Transdermal delivery of nobiletin using ionic liquids

Nobiletin (NOB), a flavonoid, has extremely low water solubility and low oral bioavailability; however, despite these problems, various physiological effects have been investigated in vitro. In the present study, we investigated the transdermal delivery of NOB using choline and geranic acid (CAGE), which is a biocompatible material that has been reported to be a promising transdermal delivery approach. The feasibility was evaluated by a set of in vitro and in vivo tests. A solubility evaluation demonstrated that CAGE induced excellent solubility of NOB induced by multipoint hydrogen bonding between NOB and CAGE. In vitro transdermal tests using a Franz diffusion cell showed that CAGE was effective in enhancing transdermal absorption of NOB, compared to other penetration enhancers. Subsequent in vivo tests demonstrated that CAGE significantly improved area under the concentration-time curve of NOB in vivo and NOB/CAGE sample showed 20-times higher bioavailability than oral administration of NOB crystal. Furthermore, NOB/CAGE sample also showed significant drops of the blood glucose level in rats derived from hypoglycemic activity of NOB. Thus, transdermal administration of NOB using CAGE was shown to be feasible, which indicates that the use of CAGE may be adapted for other flavonoids that also show both low water solubility and low permeability.

Synthesis of Effective Food Constituents toward the Development of Chemical Biology Investigations

This article describes the development of various probes and immunogens for chemical-biological investigations of food flavonoids. We accomplished a large (gram)-scale asymmetric synthesis of a key intermediate, 5-aminopentyl deoxy epigallocatechin-3-gallate (APDOEGCg; 3), an analogue of green tea polyphenol EGCg, in which the key step was cationic cyclization utilizing neighboring group participation of the gallate carbonyl group. The synthetic APDOEGCg (3) was efficiently converted to a fluorescent probe 18 and an immunogen 19 by utilizing the high reactivity of the amine functional group. We confirmed the usefulness of these probes for imaging studies and the generation of antibodies, respectively. We also describe the efficient synthesis of a positron emission tomography (PET) probe [¹¹C]20 by incorporation of ¹¹C into EGCg (1), for which synthetic 4″-Me-EGCg (20) was utilized as an authentic sample. Our synthetic strategy was also applied for the practical synthesis of nobiletin (21), a polymethoxylated flavone from citrus. Synthetic nobiletin was readily converted to various probes by selective demethylation and incorporation of fluorescein, biotin or ¹¹C. These probes should be useful for a range of biological applications. Detailed examination of the mechanisms and further applications are in progress.

Stereoselective construction of 2-vinyl 3-hydroxybenzopyran rings: total syntheses of teadenols A and B

Total syntheses of teadenols A and B, isolated from fermented tea, were accomplished in a highly stereocontrolled manner.

Practical synthesis of natural plant-growth regulator 2-azahypoxanthine, its derivatives, and biotin-labeled probes

AHX derivatives and their probe molecules.