The effect of ubiquinone-7 and its metabolites on the immune response. IV. Chemical structure-adjuvant activity relationship of quinonyl derivatives on humoral immune response.

The effects of the emulsion of quinonyl acids (QS-n, ES-n, KS-n) and related compounds (QSA-n) in Freund's incomplete adjuvant on the humoral immune response to bacterial alpha-amylase were assayed, and their structure-adjuvant activity relationships were discussed. All the quinonyl acids tested (500 microgram/mouse) enhanced the humoral immune response two to seven times as much as that of the control group, five weeks after immunization. 3'-Methyl and 2', 3'-double bond in the carboxy side chains of ubiquinone metabolites (Q acid-I, -II) were not essential for the adjuvant activity. The conversion of methoxyls on the quinone ring into methyls, and that of benzoquinone into phenol also did not affect the activity, but the activity seemed to depend on the carbon number of the carboxy side chain, and the prominent adjuvant activity was observed in the carboxylates having the carboxyalkyl chain of five to seven carbons. High doses (1 or 5 mg/mouse) of ubiquinone-7 and -2 enhanced the humoral immune response two to three times as much as that of the control group, and quinonyl alcohols (QSA-n) enhanced that with low dose (500 microgram/mouse).