581
2010) whereas higher bioavailability of glucosides form of isoflavones is also reported
(Lim and Koffas 2010). More interestingly, Richelle et al. (2002) and Zubik and
Meydani (2003) did not observe any absorption difference when either aglycones or
glucosides were administered. In another study, isoflavones glycosides were not
found in human plasma after ingesting either 50 mg of isoflavone glycosides (daidzin
or genistin) or 250 mL of soymilk (Lim and Koffas 2010).
The bioavailability of the most active green tea antioxidant, epigallocatechin gallate (EGCG) remains uncertain (Naumovski et al. 2015). Only a small fraction of
tea catechins present in the intestinal tract after drinking tea can be absorbed, and
therefore considered to be bioavailable. The pharmacokinetics study indicated
that after oral administration of tea to rats, about 14% of (−) EGC, 31% of (−)–EC,
and (−)–EGCG is available in the blood (Chen et al. 1997). Studies on the
bioavailability of pure EGCG in humans are limited, as such studies were primarily
focused on the pharmacokinetic properties of preparations where EGCG was
imbedded in a polyphenolic complex, as part of green tea extracts (Lee et al. 2002;
Naumovski et al. 2015).
Other Phytochemical Nutrients Several miscellaneous phytochemicals like resveratrol, curcumins and glucosinolates also exhibit nutraceutical properties.
Resveratrol is a major contributor to the health benefits related with the consumption of grape products. In vitro studies confirmed the potential of resveratrol as a
‘therapeutic agent’ and yet animal and clinical trials revealed inconsistent and less
promising results which might be due to low bioavailability (De Vries et al. 2018;
Sahebkar et al. 2015). The low bioavailability of resveratrol results in low plasma
concentrations which gives rise to limited systemic distribution and concentration
that is not high enough in some active sites to elicit significant pharmacological
effects. A study has revealed that when resveratrol is combined with some other
phytochemical, the bioactivity get enhanced (Johnson et al. 2011).
Poor water solubility, low oral bioavailability, poor absorption in GIT, extensive
pre–systemic metabolism, rapid systemic elimination, low intrinsic activities are
major drawbacks for curcumin derived phytochemicals (Anand et al. 2007). Clinical
trials have depicted that curcumin is safe at higher doses (12 g day
−1
) in humans but
unfortunately exhibit poor bioavailability. To improve the bioavailability further
numerous approaches involving liposome, phytosome, nano–particles, nano–emulsions, cyclodextrin encapsulation and use of adjuvant like piperine, and the use of
curcumin phospholipid complex (Anand et al. 2007) have been followed to enhance
their activity and bioavailability (Mobasheri et al. 2012). In another study oral
administration of liposome–encapsulated curcumin enhanced the bioavailability of
curcumin. In another study, broccoli sprouts combined with glucoraphanin powder
synergistically enhanced the bioavailability of sulforaphane (glucosinolate) and
proved that regular intake of broccoli sprouts enriched with glucoraphanin powder
reduces the risk of cancer compared with glucoraphanin powder or sprouts alone
(Cramer et al. 2012).
25 Bioavailability of Nutrients and Safety Measurements
2010) whereas higher bioavailability of glucosides form of isoflavones is also reported
(Lim and Koffas 2010). More interestingly, Richelle et al. (2002) and Zubik and
Meydani (2003) did not observe any absorption difference when either aglycones or
glucosides were administered. In another study, isoflavones glycosides were not
found in human plasma after ingesting either 50 mg of isoflavone glycosides (daidzin
or genistin) or 250 mL of soymilk (Lim and Koffas 2010).
The bioavailability of the most active green tea antioxidant, epigallocatechin gallate (EGCG) remains uncertain (Naumovski et al. 2015). Only a small fraction of
tea catechins present in the intestinal tract after drinking tea can be absorbed, and
therefore considered to be bioavailable. The pharmacokinetics study indicated
that after oral administration of tea to rats, about 14% of (−) EGC, 31% of (−)–EC,
and (−)–EGCG is available in the blood (Chen et al. 1997). Studies on the
bioavailability of pure EGCG in humans are limited, as such studies were primarily
focused on the pharmacokinetic properties of preparations where EGCG was
imbedded in a polyphenolic complex, as part of green tea extracts (Lee et al. 2002;
Naumovski et al. 2015).
Other Phytochemical Nutrients Several miscellaneous phytochemicals like resveratrol, curcumins and glucosinolates also exhibit nutraceutical properties.
Resveratrol is a major contributor to the health benefits related with the consumption of grape products. In vitro studies confirmed the potential of resveratrol as a
‘therapeutic agent’ and yet animal and clinical trials revealed inconsistent and less
promising results which might be due to low bioavailability (De Vries et al. 2018;
Sahebkar et al. 2015). The low bioavailability of resveratrol results in low plasma
concentrations which gives rise to limited systemic distribution and concentration
that is not high enough in some active sites to elicit significant pharmacological
effects. A study has revealed that when resveratrol is combined with some other
phytochemical, the bioactivity get enhanced (Johnson et al. 2011).
Poor water solubility, low oral bioavailability, poor absorption in GIT, extensive
pre–systemic metabolism, rapid systemic elimination, low intrinsic activities are
major drawbacks for curcumin derived phytochemicals (Anand et al. 2007). Clinical
trials have depicted that curcumin is safe at higher doses (12 g day
−1
) in humans but
unfortunately exhibit poor bioavailability. To improve the bioavailability further
numerous approaches involving liposome, phytosome, nano–particles, nano–emulsions, cyclodextrin encapsulation and use of adjuvant like piperine, and the use of
curcumin phospholipid complex (Anand et al. 2007) have been followed to enhance
their activity and bioavailability (Mobasheri et al. 2012). In another study oral
administration of liposome–encapsulated curcumin enhanced the bioavailability of
curcumin. In another study, broccoli sprouts combined with glucoraphanin powder
synergistically enhanced the bioavailability of sulforaphane (glucosinolate) and
proved that regular intake of broccoli sprouts enriched with glucoraphanin powder
reduces the risk of cancer compared with glucoraphanin powder or sprouts alone
(Cramer et al. 2012).
25 Bioavailability of Nutrients and Safety Measurements