Home | English | | | UGC | RGC

  Theme-based Research Scheme–Call for Proposal Chinese children

  Theme-based Research Scheme–Call for Preliminary Proposals

  Launch of New Joint Research Schemes

  Nanotherapeutics in Angiogenesis: Synthesis and in Vivo Assessment of Drug Efficacy and Biocompatibility in the Zebrafish Embryos

  Nimodipine suppresses chemokine release via inhibition of adenosine uptake in endothelial cells

  DNA-binding Activities of Some Alkaloids from Chinese Medicinal Herbs

  Development of a High Performance Liquid Chromatographic Method for the Quality Control of Rhizoma Smilacis Glabrae and its Derived Products

  Interactions between UGT isoenzymes and MRP transporters during the oral absorption process of Baicalein

  Gender Differences in the Regulation of Endothelium-Dependent Contracting Factor

  Areas of Excellence Scheme Project: Introducing the Work of the Hong Kong Institute of Economics and Business Strategy

  Areas of Excellence of Scheme Project: Building excellence in plant and agricultural biotechnology research

  RGC Collaborative Research Fund – Layman Summaries of Projects Funded in 2009/10 Exercise


Flavonoids are polyphenolic phytochemicals present extensively in our dailydiet, medicinal plants and herbal remedies. Since 2001, with the continuous support of RGC grants and CUHK Direct Grants, a series of investigations on Baicalein (B), a bioactive flavonoid isolated from the root of Scutellaria baicalensis Georgi, and related flavonoids have been conducted in our research group. Previous studies from us and others have indicated that extensive intestinal first-pass metabolism, mainly glucuronidation catalyzed by UDP-glucuronsyltransferase (UGT) isozymes, and a subsequent unfavorable efflux transport mediated by multidrug resistance associated protein (MRP) are the two major reasons responsible for the low oral bioavailability of B. The current study is a continuous mechanistic investigation on the potential interactions between UGT isoenzymes and MRP transporters during the absorption of flavonoids. Both in vitro Caco-2 cell culture model and rat single pass in situ intestinal perfusion model were used. It was found that inhibitions on either the efflux transport mediated by MRP transporters or UGT isozymes would lead to reduction in formation and transport of glucuronide and sulfate conjugates of B. Once the interactions between UGT isoenzymes and MRP transporters have been confirmed from the in vitro and in situ model, their impacts on the overall bioavailability of B were conducted in rats. In vivo studies in rats suggested that co-administered inhibitors of either MRP transporters or UGT isozymes would lead to increased absorption of B and reduced formation of its glucuronide and sulfate conjugated metabolites of B. In order to apply such mechanistic findings to herbdrug/herb-herb interaction investigations, we have studied interactions between B and a series of herbal components or western 
drugs, which mechanistically share similar metabolic and transport pathways as B. It was found that Wogonin and Oroxylin A, the two major co-occurring components of B in the Radix Scutellariae, were sharing the similar metabolic and transport pathway as B. Co-administration of these components together with B would lead to enhanced oral bioavailabilities of each component and reduced formation of their corresponding glucuronides and sulfates metabolites. Comparison between in vitro and in vivo results indicated that the trend of changes in B absorption is more significant in vitro than that in vivo. The current findings on B could also apply to other flavonoids, which would enable us to recognize or even predict potential herb/herb or herb/drug interactions so as to effectively avoid their occurrence. 

In addition to 3 full papers published in international peer reviewed journals, 4 conference abstracts (one of them has obtained the First Place in Poster Award for Postdoctoral Fellow Category), 2 manuscripts under review, the project has trained 1 Postdoctoral fellow, 1 PhD student and 1 undergraduate student. Recently, due to our established reputations in flavonoids research, we were able to attract international student exchange via the "Global Scholarship Programme for Research Excellence–CNOOC Grants for 2009-10" to further our international collaborative research in novel flavonoids.

Prof Zhong Zuo
School of Pharmacy
The Chinese University of Hong Kong

Prof Ge Lin
School of Biomedical Sciences
The Chinese University of Hong Kong