Phytochemicals include a heterogeneous class of compounds (polyphenols, carotenoids, tocopherols, phytosterols, and organosulfur compounds) with different chemical structures (hydrophilic or lipophilic), distribution in nature (specific or ubiquitous), range of concentrations both in foods and in the human body, possible site of action, effectiveness against oxidative species, specificity, and biological action. Factors such as food source, chemical interactions, other biomolecules present in the food, restricted release of compounds from plant matrix, the solubility in gastrointestinal fluid, the permeability across intestinal epithelial cells, enzymatic and chemical reactions occurring within the gastrointestinal tract, drastically affect the bioavailability of these bioactive compounds. The chapter will present the essential aspects of bioavailability and bio accessibility of phytochemicals, factors limiting the oral bioavailability, as well as the new delivery approaches that have potential and can be explored to enhance the bioavailability of phytochemicals.
TopIntroduction
Human beings are using plant-derived materials as a source for treating many diseases. A lot of processed foods as well as naturally-occurring compounds are found to have positive effect on the health of human beings. These compounds are called as nutraceuticals and the examples include carotenoids, vitamins, polyunsaturated fatty acids, flavonoids, peptides, proteins, curcuminoids, minerals, oligosaccharides, and dietary fibers (Espin et al., 2007; Wildman & Kelley, 2007). For assessing the chemotherapeutic and chemo-preventive efficiency of these plant-based materials, they are being tested in various systems. The definition of bioavailability in the human beings states it as a substance that reaches the circulatory system after ingestion of the food material which is then delivered into specific tissues to ensure the biological availability for imparting health benefits. The potential advantages of many nutraceuticals are not very well known as they have low or variable oral bioavailability (Patel & Velikov, 2011; Fernandez-Garcia et al., 2012; Rein et al., 2013). The reason behind the nutraceutical’s poor bioavailability is a lot of physiological and physicochemical processes such as decreased solubility in gastric juices (Porter et al., 2007; Pouton & Porter, 2008), controlled release from the food matrix (Moelants et al., 2012), less permeability through the epithelial cells or mucus membrane (Fleisher et al., 1999; Martinez & Amidon 2002; Actis-Goretta et al., 2013), development of insoluble components with other materials in the gastrointestinal tract (Rimbach et al., 2008), and molecular alterations in the GIT (Hurst et al., 2007; D’Ambrosio et al., 2011; Fernandez-Garcia et al., 2012).
Knowing these problems associated with bioavailability of different food materials could be helpful in finding different tactics to surpass its shortcomings. The major part for improving the bio-efficacy is the improvement of bioavailability of biologically active food materials. For this, the molecules are chemically or technologically modified to enhancing their solubility at the absorption site. Many research studies have also been conducted on knowing the possibility of enhancing the oral bioavailability by utilizing certain biologically active mediators like nano emulsions, microemulsions, emulsions, biopolymer nanoparticles, solid lipid nanoparticles, microgels, etc. as delivery approaches (Luo et al., 2014; Yang et al., 2015, Souza-Simões de et al., 2017; Jain et al., 2018; Silva et al., 2019). This chapter, thus, aims to give a thorough review on some chief factors that have an influence on the nutraceutical’s bioavailability. This chapter also put emphasis on various characteristics of plant-derived bioactive components such as digestibility and bio accessibility. Some of the new delivery approaches that have the potential to enhance bioavailability of phytochemicals are also discussed.