Antiviral effects of cranberry juice and cranberry proanthocyanidins on foodborne viral surrogates – A time dependence study in vitro

Cranberry juice (CJ) and cranberry proanthocyanidins (PAC) are widely known for their antibacterial, antiviral, and pharmacological activities. The effect of CJ and cranberry PAC on the infectivity of foodborne viral surrogates, murine norovirus (MNV-1), feline calicivirus (FCV-F9), MS2 (ssRNA) bacteriophage, and ϕX-174 (ssDNA) bacteriophage after 0 min to 1 h at room temperature was evaluated. Viruses at titers of ∼5 log 10PFU/ml were mixed with equal volumes of CJ at pH 2.6, CJ at pH 7.0, 0.30 mg/ml CJ PAC, 0.60 mg/ml PAC, or water and incubated for 0, 10, 20, 30, 40, 50 min, and 1 h at room temperature. Infectivity was determined using standard plaque assays. The viral reduction rates of the four tested viruses were found to vary considerably. Among the tested viruses, FCV-F9 titers were decreased the most by ∼5 log 10PFU/ml within 30 min. MS2 titers were decreased the least by only ∼1 log 10PFU/ml after 1 h with CJ at pH 2.6 and 0.30 mg/ml PAC, and ∼0.5 log 10PFU/ml with CJ at pH 7.0 and 0.15 mg/ml PAC. MNV-1 and ϕ-X174 showed comparable titer reductions which was between that of FCV-F9 and MS2. In most cases, viral reduction within the first 10 min of treatment accounted for ≥50% of the total reduction. Transmission electron microscopy on FCV-F9 treated with CJ and PAC revealed structural changes. This study shows potential of using natural bioactive compounds for controlling foodborne viral diseases. Further studies are necessary to elucidate the mechanism of action of CJ components and to understand the differences in viral titer reduction profiles.