Phytochemical studies on the tobacco alkaloids: III. Observations on the interconversion of dl-nicotine and dl-nornicotine in excised tobacco leaves

dl-Nornicotine was fed to excised leaves from shoots of N. glutinosa and N. tabacum, var. Cherry Red, #TR-231 grafted on tomato stock, and the isolated nornicotine from the leaves of each species exhibited the same rotatory power, [α] d = 0 °, as that of the nomicotine supplied. However, dl-nicotine which had been fed to leaves from shoots of N. tabacum, var. Bright Yellow grafted on tomato stock was isolated from the tobacco leaves after certain feeding periods, and the isolated nicotine tended toward being levorotatory, 1 degree for about each 20 hr. feeding period. On the basis of these findings the mechanism of conversion of nicotine to nornicotine and the possibility of nornicotine of predominantly the d form as a precursor of l-nicotine in the plants are discussed.