Potent bacterial neuraminidase inhibitors, anthraquinone glucosides from Polygonum cuspidatum and their inhibitory mechanism

详细信息    查看全文

• 作者：Zia Uddin^a ; ^{ziauddinrph@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Yeong Hun Song^a ; ^{yh0126@hanmail.net" class="auth_mail" title="E-mail the corresponding author} ; Marcus J. Curtis-Long^b ; ^{mjl253@cornell.edu" class="auth_mail" title="E-mail the corresponding author} ; Jeong Yoon Kim^a ; ^{yoon24@gnu.ac.kr" class="auth_mail" title="E-mail the corresponding author} ; Heung Joo Yuk^a ; ^{cupid6@gnu.ac.kr" class="auth_mail" title="E-mail the corresponding author} ; Ki Hun Park^a ; ^{khpark@gnu.ac.kr" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Polygonum cuspidatum ; Anthraquinone glucosides ; Bacterial neuraminidase ; Inhibitory mechanism
• 刊名：Journal of Ethnopharmacology
• 出版年：2016
• 出版时间：4 December 2016
• 年：2016
• 卷：193
• 期：Complete
• 页码：283-292
• 全文大小：1041 K

文摘

P. cuspidatum is a popular Chinese medicinal herb, having a long history of usage in traditional Chinese medicine for the treatment of several inflammatory diseases in the form of powders and decoctions. Similarly there are many reports that P. cuspidatum has antibacterial and anti-inflammatory effects, both of which are properties associated with compounds having activity against bacterial neuraminidase (BNA).

Aim of the study

We investigated whether P. cuspidatum's metabolites exhibited BNA inhibition. Consistent with our hypothesis, we found several inhibitors from the methanol extract of this plant, and then fully characterized their inhibitory mechanisms.

Materials and methods

Activity guided separation of methanol extract led to isolation of individual constituents, and subsequently their structures were elucidated by spectroscopic analysis. Detailed kinetic behaviors of BNA inhibitors were explored by showing the changes of K_m and V_max, the ratios of K_I/K_IS and K_ik/K_iv, and fluorescence quenching effect.

Results and conclusion

This study attempted to isolate the responsible metabolites and elucidate the BNA inhibitory mechanism. The principal BNA inhibitory compounds (2–6) were identified as emodin (2), physcion-8-O-β-D-glucopyranoside (3), emodin-8-O-β-D-glucopyranoside (4), emodin-1-O-β-D-glucopyranoside (5), and 2-methoxy-6-acetyl-7-methyljuglone (6). Unexpectedly, anthraquinone glucosides (3–5) were much more potent than their corresponding aglycones (1 and 2). For example, emodin (2) had an IC₅₀=5.4 μM, whereas its glucosides (4 and 5) had IC₅₀=0.85 μM and 0.43 μM respectively. A similar trend was observed with physcion (1, IC₅₀>200 μM) and its glucoside (3, IC₅₀=6.2 μM). The anthraquinone (2) was mixed type I inhibitor, whereas its glucosides (4 and 5) were noncompetitive. In addition, the fluorescence quenching study showed that the affinity constants (K_SV) of inhibitors increased in proportion to their inhibitory potencies. Furthermore, we quantified the major and minor metabolites through UPLC-PDA-Q-TOF/MS, and revealed that the most potent inhibitors were the major constituents. This result contributes to our understanding of P. cuspidatum utility as functional food stuff and widely used herbal medicine.