Methods to Study Bioavailability of Phytochemicals
2004
Phytochemicals have a profound influence on long-term health. However, their dietary
intake does not necessarily reflect their bioavailability, i.e., the dose reaching the target
tissue. Understanding the bioavailability of phytochemicals is critical and must always be
considered. In comparison with that of macronutrients, the beneficial intake range of
micronutrients and phytochemicals is relatively narrow and there is a possibility of both
adverse effects at higher doses and no effect at very low doses. Isothiocyanates, derived
from glucosinolates, may be cited as an example of a group of phytochemicals exhibiting
such a small beneficial dose window. At low concentrations, these compounds activate
mitogen-activated protein kinases (MAPK) such as ERK2, JNK1, or p38, leading to
expression of survival genes (c-Fos, c-Jun) and defensive genes (phase 2 detoxifying
enzymes, such as glutathione-S-transferase and quinone reductase) involved in the
“homeostasis response.” Increasing concentrations of isothiocyanates may additionally
activate the caspase pathway, leading to apoptosis: finally, pharmacological and suprapharmacological doses may lead to nonspecific necrotic cell death and genotoxicity [1].
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