HPLC Method Measures Fiber's Cholesterol Uptake

Accurately measuring how much cholesterol a dietary fiber can soak up is important for figuring out whether that fiber might help lower cholesterol levels in the body. The challenge is that the methods currently used to test this are not standardized from laboratory to laboratory, and they often rely on spectrophotometry, which can give skewed results when other substances in the sample interfere with the readings.

A research team from the Department of Pharmaceutical Sciences at the University of Perugia in Italy set out to create and test a simple, dependable method for measuring how well different parts (fractions) of artichoke leaves can absorb cholesterol. To do this, they ran laboratory tests designed to mimic conditions in the stomach and intestines, then measured how much cholesterol was left afterward using high-performance liquid chromatography (HPLC), paired with two different types of detectors—ultraviolet-visible spectroscopy (UV-vis) for the reading of light absorption (UV-Vis) and a light-scattering detector. A paper based on their work was published in the journal Foods.¹

How Does Dietary Fiber Lower Cholesterol?

Dietary fiber can help lower cholesterol in several ways: it can bind directly to cholesterol and bile acids, make the contents of the intestines thicker (which slows absorption), help the body get rid of cholesterol-related compounds through stool, and feed gut bacteria that produce short-chain fatty acids—by-products that signal the liver to make less cholesterol. Both soluble fiber (which dissolves in water) and insoluble fiber (which does not) play a role in these effects, which is why plant-based fiber has become such a major research focus.²

How is Fiber’s Cholesterol-binding Ability Typically Measured and Compared Across Sources?

Scientists are now looking at fiber from all kinds of sources, including some unconventional ones like leftover material from food processing. Several studies have zeroed in on specific types of fiber to see how well they lower cholesterol. For example, soluble fiber from soy hulls—made up mostly of pectin-like compounds—was shown to bind cholesterol and bile acids effectively and even lowered cholesterol levels in live studies. In another study, researchers looked at soluble and insoluble fiber from different types of bamboo shoots and found that, generally, the insoluble fiber was better at soaking up cholesterol than the soluble fiber from the same plant. Fiber left over from processing ginseng also showed strong cholesterol-binding ability, while fiber from foxtail millet bran was much less effective in comparison.^3-6

Chromatography-based methods—especially reversed-phase liquid chromatography (RPLC) and gas chromatography (GC)—have become the go-to, most trusted approach for analyzing sterols like cholesterol because they are especially good at telling cholesterol apart from similar compounds and its breakdown products. That said, how well these methods work still depends heavily on how the sample is prepared beforehand, especially two key steps: pulling the fats out of the sample (lipid extraction) and breaking them down chemically (saponification).^7-10

Did the New Chromatography Method Prove Reliable, and What Did It Reveal About Cholesterol Adsorption in Artichoke Leaf Fibers?

The team checked that their new chromatography method held up by testing how consistent, sensitive, and accurate it was, and then compared it against the standard, older technique (an OPA spectrophotometric assay) already used for this kind of testing. They first tried it out on some purified, commercially available fibers, and found that pectin and lignin were best at soaking up cholesterol. When they moved on to testing the artichoke leaf fractions, they found that all of them were able to absorb some cholesterol—but the outer leaves performed noticeably better at this than the tougher, woody inner parts of the plant.¹

“The proposed workflow,” write the authors of the paper,¹ “provides a reliable and consistent analytical framework for CAC determination. Furthermore, the results provide new insights into the potential cholesterol-lowering properties of dietary fiber from artichoke leaves, supporting their further investigation as functional ingredients.”

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References

1. Ali, S.; Ianni, F.; Cossignani, L. Reliable Analytical Approach for the Quantification of the Cholesterol Adsorption Capacity of Artichoke Leaves. Foods 2026, 15 (17), 3099. DOI: 10.3390/foods15173099
2. Chen, L.; He, X.; Pu, Y.; et al. Polysaccharide-based Biosorbents for Cholesterol and Bile Salts in Gastric-Intestinal Passage: Advances and Future Trends. Compr. Rev. Food Sci. Food Saf. 2023, 22, 3790–3813. DOI: 10.1111/1541-4337.13214
3. Liu, C.; Lin, X.L.; Wan, Z et al. The Physicochemical Properties, in vitro Binding Capacities and in vivo Hypocholesterolemic Activity of Soluble Dietary Fiber Extracted from Soy Hulls. Food Funct. 2016, 7, 4830–4840. DOI: 10.1039/c6fo01340f
4. Wu, W.; Hu, J.; Gao, H. et al. The Potential Cholesterol-lowering and Prebiotic Effects of Bamboo Shoot Dietary Fibers and Their Structural Characteristics. Food Chem. 2020, 332, 127372. DOI: 10.1016/j.foodchem.2020.127372
5. Hua, M.; Lu, J.; Qu, D. et al. Structure, Physicochemical Properties and Adsorption Function of Insoluble Dietary Fiber from Ginseng Residue: A Potential Functional Ingredient. Food Chem. 2019, 286, 522–529. DOI: 10.1016/j.foodchem.2019.01.114
6. Zhu, Y.; Chu, J.; Lu, Z. et al. Physicochemical and Functional Properties of Dietary Fiber from Foxtail Millet (Setaria italica) Bran. J. Cereal Sci. 2018, 79, 456–461. DOI: 10.1016/j.jcs.2017.12.011
7. Osman, H.; Yap, K.C. Comparative Sensitivities of Cholesterol Analysis using GC, HPLC and Spectrophotometric Methods. Malays. J. Anal. Sci. 2006, 10, 205–210.
8. Ndhlala, A. R.; KavazYüksel, A.; Çelebi, N. et al. A General Review of Methodologies Used in the Determination of Cholesterol (C₂₇H₄₆O) Levels in Foods. Foods 2023, 12, 4424. DOI: 10.3390/foods12244424
9. Kolarič, L.; Šimko, P. The Comparison of HPLC and Spectrophotometric Method for Cholesterol Determination. Potr. S. J. F. Sci. 2020, 14, 118–124. DOI: 10.5219/1302
10. Albuquerque, T.G.; Oliveira, M. B. P. P.; Sanches-Silva, A. et al. Cholesterol Determination in Foods: Comparison Between High Performance and Ultrahigh-Performance Liquid Chromatography. Food Chem. 2016, 193, 18–25. DOI: 10.1016/j.foodchem.2014.09.109