# In Vitro Influenza A Virus-Inactivating Activity of HIDROX®, Hydroxytyrosol-Rich Aqueous Olive Pulp Extract

## TL;DR

This study shows that HIDROX, an olive extract rich in hydroxytyrosol, can inactivate influenza A virus in a lab setting, potentially offering a natural way to control the virus.

## Contribution

The study demonstrates that HIDROX has stronger virucidal activity than pure hydroxytyrosol against influenza A virus.

## Key findings

- HIDROX and hydroxytyrosol showed concentration- and time-dependent virucidal activity against IAV.
- HIDROX induced structural changes in viral proteins without affecting hemagglutination or genome integrity.
- Hydroxytyrosol, but not HIDROX, increased reactive oxygen and nitrogen species, which could be neutralized by scavengers.

## Abstract

Influenza A virus (IAV) is an important respiratory pathogen. We evaluated the IAV-inactivation activity of hydroxytyrosol (HT)-rich aqueous olive pulp extract (HIDROX®) and its mechanisms. The HIDROX-containing solution and cream showed concentration- and time-dependent virucidal activity. The virucidal activity of HIDROX was higher than pure HT. With Western blotting (WB), the band intensities of multiple viral structural proteins in HIDROX- and HT-treated viruses were weaker than in the control, and high-molecular-mass bands were observed. These results suggest that HIDROX and HT may have induced the structural changes or abnormalities of viral proteins. HIDROX and HT had no or limited impact on hemagglutination and neuraminidase activities, as well as the virus genome. No apparent abnormalities in the viral particles were observed through electron microscopy following treatment with HIDROX and HT. Treatment with HT, but not HIDROX, resulted in the production of high levels of reactive oxygen species (ROS) and/or reactive nitrogen species (RNS). In HT treatment but not HIDROX treatment, the virucidal activity disappeared, and the induction of abnormal band patterns of a viral protein in WB was cancelled by ROS/RNS scavenger activity. These findings showed the possible utility of HIDROX as a naturally derived IAV virucidal component that may contribute to IAV control.