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Precipitation of curcumin, a poorly water-soluble drug, has been carried out by the liquid antisolvent technique in the presence of ultrasound and stabilizers. Curcumin particles with varied morphology were observed to have formed during precipitation in the presence of ultrasound and additives such as sodium dodecyl sulfate (SDS), Tween 80, hydroxyl propyl methylcellulose (HPMC), polyvinyl pyrrolidone (PVP), and bovine serum albumin (BSA). Characterization of the precipitated particles reveals that curcumin particles precipitated with ultrasound and large polymeric stabilizers such as HPMC, PVP, and BSA are superstructures formed by aggregation of several primary curcumin nanoparticles. The particles in these cases appeared to be loose aggregates (of~1-5 μm in size) composed of several curcumin nanoparticles (~50-200 nm in size). On the other hand, curcumin particles precipitated in the presence of ultrasound and without additive as well as small-molecule stabilizers like SDS and Tween 80 appear more fused (the primary building blocks of these particles were not clearly visible). Moreover, curcumin particles precipitated in the presence of ultrasound only and particles precipitated in the presence of ultrasound along with additives were found to exist in the orthorhombic form, whereas raw curcumin and curcumin particles precipitated without any additive and without ultrasound were found to exist in the monoclinic form. The results obtained in this work suggest that curcumin particles with the desired physical form and morphology can be engineered through a careful manipulation/choice of ultrasound and additives during precipitation. [6][7][8] DL-glutamic acid, 11 and 11102 | CrystEngComm, 2014, 16, 11102-11114 This journal is † Electronic supplementary information (ESI) available: Experimental materials and methods, table on precipitated curcumin form details, comparative XRPD patterns of form 1, form 2 and form 3 with the precipitated curcumin particles, hydrogen bonding in different curcumin forms, FTIR spectra of precipitated curcumin particles, and the SEM micrograph of raw curcumin. See

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Curcumin crystallizes in three polymorphic forms. Form 1 exists as a monoclinic structure, whereas Forms 2 and 3 exist as orthorhombic structures. The aim of this work was to understand the polymorphic behavior of curcumin and the stability of the forms of curcumin. Liquid antisolvent precipitation of curcumin in the presence of ultrasound and additives results in the precipitation of curcumin in orthorhombic forms (Form 2 or Form 3), whereas raw curcumin and curcumin particles precipitated without ultrasound and without additives exist in monoclinic form. Differential scanning calorimetery (DSC) experiments reveal that both of the orthorhombic forms (Forms 2 and 3), which precipitated in the presence of ultrasound and additives, transform to a monoclinic form (Form 1) upon heating. The orthorhombic form (Form 3) in particles, which precipitated in the presence of ultrasound only (no additives), transforms directly to a monoclinic form (Form 1) upon heating. On the other hand, the orthorhombic form (Form 3) in particles, which precipitated in the presence of additives such as HPMC and BSA along with ultrasound, first transforms to Form 2 before finally converting to Form 1 upon heating. All of these transformations occur below the melting points of all three forms. These polymorphic transformations also result in a visible change in particle morphology from rice seed-like or spherical to acicular. While Form 2 and Form 3 were found to be unstable at higher temperatures, these forms, when stored in aqueous suspensions at room temperature (25°C), were found to be stable even after 3 years, with no significant change in particle size or morphology.