Self-gelation involved in the transformation of resveratrol and piperine from a co-amorphous system into a co-crystal system†
*a
and
Zunting
Pang
*a
Abstract
Co-amorphous and co-crystal systems are attractive crystal-engineering strategies for poorly soluble drugs. Intermolecular interactions between components play a key role in the formation of the two systems, making the exploration of transformation between them particularly interesting. Thus, the main purpose of this study was to improve drug solubility/dissolution and to investigate the potential transformation of the two systems. Herein, a classic combination of resveratrol (RES) and piperine (PIP) was prepared as a co-amorphous system (RES–PIP CM) and a co-crystal system (RES–PIP CC). The RES–PIP CC system showed enhanced dissolution for both drugs and maintained supersaturation for a long time, while the RES–PIP CM system exhibited decreased dissolution in comparison to their crystalline forms owing to their gel formation during dissolution. Furthermore, such self-gelation increased the molecular motion and rearrangement, and promoted the recrystallization of RES–PIP CM. Meanwhile, the higher binding energy of RES/PIP molecules than RES/RES molecules or PIP/PIP molecules indicated stronger intermolecular interactions between RES and PIP, resulting in a directional rearrangement of RES/PIP molecules in the gel of RES–PIP CM to form RES–PIP CC.
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