In our prior study, TLFA exhibited significant antidiabetic activity, and a notable increase in the serum insulin level was observed at the same time.
In this study, we analyzed the constituents in the serum of the GK rats after TLFA was given orally.
Purity of TLFA was determined by ultraviolet spectrometry (Zhai et al.
The TLFA (200 g) was fractionated by column chromatography at atmospheric pressure over silica gel G using petroleum ether, chloroform, ethyl acetate, acetone and methanol successively, as a result, five fractions were obtained.
Analysis of the constituents in the rat serum after oral administration of TLFA
Then vacuum dried powder of TLFA was dissolved with the solvent composed by ethanol:Tween 80:distilled water (1:1:8) as a stock solution (35 mg/ml) and was orally administrated to rats (1 ml/100 g body weight).
Typical TIC chromatograms of the control serum, the serum after oral administration of TLFA, AA and TLFA in methanol are shown in Fig.
2, the components of TLFA were almost not detected in rat serum after oral administration, while a metabolite whose retention time equaled with that of AA was detected in this sample using UPLC/MS.
In previous study, we have observed the hypoglycemic activity of TLFA in alloxan-induced diabetic mice and rats.
We found that if the lactone ring structure of arctigenin (2(3H)-furanone, 4-[(3,4-dimethoxyphenyl)methyl]dihydro-3-[(4-hydroxy3-methoxyphenyl)methyl]-, (3R, 4R)-), the main component of TLFA and the mother nucleus of chemical structure of the eight compounds, could be hydrolyzed in vivo, it will be converted to AA.
So we speculated that AA probably was the main active metabolite of TLFA, which possessed hypoglycemic activity similar to that of nateglinide.
Its hypoglycemic activity is in agreement with the reported antidiabetic activity of TLFA in alloxan diabetic mice and rats.