Development and Validation of a Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of epsilon-Acetamidocaproic Acid in Rat Plasma

A simple and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of epsilon-acetamidocaproic acid (AACA), the primary metabolite of zinc acexamate (ZAC), in rat plasma by using normetanephrine as an internal standard. Sample preparation involved protein precipitation using methanol. Separation was achieved on a Gemini-NX C18 column (150 mm x 2.0 mm, i.d., 3 microm particle size) using a mixture of 0.1% formic acid-water : acetonitrile (80 : 20, v/v) as the mobile phase at a flow rate of 200 microl/min. Quantification was performed on a triple quadrupole mass spectrometer employing electrospray ionization and operating in multiple reaction monitoring (MRM) and positive ion mode. The total chromatographic run time was 4.0 min, and the calibration curves of AACA were linear over the concentration range of 20~5000 ng/ml in rat plasma. The coefficient of variation and relative error at four QC levels were ranged from 1.0% to 5.8% and from -8.4% to 6.6%, respectively. The present method was successfully applied for estimating the pharmacokinetic parameters of AACA following intravenous or oral administration of ZAC to rats.

Effects of R. Glutinosa and E. Senticosus on Postmenopausal Osteoporosis

In this study, we investigated the therapeutic effects of a novel formulation of low-dose calcium and vitamin D3, blended with Rehmannia glutinosa Libosch and Eleutherococcus senticosus Max (RE+), in postmenopausal women. The controls were given either a placebo or high dose calcium and vitamin D3 (Ca+D). Bone mineral density (BMD) in the L2-3 lumber spines and femur regions was assessed, and serum osteocalcin, bone-specific alkaline phosphatase (BALP), and cross-linked N-telopeptide of type I collagen (NTx) were used as markers of osteoblast and osteoclast activity. Furthermore, all variables were measured before and after 6 and 12 months of treatment. The osteocalcin level was higher in the RE+ group, and BALP was almost the same in all groups. Serum NTx was significantly decreased in the RE+ group after 12 months (p<0.05). The NTx in the Ca+D and placebo groups showed no significant change. The decrease of femur BMD was further demonstrated in the placebo group, but significantly increased in the RE+ group after 6 and 12 months of treatment (p<0.05). There were significant differences in the percent changes of femur BMD between the placebo and RE+ groups (p<0.01) and Ca+D and RE+ groups (p<0.05). The decrease of spine BMD in the placebo group was inhibited both in the Ca+D and RE+ groups, however, there was significant difference only between the placebo and RE+ groups (p<0.05). These findings suggest that continuous oral therapy of the RE+ formulation reduces rapidly decreasing bone mineral density in postmenopausal women more effectively than high doses of calcium and vitamin D3 alone by inhibiting osteoclastic activity. Therefore, it seems that the RE+ has its own antiosteoporotic effects. We suggest larger clinical studies to determine the most efficacious dosage and benefits of this novel treatment.