Luminescence of coelenterazine derivatives with C-8 extended electronic conjugation

The oxygen-containing coelenterazine derivative 2 exhibited a more significant red-shifted (63 nm) bioluminescence signal maximum relative to coelenterazine 400a (DeepBlueC™, 1). In cell imaging, the sulfur-containing coelenterazine derivative 3 displayed a significantly (1.77 ± 0.09; P ≤ 0.01) higher luminescence signal compared to 1 while the oxygen-containing coelenterazine derivative 2 exhibited a slightly (0.74 ± 0.08; P ≤ 0.05) lower luminescence signal.