Apparently, you have to take a Lot of curcuman for it to be effective but there may be curcuman in nano sized particles that can cross the bbb. Saw an add for something like that somewhere.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3744901/
The accolade and credentials of curcumin as a multi-functional therapeutic compound in neurodegenerative diseases, cardiovascular, malignancies and other diseases have been supported by extensive published studies over the few decades. The therapeutic effects of curcumin were further strengthened in epidemiological evidences in curcumin-consuming populations such as India whereby long term consumption of curcumim showed remarkably lower incidence rate of neurodegenerative cases. The outcomes of numerous laboratory data performed in in vivo and in vivo studies have made it clear that curcumin also posed minimal toxicity towards neuronal cells. Although experimental laboratory results seem very promising, data on human clinical trial is limited. Data collected from numerous studies over the last thirty years stated that a multi-targeted and pleotropic therapy showed higher success in curing neurodegenerative diseases as opposed to a mono-targeted therapy. For instance, in the case of treating AD and PD, therapeutic strategies earmarked include compounds with anti-inflammatory, anti-amyloid deposition and anti-oxidant properties. In addition, these compounds should be tolerable (non-toxic) even in high doses, orally available, low cost and easily accessible. As a result, compounds with multiple cellular targets such as curcumin become the subject of intense research works. As mentioned in the review, curcumin could modulate multiple signaling pathways involved in virtually most neurodegenerative diseases and effectively treat neurodegenerative diseases as an improved therapeutic modality. Secondly, curcumin could easily cross the tight junction of BBB as this is important to ensure effective pharmacokinetic actions in CNS. Thirdly, low bioavailability and pre-mature degradation of curcumin resulting in sub-therapeutic levels remains the main disadvanteges of curcumin therapy that poses great challenges to date. As discussed in the review, several studies have showed that curcumin is insoluble in aqueous solution, extremely unstable in alkaline condition, easily degraded and metabolized by human body. Recent trend showed a large surge of scientific data reporting the conversion of water-insoluble curcumin into nano-sized particles, which greatly improved curcumin’s solubility and consequently its bioavailability in vivo [432, 433]. Significant improvement in cell uptake and longer circulation time of curcumin in human is achieved via coating with special biopolymers [434]. As majority of therapeutic data of curcumin are based on in vitro and in vivo model, more extensive and well-controlled human trials should be established to accurately determine its optimal administration dose, route of administration and interactions with different organs.