Neoline, fuziline, songorine and 10-OH mesaconitine are potential quality markers of Fuzi: In vitro and in vivo explorations as well as pharmacokinetics, efficacy and toxicity evaluations

ETHNOPHARMACOLOGICAL RELEVANCE

Fuzi, the lateral roots of Aconitum carmichaelii Debx, plays an irreplaceable role in treating Yang deficiency and cold coagulation syndromes. However, Fuzi has a narrow margin of safety since its pharmacological constituents, Aconitum alkaloids, have potential cardiotoxicity and neurotoxicity. The current quality markers (Q-markers) for the control of Fuzi's efficacy and toxicity are 3 monoester-diterpenoid alkaloids, namely, benzoylaconine (BAC), benzoylhypaconine and benzoylmesaconine (BMA) and 3 diester-diterpenoid alkaloids, namely, aconitine (AC), hypaconitine and mesaconitine (MA). However, mounting evidence indicates that the current 6 Q-markers may not be efficacy- or toxicity-specific enough for Fuzi.

AIM OF THE STUDY

The aim of this study was to explore and evaluate efficacy- or toxicity-specific potential quality markers (PQ-markers) of Fuzi.

MATERIALS AND METHODS

PQ-markers were explored by analyzing 30 medicinal samples and alkaloids exposed in mouse. Pharmacokinetics of PQ-markers on C57BL/6J mice were determined. Anti-inflammatory effects of PQ-markers were evaluated by λ-carrageenan-induced paw edema model and lipopolysaccharide-induced RAW264.7 cell inflammatory model, while analgesic effects were assessed by acetic acid-induced pain model and Hargreaves test. Cardiotoxicity and neurotoxicity of PQ-markers were assessed by histological and biochemical analyses, while acute toxicity was evaluated by modified Kirschner method.

RESULTS

After in vitro and in vivo explorations, 7 PQ-markers, namely, neoline (NE), fuziline (FE), songorine (SE), 10-OH mesaconitine (10-OH MA), talatizamine, isotalatizidine and 16β-OH cardiopetalline, were found. In the herbal medicines, NE, FE, SE and 10-OH MA were found in greater abundance than many other alkaloids. Specifically, the amounts of NE, FE and SE in the Fuzi samples were all far higher than that of BAC, and the contents of 10-OH MA in 56.67% of the samples were higher than that of AC. In mouse plasma and tissues, NE, FE, SE, talatizamine, isotalatizidine and 16β-OH cardiopetalline had higher contents than the other alkaloids, including the 6 current Q-markers. The pharmacokinetics, efficacy and toxicity of NE, FE, SE and 10-OH MA were further evaluated. The average oral bioavailabilities of NE (63.82%), FE (18.14%) and SE (49.51%) were higher than that of BMA (3.05%). Additionally, NE, FE and SE produced dose-dependent anti-inflammatory and analgesic effects, and their actions were greater than those of BMA. Concurrently, the toxicities of NE, FE and SE were lower than those of BMA, since no cardiotoxicity or neurotoxicity was found in mice after NE, FE and SE treatment, while BMA treatment notably increased the creatine kinase activity and matrix metalloproteinase 9 level in mice. The average oral bioavailability of 10-OH MA (7.02%) was higher than that of MA (1.88%). The median lethal dose (LD₅₀) of 10-OH MA in mice (0.11 mg/kg) after intravenous injection was close to that of MA (0.13 mg/kg). Moreover, 10-OH MA produced significant cardiotoxicity and neurotoxicity, and notable anti-inflammatory and analgesic effects that were comparable to those of MA.

CONCLUSIONS

Seven PQ-markers of Fuzi were found after in vitro and in vivo explorations. Among them, NE, FE and SE were found to be more efficacy-specific than BMA, and 10-OH MA was as toxicity-specific as MA.

The effect of compatibility of Aconiti Radix and honey on the pharmacokinetics of five Aconitum alkaloids in rat plasma

Aconiti Radix (Chuanwu [CW]), is widely used for the treatment of the chronic and intractable diseases due to its remarkable curative effect. CW has been combined with honey for thousands of years to reduce toxicity and enhance efficacy. This study first clarified compatibility mechanism of CW co-used with honey using a comparative pharmacokinetic idea. We developed and validated a simple, sensitive, specific, and accurate UHPLC-MS/MS method to simultaneously determine five Aconitum alkaloids in rat plasma after oral administration of CW decoction and CW-honey concentrated solution. Pharmacokinetic parameters were significantly different between the two groups (P<0.01 and P<0.05). Compared with CW group, C_max and AUC_0→t were decreased in CW-honey group for three diester-diterpenoid alkaloids (hypaconitine, mesaconitine and aconitine); T_max and T_1/2 were prolonged. However, C_max and AUC_0→t were increased in CW-honey group for two monoester-diterpenoid alkaloids (benzoylaconine and benzoylmesaconine); T_max was shortened; T_1/2 was prolonged. These findings suggest that honey affected the pharmacokinetic behaviors of five Aconitum alkaloids. We speculate that the detoxification and synergism of honey might result from reducing the toxicity of diester-diterpenoid alkaloids and promoting the biological activity of monoester-diterpenoid alkaloids in vivo. This study provides a theoretical basis for the clinical use of CW combined with honey.

A systematic review of pharmacological activities, toxicological mechanisms and pharmacokinetic studies on Aconitum alkaloids

The tubers and roots of Aconitum (Ranunculaceae) are widely used as heart medicine or analgesic agents for the treatment of coronary heart disease, chronic heart failure, rheumatoid arthritis and neuropathic pain since ancient times. As a type of natural products mainly extracted from Aconitum plants, Aconitum alkaloids have complex chemical structures and exert remarkable biological activity, which are mainly responsible for significant effects of Aconitum plants. The present review is to summarize the progress of the pharmacological, toxicological, and pharmacokinetic studies of Aconitum alkaloids, so as to provide evidence for better clinical application. Research data concerning pharmacological, toxicological and pharmacokinetic studies of Aconitum alkaloids were collected from different scientific databases (PubMed, CNKI, Google Scholar, Baidu Scholar, and Web of Science) using the phrase Aconitum alkaloids, as well as generic synonyms. Aconitum alkaloids are both bioactive compounds and toxic ingredients in Aconitum plants. They produce a wide range of pharmacological activities, including protecting the cardiovascular system, nervous system, and immune system and anti-cancer effects. Notably, Aconitum alkaloids also exert strong cardiac toxicity, neurotoxicity and liver toxicity, which are supported by clinical studies. Finally, pharmacokinetic studies indicated that cytochrome P450 proteins (CYPs) and efflux transporters (ETs) are closely related to the low bioavailability of Aconitum alkaloids and play an important role in their metabolism and detoxification in vivo.

A proton-coupled organic cation antiporter is involved in the blood-brain barrier transport of Aconitum alkaloids

ETHNOPHARMACOLOGICAL RELEVANCE

The herbs of Aconitum are the essential Traditional Chinese medicine and have played an indispensable role in many Asian countries for thousands of years to treat critical illnesses, and chronic, stubborn diseases. However, Aconitum may induce severe neurotoxicity and even death. So far the mechanism of Aconitum penetrating the blood-brain barrier (BBB) is still unclear.

AIM OF THE STUDY

To determine whether influx transporters contribute to the brain uptake of the highly toxic alkaloids in Aconitum including aconitine (AC), mesaconitine (MA) and hypaconitine (HA).

MATERIALS AND METHODS

The uptake of AC, MA and HA was characterized using in vitro hCMEC/D3 model and in situ mouse brain perfusion. In hCMEC/D3 cells, the effect of incubation temperature, time, initial drug concentration, energy (NaN₃), extracellular and intracellular pH (FCCP and NH₄Cl), the prototypical substrates/inhibitors of known organic cation transporting carriers and trans-stimulation (pre-incubating with pyrilamine and diphenhydramine) on the cellular uptake were studied. In addition, the effect of silencing OCTN1, OCTN2 and PMAT by specific siRNA was investigated. In mice, the contribution of the proton-coupled antiporter on the brain uptake of Aconitum was investigated by chemical inhibition.

RESULTS

In hCMEC/D3 cells, AC, MA and HA were each taken up in a temperature-, time- and concentration-dependent manner, which were reduced by NaN₃ and FCCP. Regulation of extracellular and intracellular pH as well as trans-stimulation studies showed that AC, MA and HA were transported by a proton-coupled antiporter expressed at the plasma membrane that could also transport pyrilamine and diphenhydramine. Each uptake was markedly inhibited by various cationic drugs, but insensitive to the prototypical substrates/inhibitors of identified organic cation transporting carriers, such as OCTs, PMAT, MATEs and OCTNs. In addition, silence of OCTN1, OCTN2 and PMAT had no significant inhibitory effect on the uptake of AC, MA and HA. In mice, the brain uptake of each alkaloid measured by in situ brain perfusion was suppressed by diphenhydramine when the transport capacity of P-gp/Bcrp at the BBB was chemically inhibited.

CONCLUSIONS

A novel proton-coupled organic cation antiporter plays a predominant role in the blood to brain influx of AC, MA and HA at the BBB, and thus affect the safety of Aconitum species.

Aconitum alkaloids, the major components of Aconitum species, affect expression of multidrug resistance-associated protein 2 and breast cancer resistance protein by activating the Nrf2-mediated signalling pathway

BACKGROUND

Aconitum alkaloids from Aconitum species are often used to treat arthritis and rheumatic diseases but have the drawback of high toxicity. Identifying their pharmacokinetic behaviour is important for the safe clinical application of Aconitum species. Efflux transporters (ETs), including P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2), and breast cancer resistance protein (BCRP), have important functions in regulating the pharmacokinetic behaviours of drugs and in herb-herb or herb-drug interactions (HDIs). The Aconitum alkaloids regulate P-gp expression and function, but their effects on MRP2 and BCRP expression remain unknown.

PURPOSE

To determine the effects of three Aconitum alkaloids, aconitine (AC), benzoylaconine (BAC), and aconine, on MRP2 and BCRP.

METHODS

The levels of the protein and mRNA expression of MRP2 and BCRP in vivo and in vitro were measured via Western blotting and real-time PCR, respectively. Fluorescence signals of MRP2 and BCRP were detected via confocal fluorescence microscopy. A reporter assay using HepG2-C8 cells, which were generated by transfecting plasmids containing the antioxidant response element (ARE)-luciferin gene into HepG2 cells, was used to examine the ARE-luciferin activity. The transport activities of MRP2 and BCRP were tested via flow cytometry using substrate probes.

RESULTS

The Aconitum alkaloids significantly up-regulated MRP2 and BCRP expression, accompanied by a marked increase in nuclear factor E2-related factor-2 (Nrf2) expression in the jejunum, ileum, and colon of FVB mice, in the order AC < BAC < aconine. In the in vitro model, the Aconitum alkaloids increased MRP2 and BCRP expression in Caco-2 and LS174T cells, in the order AC < BAC < aconine. Additionally, these alkaloids promoted the translocation of Nrf2 from the cytoplasm to the nucleus and significantly increased ARE-luciferin activity in HepG2-C8 cells. Luteolin, a potent inhibitor of Nrf2, markedly prevented MRP2 and BCRP expression from being induced by the three Aconitum alkaloids. The efflux activity of MRP2 was also significantly increased in cells receiving the same treatment.

CONCLUSIONS

The tested Aconitum alkaloids significantly increased the expression of MRP2 and BCRP by activating the Nrf2-mediated signalling pathway and enhanced the efflux activity of MRP2. The potential for herb-herb interactions or HDIs exists when Aconitum species are co-administered with substrate drugs that are transported via MRP2 and BCRP. Therefore, the Aconitum alkaloids may be used as quality indicators for the herbs of Aconitum species.

Pharmacokinetic evaluation of Shenfu Injection in beagle dogs after intravenous drip administration

Shenfu Injection (SFI) is a well-defined Chinese herbal formulation that is obtained from red ginseng and processed aconite root. The main active constituents in SFI are ginsenosides and aconitum alkaloids. In this work, ginsenosides (ginsenoside Rg1, ginsenoside Rb1 and ginsenoside Rc) and aconitum alkaloids (benzoylmesaconine and fuziline) were used as the index components to explore the pharmacokinetic behavior of SFI. A selective and sensitive HPLC–MS/MS method was developed for the quantification of ginsenosides and aconitum alkaloids in dog plasma and was used to characterize the pharmacokinetics of the five index components after intravenous drip of three different dosages of SFI in beagle dogs. The pharmacokinetic properties of the index components were linear over the dose range of 2–8 mL/kg.

Microcalorimetry studies of the antimicrobial actions of Aconitum alkaloids

The metabolic activity of organisms can be measured by recording the heat output using microcalorimetry. In this paper, the total alkaloids in the traditional Chinese medicine Radix Aconiti Lateralis were extracted and applied to Escherichia coli and Staphylococcus aureus. The effect of alkaloids on bacteria growth was studied by microcalorimetry. The power-time curves were plotted with a thermal activity monitor (TAM) air isothermal microcalorimeter and parameters such as growth rate constant (μ), peak-time (Tm), inhibitory ratio (I), and enhancement ratio (E) were calculated. The relationships between the concentration of Aconitum alkaloids and μ of E. coli or S. aureus were discussed. The results showed that Aconitum alkaloids had little effect on E. coli and had a potentially inhibitory effect on the growth of S. aureus.

Aconitum Alkaloid Poisoning Because of Contamination of Herbs by Aconite Roots

Aconitum alkaloid poisoning can occur after drinking decoction and soup made from non-toxic herbs contaminated by aconite roots. In the present review, the main objective is to describe the clinical features, investigations and possible sources of contamination. A combination of neurological, gastrointestinal and cardiovascular signs and symptoms was seen. Ventricular tachyarrhythmias could occur in 18% of subjects. Yunaconitine and crassicauline A, mainly found in certain aconite roots from Southwest China, are most commonly involved. Herbal residues and unused herbs should first be inspected for gross contamination. On-site inspection at the retailer should exclude accidental mix-up or cross-contamination when handling aconite roots. Samples of prescribed herbs are examined for gross contamination and analysed for the presence of Aconitum alkaloids. Samples of the implicated herb are also collected from the wholesaler for investigation. If post-import contamination is unlikely, the regulatory authorities of the exporting countries should be notified for follow-up actions. It is a challenging task to work out how non-toxic herbs become contaminated by aconite roots. The source control with good agricultural and collection practices and quality assurance must be enhanced.

Incidence and Causes of Aconitum Alkaloid Poisoning in Hong Kong from 1989 to 2010

Aconite roots contain Aconitum alkaloids, which are highly toxic cardiotoxins and neurotoxins. In this review, the main objective was to determine the incidence and causes of Aconitum alkaloid poisoning in Hong Kong between 1989 and 2010, based on six published reports from the territory-wide poison control units. In the New Territories East of Hong Kong, the incidence of aconite poisoning showed a sudden and sustained decrease from 0.60 (1989-1991) to 0.16 (1992-1993) and 0.17 (1996-1998) per 100 000 population, after publicity measures in late 1991 to promote awareness of the toxicity of aconite roots. In the whole of Hong Kong, the incidence of aconite poisoning was even lower in January 2000-June 2004 (0.03 per 100 000 population). However, aconite poisoning became more common again in April 2004-July 2009 and 2008-2010 (0.15 and 0.28 per 100 000 population). Overdoses and use of inadequately processed aconite roots were important causes. As from 2004 to 2009, 'hidden' aconite poisoning (toxicity caused by contaminants in other dispensed herbs) emerged as an important cause. It is important to continue the safety monitoring of potent herbs and the networking of poison control units. Further systematic studies would be required to identify the likely sources of contamination of herbs.