Eserine blue

Ellis, Krayer and Plachte have shown that the degradation products of physostigmine, eseroline and eserine-brown do not inhibit choline-esterase, but rubreserine and eserine-blue are inhibitors in vitro, having... 

Eserine blue (250), formed from a reaction of rubreserine with ammonia (315), was reported to exhibit very low potency in a horse serum butyrylcholinesterase assay (314). A later communication (316)suggests total inactivity of these latter two physostigmine derivatives. 

Orthorhombic sphenoidal prisms or clusters of leaflets from ether or benzene, mp 105-106 (also an unstable, low-melting form, mp 86-87 ). [a]J,7 — 76 (c = 1.3 in chloroform) [n]f —120" (benzene). K, 7.6 X 10 7 K, 5.7 X 10-1. Slightly sol in water sol in ale, benzene, chloroform, oils. Solid and signs turn red on exposure to heat, light, air, and on contact with traces of metals. Under certain conditions the oxidation may proceed to yield eserine blue, CK-HjjNjOj. LDjd orally in mice 4.5 mg/kg (Lynch, Coon),... 

Whilst there are no reports in the literature of crystalline products having been obtained from the interactions of adrenochrome with o-phenylenedi-amine. Auterhoff and Hamacher have prepared a phenazine derivative (103) by the interaction of o-phenylenediamine with rubreserine (66) (a compound structurally similar to the aminochromes) [193]. In the same paper, the authors describe the reaction of rubreserine with ammonia in alcohol at reflux temperatures. A complex mixture of products including the phenoxazone derivative, eserine blue was obtained [193]. 

Confirmation of the structure of the red-colored decomposition product of physostigmine, rubreserine, as the resonance hybrid XXII XXIII in which the zwitterionic mesomeric structure XXIII makes the major contribution, has been obtained (17) by comparison of its UV-, IR-, and PMR-spectra with those of adrenochrome (XXIV XXV). The structures of a further two decomposition products of physostigmine, eserine blue and eserine brown (14,16,18), still remain to be elucidated. 

---