GB2576301A

GB2576301A - Mangiferin-containing skin-care compositions and methods

Info

Publication number: GB2576301A
Application number: GB1811143.5A
Authority: GB
Inventors: Clement Idowu Olusola
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-07-06
Filing date: 2018-07-06
Publication date: 2020-02-19
Also published as: GB201811143D0

Abstract

An additive for a skin care composition, wherein the additive comprises a complex of mangiferin with β-cyclodextrin or a β-cyclodextrin derivative is provided. Preferably the β-cyclodextrin derivative is selected from hydroxypropyl-β-cyclodextrin, sulfobutylether β-cyclodextrin and mono(6-ethylene-diamino-6-deoxy)-β-cyclodextrin. The mangiferin-β-cyclodextrin complex preferably has a stoichiometric ratio of 1:1. The mangiferin-β-cyclodextrin additive is preferably for the prevention of UV-induced mitochondrial DNA (mtDNA) damage. A skin care composition comprising a mangiferin-β-cyclodextrin additive is also outlined wherein preferably the additive is included in the composition such that the concentration of the mangiferin in the composition is from 1 to 10% (w/w). preferably the composition is in the form of an emulsion where the mangiferin-β-cyclodextrin complex is in an aqueous phase. The skin care composition may further comprise at least one additional ingredient selected from an organic UV filter, an inorganic UV filter, an emulsifier, a suspending agent, a film former and a skin conditioner. A method of preparing a mangiferin-β-cyclodextrin additive is provided comprising: (i) preparing a solution of β-cyclodextrin or β-cyclodextrin derivative in water; (ii) adding mangiferin to the solution; (iii) allowing the complex to form at a temperature of between 30oC and 50oC for between 3 to 6 hours; and (iv) removing solids by filtration.

Description

Mangiferin-containing skin-care compositions and methods of their preparation

Technical Field

The invention relates to an additive for a skin care composition, wherein the additive comprises a complex of mangiferin with β-cyclodextrin or a β-cyclodextrin derivative. The invention also relates to skin care compositions comprising the complexes, as well as to methods of the preparation of the complexes. Further aspects of the invention relate to use of the skin care compositions to protect against UV-induced mtDNA damage.

Background

Skin disease represents a major health care challenge in today's world. With more than one million new cases of skin cancer diagnosed each year in the United States alone (National Cancer Institute, www.cancer.gov), reducing the risk factors to skin cancer is a significant concern. UV absorption generates oxygen-derived free radicals, which can induce DNA damage via the production of a range of photoproducts. This process can change the base pairing abilities of normal DNA, resulting in mutations. These mutations can disrupt tumour suppressor genes such as P53 and INK4A, leading to an increased risk of cancer.

While the role of nuclear DNA (nDNA) damage in pathological conditions such as cancer is well-known, increasing attention is being focused on the association between mitochondrial DNA (mtDNA) damage and various human diseases. mtDNA damage can be triggered by energy radiation from sources such as UVA, UVB and UVC radiation, and, in addition to cancer, has been implicated in the manifestation of various age-related disorders and degenerative diseases in humans, such as skin aging, melanoma neuro-degeneration, stroke, cardiomyopathy and diabetes.

Conventionally, sunscreen or suncream compositions contain additives that protect against UV damage by preventing UV rays from penetrating the skin. Nowadays, however, due to the heightened awareness of the links between DNA damage caused by UV radiation and such age-related and degenerative disorders as discussed above, the use of UV-filtering additives has spread increasingly to many other cosmetic items, such as daily moisturisers and fake tan products, in an effort to protect against DNA damage and to confer anti-aging properties on the product for cosmetic reasons. These products can be formulated differently to suncreams, and often have different formulation requirements (such as formulation consistency, colour etc.). There is additionally increasing consumer-led demand for organic products, or those containing organic or natural ingredients.

UV filtering additives typically function either physically (i.e. by reflecting UV radiation) or chemically (i.e. by absorbing UV radiation), to prevent UV radiation reaching the skin. Commonly used physical UV filtering additives include titanium dioxide (T1O2) and zinc oxide (ZnO). These function by forming an opaque layer over the skin, which reflects the UV light in both the UVA and UVB spectra. However, these additives typically result in a characteristic white colour, with the resulting formulations exhibiting poor sensorial feel and poor absorption into the skin. While consumers may accept these formulation limitations in a suncream, they tend to be less acceptable in other cosmetic products where the primary focus is not necessarily UV protection. Increasing evidence also points to mtDNA damage arising from the use of T1O2 and ZnO (Oxidative stress-induced cytotoxic and genotoxic effects of nano-sized titanium dioxide particles in human HaCaT keratinocytes; Jaeger A et al; Toxicology, vol. 296(1-3), (2012): pp. 27-36; DNA damaging potential of zinc oxide nanoparticles in human epidermal cells; Sharma V et al. Toxicol. Lett., Vol. 185(3), (2009): pp. 211-218; and Mechanism of oxidative DNA damage induced by quercetin in the presence of Cu(ll); Yamashita N et al. Mutat. Res., Vol. 425(1), (1999): pp. 107-115).

Chemical UV filtering additives can address some of these downsides; however no single active agent provides high enough protection in both the UVA and UVB spectra, requiring that they be used in combination. This can cause formulation issues, due to photoinstability and inter-reaction of the UVA and UVB filtering components. In addition, most chemical UV filtering additives offer poor UV protection in the UVA spectrum (315 to 400 nm).

It is an object of the present invention to mitigate or obviate one or more of the disadvantages associated with the prior art. In particular, it would be advantageous to provide an additive for a skin care composition comprising high levels of UV protection, and/or which could prevent mitochondrial DNA damage caused by UV rays. An organic composition, and/or one which avoids or reduces the use of inorganic particles such as titanium dioxide and zinc oxide would be particular beneficial, as would an organic composition with improved formulation characteristics, such as improved sensorial feel and/or improved skin absorbance. In addition, a method of preparing such a composition, which methods provides certain advantages such as ease of manufacture, reduction in cost, reduction in waste etc. would be useful.

Summary of the Invention

The invention relates to an additive for a skin care composition, wherein the additive comprises a complex of mangiferin with β-cyclodextrin or a β-cyclodextrin derivative, as well as to methods of preparation of such additives and compositions. Complexation of the mangiferin with β-cyclodextrin or a β-cyclodextrin derivative increases availability of the mangiferin in aqueous solution whilst retaining its high absorbance and mtDNA protection characteristics. Accordingly, aspects of the invention relate to the use of mangiferincontaining skin care compositions to protect against UV-induced mtDNA damage.

Various further features and aspects of the invention are defined in the claims.

Brief Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings where like parts are provided with corresponding reference numerals and in which:

Figure 1 shows the structure of mangiferin;

Figure 2 shows viability assays for a range of mangiferin extract concentrations;

Figure 3 shows MtDNA damage in primary human skin fibroblasts and human skin cell line (HDFn) cells following UV irradiation;

Figure 4 shows mtDNA damage in human skin cell line (HDFn) cells following UV irradiation in the presence of mangiferin;

Figure 5 shows mtDNA damage in human skin cell line (HDFn) cells following UV irradiation in the presence of commercial sun screen products (SPFO, SPF15 and SPF30);

Figure 6 is a UV absorbance scan for mangiferin at 1000pg/ml;

Figure 7 shows UV absorbance scans for mangiferin-β cyclodextrin complexes.

Detailed Description

The invention relates to an additive for a skin care composition, wherein the additive is a complex of mangiferin with β-cyclodextrin or a β-cyclodextrin derivative.

Mangiferin (MGN) is a naturally-occurring xhantone, (l,3,6,7-tetrahydroxy-2-[3,4,5trihydroxy-6-(hydroxymethyl)oxan-2-yl]xanthen-9-one) mainly found in higher plants such as Mangifera indica L (commonly known as mango). The inventors have advantageously determined that mangiferin shows good UV absorbance, while protecting against mtDNA damage. However, mangiferin has poor solubility in water, limiting its use, particularly in cosmetic products which often require aqueous compositions or phases.

The mangiferin can be a naturally-occurring mangiferin extract, or a synthetic analog thereof.

Advantageously, the additive complexes according to the invention show good solubility in water, and can be formulated into aqueous cosmetic compositions and into emulsions at functionally-relevant and economically-viable concentrations. Skin care compositions to which the additives can be incorporated include moisturisers, tinted moisturisers, primers, foundations, fake tan products, toners and serums, for example, as well as more specific sun-care products such as sunscreens.

According to the present invention, the additive comprises mangiferin complexed with βcyclodextrin or a β-cyclodextrin derivative.

In an embodiment, the β-cyclodextrin derivative is hydroxypropyl- β-cyclodextrin, sulfobutyl-ether β-cyclodextrin or mono (6-ethylene-diamino-6-deoxy)^-cyclodextrin.

In an embodiment, the stoichiometric ratio of mangiferin^-cyclodextrin^-cyclodextrin derivative is 1:1.

The additive may consist of the mangiferin^-cyclodextrin or mangiferin^-cyclodextrin derivative complex or a mixture of these, or may comprise additional components.

The invention also relates to a skin care composition, comprising the mangiferin complex additive described above. The additive can be included in the skin care composition at an effective concentration to protect against mtDNA damage. In an embodiment, the additive can be included in the skin care composition such that the concentration of the mangiferin is from 1 to 10% (w/w).

Advantageously, the inventors have determined that when the mangiferin-β cyclodextrin complex is incorporated into a formulation within this concentration range, good UV absorbance can be achieved, while the mtDNA damaging preventing functionality of the mangiferin is retained.

The skin care composition may be a pharmaceutical skin care composition or may be a cosmetic skin care composition.

The skin care composition may be an aqueous composition.

Alternatively, the skin care composition may be an emulsion. The emulsion may comprise the mangiferin complex in an aqueous phase.

As would be understood by one skilled in the art, the term emulsion is intended to encompass oil-in-water emulsions as well as water-in-oil emulsions, and multiple emulsions (such as water-in-oil-in water etc.).

In an embodiment, the mangiferin complex may be a mangiferin-p-cyclodextrin complex.

According to an aspect of the invention, there is provided a method of using the skin care compositions described above to protect against UV-induced mtDNA damage. Such methods involve topically administering the skin care compositions to the skin. In an embodiment, the skin is mammalian skin, such as human skin.

The skin care composition may be a topical composition.

The skin care composition may be in the form of a cream, oil, ointment, lotion, gel or spray.

The skin care composition may comprise additional UV protection or UV filtering additives which can work in conjunction with the additive of the invention to provide broad UV protection. Advantageously, mangiferin has been demonstrated to show good absorbance in the UVA spectrum, where traditionally, suncream ingredients have shown poor protection.

The invention also relates to a method of preparing an additive for a skin care composition, the method comprising:

preparing a solution of β-cyclodextrin or a β-cyclodextrin derivative in water;

adding mangiferin to the solution;

allowing the complex to form at a temperature between 30°C and 50°C for between 3 to 6 hours; and removing solids by filtration.

Surprisingly, the inventors have determined that a longer reaction/complexation time, does not lead to any increase in solubility for the resultant complex. Accordingly, when the complexation reaction is allowed to take place over a 3 to 6 hour period, this increases the efficiency of the process, particularly from a commercial perspective.

In an embodiment, the step of preparing a solution of β-cyclodextrin or a β-cyclodextrin derivative in water comprises preparing a solution comprising β-cyclodextrin or a βcyclodextrin derivative at approximately its solubility limit. In an embodiment, the βcyclodextrin or a β-cyclodextrin derivative is added at a concentration of from 1 to 3 % (w/w).

In an embodiment, the step of adding mangiferin to the solution comprising adding mangiferin at, or approximately at, its solubility limit in water. In an embodiment, mangiferin is added at a concentration of from 0.1-0.3% (w/w).

Adding the β-cyclodextriη/β-cyclodextrin derivative and/or the mangiferin at, or approximately at their solubility limits, reduces the level of unreacted compounds in the mixture after complexation and results in a more efficient process. This is particularly useful for mangiferin, which is an expensive product, and further increases its viability as a cosmetic ingredient.

In an embodiment, the β-cyclodextrin or β-cyclodextrin derivative is β-cyclodextrin.

In an embodiment, the β-cyclodextrin or β-cyclodextrin derivative is a β-cyclodextrin derivative. The β-cyclodextrin derivative can be selected from hydroxypropyl- βcyclodextrin, sulfobutylether β-cyclodextrin and mono (6-ethylene-diamino-6-deoxy)^cyclodextrin.

In an embodiment, the step of allowing the complex to form includes stirring of the solution. Preferably the stirring is continuous. Optionally, the stirring takes place at intervals.

Examples:

Materials: Mangiferin and β-cyclodextrin were purchased from Sigma Aldrich.

The following examples are included by way of illustration only, and are not intended to be limiting on the invention, the scope of which is defined by the appended claims.

Example 1: Cell viability assay for varying concentrations of mangiferin extract

Stock solutions of mangiferin were made by dissolving mangiferin extract in water, and diluting to the required concentration. The stock solutions were then added to HDFn cells at a range of concentrations from 50 pg/ml to 50,000 pg/ml, and incubated for 24 hours under standard culture conditions. Viability was then analysed using an MTS cell proliferation assay, and the results are shown in Figure 2. The differences in viability between the control (no extract) and the different extract concentrations were compared to determine significance (Figure 2 shows n=2 biological repeats, of 8 technical repeats each).

The results illustrate cell viability up to concentrations of ~5,000 pg/ml, above which concentration cell death was observed.

While the results shown are for unfiltered extract with HDFn cells, similar results were observed when the mangiferin was filtered, and also when the mangiferin extract was tested on primary human fibroblast cells grown directly from the skin of donors.

Example 2: Analysis of mtDNA damage in human skin fibroblasts and HDFn cells following UV radiation mtDNA damage in primary human skin fibroblasts and HDFn cells was determined by qPCR in primary human skin cells and in a human dermal cell line (HDFn) following UV irradiation with a Cleo Performance lamp (iSOLde, Germany). mtDNA damage was found to be induced the most in HDFn. As illustrated in Figure 3, primary fibroblasts showed an increase in mtDNA damage of 1.6 Cts following UV irradiation at 2 standard erythemal doses (SED) compared to the foil-covered control cells. HDFn cells showed a difference in mtDNA damage of 3.1 Cts following irradiation. Since a 1 Ct difference is equivalent to a 2-fold difference in damage, the primary fibroblast cells showed ~ 3-fold more damage (2^Λ1.6), whereas the HDFn cells showed a much larger increase in damage of ~ 8-fold (2^Λ3.1). HDFn cells were therefore chosen to assess the protective effect of mangiferin extract in further studies.

Example 3: Analysis of protective effect of mangiferin extract on mtDNA damage in HDFn cells

1,000 pg/ml solutions of mangiferin extract were prepared as outlined in Example 1 above. 3 ml of the mangiferin solution was added to a 45 mm diameter quartz glass petri dish. Quartz was chosen as it is known to permit both UVA and UVB rays to pass through. The quartz glass dish was then placed on top of a slightly smaller dish containing the cultured HDFn cells. The cells were then irradiated through the quartz glass petri dish, using either a Cleo Performance (iSOLde, Germany) or Aramid B (Cosmedico, Germany) lamp at 2 standard erythemal doses (SED). In order to assess damage caused by irradiation, controls were carried out with water in the quartz glass dish, and by providing non-irradiated cell dishes wrapped in foil to protect against UV-induced DNA damage.

Following irradiation, total DNA was extracted and mtDNA damage analysed using a 1 kb real-time qPCR assay. mtDNA damage is expressed as a Ct value (where a 1 Ct difference is equivalent to a 2-fold difference in damage), and is based on the observation that damaged mtDNA takes longer to be amplified via qPCR. To find the acellular UV transmission of extracts, the dish containing the diluted extract was placed on top of a spectroradiometer and the amount of UV which passes through the dish was measured. All statistical differences were determined using one-way ANOVA with Dunnett's test to compare to a control column (0.05*, P<0.01**, P<0.001***).

As illustrated in Figure 4, mangiferin extract showed significant prevention of mtDNA damage. The difference between the foil-covered cells and the water control was 3.1 Cts, or an approximately 8-fold increase in damage. In the presence of mangiferin, this increase in damage was reduced to 1.6 Cts, or an approximately 3-fold increase in damage compared with the foil-wrapped samples (i.e. no irradiation). This study therefore indicates that mangiferin extract may have excellent UV preventative properties.

Example 4: Comparison of protective effect of mangiferin extract on mtDNA damage with that provided by SPF15 and SPF30 products

To determine the efficacy of mangiferin extract in comparison with known UV-protection compounds, the experiments of Example 3 were repeated using SPFO, SPF15 and SPF30 cream products. The results of this study are shown in Figure 5 and suggest that mangiferin extract may provide similar protective effects to known commercial products.

Example 5: UV absorbance of mangiferin extract

A UV absorbance scan was performed on mangiferin extract at a concentration of 1,000 pg/ml, and the results are shown in Figure 6. The spectrometer was set up using a quartz cell with a 1.05 ms integration time (the minimum for the spectrometer) and the spectra was based on an average of 100 samples. Mangiferin shows peak absorbance in the UVA region, with absorbance peaks at ~ 320 nm and ~370 nm. This strongly suggests utility in UV protection of human skin, since the majority (96%) of UV rays that reach the earth's surface are within the UVA spectrum, compared with UVB (only 4%).

Example 6: Solubility of mangiferin

In order to assess the solubility of mangiferin in aqueous solution, 0.18 g of mangiferin was added to 100 mis of deionised water. The solution was heated to 40 °C and stirred at 500 rpm for 4 hours or for 12 hours. The solution was then Buchner filtered, and the mass of the undissolved material weighed. Solubility was calculated based on the difference between the initial mass of mangiferin and that of the undissolved material. The results are shown in Table 1, and indicate that mangiferin is very insoluble in water, even after stirring for 24 hours.

Stirring time (40 °C, 500 rpm)	Initial mass of mangiferin (g)	Mass of undissolved material (g)	Mass of mangiferin in solution (g)	Solubility of mangiferin (g/L)	Precipitate formed
4 hours	0.1826	0.1783	0.0043	0.043	Very small amount of yellow precipitate (< 01%)
24 hours	0.1831	0.1692	0.0139	0.139	Yellow precipitate (< 0.1%)

Table 1: Solubility of mangiferin

Example 7: Preparation of mangiferin- β-cyclodextrin complex

A mangiferin- β-cyclodextrin complex was prepared as follows. 1.85 g of β-cyclodextrin was added to 100 ml of deionised water and stirred at room temperature until dissolution of all of the solids had occurred. 0.18g of mangiferin was added to the β-cyclodextrin solution and the solution was stirred at 500 rpm for 4 hours. The solution was filtered using Buchner filtration. Formation of the mangiferin- β-cyclodextrin complex was confirmed by FTIR.

Example 8: Solubility of mangiferin- β-cyclodextrin complex

In order to assess the solubility of the mangiferin- β-cyclodextrin complex in aqueous solution, 1.85 g of β-cyclodextrin was dissolved in 100 ml of deionised water at 40 °C. ~0.18 g of mangiferin was added to the β-cyclodextrin solution, and the solution was stirred at 500 rpm for 4 or 24 hours at 40 °C. The solution was then Buchner filtered at 40°C (Examples 1, 2, 6 and 7), hot filtered (Example 3), cold filtered (Exam pie 4), or unfiltered (Example 5). Example 6 used β-cyclodextrin hydrate, and Example 7 studied the effect of using a cosolvent. Solubility was calculated based on the difference between the initial mass of mangiferin and β-cyclodextrin and that of the undissolved material. The results are shown in Table 2.

Ex. No.	Stirring time (500 rpm) hours	Stirring temp. °C	Filtration temp	Initial mass of MGN (g)	Mass of residual MGN (g)	Volume of water (ml)	Solubility of MGN (g/D	Precipitate formed
1	4	40	40	0.1837	0.1064	100	0.773	Clear/white precipitate (< 1%)
2	24	40	40	0.1850	0.1153	100	0.697	Clear/white precipitate (< 1%)
3	4	60	Hot	0.0912	0.0575	50	0.674	Clear precipitate (< 1%)
4	4	60	cold	0.0912	0.0503	50	0.818	Very narrow supernatant yellow insoluble (< 1%)

5	4	40	NONE	0.0695	n/a	100	0.0695	Dark solids suspended in solution (impurities) small amount of clear precipitate (< 1%)
6*	4	40	40	0.1814	0.1195	100	0.619	Clear precipitate (< 1%)
y**	4	40	40	0.1850	0.1233	100	0.617	None

Table 2: Solubility of mangiferin- β-cyclodextrin complex * cyclodextrin hydrate used instead of cyclodextrin **10:90 Ethanohwater used instead of water

These results indicate that the complexed mangiferin is ~18-fold more soluble than mangiferin on its own over a 4-hour complexation period (i.e. from 0.043 g/l to 0.773 g/l). A ~ 5.6 fold increase was observed over the 24 hour solubility of mangiferin (i.e. from 0.139 g/l to 0.773 g/l). An increased complexation time did not result in an increase in solubility.

An increase in temperature (i.e. from 40°C to 60 °C) also did not result in increased solubility (in fact a minor insignificant decrease was observed).

Example 9: UV absorbance of mangiferin- β-cyclodextrin complex

UV absorbance scans were performed on stock solutions of the mangiferin-complexes prepared in example 8 above and the results are shown in Figure 7. The spectrometer was set up using a quartz cell with a 1.05 ms integration time (the minimum for the spectrometer) and the spectra was based on an average of 100 samples. The mangiferinonly solution required to be diluted to 25% of its original concentration to reach the point at which it no longer saturated the spectrometer, while mangiferin-complex solutions were diluted to 2.5%. However, good absorbance was then observed for all of the samples, with the characteristic peaks at ~ 320 nm and ~370 nm clearly visible.

These results advantageously demonstrate that complexes of mangiferin with βcyclodextrin or a β-cyclodextrin derivative protect against mtDNA damage, and as such, can be used as additives in skin care products, to protect against UV radiation and to provide positive effects such as anti-aging effects associated with a reduction or prevention of mtDNA damage. The complexation of the mangiferin with the β-ογάοάθχΐπη/ βcyclodextrin derivative, beneficially increases the availability of the mangiferin in the aqueous composition/aqueous phase, which retaining the mtDNA damage-preventing effects. This ensures that mangiferin can be used in the preparation of an economicallyviable skin care product, such as a suncream, or other cosmetic product in which mtDNA damage prevention is desirable.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

1. An additive for a skin care composition, wherein the additive comprises a complex of mangiferin with β-cyclodextrin or a β-cyclodextrin derivative.

2. An additive as claimed in claim 1, wherein the β-cyclodextrin derivative is selected from hydroxypropyl- β-cyclodextrin, sulfobutylether β-cyclodextrin and mono (6ethylene-diamino-6-deoxy)^-cyclodextrin.

3. An additive as claimed in claim 1 or claim 2, wherein the mangiferin-β cyclodextrin complex has a stoichiometric ratio of 1:1.

4. An additive as claimed in any of claims 1 to 3, for the prevention of mitochondrial DNA damage.

5. A skin care composition comprising the additive of any of claims 1 to 4.

6. A skin care composition as claimed in claim 5, wherein the additive is included in the composition such that the concentration of the mangiferin in the composition is from 1 to 10% (w/w).

7. A skin care composition as claimed in claim 5 or claim 6, wherein the composition comprises the mangiferin-β cyclodextrin complex in an aqueous phase.

8. A skin care composition as claimed in any of claims 5 to 7, wherein the composition is in the form of an emulsion.

9. A skin care composition as claimed in any of claims 5 to 8, wherein the composition further comprises at least one additional ingredient selected from an organic UV filter, an inorganic UV filter, an emulsifier, a suspending agent, a film former and a skin conditioner.

10. A skin care composition as claimed in any of claims 5 to 9, wherein the skin care composition is in the form of a cream, lotion, oil, ointment or spray.

11. A method of preparing an additive as claimed in any of claims 1 to 4, the method comprising:

- preparing a solution of β-cyclodextrin or a β-cyclodextrin derivative in water;

- adding mangiferin to the solution;

- allowing the complex to form at a temperature between 30°C and 50°C for between to 6 hours; and

- removing solids by filtration.

12. A method as claimed in claim 11, wherein the β-cyclodextrin or β-cyclodextrin derivative is added at a concentration of from 1 to 3% (w/w).

13. A method as claimed in claim 11 or claim 12, wherein the mangiferin is added at a concentration of from 0.1 to 0.3%.

14. A method as claimed in any of claims 11 to 13, wherein the β-cyclodextrin or βcyclodextrin derivative is β-cyclodextrin.

15. A method as claimed in any of claims 11 to 14, wherein the β-cyclodextrin or βcyclodextrin derivative is a β-cyclodextrin derivative selected from hydroxypropyl- βcyclodextrin, sulfobutylether β-cyclodextrin and mono (6-ethylene-diamino-6deoxy)^-cyclodextrin.