Elsevier

Fitoterapia

Volume 122, October 2017, Pages 144-149
Fitoterapia

New phenolic glycosides from Curculigo orchioides and their xanthine oxidase inhibitory activities

https://doi.org/10.1016/j.fitote.2017.09.009Get rights and content

Abstract

Seven new phenolic glycosides including two heterocyclic phenolic derivatives orcinosides I-J (1–2) and five chlorophenolic glycosides curculigines J-N (37), together with nineteen known compounds were isolated from the rhizome of Curculigo orchioides. Based on extensive spectroscopic analyses (UV, IR, HRESIMS, 1D and 2D NMR), the structures of the new compounds were identified. Orcinoside I (1) and J (2) displayed xanthine oxidase inhibitory activities with IC50 values 0.25 and 0.62 mM respectively.

Introduction

Curculigo orchioides, with a widespread Chinese name “Xianmao”, is a traditional Chinese medicine known for its medical value of the rhizome for the treatment of impotence, enuresis, cold sperm, cold pain of back and knee, numbness of the limbs, and decline in physical strength [1], [2]. Meanwhile, various pharmacological activities of C. orchioides including hepatoprotective effect [9], anti-HBV activity [4], immunostimulatory effect [10], [11], estrogenic activity [12] and antioxidative activity [13] have also been reported. Phenolic glycosides, chlorophenolic glycosides and cycloartane saponins were recognized as the main chemical constituents of C. orchioides[3], [4], [5], [6], [7], [8]. Surprisingly, in our continuous phytochemical investigations on the rhizome of C. orchioides, a series of new and active compounds were obtained [4], [5], [8], [14], [15].

Gout is a recurrent disease which caused by the overproduction of uric acid and/or impaired renal excretion of uric acid. The acute pains of joints especially keen joints, as the main symptoms of gout, may terribly lead to arthritis [16], [17], [18]. Xanthine oxidase (XO) plays an important role in catalyzing the hydroxylation of hypoxanthine and xanthine at the last two steps of urate biosynthesis [19], [20] which has a close relationship with the occurrence of gout. Hence the inhibitor of XO can conversely block the synthesis of uric acid, which may alleviate the bearing of kidney and improve the renal function greatly, thus providing us with an alternative therapeutic approach of gout. Considering the effect of Curculigo orchioide on curing arthritis in traditional Chinese medicinal formulae [21], we speculated that “Xianmao” might also display anti-gout activity especially XO inhibitory bioactivity.

In order to elaborate the anti-gout chemical constituents of “Xianmao”, we investigated the constituents of the 70% EtOH extract of it which led to the isolation of seven new phenolic glycosides orcinosides I-J (12) and curculigines J-N (37), together with nineteen known compounds (826). Orcinosides I-J are two new phenolic glycosides linked with heterocycle unit, both of which displayed XO inhibitory activities at the tested concentrations and the IC50 of them were measured. Curculigines J-N are phenolic glycosides containing chlorine atoms. This paper reported the isolation and structure elucidation of the seven new phenolic glycosides by UV, IR, MS, 1D and 2D NMR techniques as well as their XO inhibitory activities.

Section snippets

General

General chemical samples and instruments were listed in the Supplementary data.

Plant material

The rhizomes of C. orchioides were collected in Wenshan County, Yunnan Province, China, in November 2005, and authenticated by Dr. Li-Gong Lei, Kunming Institute of Botany, Chinese Academy of Sciences. A voucher specimen (No. 20051106) has been deposited in the Group of Anti-virus and Natural Medicinal Chemistry, Kunming Institute of Botany, Chinese Academy of Sciences.

Extraction and isolation

Fractions III and IV were obtained based on our

Structure elucidation of new compounds (Fig. 1)

Compound 1, white powders, [α]D24 =  38.4 (c, 0.19, MeOH), had the molecular formula of C19H22O9 by HRESIMS at m/z 393.1180 [(M  H], calcd for 393.1191). Its IR spectrum showed absorptions for the hydroxyl group (3418 cm 1), the conjugated carbonyl unit (1658 cm 1) and the aromatic ring (1620, 1512 and 1460 cm 1). The 1H NMR spectrum of 1 gave two aromatic hydrogen signals at δH 6.56 (1H, br.s) and δH 6.38 (1H, br.s), one methyl signal at δH 2.23 (3H, s), one anomeric proton at δH 4.87 (1H, d, 7.6)

Conflict of interest

The authors declare no conflict of interest.

Acknowledgments

This work was supported by the Youth Innovation Promotion Association CAS, the Program of Yunling Scholar, the Hundred Talents Program of the Chinese Academy of Sciences and the CAS “Light of West China” Program (Western Youth Scholars “A”).

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