Figure 4. Incorporation of ¹⁵N-labeled intermediates (3′, 4′, 7′) into the other intermediates in the cells of A. circinalis (TA04).

Isotopic patterns of Arg (2), Int-A’ (3) Int-C’2 (4) and Cyclic-C’ (7) in the cell extracts of the 7-day culture of control (not administered) (a) and ¹⁵N-labeled intermediates (3′, 4′, 7′) independently administered in cultures at 5.0 μM (b–d), analyzed using LC/MS. [M + H]⁺ions for the authentic [¹⁵N₂]Int-C’2 (4′) and [¹⁵N₂]Cyclic-C’ (7′) were detected at m/z 213.1606 and 211.1450, respectively. The ¹⁵N-labels incorporated ratios were shown in the spectra.