Biosynthesis of highly enriched 13C-lycopene for human metabolic studies using repeated batch tomato cell culturing with 13C-glucose

While putative disease-preventing lycopene metabolites are found in both tomato (Solanum lycopersicum) products and in their consumers, mammalian lycopene metabolism is poorly understood. Advances in tomato cell culturing techniques offer an economical tool for generation of highly-enriched 13C-lycopene for human bioavailability and metabolism studies. To enhance the 13C-enrichment and yields of labelled lycopene from the hp-1 tomato cell line, cultures were first grown in 13C-glucose media for three serial batches and produced increasing proportions of uniformly labelled lycopene (14.3 ± 1.2%, 39.6 ± 0.5%, and 48.9 ± 1.5%) with consistent yields (from 5.8 to 9 mg/L). An optimised 9-day-long 13C-loading and 18-day-long labelling strategy developed based on glucose utilisation and lycopene yields, yielded 13C-lycopene with 93% 13C isotopic purity, and 55% of isotopomers were uniformly labelled. Furthermore, an optimised acetone and hexane extraction led to a fourfold increase in lycopene recovery from cultures compared to a standard extraction.