A Validated Liquid Chromatographic Method for Berberine Analysis in Tissue and Application

Intestines-erythrocytes-mediated bio-disposition deciphers the hypolipidemic effect of berberine from Rhizoma Coptidis: A neglected insight

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizoma Coptidis (RC), the dried rhizome of Coptis Chinensis Franch., can dispel dampness and heat within the body and has been traditionally used for the treatment of cardiovascular disease (CVD)-associated problems including hyperlipidemia in China. Berberine (BBR) is the main active component of RC, which has been shown to possess significant therapeutic potential. However, only 0.14% of BBR is metabolized in the liver, and the extremely low bioavailability (<1%) and blood concentration of BBR in experimental and clinical settings is insufficient to achieve the effects as observed under in vitro conditions, which imposes challenges to explain its excellent pharmacological actions. Intense efforts are currently being devoted to defining its specific pharmacological molecular targets, while the exploration from the perspective of its pharmacokinetic disposition has rarely been reported to date, which could hardly make a comprehensive understanding of its hypolipidemic enigma.

AIM OF THE STUDY

This study made a pioneering endeavor to unveil the hypolipidemic mechanism of BBR from RC focusing on its unique intestines-erythrocytes-mediated bio-disposition.

MATERIALS AND METHODS

The fate of BBR in intestines and erythrocytes was probed by a rapid and sensitive LC/MS-IT-TOF method. To analyze the disposition of BBR, a reliable HPLC method was subsequently developed and validated for simultaneous determination of BBR and its key active metabolite oxyberberine (OBB) in whole blood, tissues, and excreta. Meanwhile, the enterohepatic circulation (BDC) of BBR and OBB was verified by bile duct catheterization rats. Finally, lipid overloading models of L02 and HepG2 cells were employed to probe the lipid-lowering activity of BBR and OBB at in vivo concentration.

RESULTS

The results showed that BBR underwent biotransformation in both intestines and erythrocytes, and converted into the major metabolite oxyberberine (OBB). The AUC_0-t ratio of total BBR to OBB was approximately 2:1 after oral administration. Besides, the AUC_0-t ratio of bound BBR to its unbound counterpart was 4.6:1, and this ratio of OBB was 2.5:1, indicative of abundant binding-type form in the blood. Liver dominated over other organs in tissue distribution. BBR was excreted in bile, while the excretion of OBB in feces was significantly higher than that in bile. Furthermore, the bimodal phenomenon of both BBR and OBB disappeared in BDC rats and the AUC_0-t was significantly lower than that in the sham-operated control rats. Interestingly, OBB significantly decreased triglycerides and cholesterol levels in lipid overloading models of L02 and HepG2 cells at in vivo-like concentration, which was superior to the prodrug BBR.

CONCLUSIONS

Cumulatively, BBR underwent unique extrahepatic metabolism and disposition into OBB by virtue of intestines and erythrocytes. BBR and OBB were mainly presented and transported in the protein-bound form within the circulating erythrocytes, potentially resulting in hepatocyte targeting accompanied by obvious enterohepatic circulation. The unique extrahepatic disposition of BBR via intestines and erythrocytes conceivably contributed enormously to its hypolipidemic effect. OBB was the important material basis for the hypolipidemic effect of BBR and RC.

Quality by design-based optimization of formulation and process parameters for berberine nanosuspension for enhancing its dissolution rate, bioavailability, and cardioprotective activity

Berberine (BER) possesses dissolution rate limited oral bioavailability. The present study deciphers the formulation of nanosuspension loaded with BER for enhancing its cardioprotective potential. The nanosuspension was prepared by a liquid antisolvent precipitation technique using sodium lauryl sulfate as a surfactant and polyvinyl pyrrolidone K30 (PVP K30) as a polymer. The optimized formulation showed a particle size of 251.32 ± 4.18 nm, zeta potential of -24.10 ± 1.16 mV, and drug loading capacity of 98.22 ± 2.24%. The results showed about 6.01-fold and 3.54-fold enhancement in the dissolution rate and permeability, respectively, upon loading berberine into nanosuspension. About 8.44-fold increase in C_max , 27.22-fold increase in AUC_0-t , and 27.38-fold increase in AUC_0-∞ were observed in the case of BER nanosuspension, compared to its naïve form. The results of particle size, zeta potential, and drug loading showed a nonsignificant change in the response of fresh and aged nanosuspension, which indicated that the formulation was stable. In vitro results on H9C2 cell line indicated a lower cellular proliferation rate after treatment with BER nanosuspension with decreased cytoplasmic expression of angiotensin converting enzyme (ACE) protein. Overall, the results indicated the successful development of BER nanosuspension with an enhanced dissolution rate, permeability, bioavailability, and cardioprotective activity. Practical applications The present study provides the evidence that the formulation of nanosuspension loaded with berberine enhance the cardioprotective activity of berberine. The results of the study supports the improved bioavailability of nanosuspension of berberine showed enhanced cardioprotective activity.