To develop a simple and highly sensitive high performance liquid chromatography with electrospray ionization mass spectrometric (LC-ESI-MS) method for the simultaneous determination of
madecassoside and its major metabolite
madecassic acid in rat plasma, and compare the pharmacokinetics of the two compounds in normal and
collagen-induced arthritis (CIA) rats.
Glycyrrhetinic acid was used as the internal standard (IS). Chromatographic separation was accomplished on an Inertsil ODS-3 column, using a gradient elution with the mobile phase composed of
acetonitrile and water acidified with 0.1% (V/V)
formic acid. Detection was achieved by ESI-MS under the negative selected ion monitoring (SIM) mode. In normal and CIA rats,
madecassoside (30 mg·kg(-1)) was orally administered for 21 consecutive days from the day of
arthritis onset. For
madecassoside, the linear range was 10-1 000 ng·mL(-1) with the square regression coefficient (r) of 0.998 9, while for
madecassic acid, the linear range was 10-500 ng·mL(-1) with the square regression coefficient (r) of 0.996 1. The lower limit of quantification was 10 ng·mL(-1) for both analytes. The intra- and inter-day precision ranged from 1.78% to 13.42% for
madecassoside and 2.30% to 14.90% for
madecassic acid, and the accuracy was between -0.95% and 6.30% for
madecassoside and between -1.48% and 5.34% for
madecassic acid. The average recoveries of
madecassoside,
madecassic acid and IS from spiked plasma samples were > 81%. The developed method was successfully applied to the pharmacokinetic study of
madecassoside and
madecassic acid in rats after an
oral administration of
madecassoside. During initial 7 days of dosing, the cmax and AUC of
madecassoside were greatly decreased and Vd/F was markedly increased in CIA rats, and no significant difference was observed on the first day of dosing. In contrast, the T1/2, cmax and AUC of
madecassic acid were significantly increased, and Ke of
madecassic acid was greatly decreased in CIA rats compared with normal rats. Along with repeated administration of
madecassoside, the differences of pharmacokinetic parameters of both
madecassoside and
madecassic acid between CIA and normal rats gradually subsided. The pharmacokinetic characteristics of both
madecassoside and
madecassic acid in rats were significantly altered by
arthritis status, and the differences of pharmacokinetic parameters between
arthritis and normal rats coincide with the severity of
arthritis.