Identification of the ortho-Benzoquinone Intermediate of 5-O-Caffeoylquinic Acid In Vitro and In Vivo: Comparison of Bioactivation under Normal and Pathological Situations

Abstract

ABSTRACT:5-O-Caffeoylquinic acid (5-CQA) is one of the major bioactive ingredients in some Chinese herbal injections. Occasional anaphylaxis has been reported for these injections during their clinical use, possibly caused by reactive metabolites of 5-CQA. This study aimed at characterizing the bioactivation pathway(s) of 5-CQA and the metabolic enzyme(s) involved. After incubating 5-CQA with GSH and NADPH-supplemented human liver microsomes, two types of GSH conjugates were characterized: one was M1-1 from the 1,4-addition of GSH to ortho-benzoquinone intermediate; the other was M2-1 and M2-2 from the 1,4-addition of GSH directly to the ␣,␤-unsaturated carbonyl group of the parent. The formation of M1-1 was cytochrome P450 (P450)-mediated, with 3A4 and 2E1 as the principal catalyzing enzymes, whereas the formation of M2-1 and M2-2 was independent of NADPH and could be accelerated by cytosolic glutathione transferase. In the presence of cumene hydroperoxide, M1-1 formation increased 6-fold, indicating that 5-CQA can also be bioactivated by P450 peroxidase under oxidizing conditions. Furthermore, M1-1 could be formed by myeloperoxidase in activated human leukocytes, implying that 5-CQA bioactivation is more likely to occur under inflammatory conditions. This finding was supported by experiments on lipopolysaccharideinduced inflammatory rats, where a greater amount of M1-1 was detected. In S-adenosyl methionine-and GSH-supplemented human S9 incubations, M1-1 formation decreased by 80% but increased after tolcapone-inhibited catechol-O-methyltransferase (COMT) activity. In summary, the high reactivities of the orthobenzoquinone metabolite and ␣,␤-unsaturated carbonyl group of 5-CQA to nucleophiles have been demonstrated. Different pathological situations and COMT activities in patients may alter the bioactivation extent of 5-CQA.

Protective Effect of Sinapine against Hydroxyl Radical-Induced Damage to Mesenchymal Stem Cells and Possible Mechanisms

“…In addition, the largest molecular ion peak (m/z 703.6) was further fragmented to yield several losses (including m/z 59, 31, and so on). Based on the above results and the literature, 10,33) we hypothesized that the reaction of sinapine (thiocyanate) with DPPH· might be via HAT (or SEPT) RAF multi-pathways (Fig. 7).…”

Characterization of metabolites of GLS4 in humans using ultrahigh‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry

“…Firstly, the peaks corresponding to potential metabolites were determined by comparing the automated mass chromatograms of the blank and drug‐treated samples. With the benefit of accurate mass measurements by TOF, it is feasible to obtain the elemental composition differences between the target metabolites and their precursors . Subsequently, the reasonable elemental composition difference could be determined based on the current understanding of potential biotransformation reactions (e.g.…”

“…With the benefit of accurate mass measurements by TOF, it is feasible to obtain the elemental composition differences between the target metabolites and their precursors. [8][9][10][11] Subsequently, the reasonable elemental composition difference could be determined based on the current understanding of potential biotransformation reactions (e.g. dealkylation, oxidation and glucuronic acid conjugation).…”

“…Blood, urine and fecal samples were obtained as part of a pharmacokinetics study performed in our lab. Venous blood samples (3 mL) were obtained at pre-dose and 0.17, 0.33, 0.5, 0.75, 1,2,3,4,6,8,12,24,36,72,96,120,144 and 168 h post-dose. Blood samples were placed in heparin-containing tubes and immediately centrifuged at 2000 g for 10 min at approximately 4°C.…”

Clinical tolerability and pharmacokinetics of Erigerontis hydroxybenzene injection: Results of a randomized phase I study in healthy Chinese volunteers

“…The plasma concentrations of metabolites derived from either DCQAs or CQAs from EHI should be determined to elucidate the potential toxicity of EHI. It has been speculated that CQA molecules may undergo metabolism by cytochrome P450 (P450) enzymes, horseradish peroxidase/H 2 O 2 , and tyrosinase/O 2 to form cytotoxic quinone intermediate metabolites and cause adverse effects to human health, due to a catechol and an α,β-unsaturated carbonyl group in the chemical structures (Xie et al 2012). In addition, due to the fact that healthy volunteers were used in this study, caution is advised in extrapolating tolerability data as well as pharmacokinetic data from this study to actual patient populations who might have abnormal liver and kidney function.…”