Applications of Romanian Propolis in Phyto-Inhibitory Activity and Antimicrobial Protection: A Comparative Study

Propolis use in medicine, pharmaceutical, cosmetic, and food industries is well known. This study aimed to investigate propolis' phyto-inhibitory and antimicrobial potential. Nine propolis samples obtained from distinct Romanian regions and characterized in terms of physical-chemical parameters, phenols and flavonoid contents, and antioxidant properties were prepared as dry propolis and aqueous extracts. The phyto-inhibitory effect was comparatively tested on different cereals: hexaploid bread wheat (Triticum aestivum), maize (Zea mays L.), oats (Avena sativa L.), and barley (Hordeum vulgare L.), while their in vitro antimicrobial activity was evaluated against bacterial and fungal strains specific to cereals: Bacillus subtilis, B. cereus, Proteus mirabilis, Fusarium oxysporum, Penicillium chrysogenum, and Aspergillus niger. All propolis samples showed a phyto-inhibitory effect on the cereals, the most pronounced being corn and oats. Propolis powder samples displayed a lower phyto-inhibitory activity than propolis extracts. Also, all tested products showed inhibitory efficacy against both bacteria and fungi. Furthermore, principal component analysis showed differences between the samples' phyto-inhibitory and antimicrobial properties depending on the geographical origin. Positive correlations were found between the polyphenols, flavonoid content, and antioxidant activity, respectively. These data support propolis' phyto-pharmaceutical potential related to its use in plant crop management as an alternative in ecological agriculture.