Development and validation of a highly sensitive UPLC-MS/MS method for simultaneous determination of aconitine,mesaconitine, hypaconitine,and five of their metabolites in rat blood and its application to a pharmacokinetics study of aconitine,mesaconitine, and hypaconitine

1. A rapid, specific and sensitive method was developed for the simultaneous determination of eight Aconitum alkaloids: aconitine (AC), mesaconitine (MA), hypaconitine (HA), benzoylaconine (BAC), benzoylmesaconine (BMA), benzoylhypaconine (BHA), aconine and mesaconine in rat blood by ultra-performance liquid chromatography coupled tandem mass spectrometry (UPLC-MS/MS).

2. The UPLC-MS/MS system coupled with an electrospray ionization (ESI) source was operated in a positive mode via multiple-reaction monitoring (MRM). Samples were treated with methanol to remove protein prior to analysis by UPLC-MS/MS. The analytes were separated with a Waters C18 column (1.7 µm, 50?×?2.1?mm) and a gradient elution using acetonitrile and 0.1% formic acid-water as the mobile phases.

3. The linear response range was from 0.125 to 1000 nmol/L for these eight alkaloids and the correlation coefficients (r² values) were all higher than 0.997. The method was validated with respect to precision, accuracy, recovery, matrix effect, carryover effect and sample stability, and found to be within the acceptable limits.

4. The developed and validated method was successfully applied to simultaneously determine the eight Aconitum alkaloids in rats blood after intravenous administration of a mixture of AC, MA and HA.

     

Effects of liquorice on pharmacokinetics of aconitine in rats

Abstract

1. Aconite alkaloids are the main bioactive ingredients existing in Aconitum, for instance aconitine (AC), which exhibit potent analgesic, antirheumatic and other pharmacological effects. In this study, effects of long-term treatment with liquorice on pharmacokinetics of AC in rats were investigated.

2. Pharmacokinetics of AC after oral administration of AC at 1.5?mg/kg either with pre-treatment of liquorice water extracts at 0.433 or 1.299?g/kg (crude drug), respectively, for one week or not were studied. Additionally, LS-180 cells and human primary hepatocytes were utilized to explore the potential effects of bioactive ingredients of liquorice on P-glycoprotein (P-gp) and Cytochromes P450 (CYPs), respectively.

3. The results revealed that exposure of AC after pre-treatment with liquorice was altered remarkably. Area under the concentration-time curve (AUC) decreased from 161?±?37.8 to 58.8?±?8.97 and 44.7?±?8.20?ng/mL*h, respectively. Similarly, C_max decreased from 26.2?±?5.19 to 11.8?±?1.15 and 6.86?±?0.600?ng/mL, respectively. In addition, expressions of CYPs of human primary hepatocytes were enhanced to various contents after induction. Moreover, accumulation of AC and hypaconitine (HA), not mesaconitine (MA) inside of LS-180 cells were reduced after pre-treatment by comparison with control.

4. In conclusion, the exposure of AC in vivo declined after pre-treatment with liquorice extract, which may be highly associated with upregulated expression and/or function of CYPs and P-gp.

     

Intestinal transport of pure diester-type alkaloids from an aconite extract across the Caco-2 cell monolayer model

Aconitine (AC), mesaconitine (MA), and hypaconitine (HA) are the active alkaloids identified in aconite tuber, an important traditional Chinese medicine. The study is aimed to investigate their intestinal transport profiles and potential interaction during the intestinal absorption using the Caco-2 cell monolayer model. All three alkaloids had good permeability with P(app) values greater than 1 × 10 (-6) cm · s (-1). However, AC, MA, and HA in a mixture and as an extract, in both cases with the same content of alkaloids, showed higher transport efficiency in the apical to basolateral, and lower transport efficiency in the basolateral to apical directions. Digoxin, as a P-glycoprotein (P-gp) substrate, was substantially effluxed in the basolateral to apical direction but inhibited by the three alkaloids. Furthermore, the backwards transport of MA and HA was inhibited by the P-gp inhibitor verapamil. These observations indicated that the three alkaloids may not only be P-gp inhibitors but also its substrates; they interact with each other and can potentially enhance their own bioavailability when taken concomitantly.     

An online coupled cell membrane chromatography with LC/MS method for screening compounds from Aconitum carmichaeli Debx. acting on VEGFR-2

An online analytical method coupling high expression vascular endothelial growth factor receptor (VEGFR) cell membrane chromatography (VEGFR-CMC) with high performance liquid chromatography mass spectrometry (LC/MS) for screening and identification of active component from traditional Chinese herb Aconitum carmichaeli Debx. acting on VEGFR-2 was established. Through a 10-port column switcher, factions separated by VEGFR-CMC column (first dimension) were transferred and were adsorbed on an enrichment column. Then, these fractions were sent into LC/MS system (second dimension) immediately and directly for separation and preliminary identification, respectively. Sunitinib malate (SN) was used as positive control, while nifedipine (NF), dexamethasone acetate (DX), methoxyamine hydrochloride (MT) and atenolol (AT) as negative controls. The specification of this VEGFR-CMC-online-LC/MS method was validated by competitive displacement test. As a result, mesaconitine (MSC), aconitine (AC), and hypaconitine (HPC) were identified as the active constituents acting on VEGFR-2. The in vitro inhibition activity of starting extract of Aconitum carmichaeli Debx., MSC, AC, and HPC on HEK293/VEGFR cell viability by MTT test, separately. The in vitro inhibition activity of MSC, AC, and HPC on vascular endothelial growth factor (VEGF) secretion of HEK293/VEGFR cell was tested by VEGF-ELISA assay. The screening results given by the system offered additional exemplification supporting this online coupling method and gave new evidence to the development of anti-tumor drug from natural products.     

Determination of aconitine alkaloids in aconitum roots

A reliable method for extraction of the crude drug, Aconitum roots, and purification of the extract for its eventual separation and quantitation of the aconitine alkaloids by HPLC technique has been developed. The method comprises extraction of aconite powder first with ammoniacal ether and then with methanol (x 3 each), chromatography of the resultant extract over neutral alumina and elution with ethyl acetate-methanol (7:3) prior to HPLC. The method has been found to be reproducible and suitable for routine analysis of aconite and its pharmaceutical preparations.     

Biological activities and pharmacokinetics of aconitine,benzoylaconine, and aconine after oral administration in rats

Aconitine (AC), benzoylaconine (BAC), and aconine (ACN) are three representative alkaloids in Aconitum tubers. Knowing that the drug disposal process in vivo is closely related to the toxicity and efficacy of a drug, it is important to classify the disposal properties of these alkaloids. In this study, the pharmacokinetics of the three alkaloids was investigated. The results showed that the three alkaloids could be quickly absorbed, especially BAC, whose T_max was 0.31 ± 0.17 h. Their C_max was 10.99, 3.99, and 4.29 ng·mL^‐1 respectively, indicating that AC had better absorption than BAC and ACN. Subsequently, we further investigated their absorption mechanism using the Caco‐2 cell monolayer model in vitro. The results showed that they were poorly absorbed, and the absorption of AC and BAC was inhibited by P‐gp, while the absorption of ACN was in a form of passive diffusion. The t_1/2 of AC, BAC and ACN was 1.41, 9.49, and 3.32 h, respectively, indicating that the metabolic or excretion rate of AC was quicker than that of BAC and ACN. Therefore, their metabolic stability was further investigated by using rat liver microsomes in vitro, which showed that AC was easier to be metabolized than BAC and ACN. The excretion experiments showed that AC and ACN were primarily excreted in urine, while BAC was excreted in faeces. In addition, the results of tissue distribution experiments showed that the three alkaloids distributed throughout all the organs, although the distribution rate of AC was slower than that of BAC and ACN. Copyright © 2015 John Wiley & Sons, Ltd.     

Simultaneous quantification of ten key Kratom alkaloids in Mitragyna speciosa leaf extracts and commercial products by ultra‐performance liquid chromatography−tandem mass spectrometry

Kratom (Mitragyna speciosa) is a psychoactive plant popular in the United States for the self‐treatment of pain and opioid addiction. For standardization and quality control of raw and commercial kratom products, an ultra‐performance liquid chromatography?tandem mass spectrometry (UPLC?MS/MS) method was developed and validated for the quantification of ten key alkaloids, namely: corynantheidine, corynoxine, corynoxine B, 7‐hydroxymitragynine, isocorynantheidine, mitragynine, mitraphylline, paynantheine, speciociliatine, and speciogynine. Chromatographic separation of diastereomers, or alkaloids sharing same ion transitions, was achieved on an Acquity BEH C18 column with a gradient elution using a mobile phase containing acetonitrile and aqueous ammonium acetate buffer (10mM, pH 3.5). The developed method was linear over a concentration range of 1–200 ng/mL for each alkaloid. The total analysis time per sample was 22.5 minutes. The analytical method was validated for accuracy, precision, robustness, and stability. After successful validation, the method was applied for the quantification of kratom alkaloids in alkaloid‐rich fractions, ethanolic extracts, lyophilized teas, and commercial products. Mitragynine (0.7%–38.7% w/w), paynantheine (0.3%–12.8% w/w), speciociliatine (0.4%–12.3% w/w), and speciogynine (0.1%–5.3% w/w) were the major alkaloids in the analyzed kratom products/extracts. Minor kratom alkaloids (corynantheidine, corynoxine, corynoxine B, 7‐hydroxymitragynine, isocorynantheidine) were also quantified (0.01%–2.8% w/w) in the analyzed products; however mitraphylline was below the lower limit of quantification in all analyses.     

草乌花及其煎煮液中二萜生物碱的电喷雾串联质谱研究草乌花及其煎煮液中二萜生物碱的电喷雾串联质谱研究

目的 对草乌花及其煎煮液中的二萜生物碱进行定性分析,说明煎煮前后化学成分发生的变化。 方法用注射泵自动进样,电喷雾离子阱串联质谱直接分析草乌花及其煎煮液中生物碱混合物。结果 在生草乌花中发现3个新生物碱,草乌花煎煮后其中的双酯型生物碱和三酯型生物碱都发生水解,前者水解为苯甲酰乌头原碱和乌头原碱类生物碱,后者水解为3-乙酰-乌头原碱类生物碱。结论 该法简便、快速、灵敏、特异性强,为乌头属植物煎煮液中的生物碱分析提供了新途径。     

A rapid, simple and sensitive liquid chromatography-tandem mass spectrometry method for routine clinical monitoring of tacrolimus with the Waters Masstrak™ immmunosuppressant kit

Advances in mass spectrometry instruments have led to increased utilization of high performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and it would be necessary to standardize blood quantification of immunosuppressant drugs. The aim of the study was to validate and assess the robustness of an LC-MS/MS method for quantification of tacrolimus in whole blood using the Waters Masstrak? Immunosuppressant Kit. After protein precipitation from whole blood samples, chromatographic separation was performed in 2 min. Detection was performed with a Waters Tandem Quadrupole MS Quattro Premier XE, operated in multiple-reaction monitoring in positive electrospray ionization mode. This method was validated and compared to Enzyme Multiplied Immunoassay Technique (EMIT) method in accordance with actual guidelines. The limit of quantification was 1.0 ng/mL and the calibration curve was linear to 27.6 ng/mL. Between-day and within-day trueness and precision were < 15% at three concentrations spanning the linear range. The EMIT assay showed an average positive bias of 28.3% compared with the LC-MS/MS. Internal and external quality control were always accepted and demonstrated the robustness of this method. In conclusion, we validated a rapid, simple and robust quantification of tacrolimus in blood samples with the Waters Masstrak? Immunosuppressant Kit.     

Distribution of Aconitum alkaloids in body fluids and tissues in a suicidal case of aconite ingestion

A case involving a suicidal ingestion of Aconitum tubers is presented. A 40-year-old woman in Hokkaido, Japan ingested ground aconite and died of aconite intoxication about 4 h after ingestion. The Aconitum alkaloids were quantitated using gas chromatography-selected ion monitoring from extracts of the body fluids and organs. The blood and urine concentrations of jesaconitine, the main alkaloid of the aconite in this case, were 69.1 ng/mL and 237.8 ng/mL, respectively. Higher values of the alkaloid were demonstrated in the kidneys, the liver, and in the bile rather than other organs or serum, suggesting the alkaloids were eliminated by the liver and kidneys. In the gastrointestinal tract, the highest value of jesaconitine (471.3 ng/g) was in the ileal contents. These findings show that Aconitum alkaloids were found in the liver and kidneys in much higher concentrations than in serum and suggest that they were eliminated not only via urine but also in feces. Feces may be useful to detect Aconitum alkaloid if other biological samples are not available.     

黄花乌头中Hetisine型生物碱的高速逆流色谱分离与结构鉴定

目的研究黄花乌头块根的化学成分，寻找更多天然活性物质。方法采用高速逆流色谱法分离纯化黄花乌头块根中的生物碱类化学成分，根据理化性质、波谱学分析鉴定化合物的结构。结果高速逆流色谱的两相溶剂分离系统采用氯仿-甲醇-0.2 mol·L^-1 HCl(体积比为10∶3∶3)，从黄花乌头块根中一次性分离得到8个化合物，分别鉴定为2α-propionyl-11α,13β-diacetyl-14-hydroxyhetisine (I)、关附巳素(II)、关附庚素(III)、关附己素(IV)、关附Z素(V)、关附辰素(VI)、关附甲素(VII)、关附壬素(VIII)。结论化合物I为新化合物，命名为关附未素(Guanfu base R)。     

Pharmacokinetic interaction of aconitine,liquiritin and 6-gingerol in a traditional Chinese herbal formula,Sini Decoction

1.?This study aimed to investigate the pharmacokinetic interaction of the three ingredients in a traditional Chinese herbal formulation, Sini Decoction, and provide evidence for its compatibility mechanism.

2.?First, the effect of liquiritin and 6-gingerol on the pharmacokinetic parameters of aconitine was investigated in rats by using a sensitive and reliable LC–MS/MS method. Then the Caco-2 cell monolayer model and Rhodamine-123 uptake assay were used to investigate the effect of liquiritin and 6-gingerol on the absorption of aconitine and the activity of P-gp.

3.?The C_max of aconitine increased significantly (p?C_max and AUC_(0–t) of aconitine increased approximately twofold, and while t_1/2 only increased 1.2-fold. The Caco-2 cell monolayer model and Rhodamine-123 uptake assay indicated that both liquiritin and 6-gingerol could increase the absorption of aconitine by inhibiting the activity of P-gp.

4.?These results indicated that both liquiritin and 6-gingerol could promote the absorption of aconitine and increase its drug concentration in blood by inhibiting the activity of P-gp, and it could also provide evidence for compatibility mechanism of the traditional Chinese herbal formula, Sini Decoction.     

Characterization of metabolites and human P450 isoforms involved in the microsomal metabolism of mesaconitine

Mesaconitine (MA), a major Aconitum alkaloid, provides effects against rheumatosis with high toxicity. To supply information for clinical safety, this study aims to investigate the metabolism of MA in male human liver microsomes (MHLMs) and the CYP isoforms involved in its metabolism. Metabolism studies were performed in vitro using MHLMs. Selective chemical inhibitors and recombinant human cytochrome P450 enzymes were used to confirm that the CYP isoforms contributed to MA metabolism. A total of nine metabolites were found and characterized in the MHLM incubations. The metabolic pathways were demethylation, dehydrogenation, hydroxylation, and demethylation-dehydrogenation. Results showed that the inhibitor of CYP3A had a strong inhibitory effect; the inhibitors of CYP2C8, CYP2C9, CYP2C19, and CYP2D6 had modest inhibitory effects, whereas inhibitors of CYP1A2 and CYP2E1 had no obvious inhibitory effects on MA metabolism. Recombinant human cytochrome P450 isoforms CYP3A4 and CYP3A5 contributed greatly to the formation of MA metabolites, and CYP2C8, CYP2C9, and CYP2D6 played a minor role in the formation of MA metabolites. MA could be transformed into at least nine metabolites in MHLMs. MA might be metabolized by CYP3A4, CYP3A5, CYP2C8, CYP2C9, and CYP2D6 in MHLMs.     

Analgesic effects of Tsumura-shuuji-bushi-matsu and mesaconitine]

"Tsumura-shuuji-bushi-matsu" (TJ-3021) is a herbal medicine produced from Aconiti tuber through autoclaving to decrease its toxicity. In this study, the analgesic effects of TJ-3021 and mesaconitine (MA) was examined in rats and mice. TJ-3021 (300 mg/kg, p.o.) or MA (0.5 mg/kg, p.o.) depressed the acetic acid-induced writhing significantly. In Randall-Selitto's method, TJ-3021 (1000 mg/kg) increased the pain threshold ratio in the inflamed foot significantly but not in the normal foot. In the hot plate method or on adjuvant-induced arthritic pain, TJ-3021 (1000 mg/kg) significantly increased the pain threshold, and its effect was less than that of "nama-bushi-matsu" (TNB), which was produced from the same Aconiti tuber without autoclaving. Repeated cold stress (RCS) for 65.5 hr decreased the pain threshold ratio on the paw pressure in rats by 60%. TJ-3021 (300 mg/kg) significantly increased the pain threshold ratio in RCS rats, and its activity was almost the same degree as that of TNB. MA (0.5 mg/kg) significantly increased the pain threshold ratio in RCS rats or on the adjuvant-induced arthritic pain; and in RCS rats, it was more potent than morphine (1 mg/kg, p.o.).     

A conscious rat model involving bradycardia and hypotension after oral administration: a toxicokinetical study of aconitine

1.?A model of aconitine-induced bradycardia and hypotension, which is similar to aconitine poisoning in humans, was constructed in conscious rats by oral administration.

2.?Blood pressure (BP) and heart rate (HR) of Sprague-Dawley rats were measured using a volume pressure recording (VPR) system. The pharmacokinetics of toxic doses of aconitine and its metabolites were analyzed using UPLC-MS/MS.

3.?The HR was significantly decreased by 29% at 2?h after oral administration of 200?μg/kg aconitine. When the dose was increased to 400?μg/kg, systolic BP and diastolic BP were significantly decreased by 11% and 12% at 2?h after the administration, except when bradycardia occurred at 2?h and 4?h. The drug concentration-time curve showed a double-peak phenomenon in rats administered a 400?μg/kg dose. The AUC_0–12?h value in the 400?μg/kg group significantly increased 0.8-fold compared to the 200?μg/kg group. Moreover, a high plasma concentration of 16-O-demethyaconitine was found in the rats that received two toxic doses.

4.?In conclusion, bradycardia and hypotension are induced in conscious rats by a toxic dose of aconitine (400?μg/kg), and there was no significant difference in dose-normalized AUC_0–12?h values between oral administrations of 200?μg/kg and that of 400?μg/kg. However, the dose-normalized C_max and AUC_0–12?h values in 200?μg/kg and 400?μg/kg groups were significantly smaller than those in 100?μg/kg group. The metabolites of aconitine, 16-O-demethyaconitine, and benzoylaconitine may also contribute to the hypotensive response.     

Metabolite fingerprinting of Camptotheca acuminata and the HPLC–ESI-MS/MS analysis of camptothecin and related alkaloids

The major phytochemical constituents, namely, alkaloids, flavonoids and ellagic acid derivatives, of leaves of Camptotheca acuminata were identified using high performance liquid chromatography (HPLC) coupled with electrospray mass spectrometry (ESI-MS) in extracts of plants cultivated in Italy and collected at different growth stages. Alkaloids related to camptothecin were identified and quantified by HPLC coupled with ESI-tandem mass spectrometry (MS/MS) employing, respectively, an ion trap and a triple quadrupole mass analyser. The fragmentation patterns of alkaloids related to camptothecin were analysed and a specific Multiple Reaction Monitoring HPLC–MS/MS method was developed for the quantitative determination of these constituents. The described method provides high sensitivity and specificity for the characterisation and quantitative determination of the alkaloids in C. acuminata.     

Postmortem drug screening by non-targeted and targeted ultra-performance liquid chromatography-mass spectrometry technology

In the medical examiner setting, comprehensive drug screening is an essential analytical tool in the investigation of cause and manner of death.We have validated non-targeted and targeted screening assays for drugs and metabolites using ultra-performance liquid chromatography (UPLC) interfaced with mass spectrometry (MS) in single and tandem stages. For non-targeted screening by UPLC-MS electrospray interface, in-source fragmentation was used along with MS scanning (m/z 80-650) and library search for over 700 drug and metabolite analytes. Targeted detection of over 200 analytes by UPLC-MS-MS was performed with dual transition ion monitoring. Validation studies confirmed reproducibility of both mass spectra produced by in-source fragmentation and transition ion ratios by collision-cell dissociation. Lower limit of detection by UPLC-MS (10-150 ng/mL) and UPLC-MS-MS (1-50 ng/mL) was determined for a subset of drugs and correlated with extraction recovery and matrix effect. Drug findings by UPLC-MS and UPLC- MS-MS were compared with gas chromatography-mass spectrometry (GC-MS) screening in postmortem blood from 410 medical examiner cases with 1121 positive drug findings by all methods. Accuracy, based on results of confirmation testing, was high (98-99%) across all screening assays and detection sensitivity by GC-MS (71%), UPLC-MS (73%), and UPLC-MS-MS (76%) was determined. UPLC-MS plus UPLC-MS-MS screening resulted in the highest drug detection rate (95%) and provided optimal dual-screening for the postmortem casework.     

Studies on structural elucidation of Aconitum diterpenoid alkaloid by LC-APCI-MS and effects of Aconitum diterpenoid alkaloid on cutaneous blood flow

The chemical constituents of Aconitum yesoense var. macroyesoense and Aconitum japonicum were examined using high-resolution spectral analysis. Twelve novel alkaloids were isolated from A. yesoense var. macroyesoense together with 20 known alkaloids. Eight novel alkaloids were isolated from A. japonicum together with 15 known alkaloids. An HPLC-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS) method was useful for the simultaneous determination of 21 Aconitum alkaloids found in A. yesoense var. macroyesoense and A. japonicum. These compounds were fairly stable under the conditions used, and the protonated molecules or fragment ions characteristic of the molecule appeared as base peaks in the mass spectra and were used for selected ion monitoring. HPLC-APCI-MS is a very promising approach for structural investigations of positional isomers and stereoisomers. This method was applied successfully to stereoisomeric Aconitum alkaloids differing in configuration at C-1, -6, or -12. Comparison of the APCI spectra showed that the abundance of fragment ions was significantly higher for the C-1, -6, or -12 beta-form alkaloid than for C-1, -6, or -12 alpha-form alkaloid. The main alkaloid constituents in the root of A. yesoense var. macroyesoense, Aconitum alkaloids of the C20-diterpenoid type, kobusine and pseudokobusine, and their acyl derivatives were examined for their peripheral vasoactivities by measuring laser-flowmetrically the cutaneous blood flow in the hind foot of mice after intravenous administration. It is thought that the hydroxyl groups of alkaloids, especially a free OH group of pseudokobusine at C-6, were important for action on the peripheral vasculature leading to dilatation, and the results indicated that esterification of the hydroxyl group at C-15 with either anisoate, veratroate, or p-nitroben-zoate may contribute to enhancement of the activity of the parent alkaloids.     

硫酸阿托品拮抗次乌头碱毒性的荧光光谱研究

目的研究次乌头碱(HA)与牛血清白蛋白(BSA)非共价结合特征,并进一步探讨硫酸阿托品(AT)对HA与BSA结合的影响。方法模拟人体生理pH条件,应用荧光光谱及紫外光谱技术,确定HA与BSA作用方式、作用力类型及AT对它们结合的影响。结果 HA通过动态猝灭机制导致BSA荧光猝灭。HA与BSA表观结合常数K2b98K=1.10×102、K3b10K=3.18×105L.mol-1,结合位点数n298K=0.59、n310K=1.24;结合距离4.64 nm;主要作用力为疏水力;HA与BSA的结合反应是一个高温自发过程;HA与BSA结合后色氨酸残基所处微环境疏水性增强。AT使HA与BSA的Kb和n均减小。结论 HA与BSA作用形成一种超分子。AT能降低二者的结合程度,通过减少HA在生物体内的积累,加快代谢,发挥解毒作用。     

Microsomal cytochrome P450-mediated metabolism of hypaconitine, an active and highly toxic constituent derived from Aconitum species

Hypaconitine (HA), an active and highly toxic constituent derived from Aconitum species, is widely used to treat rheumatism. Little is known about the hepatic cytochrome P450-catalyzed metabolism of HA. The present study investigated the metabolism of HA in vitro using male human liver microsomes (MHLMS). Chemical inhibitors of specific CYP enzymes, CYP-specific inhibitory monoclonal antibodies (mAbs), and cDNA-expressed CYP enzymes were used to confirm the enzyme subtypes involved in the metabolism. Liquid chromatography-high resolution mass spectrometry (LC-MS) was used to detect and identify metabolites. A total of 11 metabolites were identified in MHLMS incubations. The major metabolic pathways included demethylation (M1-M3), demethylation-dehydrogenation (M4-M6), hydroxylation (M7, M8), and didemethylation (M9-M11). M8 was identified as mesaconitine (MA), another active and highly toxic constituent of Aconitum. The results of chemical inhibition, monoclonal antibody inhibition, and cDNA-expressed CYP enzyme studies showed that the primary contributors toward HA metabolism were CYP3A4 and 3A5, with secondary contributions by CYP2C19, 2D6, and CYP2E1. CYP1A2 and 2C8 provided minor contributions.