Interest in natural products has led to

Interest in natural products has led to the study of plant extracts as sources of ARIs. However, chemical complexity of natural extracts makes the identification of ARIs challenging and time-consuming. Identification of bioactive compounds with the desired biological effect from natural products, continues to be a challenge in the development of novel drugs and functional foods. Since the advent of high-throughput screening in the early 1990s, the concept of off-line high-performance liquid chromatography (HPLC)-based activity profiling has been proposed and implemented for the effective tracking of bioactive compounds in natural product extracts (Cieśla & Moaddel, 2016). Alternatively, in recent years, numerous studies have reported the successful application of affinity-based ultrafiltration-HPLC in the identification of protein receptor ligands and enzyme inhibitors (Choi et al., 2011; Wang et al., 2017; Choi, Jung, & Kim, 2015), indicating that it might be a suitable method for rapid profiling of ARIs from natural products. Lysimachia christinae, a herbaceous plant of the family Primulaceae, is a common wild plant widely distributed in southwestern China and the Yangzi River basin. L. christinae is eaten as a vegetable and consumed as an infusion tea in China, and is thought to prevent calculi. Phytochemical investigations have shown that its typical chemical constituents are flavonoids, phenolics, and triterpenoids such as isoquercitrin, kaempferol, trifolin, 3,2′,4′,6′-tetrahydroxy-4,3′-dimethoxy chalcone, kaempferol-3-O-lysimachiatrioside, rhamnocitrin-3,4-diglucoside, kaempferol-3-O-rutinoside, kaempferol-3-O-rhamnoside-7-O-rhamnosyl (1-3)-rhamnoside, and p-hydroxy benzoic Sildenafil mesylate (Podolak, Koczurkiewicz, Galanty, & Michalik, 2013; Tóth, Végh, Alberti, Béni, & Kéry, 2015). Moreover, it is also rich in dietary minerals such as Ca, Mg, Fe, Zn, Cu, Mn, Cd, Ni, and Co. Additionally, dried L. christinae has also been used in traditional Chinese medicine as a diuretic, cholagogue, anti-inflammatory agent, antioxidant, and analgesic, and for effective treatment of biliary calculus, hepatolithiasis, and urinary calculi (Yasukawa & Takido, 1993; Tian, Yang, & Chen, 2008; Choi, Park, & Lee, 1997; Gan et al., 2010; Yang et al., 2011). However, no experimental studies relevant to its effect on AR inhibition are known. We therefore studied the effect of L. christinae on AR inhibition, and isolated a novel polyphenolic ARI from L. christinae, guided by AR affinity-based ultrafiltration-HPLC profiling. The structure of the isolated compound, DHDP, was determined by one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR), fast atom bombardment ionization mass spectrometry (FAB-MS), and ultraviolet (UV) and (IR) infrared spectroscopy. Further, the AR inhibitory activity and mechanism of DHDP were characterized by AR inhibition assays, enzyme kinetics analysis, computer simulation, and a rat lens ex vivo assay.
Materials and methods
Results and discussion
Conclusions In summary, the ethyl acetate fraction of Lysimachia christinae (EALC) showed excellent aldose reductase (AR) inhibitory activity, and a new aldose reductase inhibitor (ARI), DHDP (1,5-di-hydroxy-1,5-di-[(E)-3-(4-hydroxyphenyl)-2-propenoic]-3-pentanonyl ester), was isolated from the EALC guided by an affinity-based ultrafiltration-HPLC assay. The AR inhibition property of DHDP was also characterized in this study. These results suggest that L. christinae might be a functional food with potent AR inhibition activity, and DHDP might be an effective ARI lead compound. Moreover, this study demonstrates that the affinity-based ultrafiltration-HPLC assay is a convenient screening method for accelerating discovery of novel ARIs from natural sources.
Acknowledgment The authors would like to thank Soo Kyeong Lee for her contribution towards the experiments in this study. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2015R1D1A1A01059199) and Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries (IPET) through High Value-added Food Technology Development Program, funded by Ministry of Agriculture, Food and Rural Affairs (MAFRA) (116020-3).