Chemical Constituents from the Rhizome of Ligusticum chuanxiong Hort. and Their Nrf2 Inducing Activity

Phthalides from the rhizome of Ligusticum chuanxiong Hort. attenuate diabetic nephropathy in mice

ETHNOPHARMACOLOGICAL RELEVANCE

In many famous formulas of traditional Chinese medicine (TCM), the rhizome of Ligusticum chuanxiong (L. chuanxiong) is commonly used as an ingredient for promoting blood circulation and resolving blood stasis to treat diabetic nephropathy. However, its material basis and mechanism of action are still needed to be explored.

AIM OF THE STUDY

The aim of this work is to elucidate the potential effective parts (phthalides) of L. chuanxiong responsible for renal protection and to explore the possible mechanism of renal protection.

MATERIALS AND METHODS

A method based on column chromatography of macroporous resin was established to enrich an effective part (LCE70), and the composition of LCE70 was identified by HPLC-UV and UPLC-MS/MS methods. Mice model was induced by streptozotocin (STZ) to evaluate the protective effect of LCE70 on diabetic nephropathy (DN). In vitro, the suppressive effect of LCE70 on oxidative damage, inflammation and its mechanism were tested using immunoblot analysis, ELISA, etc. Cellular thermal shift assay (CETSA) was adopted to verify the interaction between the phthalides and the key targets involved in renal injury.

RESULTS

LCE70 displayed therapeutic potential against metabolic disorders, renal dysfunction, and fibrosis in a DN model induced by STZ in mice. Furthermore, it markedly reduced oxidative stress of the kidney in DN mice by activating Nrf2 pathway. Z-ligustilide, the main component of LCE70, reacted with Keap1, and thus promoted Nrf2 dissociating from Keap1 to activate Nrf2 pathway.

CONCLUSIONS

LCE70 improved hyperglycemia-induced renal function by enhancing the Nrf2 activation, reducing collagen deposition, and alleviating inflammation and oxidative stress, which suggested its potential as a therapeutic agent for DN.

Induction of Nrf2-EpRE-mediated gene expression by hydroxyanthraquinones present in extracts from traditional Chinese medicine and herbs

Hydroxyanthraquinones that can be present in traditional Chinese medicine (TCM) and herbal extracts have claimed beneficial intestinal effects. We examined the ability of a panel hydroxyanthraquinones, and methanolic extracts from selected TCM and herbal granules to activate Nrf2-EpRE mediated gene expression using a reporter-gene assay. The results indicate that purpurin, aloe-emodin, 2-hydroxy-3-methylanthraquinone and rhein induced Nrf2 mediated gene expressions with a high induction factor (IFs>10), with BMCL₁₀ values (the lower confidence limit of the concentration giving 10% added response above background) of 16 μM, 1.1 μM, 23 μM and 2.3 μM, respectively, while aurantio-obtusin, obtusifolin, rubiadin 1-methyl ether and emodin were less potent (IFs<5), with BMCL₁₀ values for added response above background level of 4.6 μM, 15 μM, 9.8 μM and 3.8 μM, respectively. All TCM extracts and the herbal extracts of Aloe Vera, Polygonum multiflorum, Rubia (cordifolia) and Rheum officinale activated the Nrf2-EpRE pathway. Of the TCM extracts, Chuan-Xin-Lian-Kang-Yan-Pian was the most potent Nrf2-inducer. LC-MS/MS analysis indicated the presence of selected hydroxyanthraquinones in the extracts and herbs, in part explaining their Nrf2-EpRE mediated activity. In conclusion, different hydroxyanthraquinones have different potencies of Nrf2 activation. The Nrf2 activation by extracts from TCM and herbs can be partially explained by the presence of selected hydroxyanthraquinones.

Six pairs of enantiomeric phthalide dimers from the rhizomes of Ligusticum chuanxiong and their absolute configurations and anti-inflammatory activities

Six pairs of enantiomeric phthalide dimers (1-6) were isolated from the rhizomes of Ligusticum chuanxiong. Their structures and absolute configurations were elucidated by NMR spectroscopy, X-ray diffraction analyses, and electronic circular dichroism calculations. Compounds (+)-1 and (-)-1 are new phthalide dimers, featuring two classes of monomeric units (a phthalide and an unusual 2,3-seco-phthalide) with an uncommon linkage (3,6'/8,3'a). Compounds (+)-2 and (-)-3 are also novel phthalide dimers that had not been reported previously. Although (-)-2 and (+)-3 have been successfully isolated in previous studies, their absolute configurations were not unambiguously determined. As for compound 4, it was reported as a racemate in one study, and one of its enantiomers was identified in a subsequent study. Herein, all enantiomeric phthalide dimers were successfully separated, and their absolute configurations were determined. The inhibitory effects of all isolates against lipopolysaccharide-induced nitric oxide production were tested using RAW264.7 cells. The results show that compounds (+)-2, (-)-2, (+)-3, (-)-3, (+)-4, (-)-4, (+)-5, (+)-6, and (-)-6 have inhibitory activities, with compound (+)-5 being the most active (IC₅₀ value of 4.3 ± 1.3 μM).