A NOVEL APPROACH TO ENHANCE BIOAVAILABILITY OF PHYTOMEDICINES

Phytosomes

INTRODUCTION Phytoconstituents, despite having excellent bioactivity in

vitro, demonstrate less or no in vivo actions due to their poor lipid solubility or higher molecular size or both, resulting in poor absorption and poor bioavailability.

Lipid solubility and molecular size are the major limiting factors for molecules to pass the biological membrane and to be absorbed systematically following oral or topical administration

Multiple approaches for improving bioavailability include Chemical derivatization Combination of active molecules with other compounds New drug delivery systems

phytosomes

Term “phyto” means plant, while “some” means cell-like. Phytosomes are novel drug delivery systems containing

hydrophilic bioactive phytoconstituents of herbs surrounded and bound by phospholipids.

Phytosome is a patented technology developed by a leading manufacturer of drugs and nutraceuticals (Indena), which are prepared by incorporating standardized plant extracts or water soluble phytoconsituents into phospholipids to produce lipid compatible molecular complexes.

Phytosomes exhibit a better pharmacokinetic and pharmacodynamic profile than conventional herbal extracts.

The lipid-phase substances employed to make phytoconstituents lipid compatible are phospholipids from soy, mainly phosphatidylcholine .

PC is the principal molecular building block of the cell membranes, miscible both in water and in oil environments, and is well absorbed when taken orally.

phytosome is usually a phytoconstituent molecule linked with at least one PC molecule. phospholipid–substrate interaction is due to the formation of hydrogen bonds between the polar head of the phospholipids (i.e., phosphate and ammonium groups) and the polar functionalities of the substrate.

Two long aliphatic chains are wrapped around the active principle, producing a lipophilic envelope that shields the polar head of the phospholipid and the phytoconstituents.

Phytosomes are lipophilic substances with a definite melting

point.

The size of phytosome varies from 50 nm to a few hundred μm.

Freely soluble in aprotic solvents, moderately soluble in fats,

insoluble in water and relatively unstable in alcohol.

When treated with water, they assume a micellar shape, forming

structures that resemble liposomes exhibiting fundamental

differences.

Preparation of Phytosomes

Phytosomes are prepared by reacting 3-2 moles or preferably 1 mole of phosphatidylcholine with 1 mole of activ phytoconstituents mostly the flavonoids and the terpenoids in an aprotic solvent such as dioxane or acetone from which complex can be isolated by precipitation with non solvent such as aliphatic hydrocarbons or by lyophilization or by spray drying. In the phyto-phospholipid complex formation the ratio between these two components is in the range of 0.5-2 moles The most preferable ratio of phospholipid to phytoconstituents is 1:1 .The phospholipids mostly selected for phytosome preparations are selected from group consisting of soy lecithin(Glycinemax);phosphatidylcholine,phosphatidylethanolamine phosphatidyiserine, in which acyl group may be same or different and mostly derived from palmitic, stearic, oleic, linoleic acid. The phospholipid mostly selected is phophatidylcholine

Phytosomes are prepared by reacting a synthetic or natural phospholipid with the standardized plant extract in a ratio ranging from 0.5-2.0. But usually 1:1 ratio is preferable. The reaction is carried out alone or in the natural mixture in aprotic solvent, such as, dioxane, methylene chloride, acetone; from which the novel complex can be isolated by precipitation with a non-solvent, usually an aliphatic hydrocarbon or by lyophilisation or by spay drying. The solubilization or complex formation is sometimes carried out by refluxing the stoichiometric ratio mixture for a specified period in the aprotic solvent. The phospholipids mostly selected for phytosome preparations are selected from group consisting of soy lecithin(Glycinemax); phosphatidylcholine, phosphatidylethanolamine phosphatidyiserine, in which acyl group may be same or different and mostly derived from palmitic, stearic, oleic, linoleic acid

(by lyophilization or spray drying)

Isolation by precipitation

Formation of Phytosomal complex

Hydration

Thin Film Formation

Drying

Solution of phospholipid in solution containing organic solvent+extract

Dissolve in solution containing organic solvent

Phospholipid

Stages of Phytosome preparation

Advantages of Phytosomes

It enhances the absorption of lipid insoluble polar phytoconstituents through oral as well as topical route showing better bioavailability, hence significantly greater therapeutic benefit.

As the absorption of active constituent(s) is improved, its dose requirement is also reduced.

Phosphatidylcholine used in preparation of phytosomes, besides acting as a carrier also acts as a hepatoprotective, hence giving the synergistic effect when hepatoprotective substances are employed.

Chemical bonds are formed between phosphatidylcholine molecule and phytoconstituent, so the phytosomes show better stability profile.

Added nutritional benefit of phospholipids.

Property Phytosome LiposomeBonding It is a unit of few

molecules bonded together

It is an aggregate of many phospholipid molecules that encloses other phytoactive molecules without specifically bonding to them.

Bioavailability and

Absorption

It has much better bioavailability and absorption

Its bioavailability and absorption is lesser than phytosome.

Arrangement of molecules

In phytosome, phospholipid (phosphatidylcholine) and an individual phytoconstituent are present in 1:1 or 2:1 ratio depending on the substance.

In liposomes, hundreds and thousands of phosphatidylcholine molecules surround the water soluble molecule.

Differences between phytosome and liposome

Characterization of Phytosomes Visualization: visualization of phytosomes can be achieved

using transmission electron microscopy (TEM) and by scanning elctron microscopy (SEM).

Transition temperature: The transition temperature of vesicular lipid system can be determined by Differential scanning calorimetry.

Entrapment efficiency: The entrapment efficiency of a phytosomal formulation can be determined by subjecting the formulation to ultracentrifugation technique.

Vesicle size and Zeta potential: The particle size and zeta potential of phytosomes can be determined by dynamic light scattering (DLS) which uses a computerized inspection system and photon correlation spectroscopy.

Surface tension activity measurement: The surface tension activity of drug in aqueous solution can be measured by ring method Du Nouy ring tensiometer.

Vesicle stability: the stability of vesicles can be determined by assessing the size and structure of the vesicles over time. The mean size is measured by DLS and structural changes can be monitored by TEM

Drug content: the amount of drug can be quantified by chrmatographic or spectroscopic methods.

ADVANCEMENT & RECENT RESEARCH ON PHYTOSOMES

Mascarella et al, 1999, reported better bioavailability of silymarin phytosome than the uncomplexed form using 232 patients with chronic hepatitis.

Grange et al, and Busby et al, conducted series of experiments on silymarin phytosomes and reported the better fetoprotectant activity of the phytosomal form.

Jhiang et al, 2001, prepared Herba Epimedii flavonoid phytosome (EPF) by means of solvent evaporation technique and the accumulative dissolution of different ratios of EPF-PVP precipitate was investigated by dissolution study. The study showed that the dissolution of the precipitate was significantly higher than that of its physical mixture and Herba Epimedii extract tablets.

Bombardelli et al, 2005, reported that the silymarin phytosomes showed much higher specific activity and a longer lasting action than the single constituent, with respect to percent reduction of edema, inhibition of myeloperoxidase activity, antioxidant and free radical scavenging activity.

Maiti et al, 2005, developed a quercetin phytosome and reported that the phytosomal complex shows better therapeutic efficacy than the uncomplexed molecule in rat liver injury induced by carbon tetrachloride. They also recently reported the enhanced bioavailability and hepatoprotective activity of andographolide herbosome by an experiment on rats and found that the phytosomal form has an enhanced activity than that of uncomplexed andrographolide at the same dose leevel.

Maiti et al, 2006, 2007, also developed naringenin and curcumin phytosomes in two different studies and reported that antioxidant activity of the phytosomal complex has better therapeutic efficacy. They developed simple methods of preparation of phytosomes.

Xiao et al, 2006, Prepared silymarin phytosomes and studied its pharmacokinetics in rats and reported that the bioavailability of silybin has increased markedly in phytosomal formulation. Hepatoprotective activity of silymarin phytosomes was found to be more than silymarin alone against aflatoxin B1, as reported by Tedesco et al, 2008, after performing the experiment on broiler chicks

Yanyu et al, (2006) investigated that the well known soothing activity of silymarin is increased by more than six times in sylimarin phytosome in experimental models.

Kidd (2009) reported that. Ginselect phytosomes posses a transdermic action which helps the ginseng saponin present in the phospholipid complex to penetrate into the skin.

Gupta and Dixit, (2011) compared the activity of curcumin in vesicular systems like liposome, niosome, phytovesicle and observed that phytovesicles are having excellent antioxidant and antiaging properties than the other vesicular systems

Cuomo et al, (2011) investigated the relative absorption of a standardized curcuminoids mixture and its corresponding lecithin formulation (Meriva) in a randomized, double blind cross over design human study. They reported the improved absorption and a better plasma curcuminoid profile of the Meriva at a dose significantly lower than unformulated curcuminoid mixture. Zaveri et al, (2011) have prepared the curcumin-phospholipid complex in a molar ratio of (1:2) of curcumin and phospholipid. They confirmed the formation of complex by FT-IR Spectroscopy and DSC analysis. They compared the skin permeation of curcumin with the complexed curcumin and found that the complexed curcumin showed 60% greater permeation of curcumin through rat skin. They reported that the phospholipid complex has more transdermal penetration than pure curcumin.

Commercially available Phytosomes

Phytosome Herbal drug indication

Green select Camellia sinensis Antioxidant,cardioprotective,

Mirtoselect Vaccinium myrtillus antioxidant

leucoselect Vitis vinifera cardiovascular protectant, antinflammatory, antioxidant

Sabaselect Serenoa repens Non cancerous prostate enlargement

lymphaselect Melilotus officinallis Effective in haemorrhoids ,thrombophlebitis, post surgical edema formation, lymphoedema

Olea select Olea europaea Antioxidant, inhibit harmful oxidation of LDL

Polinacea Echinacea angustifolia

Enhance immune function in response to toxic challenge

Silimostm Milk Silybum marianum Antiaging, antioxidant, hepatoprotective