Analysis of saikosaponins in Bupleuri Radix and Caihu-shugan-san using reversed-phase HPLC with pulsed amperometric detection

Chinese Pharmacopoeia Revisited: A Review of Anti-Depression Herbal Sources

Depression, which can be accompanied by many fatal diseases and a low life quality, has become the leading cause of ill health and disability worldwide. However, Chinese Pharmacopoeia, the most authoritative and evidence-based encyclopedia of Traditional Chinese Medicine (TCM), could contain leads and insights into the development of new antidepressant drugs. In this work, nine herbal medicines with ‘dispel melancholy functions’ specifically documented in Chinese Pharmacopoeia have been comprehensively reviewed with respect to clinical trials, and phytochemical and pharmacological aspects. The nine drugs are Rosae Chinensis Flos, Croci Stigma, Albiziae Cortex and Flos, Roase Rugosae Flos, Curcumae Radix, Hyperici Perforati Herba, Cyperi Rhizoma and Bupleuri Radix. The mechanisms of action of their functional antidepressant compounds, including gallic acid, hypericin, kaempferol, crocetin, crocin, quercetin, luteolin, isorhamnetin, curcumin, hyperforin, adhyperforin, catechin, rutin, puerarin, and saikosaponins A and D, have been collected and discussed. These traditional Chinese herbs and their active compounds provide a promising resource to develop effective new antidepressant drugs in future. Moreover, mechanistic investigations, safety verification and large-scale clinical trials are still expected to finally transform such TCM-based antidepressant resources to new drugs for patients suffering from depression.

Saikosaponins and the deglycosylated metabolites exert liver meridian guiding effect through PXR/CYP3A4 inhibition

ETHNOPHARMACOLOGICAL RELEVANCE

Radix Bupleuri (RB), traditionally used to treat inflammatory disorders and infectious diseases, represents one of the most successful and widely used herbal drugs in Asia over the past 2000 years. Being realized the role in regulating metabolism and controlling Yin/Yang, RB is not only chosen specifically for treating liver meridian and the corresponding organs, but also believed to have liver meridian guiding property and help potentiate the therapeutic effects of liver. However, the ingredients in RB with liver meridian guiding property and the underly mechanism have not been comprehensively investigated.

AIM OF STUDY

Considering the important role of CYP3A4 in first-pass metabolism and the liver exposure of drugs, the present study aimed to determine whether saikosaponins (SSs) and the corresponding saikogenins (SGs) have a role in inhibiting the catalytic activity of CYP3A4 in human liver microsomes and HepG2 hepatoma cells and whether they could suppress CYP3A4 expression by PXR-mediated pathways in HepG2 hepatoma cells.

MATERIALS AND METHODS

The effect of SSs and SGs on CYP3A4-mediated midazolam1'-hydroxylation activities in pooled human liver microsomes (HLMs) was first studied. Dose-dependent experiments were performed to obtain the half inhibit concentration (IC₅₀) values. HepG2 cells were used to assay catalytic activity of CYP3A4, reporter function, mRNA levels, and protein expression. The inhibitory effects of SSa and SSd on CYP3A4 activity are negligible, while the corresponding SGs (SGF and SGG) have obvious inhibitory effects on CYP3A4 activity, with IC₅₀ values of 0.45 and 1.30 μM. The similar results were obtained from testing CYP3A4 catalytic activity in HepG2 cells, which correlated well with the suppression of the mRNA and protein levels of CYP3A4. Time-dependent testing of CYP3A4 mRNA and protein levels, as well as co-transfection experiments using the CYP3A4 promoter luciferase plasmid, further confirmed that SSs and SGs could inhibit the expression of CYP3A4 at the transcription level. Furthermore, PXR protein expression decreased in a concentration- and time-dependent manner after cells were exposed to SSs and SGs. PXR overexpression and RNA interference experiments further showed that SSs and SGs down-regulate the catalytic activity and expression of CYP3A4 in HepG2 may be mainly through PXR-dependent manner.

CONCLUSION

SSs and SGs inhibit the catalytic activity and expression of CYP3A4 in a PXR-dependent manner, which may be highly related to the liver meridian guiding property of RB.

Effect of saikosaponins and extracts of vinegar-baked Bupleuri Radix on the activity of β-glucuronidase

In Traditional Chinese Medicine, liver targeting is usually achieved by coadministration with Vinegar-baked Radix Bupleuri (VBRB), but the mechanism is unclear. In this paper, the influence of VBRB on the activity of β-glucuronidase was investigated and compared with that of saikosaponins. The activity of β-glucuronidase was measured by microplate reader using a 4-nitrophenyl-β-d-glucuronide substrate. The change of 4-nitrophenol content was used to characterize the activity of β-glucuronidase. Bupleurum chinenes were found to be the inhibitor of β-glucuronidase. The inhibition rate of Bupleurum chinenes extracts BC1 (high molecular weight polysaccharides), BC2 (ethanol soluble/water insoluble component), BC3 (extracted by n-butanol, soluble in water), and BC4 (low molecular weight water soluble parts) on the activity of β-glucuronidase was found to be 45.15%, 33.94%, 24.94%, and 34.54%, respectively, after 1 h incubation, with BC1 showing the highest inhibition rate. In contrast, the saikosaponins were demonstrated to be the promoter of β-glucuronidase, with promotion rates of 333.56%, 217.04%, 247.87%, 149.75%, and 92.50% for saikosaponin standard samples A, B, B2, C, and D, respectively, (p<0.05). In conclusion, inhibiting the activity of β-glucuronidase might be one of the reasons why VBRB could influence drug distribution upon its coadministration with other drugs. Since saikosaponins and VBRB extracts have opposite effect, more attention should be paid to the content of saikosaponins in the extracts upon its application.

Determination of astragalin and astragaloside content in Radix Astragali using high-performance liquid chromatography coupled with pulsed amperometric detection

Astragalin and astragalosides were measured in Radix Astragali using reversed-phase chromatography coupled with pulsed amperometric detection. Because the target compounds showed poor stability in aqueous solutions, they were extracted in 100% methanol under reflux. All compounds were detected with high sensitivity under highly alkaline conditions using sodium hydroxide as a post-column eluent. The limits of detection and quantification of target compounds were 0.02-0.36 μg/mL and 0.06-1.09 μg/mL, respectively, and the linear regression coefficients were 0.9982-1.0000. The intra- and inter-day precisions were <0.92% in retention time and <4.78% in calculated contents. Average recoveries were >91.33%. Astragalin and astragaloside contents between Radix Astragali at different ages and in different parts were successfully determined without sample purification or concentration.