A Path to the Formation Mechanism of Propolis Nanoparticles, their Cytotoxicity on 3T3 Fibroblasts, Metastatic Murine B16F10 Cells, and their In vivo Irritability in Animals

Background: Natural products such as propolis are an important source of biologically active compounds with the potential to treat health disorders. Propolis is a well-known waxy resin recognized for its antimicrobial immunomodulatory and cytotoxic effects Objective: In this study we aimed to clarify the formation mechanism of propolis nanoparticles from the perspective of their stability and chemical composition. By evaluating the light absorption behaviour of the nanoparticles formed in different media and quantifying the polyphenols we show that they are superficially hydrophobic nanoparticles with the capacity to encapsulate some polar compounds Methods: Biological activity was evaluated by in vitro cell viability performed on NIH/3T3 fibroblasts incubated with 10 100 and 1000 μg/mL of propolis nanoparticles for 48 hours Results: The results show that nanoparticles are cytocompatible with a proliferation effect. In contrast the results of the viability of metastatic murine B16F10 cells indicate that a dose with a concentration of 5 µg/mL in the cell culture media is sufficient to stop the abnormal cell growth having an antitumor effect. This effect might be related to the flavonoids present in the propolis nanoparticles. In vivo dermal irritability tests on New Zealand rabbits show that propolis nanoparticles' aqueous dissolution was non-irritant Conclusion: According to the results obtained from this study reducing the size of raw propolis down to nanoparticles and dispersing them in water solvents enhance its positive effects.