A quantum leap in carotenoid analysis: Speed and precision unlocked

Carotenoids, the pigments responsible for the vibrant hues of tomatoes, carrots, and some seafood, are well-regarded for their antioxidant effects and health benefits. A few examples of commercially significant carotenoids are lycopene, β-carotene, and astaxanthin. These compounds are frequently used in functional foods, skincare products, and dietary supplements. However, the bioactivity of these carotenoids depends heavily on their isomeric form, with Z-isomers typically showing higher biological activity but being more challenging to quantify. Traditional methods often require months of analysis and can produce error rates reaching up to 100 %.

In this view, a team of researchers with Dr. Yasushi Honda from HPC Systems Inc. and Dr. Masaki Honda from Meijo University have now introduced an innovative solution. “Our new technique leverages quantum chemical calculations, enabling us to analyze carotenoid isomers quickly and accurately, reducing the margin of error to just 2%,” explains Dr. Yasushi Honda. This study was published in the journal Biochemical and Biophysical Research Communications on 19th October 2024.

Using density functional theory (DFT), the team successfully simulated the UV-visible spectra such as peak shifts and intensity changes of both all-E- (trans) and Z- (cis) isomers. The computational data closely matched experimental measurements, accurately reproducing key spectral features. Crucially, this approach enabled precise calculation of response factors for the Z-isomers, which are difficult to determine through conventional lab methods. This method, believed to be a world-first application of quantum chemistry for quantitative purposes, significantly boosts both the precision and speed of analysis. Traditional methods for analyzing (Z)-carotenoids could take months (because it is necessary to prepare a large amount of high-purity (Z)-carotenoids), but this new approach reduces the time to just a few ten minutes.

The findings highlighted the utility of quantum chemical calculations in obtaining precise Q-ratios, which describe the relative intensity of Z-peaks to main absorption peaks. These ratios are crucial for identifying isomers in complex mixtures. The study also identified that the sum of intensities of main peaks and Z-peaks almost remained consistent across isomers, providing a novel analytical marker for carotenoid characterization.

Also, parameters such as response factors essential for correcting HPLC detection sensitivity differences were predicted with exceptional precision. The average deviation between theoretical and experimental response factors was less than 2.5%. This breakthrough eliminates the reliance on experimentally derived response factors, which are often limited in scope and accuracy. At present, many product labels only include the content of the more stable all-E-isomers, potentially underestimating the accurate amount of bioactive compounds. The new method offers a path to more detailed and truthful labelling, benefiting both manufacturers and end-users.

While the results of the study are promising, the researchers acknowledge that their simulations were conducted in a vacuum environment, which might not entirely reflect conditions in real-world applications involving solvents. Future research will focus on refining the method to account for these environmental factors and expanding its use to a wider variety of compounds.

“This approach goes beyond carotenoids. We’re optimistic that it can be adapted to analyze other rare or unstable molecules, which could have significant implications on the industrial world in various fields, including food, cosmetics, and pharmaceuticals,” says Dr. Masaki Honda while highlighting the impact of the study.

The research team plans to explore further the use of quantum chemical calculations for various functional compounds, potentially opening new avenues for innovation, quality control, and research across multiple industries.

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