Abstract:
Polyphenols are one of the most abundant classes of secondary metabolites in plants and particularly
relevant in leafy vegetables, fruits, berries, tea, and other beverages, with a wide range of health-promoting
activities reported. They are also among the most widely studied natural products regarding their
biosynthesis, chemical properties, and pharmacological activities. Different polyphenols such as
anthocyanins, coumarins, carotenoids, flavonoids, and xanthones have been reported to be
promising anti-inflammatory, anticancer, antidiabetic, antihyperlipidemic, antioxidant, and
neuroprotective agents (Ganesan and Xu, 2017; Khan et al., 2019). In recent years, there is a
growing number of papers that deal with the isolation, characterization, and bioactivity evaluation of
polyphenols. However, many published results are mostly based on in vitro evidence. At the same time,
there is less focus on the bioavailability, study of detailedmechanisms of action using animal models, and
possible toxicities. There have also been concerns about the specificity of the compounds’ effects and the
dose levels needed to achieve such outcomes. Althoughmany polyphenols show potent bioactivity during
testing with in vitro evaluation systems, there are various challenges at an in vivo level. The in vitro results
often cannot be translated to similar effects in animal models and clinical studies (Hu, 2007).
