Isolation, structural elucidation, and antioxidant potential of phytomelatonin from tomato (Solanum lycopersicum L.)...

Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine compound present in both animal and plant kingdoms. Melatonin, a potent antioxidant, is currently produced synthetically, which is often associated with the presence of toxic by-products. This study presents a high-yield alternative by isolating and characterizing pure phytomelatonin (PMT) from underutilized agricultural waste, specifically tomato leaves (Solanum lycopersicum L.). By utilizing a multistep extraction and purification process, a yield of 53.12 mg of pure phytomelatonin was achieved. The structural elucidation and purity of the isolate were confirmed through multiple analytical techniques, including ultraviolet-visible (UV-VIS) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, proton nuclear magnetic resonance (¹H NMR), carbon-13 nuclear magnetic resonance (¹³C NMR), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The plant-derived phytomelatonin exhibited potent ABTS radical scavenging activity with near equivalence to the synthetic standard while also demonstrating strong DPPH radical scavenging activity with comparatively higher efficiency, maintaining >90% inhibition at elevated concentrations. This research validates the isolation of phytomelatonin from tomato leaves, positioning agricultural by-products as a sustainable and bioavailable source of this valuable bioactive molecule. These findings provide a foundation for future functional and exploration of melatonin's role in the pharmaceutical, nutraceutical, and agricultural industries.