Table 1. Some important m/z values for fragment ions of deprotonated OA and metabolites 1-4 in negative ESI mode.

	OA	1	2	3	4
[M-H]-	803	819	819	819	817
- H2O	785	801	801	801	799
- H2O	767	783	783	783	781
Frag B	563	563	579	579	577
- H2O	545	545
Frag A	255	255	271	271	269
- H2O			253	253	251
Frag D	321	337	321	321	321