Modification of hygroscopicity and tabletability of L-carnitine by a cocrystallization technique

The deliquescent property of L-carnitine (LC) makes it inconvenient during production and storage. The current study aims to develop a new solid form of LC by co-crystallization with myricetin (MYR) and its hygroscopicity, dissolution, and tabletability were also investigated. The cocrystal was prepared by a slurry method and analyzed using DSC/TGA, PXRD, FTIR, Raman, 13C ss NMR and Materials Studio software. The physicochemical properties of the cocrystal were investigated by dissolution testing, moisture sorption analysis and tabletability analysis. Crystal structure analysis based on XRD demonstrated that three types of intermolecular hydrogen bonds (i.e., O5–H⋯O3′, O7–H⋯O2′, and O13–H⋯O1′) formed in the prepared LC-MYR cocrystal, which agreed with wavenumber/resonance shifts in FTIR, Raman and 13C ss NMR. In comparison to the commercial LC salts, the LC cocrystal exhibited extremely lower hygroscopicity (∼16-fold) and enhanced tabletability, and was more suitable for manufacturing solid dosage forms. Additionally, the LC-MYR cocrystal demonstrated an apparently improved dissolution rate with persistently enhanced supersaturation dissolution of MYR, which would benefit its in vivo absorption. This could provide a novel solid form of LC and MYR with superior processability.