The unexpected reduction of the vinyl group of chlorophyll B by sodium borohydriede in methanolic extracts of maize leaves and its inhibition by 8-hydroxyquinoline

During rapid extraction of chlorophylls from maize leaves under reducing conditions with methanol containing NaBH4, chlorophyll a remained unchanged but chlorophyll b yielded [7-hydroxymethyl]-chlorophyll b. The 3-vinyl group of chlorophyll b was also reduced forming significant am ounts, up to 60%, of [3-ethyl]-[7-hydroxymethyl]-chlorophyll b. This was unexpected since this reduction of the 3-vinyl group does not occur when isolated chlorophyll b is treated in an identical manner with methanolic borohydride. The vinyl-group of chlorophyll a is not reduced during the same extraction conditions suggesting that the presence of a formyl or hydroxyethyl group at C-7 is necessary. The presence of 8-hydroxyquinoline and NaBH4 in equimolar (16.5 m M) concentrations strongly inhibits the reduction of the 3-vinyl group of chlorophyll b in leaf extracts