Herbal formulation, Novel dosage forms (Part - 2), T.Y B.Pharm, Sem VI, Herbal drug technology, Unit

NOVEL HERBAL DOSAGE FORMS (PART - 2)

NOVEL HERBAL FORMULATION

Topics covered:-

Liposomes
Pharmacosomes
Nanoparticles

2. LIPOSOMES:-

WHAT IS A LIPOSOME:-

Liposomes are simple microscopic vesicles in which an aqueous

volume is entirely enclosed by a Phospholipids bilayer molecule.

The size of a liposome ranges from some 20 nm up to several

micrometers.

COMPOSITION OF LIPOSOME:- The main components of liposomes are…..

1. Phospholipids

2. Cholesterol

PHOSPHOLIPIDS:- Phospholipids are the basic molecular building block of the liposome.

Phospholipids is a lipid which is Amphiphatic which consist of - 1 hydrophilic polar head

2 hydrophobic tails hence have affinity for both aqueous and polar moiety i.e. both

hydrophilic drugs can be encapsulated in the aqueous phase and hydrophobic drug

molecules can be incorporated in the lipid bilayers. Most commonly used phospholipid is

- Phosphotidylcholine or PC – phosphatidylethanolamine.

CHOLESTROL:- Role of cholesterol in bilayer formation….

1. Cholesterol acts as fluidity buffer.

2. After intercalation with phospholipids molecules alter the freedom of motion of carbon molecules in the acyl chain.

3. Restricts the transformation of trans to gauche conformation.

4. Enhances the stability of the membrane.

5. Enhances the rigidity of the phospholipid bilayer

6. Reduces the permeability of water soluble substance

The liposomes are spherical particles that encapsulate a fraction of the solvent, in

which they freely pass around or float into their interior. They can carry one, several, or

multiple concentric membranes.

Liposomes are constructed of polar lipids, which are characterized by having a

lipophilic and hydrophilic group of the same molecules. On interaction with water,

polar lipids self-layup and form self-organized colloidal particles.

Liposome-based drug delivery systems offer the potential to raise the therapeutic index

of anticancer agents, by increasing the drug concentration in tumor cells or by lessening

the exposure in normal tissues exploiting enhanced permeability and retention effect

phenomenon or by utilizing targeting strategies.

ADVANTAGES:- The primary advantages of using liposomes include....

1. The high biocompatibility,

2. The easiness of preparation,

3. The chemical versatility that allows the loading of hydrophilic, amphiphilic, and lipophilic compounds, and

4. The simple modulation of their pharmacokinetic properties by varying the chemical composition of the player components.

Some examples of herbal liposomes and there application.

3. PHARMACOSOMES:-

Pharmacosomes is derived from the word “Pharmakon “which means drug and “soma“
meaning carrier. It means a vesicular system in which the drug is associated with the carrier.

Pharmacosomes are defined as colloidal dispersions of drugs covalently bound to lipids and
may exist as ultrafine vesicular, micellar or hexagonal aggregates, depending on the
chemical structure of drug-lipid complex

In the pharmacosomes, the prodrug conjoins hydrophilic and lipophilic properties, and
therefore acquires amphiphilic characters. Similar to other vesicle forming components, it
was found to reduce interfacial tension and at higher concentrations exhibits mesomorphic
behaviour.

These lipid conjugated vesicles may exist as colloidal, nanometre size micelles, vesicles or
may be in the form of hexagonal assembly enjoying a functional hydrogen atom banking
upon the architecture of the complex. The drug molecule with a free carboxylic or
functional hydrogen atom like amino, hydroxyl groups is converted to an ester with the
help of the hydroxyl moiety of the lipid, resulting in the formation of a prodrug.

The prodrug possesses both hydrophilic and lipophilic properties. Despite these
properties, prodrugs have the capability to reduce interfacial tension, increase the area of
contact, and hence improve bioavailability.

They aid the deportation through the cell membrane, cell wall, and tissues. If the
concentration is increased beyond a level, it may exist in an intermediate state between the
liquid and the crystal.

4. NANOPARTICLES:-

Nanoparticles are solid colloidal particles ranging from 1 to 1000 nm in size, they consist of
macromolecular materials in which the active ingredients (drug or biologically active material) is
dissolved, entrapped, or encapsulated, or adsorbed.

Definition Nanocapsules: in which the drug is confined to an aqueous or oily core
surrounded by a shell-like wall. Alternatively, the drug can be covalently attached to the
surface or into the matrix.

Nanoparticles are efficient delivery systems for the delivery of both hydrophilic and
hydrophobic drugs. The major goal behind designing nanoparticle as a delivery
arrangement is to control particle size, surface properties, and release of
pharmacologically active agents in order to achieve the site-specific action of the drug at
the therapeutically optimal rate and dose regimen.

Two types of nanoparticles….
1. Nanospheres
2. Nanocapsules

TYPES OF NANOPARTICLES

The nanospheres have a matrix type structure in which the active ingredient is dispersed throughout (the molecules), whereas the nanocapsules have a polymeric membrane and an active ingredient core (Membrane wall structure with an oil core containing drug).

ADVANTAGES:-

1) Nanoparticle drug carriers have higher stabilities.

2) Nanoparticles have higher carrier capacity.

3) Feasibility of incorporation of both hydrophilic and hydrophobic substances.

4) Feasibility of variable routes of administration.

5) Nanoparticles are biodegradable, non-toxic and capable of being stored for longer

periods.

6) Nanoparticles can also be used for controlled delivery of drug.

DISADVANTAGES:-

1) Polymeric nanoparticles posses limited drug-loading capacity

2) On repeated administration, toxic metabolites may be formed during the

biotransformation of polymeric carriers.