Development and assessment of a complete-detoxication strategy for Fuzi (lateral root of Aconitum carmichaeli) and its application in rheumatoid arthritis therapy

Abstract

Ethnopharmacological relevance: Fuzi (lateral root of Aconitum carmichaeli) is a popular traditional Chinese medicine well known for its both therapeutic and high-toxic activities. Its toxic alkaloid ingredients, mainly aconitine, mesaconitine, and hypaconitine, are responsible for the high toxicity. However, to date, no detoxication strategy is available to completely eliminate Fuzi's toxicity, and, whether Fuzi's efficacy could be kept after detoxication, remain unknown and debatable.

Materials and methods: The purpose of this study was to establish and validate a complete-detoxication strategy for Fuzi via acute toxicity test, to clarify the detoxication mechanism by HPLC and titrimetric analyses, and to evaluate the therapeutic effect of detoxicated Fuzi on adjuvant arthritis (AA). Three processed Fuzi (Bai-fu-pian) with 30-min, 60-min, and 120-min decoctions, respectively, named dBfp-30, dBfp-60, and dBfp-120, were prepared for this study. For the acute toxicity test, their oral doses to male and female Kunming mice were up to 70-190g/kg body weight, and their toxicological profiles were evaluated by median lethal dose (LD50), maximal tolerance dose (MTD), minimal lethal dose (MLD), no-observed-adverse-effect-level (NOAEL), and time-concentration-mortality (TCM) modeling methods using a 14-day schedule with up to five doses. The HPLC analysis was performed to determine the detoxication-induced changes in composition and amount of aconitine, mesaconitine and hypaconitine in Fuzi, whilst the titrimetric method was adopted to estimate the amount changes of Fuzi's total alkaloids. AA model was established by incomplete Freund's adjuvant injection in Wistar rats, and the animal's physiological (body weight, food intake, etc.), clinical (hind paw volume), and immunological (IL-1 and TNF-α) parameters were assessed as markers of inflammation and arthritis.

Results: With increasing decoction time, the acute toxicity of detoxicated Fuzi became decreased in the following order: dBfp-30 (LD50 of 145.1g/kg; MTD of 70g/kg; MLD of 100g/kg; NOAEL of 70g/kg) >dBfp-60 (too large LD50; MTD of 160g/kg; MLD of 190g/kg; NOAEL of 100g/kg) >dBfp-120 (no LD50; unlimited MTD; unlimited MLD; NOAEL of 130g/kg). dBfp-30 and dBfp-60 displayed the toxicity at a dose-dependent manner with maximum mortalities reaching 100% and 50% respectively, whereas no mortality or signs of intoxication was induced by dBfp-120. The chemical analyses revealed a dramatic reduction of the toxic alkaloids as well as total alkaloids in Fuzi after the detoxication, from which no level of aconitine and only minimum residual of mesaconitine (0.56±0.02μg/g) and hypaconitine (8.73±0.13μg/g) were detected in dBfp-120. However, no significant difference of total alkaloid amount was found among dBfp-30, dBfp-60, and dBfp-120 (P>0.05), suggesting an equivalent conversion from toxic alkaloids to its non-toxic derivants in dBfp-120. Further, also no significant differences were seen among dBfp-30, dBfp-60, and dBfp-120 for the therapeutic effects on physiological, clinical, and immunological parameters in AA rat, indicating that dBfp-120 is of non-toxicity and efficacy.

Conclusions: A complete-detoxication strategy has been developed successfully for ensuring the safe and effective use of Fuzi. The detoxication mechanism associated with elimination of toxic alkaloids has kept Fuzi's efficacy, indicating a non-interdependent relationship between its efficacy and toxicity. This is the first report on such an optimal detoxication strategy and on the application of detoxicated Fuzi in AA. It may provide in depth understanding to the toxicological and pharmacological profiles of Fuzi and further benefit the herbal drug development with safety and efficacy for disease especially RA therapy.