibiscus sabdariffa Calyces to Control Aichi Virus.

Abstract

Aqueous Hibiscus sabdariffa extracts possess antimicrobial properties with limited information available on their antiviral effects. Aichi virus (AiV) is an emerging foodborne pathogen that causes gastroenteritis. Vaccines are currently unavailable to prevent their disease transmission. The objective of this study was to determine the antiviral effects of aqueous H. sabdariffa extracts against AiV. AiV at ~5 log PFU/ml was incubated with undiluted (200mg/ml), 1:1 (100mg/ml) or 1:5 (40mg/ml) diluted aqueous hibiscus extract (pH 3.6), phosphate-buffered saline (pH 7.2 as control), or malic acid (pH 3.0, acid control) at 37°C over 24h. Treatments were stopped by serially diluting in cell-culture media containing fetal bovine serum and titers were determined using plaque assays on confluent Vero cells. Each treatment was replicated thrice and assayed in duplicate. AiV did not show any significant reduction with 1:1 (100mg/ml) or 1:5 (40mg/ml) diluted aqueous hibiscus extracts or malic acid after 0.5, 1, or 2h at 37°C. However, AiV titers were reduced to non-detectable levels after 24h with all the three tested concentrations, while malic acid showed only 0.93 log PFU/ml reduction after 24h. AiV was reduced by 0.5 and 0.9 log PFU/ml with undiluted extracts (200mg/ml) after 2 and 6h, respectively. AiV treated with 1:1 (100mg/ml) and 1:5 (40mg/ml) diluted extracts showed a minimal ~0.3 log PFU/ml reduction after 6h. These extracts show promise to reduce AiV titers mainly through alteration of virus structure, though higher concentrations may have improved effects.