Borneol and Α-asarone as adjuvant agents for improving blood-brain barrier permeability of puerarin and tetramethylpyrazine by activating adenosine receptors.

Puerarin (PUE) and tetramethylpyrazine (TMP) are central nervous system (CNS) drugs used in cerebrovascular diseases. Poor brain-blood barrier (BBB) permeability limited their clinical application. Borneol and α-asarone have been proposed as an oral brain-targeting enhancer. In this study, we aimed to first evaluate the 'orifice-opening' effect of borneol and α-asarone, both aromatic resuscitation drugs, on improvement of brain delivery of PUE and TMP and second to investigate whether the enhancing effects were associated with adenosine receptors (ARs)-mediated trans-BBB pathway. In vitro BBB model was established and borneol and α-asarone significantly increased the cumulative amount of permeated PUE and TMP and the enhancing effects could be counteracted by AR inhibitors. Borneol and α-asarone could decrease expression of ZO-1, an important BBB junction protein, but inversely increase the expression of A1AR and A2AAR. In vivo pharmacokinetic study also confirmed that oral co-administration of borneol or α-asarone significantly increased AUCbrain for PUE and TMP. These results suggested that borneol and α-asarone are both effective adjuvant agents for delivery of PUE and TMP to the brain.