Introduction:
Bad eating habits are often linked to pathological conditions such as diabetes, cancer, and cardiovascular disorders. Frequent consumption of plant origin foods has been considered as beneficial in preventing these diseases due to their bioactive compounds such as phytochemicals like polyphenols and carotenoids. Phytochemicals have a strong antimicrobial, antioxidant, anti-inflammatory, and epigenetic action. For this purpose, nowadays, both nutraceuticals and functional foods based on phytochemicals are very popular.

Methods:
A systematic search of the available literature in the PubMed, EMBASE, Scopus and Google Scholar databases was performed. The following search terms were applied: “phytochemicals, bioactive compounds, functional foods, nutraceuticals, food matrix” and all articles published in English were evaluated.

Results:
The effectiveness of plant bioactive compounds included to nutraceuticals and functional foods has been evaluated through their bioavailability and bioaccessibility. As many plant ingredients, phytochemicals have a low solubility, poor permeability, and short shelf life while any chemical structural change of the original bioactive compound during storage or digestion can modify their effectiveness. In recent years, new food production and processing techniques have been used in order to preserve and stabilize the bioactive compounds and improve their absorption. Furthermore, food matrices based on nanotechnology can increase biological efficiency and food safety preserving plant bioactive compounds. However, toxicity of phytochemicals has been reported because of the complex nature of plant products, mainly to possible interaction with other ingredients

Conclusions:
Both phytochemicals and nanotechnology based food matrices using are becoming a growing trend in food and drug industries as a potential source of bioactive compounds improving consumer health and well-being through prevention rather than treatment. However, further research must be done so that the legal framework for their safety and suitability is defined, the required doses are established and their bioavailability is improved.