DESC:Related Application(s)
This present Application is a Patent of Addition application which is a modification of the invention claimed in Complete Cognate Application No. 3190/CHE/2010 filed on 10/10/2011 with priority date 27/10/2010 entitled Novel Polymorphs and Cocrystals of Curcumin, the contents of which, is specifically incorporated herein by reference.

Technical field:
The invention relates to novel co-amorphous solids of curcumin with naturally occurring molecules such as Artemisinin, Artesunate, Piperine, and cocrystals with Quercetin with improved bioavailability. The invention further relates to process for preparation of novel co-amorphous solids of curcumin-artemisinin (1:1), curcumin-artesunate (1:1), curcumin-piperine (1:1), and curcumin-quercetin cocrystals (1:1 and 1:2).

Background of the Invention:
Curcumin (diferuloylmethane) is a hydrophobic polyphenol derived from the rhizome of the herb Curcuma longa, the dietary Indian spice turmeric (Curcumin: from ancient medicine to current clinical trials. H. Hatcher, R. Planalp, J. Cho, F. M. Torti, S.V. Torti. Cell Mol. Life Sci. 2008, 65, 1631–1652).

Curcumin exhibits anticancer activity by suppressing multiple signaling pathways and inhibit cell proliferation, invasion, metastasis and angiogenesis. Further, curcumin possess activity against bacteria, fungi, and protozoa. Cytotoxic and parasiticidal effects on protozoan parasites have been demonstrated in cultures against Plasmodium falciparum (Cytotoxic Effect of Curcumin on Malaria Parasite Plasmodium falciparum: Inhibition of Histone Acetylation and Generation of Reactive Oxygen Species. L. Cui, J. Miao, L. Cui, Antimicrob. Agents Chemother. 2007, 51, 488–494). Myocardial infarction protective, hypoglycaemic, and anti-rheumatic effects are well established with curcumin. Despite safety levels of up to 12 g/day in humans (C. D. Lao, M. T. Ruffin, D. Normolle, D. D. Heath, S. I. Murray, J. M. Bailey, M. E. Boggs, J. Crowell, C. L Rock, D. E. Brenner. BMC Complement Altern. Med. 2006, 6, 10–13), the efficacy of curcumin as a drug is limited by low aqueous solubility (7.8 µg/L) and poor bioavailability (0.051 µg/mL), mainly due to its rapid metabolism (Biotransformation of curcumin through reduction and glucuronidation in mice. M.-H. Pan, T.-M. Huang, J.K. Lin. Drug. Metab. Dispos. 1999, 27, 486-494; Bioavailability of Curcumin: Problems and Promises. P. Anand , A. B. Kunnumakkara, R.A. Newman, B. B. Aggarwal. Mol. Pharmaceutics,2007, 4, 807–818; Toxicity studies on Alpiniagalanga and Curcuma longa. S. Qureshi, A. H. Shah, A. M. Agee. Planta Med. 1992, 58, 124–127). Curcumin decomposes in neutral and alkaline medium with >90% decomposition occurring within 30 min in pH 7.4 buffer medium (Stability of curcumin in buffer solutions and characterization of its degradation products. Y. J. Wang, M. H. Pan, A. L Cheng, L. L. Lin, Y. S. Ho, C. Y. Hsieh, J. K. Lin, J. Pharm. Biomed Anal. 1997, 15, 1867–1876).

Using the amorphous form of a drug, instead of its crystalline counterpart is one way to enhance the bioavailability of poorly water-soluble drugs. However, in order to fully benefit from the solubility advantages of amorphous drugs, it is necessary to overcome physicochemical limitations including poor physical stability associated with the amorphous form.

To overcome the stability problem, amorphous drug was incorporated into a water-soluble, amorphous polymer, creating a glass solution (A. Forster, J. Hempenstall, T. Rades, and Characterization of glass solutions of poorly water-soluble drugs produced by melt extrusion with hydrophilic amorphous polymers. J. Pharm. Pharmacol.2001, 53, 303–315]. However, since the glass solutions resulted in very large bulk volumes in tablets or capsules, due to the low solubility of the solid drug in the polymer, the approach was unfeasible for application in formulations with intended dose of the drug.

Co-amorphous formulations which can stabilize the amorphous form of a drug by strong and specific molecular interactions between the drug and its low molecular weight co-amorphous partner molecule is one of the emerging and promising formulation approaches to enhance the bioavailability of poorly water soluble drugs.
Pharmaceutical co-crystals are amorphous or crystalline molecular complexes containing therapeutic molecules. These co-crystals represent a class of pharmaceutical materials offering higher solubility, dissolution rates of the poorly water soluble drugs, they are found to be stable and thus suitable in preparing pharmaceutical compositions.

In case of curcumin, there is one more factor which needs to be looked into while simultaneously formulating a drug delivery system. This includes occurrence of rapid drug metabolism. This can be mitigated by the application of combinationtherapies such as use of enzyme inhibitor like piperine or other natural molecules.

Complexes of curcumin with natural molecules are known in the art for their anti-viral, anti-bacterial, anti-inflammatory, anti-cancer or anti-malarial activities. Of these, Artemisinin anti-malarial drug (10-25 mg/kg/day) was first identified by Chinese researchers in the plant of Artemisia annua (Qinghaosu Artemisinin): The Price of Success. N. J. White, Science. 2008, 320, 330–334).

Curcumin and Artemisinin exhibit anticancer activity by suppressing multiple signaling pathways and inhibit cell proliferation, invasion, metastasis and angiogenesis.Quercetinis a neutraceutical molecule and it shows antioxidant and anti-inflammatory properties. (Antioxidant properties of quercetin. M. Zhang, S.G. Swarts,L. Yin, C. Liu, Y. Tian, Y. Cao, M. Swarts, S. Yang, S.B. Zhang, K. Zhang, S. Ju,D.J. Jr. Olek, L. Schwartz, P.C. Keng, R. Howell, L. Zhang , P. Okunieff.Adv. Exp. Med. Biol., 2011, 701, 283).

Artesunate is a derivative of artemisinin (sesquiterpene lactones). Artesunate has an excellent anti-malarial activity on malaria parasites with high, quick efficiency to bring about rapid control of an acute attack. Artesunate are indicated for the treatment of uncomplicated cases of malaria due to Plasmodium falciparum strains which are susceptible to ARTS. The most recent official guidelines on the appropriate use of antimalarial agents and local information on the prevalence of resistance to antimalarial drugs must be taken into consideration for deciding on the appropriateness of therapy with Artesunate. According to current WHO recommendations, oral Artesunate should be used as first line therapy for uncomplicated falciparum malaria in combination with amodiaquine, sulfadoxine-pyramethamine, or mefloquine. In addition to that Artesunate also exhibits anticancer activity and artesunate is combined with curcumin, artesunate adverse effects were decreased (Ketaki R.D., Dhrupadsinh K.R., Pragnesh B.P., and Hyacinth N.H., Dose-Response., 2015, 1-8).

Piperine is a natural alkaloid and it used as traditional medicine. (Antioxidant and antimicrobial activities of various solvent extracts, piperine and piperic acid from Piper nigrum. Z. Zarai Emna, Boujelbene, N. Ben Salem, Y. Gargouri, A. Sayari, LWT – Food Sci. Tec. 2013, 50, 634).

Quercetin is a plant-derived flavonoid, specifically a flavonol, used as a nutritional supplement. It is also known for its anti –tumor activity, inhibits various enzymes, is also known for its anti-inflammatory effects, anti-thrombotic or anti-hypertensive effect.

In spite of diverse pharmaceutical activities, the utility of curcumin as a drug is limited by poor water solubility and limited bioavailability. It is therefore necessary to develop novel solid-state forms which can enhance the bioavailability of curcumin. Novel polymorphs of curcumin I-III and an amorphous phase, together with cocrystals of curcumin in combination with coformers such as resorcinol, pyrogallol were reported in our earlier cognate patent Application No. 3190/CHE/2010, priority date 10/10/2011 entitled Novel Polymorphs and Cocrystals of Curcumin. However the utility of curcumin cocrystals can be further enhanced with the coformer being selected from active drugs and natural products to make drug-drug compositions. Because neither pyrogallol nor resorcinol is an active drug molecule in itself, the enhanced solubility of curcumin with these conformers cannot be utilized for pharmaceutical applications.

With a view to address the issues of poor bioavailability, rapid drug metabolism and the need for frequent parenteral dosing, in order to maintain effective therapeutic concentrations in the blood in case of curcumin having diverse chemopreventive/ chemotherapeutic potential, the present inventors persuaded to develop novel co-amorphous or cocrystal solid state forms of curcumin to achieve the desired effect suitable for combination therapy.

Object of the invention:
It is an object of the invention to provide a novel co-amorphous solid form of curcumin with natural low molecular weight amorphous components selected from Artemisinin, Artesunate or Piperine, to improve the bioavailability and solubility.

The other object of the invention is to provide co-crystal of curcumin and quercetin with improved solubility and bioavailability.

Yet other object of the invention is to provide a simple process for preparation of the novel solid forms of curcumin.

Summary of the Invention:
In an aspect, the present invention provides co-amorphous solid composition comprising curcumin and artemisinin in 1:1 ratio with improved bioavailability and high dissolution rate.

In yet another aspect, the present invention provides co-amorphous solid composition comprising curcumin and artesunate in 1:1 ratio with improved bioavailability and high dissolution rate.

In another aspect, the present invention provides co-amorphous solid form composition comprising curcumin and piperine in 1:1 ratio with improved bioavailability and high dissolution rate.

In yet another aspect, the present invention provides co-crystal composition of curcumin with quercetin in the ratio of 1:1 to 1:2 with improved bioavailability and high dissolution rate.

In another aspect, the invention provides a process for preparation of solid co-amorphous and co-crystal forms which comprises dissolving curcumin and natural, low molecular, amorphous component selected from artemisinin, artesunate, piperine or quercetin in fixed stoichiometric molar ratio in ethanol and rotavaporizing the mix at a temperature in the range of 50-55 °C.
In yet another aspect, the solid co-amorphous and co-crystal forms of curcumin with artemisinin, artesunate, piperine or quercetin prepared by the present process are characterized by IR, DSC and PXRD.

In another aspect, the present invention provides a pharmaceutical composition comprising co-amorphous solid of curcumin and artemisinin in 1:1 ratio along with one or more suitable pharmaceutically acceptable excipients.

In yet another aspect, the present invention provides a pharmaceutical composition comprising co-amorphous solid of curcumin and artesunate in 1:1 ratio along with one or more suitable pharmaceutically acceptable excipients.

In yet another aspect, the present invention provides a pharmaceutical composition comprising co-amorphous solid of curcumin and piperine in 1:1 ratio along with one or more suitable pharmaceutically acceptable excipients.

In another aspect, the invention provides a pharmaceutical co-crystal composition of curcumin and quercetin 1:1 to 1:2 ratios along with one or more suitable pharmaceutically acceptable excipients.

Brief description of the drawings:
Figure 1 depicts overlay of FT-IR spectra of curcumin-artemisinin co-amorphous solid compared to the individual components.
Figure 2 depicts overlay of FT-IR spectra of curcumin-artesunate co-amorphous solid compared to the individual components.
Figure 3 depicts overlay of FT-IR spectra of curcumin-piperine co-amorphous solid compared to the individual components.
Figure 4 depicts overlay of FT-IR spectra of curcumin-quercetin (1:1) co-crystal compared to the individual components.
Figure 5 depicts overlay of FT-IR spectra of curcumin-quercetin (1:2) co-crystal compared to the individual components.
Figure 6 depicts PXRD of co-amorphous curcumin-artemisinin (1:1) with starting materials curcumin and artemisinin. The co-amorphous product exhibits a broad halo peak and lacks the sharp diffraction lines characteristic of the crystalline starting materials.
Figure 7 depicts PXRD of co-amorphous curcumin-artesunate (1:1) with starting materials curcumin and artemisinin. The co-amorphous product exhibits a broad halo peak and lacks the sharp diffraction lines characteristic of the crystalline starting materials.
Figure 8 depicts PXRD of co-amorphous curcumin-piperine (1:1) with starting materials curcumin and piperine. The crystalline product exhibits a broad halo peak and lacks the sharp diffraction lines characteristic of the crystalline starting materials.
Figure 9 depicts PXRD ofcurcumin-quercetin (1:1) cocrystal with starting materials curcumin and quercetin. The co-crystal product has different sharp diffraction lines at 2? 8.89, 9.73, 13.03, 16.63°, different from those of the starting materials.
Figure 10 depicts PXRDof curcumin-quercetin (1:2) co-crystal with starting materials curcumin and quercetin. The co-crystal product has different sharp diffraction lines at 2? 10.04, 13.36, 17.75, 25.35°, different from those of the starting materials.
Figure 11 depicts DSC thermogram of curcumin-artemisinin co-amorphous solid compared with the starting materials. The circles indicate glass transition of curcumin-artemisinin co-amorphous solid at 67-68 °C.
Figure 12 depicts DSC thermogram of curcumin-artesunate co-amorphous solid compared with the starting materials and its decomposition starts at 128 °C.
Figure 13 depicts DSC thermogram of curcumin-piperine co-amorphous form compared with curcumin and piperine. The circles indicate glass transition of curcumin-piperine coamorphous solid at 84.97 °C.
Figure 14 depicts comparison of curcumin-quercetin (1:1) cocrystal with three melting endotherm peaks at 169.24 °C, 261.80 °C and 272.47 °C.
Figure 15 depicts comparison of curcumin-quercetin (1:2) cocrystal with one broad melting endotherm peak at 282.35 °C and one phase transition 153.43 °C.
Figure 16 depicts Mean Plasma concentration (of Curcumin) vs. Time profile of CUR-ART coamorphous.
Figure 17 depicts curcumin-artemisinin phase stability study PXRD patterns at different time intervals in Simulated Gastric Fluid medium.
Figure 18 depicts curcumin-artemisinin phase stability study PXRD patterns at different time intervals in Simulated Intestinal Fluid medium.
Figure 19 depicts curcumin-artemisinin coamorphous solid phase stability FE-SEM analysis Simulated Gastric Fluid medium (1, 2 and 24 hours) and Simulated Intestinal Fluid medium (24 hours).

Disclosure of the invention:
The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.

The poor bioavailability of curcumin is due to its rapid metabolism and low aqueous solubility which has a marked influence on its therapeutic efficacy. Accordingly, novel solid forms of Curcumin are designed in the present invention such as coamorphous solid form or co-crystal forms which improves the physical and pharmacological property of curcumin which is suitable for combination therapy.

As used herein the term ‘co-amorphous’ refers to an amorphous blend consisting only of low molecular weight components.

In an embodiment, the present invention relates to novel coamorphous or cocrystal composition comprising curcumin and natural, low molecular weight molecules selected from artemisinin, artesunate, piperine or quercetin in stoichiometric molar ratio with improved bioavailability and high dissolution rate.

Accordingly, the present invention discloses co-amorphous solid composition comprising curcumin and artemisinin in 1:1 molar ratio with improved bioavailability and high dissolution rate.

In another aspect, the present invention discloses co-amorphous solid composition comprising curcumin and artesunate in 1:1 molar ratio with improved bioavailability and high dissolution rate.

In another embodiment, the present invention discloses co-amorphous solid composition comprising curcumin and piperine in 1:1 molar ratio with improved bioavailability and high dissolution rate.

In yet another embodiment, the present invention discloses co-crystal composition of curcumin with quercetin in the molar ratio of 1:1 to 1:2 with improved bioavailability and high dissolution rate.

In another embodiment, the invention discloses a simple process for preparation of solid co-amorphous and co-crystal forms which comprises dissolving curcumin and natural, low molecular weight component selected from artemisinin, artesunate, piperine or quercetin in fixed stoichiometric molar ratio in ethanol and rotavaporizing the mix at a temperature in the range of 50-55°C.

In yet another aspect, the solid co-amorphous and co-crystal form of curcumin with artemisinin, artesunate, piperine or quercetin prepared by the present process are characterized by IR, DSC and PXRD.

In another embodiment, the present invention describes a pharmaceutical composition comprising co-amorphous solid of curcumin and artemisinin 1:1 molar ratio along with one or more suitable pharmaceutically acceptable excipients. The co-amorphous composition comprising curcumin and artemisinin in 1:1 molar ratio is characterized by; (i) having characteristic peaks in IR at 3434.7 cm-1 , 1625 cm-1, 1736.5 cm-1; (ii) by a broad hump in PXRD and (iii) Tg at 67.58 °C and (iv) DSC thermogram at 192.67 °C.

In another embodiment, the present invention provides a pharmaceutical composition comprising co-amorphous solid of curcumin and artesunate 1:1 molar ratio along with one or more suitable pharmaceutically acceptable excipients. The co-amorphous composition comprising curcumin and artesunate in 1:1 molar ratio is characterized by; (i) having characteristic peaks in IR at 3428.5 cm-1 , 1626.1 cm-1, 1740.6 cm-1; (ii) a broad hump in PXRD and (iii) decomposition was observed as broad peak at 128-160 °C.
In yet another aspect, the present invention discloses a pharmaceutical composition comprising co-amorphous solid of curcumin and piperine in 1:1 molar ratio along with one or more suitable pharmaceutically acceptable excipients. The co-amorphous solid composition comprising curcumin and piperine in 1:1 molar ratio is characterized by; (i) having characteristic peaks in IR at 3326.4 cm-1, 1627.8 cm-1, 1598.0 cm-1; (ii) a broad hump in PXRD (iii) Tg at 84.97 °C and (iv) DSC thermogram at 135 °C and 180 °C.

In another embodiment, the invention provides a pharmaceutical co-crystal composition of curcumin and quercetin in 1:1 to 1:2 molar ratios along with one or more suitable pharmaceutically acceptable excipients. The co-crystal composition comprising curcumin and quercetin in 1:1 molar ratio is characterized by; (i) having characteristic peaks in IR at 3404.5 cm-1 , 1621.6 cm-1, 1659.2 cm-1, 1601.3 cm-1; (ii) PXRD 2? peaks at 8.89, 9.73, 13.03, 16.63°, (iii) phase transition at 169.24 °C, 261.80 °C and (iv) DSC thermogram peak at 272.47 °C.

The co-crystal composition comprising curcumin and quercetin in 1:2 molar ratio is characterized by; (i) having characteristic peaks in IR at 3397.8 cm-1, 1614.8 cm-1, 1673.3 cm-1, 1512.1 cm-1; (ii) PXRD 2? peaks at 10.04, 13.36, 17.75, 25.35°, (iii) phase transition at 153.43 °C, (iv) DSC thermogram peak at 282.35 °C.

In another embodiment, the suitable pharmaceutically acceptable excipients are selected from diluents, glidents, binders, disintegrants, flavors, colors, lubricants, polymers etc., to prepare desired dosage forms. The dosage forms may be selected from oral or parenteral dosage forms prepared using conventional methods known in the art.

In yet another embodiment, the present invention provides a method for treatment or prevention of malaria and cancer, which method comprises administering an effective amount of the co-amorphous composition of curcumin-artemisinin, curcumin-artesunate or curcumin-piperine (1:1) to the subject in need thereof.

In another embodiment, the present invention provides a method for treatment or prevention of cancer comprising administering an effective amount of the co-crystal of curcumin and quercetin (in a ratio of 1:1 to 1:2) to the subject in need thereof.
The ‘effective amount’ as described above means and includes the amount required to treat/alleviate the severity of symptoms associated with these ailments as decided by the persons of ordinary skill in the art.

In another embodiment, the present invention discloses use of the co-amorphous composition comprising of curcumin-artemisinin or curcumin-artesunate or curcumin-piperine for preparing the medicament intended to treat or prevent cancer or malaria.

In another embodiment, the present inventiondiscloses use of the co-crystal composition comprising of curcumin-quercetin for preparing the medicament intended to treat or prevent cancer.

In yet another embodiment, the present invention discloses the dissolution and bioavailability measurements ofcurcumin-artemisinin co-amorphous solid vis-à-vis curcumin alone. Accordingly, the intrinsic dissolution rate and solubility measurements are performed in 60% EtOH-water medium. The intrinsic dissolution rate (IDR) of curcumin and curcumin-artemisinin co-amorphous solid was found to be 0.177 x 10-3 mg/cm2/min and 0.461 x 10-3 mg/cm2/min respectively. The dissolution rate of curcumin-artemisinin is about 2.6 times faster than that of curcumin.

In another embodiment, curcumin-artemisinin co-amorphous bioavailability experiments were studied by oral administration (200 mg/kg) to Sprague Dawley male rats (200±50 g, n = 6 for each drug). Oral bioavailability is measured by the AUC (area under the concentration curve) and Cmax (peak plasma concentration). Administration of pure curcumin did not show any detectable levels in plasma due to its very low solubility and short half-life. Oral administration of curcumin-artemisinin coamorphous (at the same molar concentration as pure curcumin), exhibited a Cmax value of 1.003 ?g/mL curcumin at Tmax of 30 min; thereafter, the concentration dropped with a half-life T1/2 of 6.4 h and AUC0–8= 24.7 µg.h /mL (Table 2).

The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of examples and for purpose of illustrative discussion of preferred embodiments of the invention.

Example 1
Preparation of co-amorphous solid and co-crystal of curcumin
Curcumin, Quercetin and Piperine (purity > 99.8%) were obtained from Sigma-Aldrich (Hyderabad, India). Artemisinin was obtained as a gift from Cipla (Mumbai, India) and Artesunate was purchased from Mangalam Drugs and Organic Limited. Solvents (purity> 99%) were purchased from Merck (India). Water filtered through a double deionized purification system (Aqua DM, Bhanu, and Hyderabad, India) was used for all experiments.
1a: Preparation of curcumin-artemisinin co-amorphous solid
Curcumin and the Artemisinin were taken in an equimolar stoichiometric ratio and dissolved in 100 mL ethanol and rotavaporized at 50-55 °C in a Büchi rotavap.The solid residue product was characterized as a coamorphous solid by IR, DSC, and PXRD and used in the next experiments.
1b: Preparation of curcumin-artesunate co-amorphous solid
Curcumin and the Artesunate were taken in an equimolar stoichiometric ratio and dissolved in 100 mL ethanol and rotavaporized at 50-55 °C in a Büchi rotavap. The solid residue product was characterized as a coamorphous solid by IR, DSC, and PXRD and used in the next experiments.
1c: Preparation of curcumin-piperine coamorphous solid
Curcumin and the piperine were taken in an equimolar stoichiometric ratio and dissolved in 100 mL ethanol and rotavaporized at 50-55 °C in a Büchi rotavap. The solid residue product was characterized as a coamorphous solid by IR, DSC, and PXRD and used in the next experiments.
1d: Preparation of curcumin-quercetin (1:1 and 1:2) cocrystals
Curcumin and quercetin were taken in molar stoichiometric ratio (1:1 and 1:2) and dissolved in 100 mL ethanol and rotavaporized at 50-55 °C in a Büchi rotavap. The solid residue product was characterized as a cocrystal by IR, DSC, and PXRD and used in the next experiments.

Example 2
Spectral analysis
(a) FT-IR spectroscopy analysis
Infrared and Raman spectroscopyprovide quantitative information about the vibrational modes of a compound and change due to the physical state of the sample, and because of hydrogen bonding and molecular conformations. Nicolet 6700 FT-IR spectrometer with a NXR FT-Raman Module was used to record IR spectra. IR spectra were recorded on samples dispersed in KBr pellet. Spectroscopic techniques have certain threshold limits above which they are not sensitive enough to quantify the strength of interactions and differences in structures for chemical interpretation. When the IR spectra of curcumin and two coamorphous forms is compared to that of the coamorphous system curcumin-artemisinin and curcumin-piperine small 1-2 cm-1 shifts were observed at carbonyl region (Figure 1 and 3). Whereas in the curcumin-artesunate coamorphous solid larger shift were observed in Artesunate carbonyl and hydroxyl regions indicates the presence strong O–H···O hydrogen bonding (Figure 2). In curcumin-quercetin cocrystal major shifts were observed in carbonyl and hydroxyl groups region (Figure 4 and 5) listed in Table 1 below.

Table 1 FT-IR spectral comparison of Curcumin cocrystal and coamorphous with staring materials.
CURCUMIN-ARTEMISININCOAMORPHOUS
CURCUMIN ARTEMISNIN CURCUMIN-ARTEMISININ
O-H stretch 3510.9 cm-1 - 3434.7 cm-1
C=O stretch 1627.5 cm-1 1736.5 cm-1 1625.9 cm-1 1736.5 cm-1
CURCUMIN-ARTESUNATE COAMORPHOUS
CURCUMIN ARTESUNATE CURCUMIN-ARTESUNATE
O-H stretch 3510.9 cm-1 3283.5 cm-1 3428.5 cm-1
C=O stretch 1627.5 cm-1 1756.8cm-1 1740.08cm-1, 1626.1 cm-1
CURCUMIN-PIPERINE COAMOPRHOUS
CURCUMIN PIPERINE CURCUMIN-PIPERINE
O-H stretch 3510.9 cm-1 - 3326.4
C=O stretch 1627.5 cm-1 1634.2 cm-1 1627.8 cm-1
C=C stretch 1602.6cm-1 1584.3 cm-1 1598.0 cm-1
CURCUMIN-QUERCETIN COCRYSTAL(1:1)
CURCUMIN QUERECETIN CURCUMIN-QUERCETIN
O-H stretch 3510.9 cm-1 3403.4 cm-1 3404.5 cm-1
C=O stretch 1627.5 cm-1 1664.7cm-1 1621.6 cm-11659.2 cm-1
C=C stretch 1602.6 cm-1 1610.3 cm-1 1601.3 cm-1
CURCUMIN-QUERCETIN COCRYSTAL (1:2)
CURCUMIN QUERECETIN CURCUMIN-QUERCETIN
O-H stretch 3510.9 cm-1 3403.4 cm-1 3397.8 cm-1
C=O stretch 1627.5 cm-1 1664.7cm-1 1614.8 cm-11673.3 cm-1
C=C stretch 1602.6 cm-1 1610.3 cm-1 1512.1cm-1

(b) X-ray Powder Diffraction (XRPD)
X-ray powder diffraction is a standard method for the characterization of solid-state forms. It is a characterization tool of the solid. When the resulting PXRD of the final product is different from the reactants, it can be concluded that a new solid phase has formed. The unique amorphous pattern of the coamorphous was monitored by the absence ofsharp diffraction peaks and the presence of a broad halo or hump. PXRDs were recorded on SMART Bruker D8 Focus Powder X-ray diffractometer using Cu-Ka radiation (? = 1.5406 Å) at 40 kV and 30 mA. PXRD of the coamorphous solid forms ofcurcumin-artemisinin and curcumin-piperine confirmed the homogeneity of the novel coamorphous phase which lacks the signature diffraction peaks of CUR (curcumin) and ART (artemisinin).

The powder X-ray diffraction of curcumin-artemisinin, curcumin-artesunate and curcumin-piperine (Figure 6, 7 and 8) exhibits a hump in powder X-ray diffraction pattern characteristic of an amorphous phase.

PXRD of the curcumin-quercetin cocrystals (1:1 and 1:2) (Figure 9 and 10) confirmed the homogeneity of novel cocrystal phase, which is having different PXRD lines compared to starting materials. The PXRD peaks of curcumin-quercetin cocrystal (1:1) appear at 2? 8.89, 9.73, 13.03, 16.63°, and for curcumin-quercetin cocrystal (1:2) at 2? 10.04, 13.36, 17.75, 25.35°.

(c) Thermal analysis
Differential scanning calorimetry (DSC) was carried out to investigate the thermal behavior of curcumin solid forms. DSC shows the exotherm/endotherm at which the solid sample undergoes phase transition and/or melting. DSC was performed on Mettler Toledo DSC 822e module by placing the samples, typically 4-6 mg, in aluminum pans and heated in the temperature range of 30-250 °C at 5 °C /min. DSC of an amorphous solid will show a glass transition temperature (Tg), the temperature at which the glassy phase converts to a rubbery phase with properties akin to a liquid phase. DSC of a coamorphous material should show a single glass transition event, indicative that one compound is completely miscible in the second component to form a homogenous phase. The melting point of curcumin is 181 °C and artemisinin (ART) shows two melting endotherms for the two polymorphs. In case of ART the inventors did not observe any amorphous form by rotavap technique. The DSC thermogram of coamorphous curcumin-artemisinin shows a single glass transition Tg (broad exotherm peak) at 67-68 °C, preferably at 67.58 °C (Figure 11) followed by decomposition at 190-200 °C and in the case of curcumin-artesunate shows a direct decomposition without passing through a rubber-like phase and it decomposes at 128-160 °C (Figure 12).Whereas in the case of CUR-PIP shows a single glass transition Tg (broad exotherm peak) at 84-85 °C (Figure 13) followed by dissociation at the melting temperature of curcumin and piperine respectively. The single exotherm peak in curcumin-artemisinin, curcumin-artesunate and curcumin-piperine coamorphous solid indicates that the three compounds are freely miscible with each other to form a homogenous phase curcumin-artemisinin, curcumin-artesunate and curcumin-piperine. The cocrystal of curcumin-quercetin (1:1) shows three melting endotherm peaks at 169.24°C, 261.80°C and 272.47 °C (Figure 14). The cocrystal of curcumin-quercetin (1:2) shows phase transition at 153.43°C followed by melting endotherm at 282.35 °C (Figure 15).

(d) Solubility and dissolution
Intrinsic Dissolution Rate (IDR) process is a kinetic or time-dependent phenomenon. The coamorphous of curcumin-artemisinin were shown to have faster dissolution because of their excess thermodynamic functions. The dissolution was carried in 60% EtOH–water medium for curcumin-artemisinin because these two components curcumin and artemisinin are insoluble in water. It was not possible to obtain equilibrium solubility of curcumin-artemisinin due to the metastable nature of coamorphous form which converted to the crystalline form during the solubility experiment. IDR experiments on curcumin-artemisinin were performed in 60% EtOH–water for 2 h by the rotating disk intrinsic dissolution rate (DIDR) method at 37°C.Curcumin-artemisininhas 2.6 fold higher IDR than curcumin but there was no change observed in the IDR of artemisinin in coamorphous system. PXRD of the residue remaining at the end of dissolution experiment matched with that of curcumin form 1.To summarize, the solubility of curcumin was increased in curcumin-artemisinin coamorphous compared to pure curcumin. IDR experiments were analyzed by HPLC.
(e) Pharmacokinetics
Curcumin-artemisinin coamorphous and pure curcumin were administered orally (200 mg/kg) to Sprague Dawley male rats (200±50 g, n = 6 for each drug). Oral bioavailability was estimated by measuring the AUC (area under the concentration curve) and Cmax (peak plasma concentration). Administration of pure curcumin did not show any detectable levels in plasma due to its very low solubility and short half-life. This observation is consistent with recent reports wherein pure curcumin could not be detected by HPLC. Oral administration of curcumin-artemisinin coamorphous (in the same molar concentration as pure curcumin), a Cmax value of 1.003 ?g/mL was recorded for curcumin at Tmax of 30 min; thereafter, the concentration dropped with a half-life T1/2 of 6.4 h and AUC0–8= 24.7 µg.h /mL (Figure 16 and Table 2). It was not possible to detect artemisinin bioavailability due to limit of quantification in HPLC being too low (20 µg/mL) since it lacks a chromophore group.
Table 2 Pharmacokinetic parameters of curcumin-artemisinin coamorphous.
Parameter curcumin-artemisinin
Mean SD
Cmax(?g/mL) 1.003 0.350
Tmax (min) 30 -
Half life (h) 6.4 2.2
AUC0-12 (µg. h /mL) 2.59 0.60
AUC0-8(µg. h /mL) 24.7 7.4

The present invention demonstrates a high bioavailability Cmax value of 1 ?g/mL at short Tmax of 30 min which is very remarkable for curcumin in a coamorphous solid form for therapeutic use.
(f) Stability of CUR-ART in SGF and SIF media (simulated gastric fluid and simulated intestinal fluid)
In this study, we have investigated the curcumin-artemisinin coamorphous phase stability in SGF/SIF media by keeping supersaturated solution at 1000rpm using magnetic stirrer at 30°C at different time intervals (1, 2, 3, 6, 12, and 24 hours) within 24 hours separately. At each time point, the suspension was filtered. The filtered material phase stability/dissociation confirmed by powder X-ray diffraction. Interestingly here we find that the curcumin-artemisinin coamorphous solid is stable up to 3 hours in SGF medium. After 3 hours ART component precipitates in crystalline form but the curcumin component is in amorphous/ crystalline state as seen by PXRD (Figure 17). Similarly in SIF medium curcumin-artemisinin coamorphous solid form was stable up to 12 hours as seen by PXRD (Figure 18). Further we have analyzed particle morphology at 1, 2 and 24 hours of precipitated curcumin-artemisinin compound by FESEM analysis. From the FESEM analysis, it has been observed that high magnification images reveals clearly that large particles are in fact agglomerates of smaller particles at 1 h and 2 h in SGF medium. Similarly at 24 h in both simulated fluids irregular dense shape particles were observed (Figure 19).
From the above, it has been concluded that providing curcumin in coamorphous solid/ cocrystal forms using low molecular weight molecules such as artemisinin, artesunate, piperine, and quercetin, as demonstrated in the present invention increases the solubility and bioavailability of curcumin, a poorly water soluble drug. ,CLAIMS:We claim,

1. Novel co-amorphous or co-crystal compositions of curcumin comprising curcumin and natural, low molecular weight molecules selected from the group consisting of artemisinin, artesunate, piperine and quercetin in stoichiometric ratios for improving bioavailability, dissolution rate and stability of curcumin in simulated gastric and intestinal fluids.
2. The co-amorphous composition according to claim 1, comprising curcumin and artemisinin in 1:1 molar ratio characterized by; (i) having characteristic peaks in IR at 3434.7 cm-1 , 1625 cm-1, 1736.5 cm-1; (ii) a broad hump in PXRD (iii) Tg a 67.58 °C and (iv) DSC thermogram at 192.67 °C.
3. The co-amorphous composition according to claim 1, comprising curcumin and artesunate in 1:1 molar ratio characterized by; (i) having characteristic peaks in IR at 3428.5 cm-1 , 1626.1 cm-1, 1740.6 cm-1; (ii) a broad hump in PXRD (iii) decomposition was observed as broad peak at 128-160 °C.
4. The co-amorphous solid composition according to claim 1, comprising curcumin and piperinein 1:1 molar ratio characterized by; (i) having characteristic peaks in IR at 3326.4 cm-1, 1627.8 cm-1, 1598.0 cm-1; (ii) a broad hump in PXRD (iii) Tg at 84.97 °C and (iv) a DSC thermogram at 135 °C and 180 °C.
5. The co-crystal composition according to claim 1, wherein co-crystal comprising curcumin and quercetin in 1:1 molar ratio is characterized by; (i) having characteristic peaks in IR at 3404.5 cm-1 , 1621.6 cm-1, 1659.2 cm-1, 1601.3 cm-1; (ii) PXRD 2? peaks at 8.89, 9.73, 13.03, 16.63°, (iii) phase transition at 169.24 °C, 261.80 °C and (iv) DSC thermogram peak at 272.47 °C.
6. The co-crystal composition according to claim 1, wherein composition comprising curcumin and quercetin in 1:2 molar ratio is characterized by; (i) having characteristic peaks in IR at 3397.8 cm-1 1614.8 cm-1, 1673.3 cm-1 1512.1 cm-1; (ii) PXRD 2? peaks at 10.04, 13.36, 17.75, 25.35°, (iii) a phase transition at 153.43 °C and (iv) DSC thermogram peak at 282.35 °C.
7. A process for preparation of co-amorphous or co-crystal composition of curcumin comprising dissolving curcumin and natural, low molecular weight component selected from artemisinin, artesunate, piperine or quercetin in fixed stoichiometric molar ratio in ethanol and rotavaporizing the mix at a temperature in the range of 50-55 °C.
8. The process according to claim 7, wherein the co-amorphous composition comprises curcumin and artemisinin, or curcumin and artesunate, or curcumin and piperine in 1:1 molar ratio.
9. The process according to claim 7, wherein the co-crystal comprises curcumin and quercetin in 1:1 to 1:2 molar ratios.
10. A pharmaceutical coamorphous or co-crystal composition comprising curcumin and natural, low molecular weight molecules selected from artemisinin, artesunate, piperine or quercetin in stoichiometric molar ratio with one or more suitable pharmaceutically acceptable excipients useful for the treatment or prevention of cancer or malaria.
11. A method for treating or preventing cancer or malaria comprising administering an effective amount of the pharmaceutical composition to the subject suffering from said disease.