Rationale of using Vinca minor Linne dry extract phytocomplex as a vincamine’s oral bioavailability enhancer

Vincamine is a poorly soluble potent neuroprotector and cerebral vasodilator, used for the treatment for CNS disorders. In some cases, the bioavailability of pure compounds is strongly influenced by the co-administration of other constituents, and in some cases, the so called ‘phytocomplex’ may act as enhancer of absorption of selected phytochemicals. In this paper, the oral bioavailability of vincamine when administered as a standardised Vinca minor L. leaf dry extract rather than pure indole alkaloid is demonstrated to be higher. The chosen alkaloid-enriched and standardised dry extract was widely characterised by means of HPLC–MS, PXRD, DSC, XPS, 13C and 15N solid-state NMR (SSNMR) using pure vincamine as a matter of comparison. Then, the in vitro dissolution performances of the two products and their in vivo bioavailability in rats were evaluated. The sevenfold improvement in oral bioavailability of the dry extract with respect to the pure vincamine was ascribed to interactions between the indole alkaloid and the corollary of ingredients of the dry extract, giving rise to the protonation of the alkaloid vincamine, thus enhancing its dissolution in physiological fluids. Present data demonstrate that alkaloid vincamine administered as a whole plant extract has a higher bioavailability compared to the pure chemical compound.