Identification of a naturally-occurring 8-[alpha-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl]daidzein from cultivated kudzu root.
BACKGROUND
Kudzu root (Radix puerariae) is a rich source of isoflavones that are effective in preventing osteoporosis, heart disease and symptoms associated with menopause. The major isoflavonoids in kudzu root extracts were reported as puerarin, daidzin and daidzein. Recently, an unknown isoflavonoid (compound 1) was detected from one-year-old kudzu root cultivated in Vietnam.


OBJECTIVE
To identify a novel compound 1 in kudzu root extract and determine the structure of the compound by ESI(+) TOF MS-MS, (1)H-, (13)C-NMR and enzymatic hydrolysis.


METHODS
Samples were prepared by extraction of one-year-old kudzu root with 50% ethanol and the isoflavonoids were purified using recycling preparative HPLC. Unknown compound 1 was detected using UV-light at 254 nm in TLC and HPLC analyses. The molecular weight of 1 was determined using a TOF mass spectrometer equipped with an electrospray ion source. The structure of 1 was determined from the (13)C and (1)H NMR spectra recorded at 100.40 and 400.0 MHz, respectively.


RESULTS
ESI(+) TOF MS-MS analysis shows that 1 is a puerarin diglycoside. The interglycosidic linkage of diglycoside determined by (1)H-, (13)C-NMR, and enzymatic hydrolysis suggests that 1 has a glucosyl residue linked to puerarin by an alpha-1,6-glycosidic bond. This compound is the first naturally-occurring 8-[alpha-D-glucopyranosyl-(1-->6)-beta-D-glucopyranosyl]daidzein in kudzu root. The concentration of glucosyl-alpha-1,6-puerarin in kudzu root was 2.3 mg/g as determined by HPLC.


CONCLUSIONS
The results indicate that puerarin diglycoside is one of the major isoflavonoids in kudzu root and has a significant impact on the preparation of highly water-soluble glycosylated puerarin.
Nguyen
Van Dao
VD
Center for Agricultural Biomaterials, and Department of Food Science and Biotechnology, Seoul National University, Shilling-dong, Gwanak-gu, Seoul 151-742, South Korea.
Min
Byoung-Cheol
BC
Kyung
Myung-Ok
MO
Park
Jong-Tae
JT
Lee
Byong Hoon
BH
Choi
Chung-Hyo
CH
Seo
Nam-Seok
NS
Kim
Yong-Ro
YR
Ahn
Dong Uk
DU
Lee
Sung-Joon
SJ
Park
Cheon-Seok
CS
Kim
Jung-Wan
JW
Park
Kwan-Hwa
KH
D002240:Carbohydrate Sequence; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D007529:Isoflavones / Q000737:chemistry* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D018517:Plant Roots / Q000737:chemistry*; D029908:Pueraria / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
C546926:8-(alpha-D-glucopyranosyl-(1-6)-beta-D-glucopyranosyl)daidzein; D007529:Isoflavones