Using Lignans from Magnolia officinalis Bark in the Assessment of the Quality of Dietary Supplements—The Application of 1H NMR and HPLC-DAD

In the present day, the use of dietary supplements is becoming increasingly common. This is due to two main reasons: a lack of nutrients from highly processed foods and the increasing popularity of dietary supplements. Supplements with anti-inflammatory properties, such as those containing magnolia bark extract, are particularly popular. Research has shown that magnolia bark extracts have anti-inflammatory, antioxidant, antidepressant, anti-anxiety, and anticancer effects, mainly due to the components magnolol and honokiol. With the increasing availability of magnolia bark extract dietary supplements, there is a need for fast analytical methods to assess their quality. This study aimed to compare the effectiveness of two analytical techniques, ¹H NMR spectroscopy and HPLC-DAD chromatography, in evaluating dietary supplements containing magnolia bark extract. The results show that both techniques provide similar results and can be used for quality control. However, there is a significant difference between the actual and declared composition of the supplements, highlighting the importance of quality control for these products. To our knowledge, this is the first study showing the use of the ¹H NMR method in the routine quantitative control of magnolia dietary supplements.