A new isoflavone glycoside from Pueraria alopecuroides

A new isoflavone glycoside, (−)-tuberosin-3-O-β-D-glucopyranoside (1), along with 10 known compounds 1a-10, was isolated from Pueraria alopecuroides. Their structures were determined on the basis of spectral data including 1D and 2D NMR and HREIMS. These compounds were isolated from this plant for the first time.


Introduction
Pueraria alopecuroides Craib is a valuable traditional Dai herb medicine, distributed in the south of Yunnan provinces of China. Dai people in that area of China use its tuberous roots to ease heart attack, improve blood circulation, treat hypertension and typhoid fever. It is a species close to Pueraria mirifica, which is a traditional health food in Thailand. The tuberous root of P. mirifica has estrogenic activity that can maintain vigour in postmenopausal women, and the major active compounds are several special isoflavonoids (Okamura et al. 2008). Therefore, it is expected that isoflavonoids with similar estrogenic activity will be discovered in P. alopecuroides, and P. alopecuroides could be developed as an alternative resource to P. mirifica.

Results and discussion
Compound 1 was isolated as a yellow amorphous powder. The molecular formula was determined as C 26 H 28 O 10 on the basis of the [M] þ peak in the HR-ESI-MS spectrum at m/z 500.49. The UV spectrum showed absorption maxima at 282.60 and 204.40 nm, while IR spectrum suggested the presence of OH groups (3442.79 cm 21 ) and a conjugated olefinic bond (1623.09 cm 21 ).

Plant material
The tuberous roots of P. alopecuroides were collected from Menglun and Mengyang, Xishuangbanna, Yunnan, China, in October 2012, and were authenticated by Professor Qi-Shi Song, Xishuangbanna Tropical Botanical Garden. A voucher specimen (no. 20121011) was deposited at the Research Group on Ethnomedicine of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences.

Conclusions
P. alopecuroides is a valuable traditional Dai medicine. A new isoflavone glycoside, (2 )tuberosin-3-O-b-D-glucopyranoside (1), along with 10 known compounds 1a-10, was isolated from P. alopecuroides. These compounds were isolated from this plant for the first time.

Supplementary material
Supplementary material relating to this paper is available online at http://dx.doi.org/10.1080/ 14786419.2015.1038813.