Flavonoids like quercetin and resveratrol suffer from low aqueous solubility,
rapid metabolism, and photosensitivity which limited their oral bioavailability when
taken orally (Li et al. 2009; Pandita et al. 2014). Formulation of quercetin into SLN
remarkably enhances its gastrointestinal absorption and pharmacokinetic study in
animal model demonstrated that the relative bioavailability of the SLN formulation
against the quercetin suspension 571.4% indicating phenomenal increase in its oral
bioavailability (Li et al. 2009). Stearic acid-based SLN of resveratrol was also
reported to increase the oral bioavailability of the bioactive compound by eightfolds
when compared to its suspension. Similarly, oral bioavailability of curcumin was
also increased in a dose-dependent manner when formulated into soy lecithin-based
SLN in animals. Improvement in oral bioavailability of curcumin-loaded SLN
against solubilized curcumin rat plasma was reported to be 155 times at the dose of
1 mg/kg, 59 times at 12.5 mg/kg, 32 times at 25 mg/kg, and 39 times at the dose of
50 mg/kg (Kakkar et al. 2011). Bioavailability enhancement through SLN formulation has also been reported for other bioactive phytochemicals like an alkaloid
vinpocetine which exhibit poor aqueous solubility and extensive first-pass metabolism (Luo et al. 2006; Medina 2010). Oral bioavailability from SLN vinpocetine
formulation was found to be 4.16–4.17 times that of the suspension (Luo et al.
2006).
Recently, SLN-based sclareol was prepared following hot homogenization
technique and evaluated its anti-proliferative activity in vitro against A549 human
lung epithelial cancer cells which showed similar cytotoxicity to the plain sclareol
but long-term stability and sustained release of sclareol were obtained with the SLN
formulation (Hamishehkar et al. 2018).
NLC-based formulations also exhibit promising results in enhancing bioavailability of bioactive compounds. Silymarin was encapsulated in NLC-based formulation using glycerol distearates, oleic acids, lecithin, and Tween-80, which
increases the oral bioavailability of silymarin against solid dispersion pellets and
commercially available silymarin preparation, Legalon
® , was 2.54- and 3.10-folds,
respectively (Shangguan et al. 2014). However, when NLC was compared against
microemulsion in its capacity to enhance oral bioavailability of luteolin in animal
model, microemulsion fared better than the NLCs (Liu et al. 2014). The relative
bioavailability of NLC-based and microemulsion-based luteolin formulations to the
luteolin suspension were found to be 515.06% and 885.46%, respectively.
20.3.2.3 Liposomes and Phytosomes
Both liposomes and phytosomes are also lipid-based formulations suitable to
facilitate the delivery of poorly aqueous-soluble phytochemicals. Liposomes are
spherical vesicles (15–100 nm) consisting of phospholipid with a liquid core and
variable layers, where the hydrophobic tails of the phospholipids face each other,
while the hydrophilic heads are projected toward the inner aqueous core or the
outside boundary of the liposome (Fig. 20.3) (Bonechi et al. 2019; Emami et al.
2018). They resemble biological membrane and can accommodate both hydrophilic
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L. Pachuau et al.
rapid metabolism, and photosensitivity which limited their oral bioavailability when
taken orally (Li et al. 2009; Pandita et al. 2014). Formulation of quercetin into SLN
remarkably enhances its gastrointestinal absorption and pharmacokinetic study in
animal model demonstrated that the relative bioavailability of the SLN formulation
against the quercetin suspension 571.4% indicating phenomenal increase in its oral
bioavailability (Li et al. 2009). Stearic acid-based SLN of resveratrol was also
reported to increase the oral bioavailability of the bioactive compound by eightfolds
when compared to its suspension. Similarly, oral bioavailability of curcumin was
also increased in a dose-dependent manner when formulated into soy lecithin-based
SLN in animals. Improvement in oral bioavailability of curcumin-loaded SLN
against solubilized curcumin rat plasma was reported to be 155 times at the dose of
1 mg/kg, 59 times at 12.5 mg/kg, 32 times at 25 mg/kg, and 39 times at the dose of
50 mg/kg (Kakkar et al. 2011). Bioavailability enhancement through SLN formulation has also been reported for other bioactive phytochemicals like an alkaloid
vinpocetine which exhibit poor aqueous solubility and extensive first-pass metabolism (Luo et al. 2006; Medina 2010). Oral bioavailability from SLN vinpocetine
formulation was found to be 4.16–4.17 times that of the suspension (Luo et al.
2006).
Recently, SLN-based sclareol was prepared following hot homogenization
technique and evaluated its anti-proliferative activity in vitro against A549 human
lung epithelial cancer cells which showed similar cytotoxicity to the plain sclareol
but long-term stability and sustained release of sclareol were obtained with the SLN
formulation (Hamishehkar et al. 2018).
NLC-based formulations also exhibit promising results in enhancing bioavailability of bioactive compounds. Silymarin was encapsulated in NLC-based formulation using glycerol distearates, oleic acids, lecithin, and Tween-80, which
increases the oral bioavailability of silymarin against solid dispersion pellets and
commercially available silymarin preparation, Legalon
® , was 2.54- and 3.10-folds,
respectively (Shangguan et al. 2014). However, when NLC was compared against
microemulsion in its capacity to enhance oral bioavailability of luteolin in animal
model, microemulsion fared better than the NLCs (Liu et al. 2014). The relative
bioavailability of NLC-based and microemulsion-based luteolin formulations to the
luteolin suspension were found to be 515.06% and 885.46%, respectively.
20.3.2.3 Liposomes and Phytosomes
Both liposomes and phytosomes are also lipid-based formulations suitable to
facilitate the delivery of poorly aqueous-soluble phytochemicals. Liposomes are
spherical vesicles (15–100 nm) consisting of phospholipid with a liquid core and
variable layers, where the hydrophobic tails of the phospholipids face each other,
while the hydrophilic heads are projected toward the inner aqueous core or the
outside boundary of the liposome (Fig. 20.3) (Bonechi et al. 2019; Emami et al.
2018). They resemble biological membrane and can accommodate both hydrophilic
698
L. Pachuau et al.