In this work, hydroethanolic plant extracts (acorn husk, laurel, eucalyptus, and rockrose leaves) were screened for their content in condensed tannins (HPLC-DAD/MS), polyphenol content, antioxidant, antimicrobial, and antiviral activities, and lack of toxicity. The results showed the highest values of condensed tannins found for laurel and eucalyptus extracts, while the total phenolic content ranged within 204.54 ± 2.0/326 ± 7.0 (mg GAE/g extract), with the acorn husk extract presenting the highest content (p < 0.05). The extracts showed good antioxidant activity, which varied with the type of assay. ABTS (1013 ± 5.0/1859 ± 6.0) with the rockrose Porto extract presented the highest content, DPPH (854 ± 6.0/1565 ± 4.0) with the acorn husk extract
presented the highest content, and ORAC (2855 ± 10/3703 ± 87) with the laurel extract presented the highest content; all results were expressed in μmol Trolox/g extract. The most antimicrobial extracts were the rockrose and acorn husk. In terms of virus inhibition, all extracts showed an inhibition over 90%, although eucalyptus and the acorn husk reached an inhibition close to 99%. No mutagenicity by AMES assays and no cytotoxicity were detected for the extracts. This work highlights the potential of these plant extracts representing the source of bioactive components with antioxidant capacity to be applied in foods, food packaging,
development of new natural cleaning agents, and/or other applications.
