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 α,β-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 lipopolysaccharide-induced 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 ortho-benzoquinone metabolite and α,β-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.
Footnotes
This work was supported by the National Natural Science Foundation of China [Grant 81173115]; and the National Basic Research Program of China [Grant 2009CB930300].
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
↵ The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material.
ABBREVIATIONS:
- 5-CQA
- 5-O-caffeoylquinic acid
- P450
- cytochrome P450
- HLM
- human liver microsomes
- 3-CQA
- 3-O-caffeoylquinic acid
- 4-CQA
- 4-O-caffeoylquinic acid
- CHP
- cumene hydroperoxide
- MPO
- myeloperoxidase
- PMA
- phorbol 12-myristate 13-acetate
- SAM
- S-adenosyl-methionine
- ABT
- 1-aminobenzotriazole
- LPS
- lipopolysaccharides
- HPLC
- high-performance liquid chromatography
- UPLC
- ultraperformance liquid chromatography
- Q-TOF
- quadrupole time-of-flight
- MS
- mass spectrometry
- ES
- electrospray ionization
- CE
- collision energy
- PBS
- phosphate-buffered saline
- 7′-SG-5-CQA
- 7′-S-glutathionyl-5-O-caffeoylquinic acid
- COMT
- catechol-O-methyltransferase
- 2′-SG-5-CQA
- 2′-S-glutathionyl-5-O-caffeoylquinic acid
- GST
- glutathione transferase
- 5-FQA
- 5-O-feruloylquinic acid
- 5-iFQA
- 5-O-isoferuloylquinic acid
- 4-FQA
- 4-O-feruloylquinic acid.
- Received March 12, 2012.
- Accepted May 2, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|