Relative contribution of small and large intestine to deglycosylation and absorption of flavonoids from Chrysanthemun morifolium extract.

The flower of Chrysanthemum morifolium Ramat (CM) is an established part of traditional Chinese medicine (TCM). Luteolin and apigenin flavonoids are the effective components of the CM extract (CME); however, they exist in the orally consumed CME as glycosides. The present study was carried out to determine the relative contribution of the small and large intestine to the deglycosylation and absorption of flavonoids from CME using a rat model system. The distribution of luteolin and apigenin in rat gastrointestinal (GI) luminal contents, tissues, and plasmas was assessed after the oral administration of CME. The hydrolysis and absorption of CME flavonoids in different rat GI segments were further evaluated by using in situ ligated models and cell-free extracts prepared from rat GI segments. The results demonstrated that after the oral administration of CME, the magnitude of deglycosylation in rats was surprisingly high (about 30%) in the stomach and upper intestine within the first 5 min after ingestion, and early absorption in the plasma was detected. The results from site-limited administration revealed that the stomach was the initial hydrolysis site, while the duodenum was the first effective absorption site for CME flavonoids. Diminishing microbial flora in the jejunum had no significant effect on the hydrolysis of the flavonoids from CME, but the cell-free extracts prepared from rat GI segments demonstrated a strong ability to hydrolyze. Taken together, our findings suggest that enteric disposition contributes to the pharmacokinetics of luteolin and apigenin after oral administration of CME. Moreover, the upper digestive tract plays a key role in the hydrolysis and absorption of flavonoids in CME.

Absorption and excretion of luteolin and apigenin in rats after oral administration of Chrysanthemum morifolium extract.

Chrysanthemum morifolium extract (CME) has the protective effect on cardiovascular diseases. Luteolin and apigenin are two major bioactive components in vivo when CME is orally administrated to experimental animal. The present paper shows the study of the absorption and excretion of luteolin and apigenin in rats after a single oral dose of CME (200 mg/kg). The levels of luteolin and apigenin in plasma, urine, feces, and bile were measured by HPLC after deconjugation with hydrochloric acid or beta-glucuronidase/sulfatase. The results showed that the plasma concentrations of luteolin and apigenin reached the highest peak level at 1.1 and 3.9 h after dosing, respectively. The area under the concentration-time curves (AUC) for luteolin and apigenin were 23.03 and 237.6 microg h mL-1, respectively. The total recovery of the dose was 37.9% (6.6% in urine; 31.3% in feces) for luteolin and 45.2% (16.6% in urine; 28.6% in feces) for apigenin. The cumulative luteolin and apigenin excreted in the bile was 2.05% and 6.34% of the dose, respectively. All of the results suggest apigenin may be absorbed more efficiently than luteolin in CME in rats, and both luteolin and apigenin have a slow elimination phase, with a quick absorption, so a possible accumulation of the two flavonoids in the body can be hypothesized.

[Determination of trigonelline by HPLC and study on its pharmacokinetics].

AIM: To develop a sensitive and specific HPLC method for determination of trigonelline in rabbit plasma, and study the pharmacokinetics in rabbit. METHODS: After ig of fenugreek extract and i.v. of trigonelline in rabbit, the biological samples could be well purified after precipitation of protein with methanol and acetonitrile. Asahipak NH2P-50 column was used, the mobile phase consisted of acetonitrile-water (90:10) at a flow-rate of 1.2 mL.min-1, and detection wavelength was set at UV 265 nm. The column temperature is 30 degrees C. RESULTS: The calibration curve was linear in the range from 0.98 mg.L-1 to 31.28 mg.L-1, with r = 0.9986, the detection limit of this method was 50 micrograms.L-1. The concentration-time curves of trigonelline in rabbits after ig and i.v. administration were shown to fit one-compartment and two-compartment open model, respectively. The main parameters after ig of fenugreek extract were as follow: T1/2(Ka) was 0.9 h, T1/2(Ke) was 2.2 h, V was 0.64 L.kg-1, AUC was 1.93 mg.min.L-1. The main parameters after i.v. of trigonelline were as follows: T1/2 alpha was 10.8 min, T1/2 beta was 44.0 min, K21 was 0.044 min-1, K10 was 0.026 min-1, K12 was 0.017 min-1, AUC was 931.0 mg.min.L-1. CONCLUSION: Trigonelline showed a middle rate of absorption and fast rate of elimination in rabbit. Meanwhile, the method is simple, accurate, with a good reproducibility, and it provide a basic method for the investigation of trigonelline and fenugreek pharmacokinetics.