Development of Micellized Antimicrobial …
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species of Escherichia, Salmonella, Klebsiella, Bacillus, and Clostridium. Antibacterial activity of allicin is due to the apparent inability of most bacteria to develop
resistance to it because the mode of action is completely different from that of other
antibiotic substances. Allicin acts by inhibiting the thiol-containing enzymes in the
microorganisms (Miron et al. 1998). However, there are several constraints in the
development of herbal drugs, the most significant of them being their nonspecific
mode of action and poor bioavailability. Moreover, most of the bioactive compounds
are highly unstable in nature, which makes the extraction process very complicated
and expensive. However, researchers are constantly stressing to develop advanced
techniques for stabilization, extraction, and sustained delivery of PDD for better
bioavailability.
5 Micellization: A Contemporary Way of Drug Stability
Enhancement
PDDs such as thiosulfinates, eugenol, essential oil, etc. are volatile and unstable in
nature. They are sparingly soluble in commonly accepted pharmaceutical solvents.
Therefore, one of the major challenges in the development of these herbal drugs
is to enhance their solubility, thereby facilitating their extraction process. The
earlier procedures applied to enhance drug stability and extractions were pH adjustment, cosolvent addition, complexation, and surfactant addition. In aqueous solution, surfactant molecules above their critical micelle concentration (CMC) selfassemble into nearly spherical clusters of micelles due to phase separation guided
by the hydrophilic heads and hydrophobic tail groups of the surfactant molecules
(Grillo et al. 2018). The hydrophobic micellar core provides an apt environment
for solubilization of the hydrophobic drug of interest, hence leading to entrapment
of drugs. The drug is incorporated into the micellar core employing noncovalent
bonds, which causes steric hindrance to the drug molecule. This phenomenon effectively hinders the interaction of the PDDs with surrounding entities, thus augmenting
the drug’s pharmacokinetic and pharmacodynamic properties, thereby renders the
stability. When administered, the release of the entrapped drug occurs at the target
site through the dissolution of the micelle at the low intestinal pH (1.5–3). Curcumin,
a slightly water-soluble drug with very poor bioavailability was stabilized and solubilized using a self-microemulsifying drug delivery system (SMEDDS). SMEDDS
was formulated by using a surfactant, cosurfactant, and an oil into which curcumin
was incorporated. The best result was obtained when SMEDDS was formulated with
emulsifier OP and Cremophor EL as surfactant, cosurfactant PEG, and ethyl oleate
oil. With this SMEDDS formulation, curcumin was reported to be stable for 3 months
when stored at 4 °C (Akula et al. 2014).
87
species of Escherichia, Salmonella, Klebsiella, Bacillus, and Clostridium. Antibacterial activity of allicin is due to the apparent inability of most bacteria to develop
resistance to it because the mode of action is completely different from that of other
antibiotic substances. Allicin acts by inhibiting the thiol-containing enzymes in the
microorganisms (Miron et al. 1998). However, there are several constraints in the
development of herbal drugs, the most significant of them being their nonspecific
mode of action and poor bioavailability. Moreover, most of the bioactive compounds
are highly unstable in nature, which makes the extraction process very complicated
and expensive. However, researchers are constantly stressing to develop advanced
techniques for stabilization, extraction, and sustained delivery of PDD for better
bioavailability.
5 Micellization: A Contemporary Way of Drug Stability
Enhancement
PDDs such as thiosulfinates, eugenol, essential oil, etc. are volatile and unstable in
nature. They are sparingly soluble in commonly accepted pharmaceutical solvents.
Therefore, one of the major challenges in the development of these herbal drugs
is to enhance their solubility, thereby facilitating their extraction process. The
earlier procedures applied to enhance drug stability and extractions were pH adjustment, cosolvent addition, complexation, and surfactant addition. In aqueous solution, surfactant molecules above their critical micelle concentration (CMC) selfassemble into nearly spherical clusters of micelles due to phase separation guided
by the hydrophilic heads and hydrophobic tail groups of the surfactant molecules
(Grillo et al. 2018). The hydrophobic micellar core provides an apt environment
for solubilization of the hydrophobic drug of interest, hence leading to entrapment
of drugs. The drug is incorporated into the micellar core employing noncovalent
bonds, which causes steric hindrance to the drug molecule. This phenomenon effectively hinders the interaction of the PDDs with surrounding entities, thus augmenting
the drug’s pharmacokinetic and pharmacodynamic properties, thereby renders the
stability. When administered, the release of the entrapped drug occurs at the target
site through the dissolution of the micelle at the low intestinal pH (1.5–3). Curcumin,
a slightly water-soluble drug with very poor bioavailability was stabilized and solubilized using a self-microemulsifying drug delivery system (SMEDDS). SMEDDS
was formulated by using a surfactant, cosurfactant, and an oil into which curcumin
was incorporated. The best result was obtained when SMEDDS was formulated with
emulsifier OP and Cremophor EL as surfactant, cosurfactant PEG, and ethyl oleate
oil. With this SMEDDS formulation, curcumin was reported to be stable for 3 months
when stored at 4 °C (Akula et al. 2014).