Plasmalogen profiling in porcine brain tissues by LC-MS/MS

Wu Y, Chen Y, Zhang M, Chiba H, and Hui S. (2023) Plasmalogen profiling in porcine brain tissues by LC-MS/MS. Food

Plasmalogens are a class of phospholipid that contain a double bond, called a vinyl-ether bond, at the sn-1 position of its glycerol backbone. This bond gives plasmalogens a more compact structure making them important components for membrane structure and fluidity as well as vesicular fusion. The bond is also able to scavenge two radical oxygen species, helping to prevent oxidative stress and the inflammation it can cause. For this reason, brains are regions with very high levels of plasmalogens, however their levels are reduced in some diseases including Parkinsons’s disease, Gaucher disease, and Alzheimer’s disease. Plasmalogens are not present in most foods we eat, but they can be found in meats such as seafood, poultry, and livestock especially in the brain. Seafood such as scallops and sea cucumbers are often studied when developing supplements and therapeutic products, but Wu et al were interested in the levels found in porcine brain since this is commonly consumed in some countries such as Thailand and China. The porcine brain is a good source of lipids but it also contains a high level of cholesterol, so the author’s wanted to determine the optimal way to use the brain for its plasmalogen content and investigate how production processes affect plasmalogen level.

When producing a supplement there are a number of manufacturing steps used to process the sample, isolate and purify the component of interest, in this case plasmalogens, and prepare the sample for supplement or healthcare product development. To evaluate how manufacturing steps could alter the plasmalogen content of a product and the use of porcine brain for providing plasmalogens, samples were retained at 9 different steps of the manufacturing process, seen in Scheme 1. Total plasmalogens were analyzed in each sample with the content dropping by nearly half between the two raw product samples (referred to as products 1 and 2). As the second product underwent an additional freeze-thaw cycle, the authors suggest that this is why there is the significant difference in plasmalogen content. Other work they have done demonstrated that plasmalogens oxidize and degrade in foods that go through repeated freeze-thaw cycles, also supporting this theory. Interestingly, they did not find a significant difference in plasmalogen content between the second raw product (that had underwent the extra freezing and thawing steps) and the samples following acetone precipitation to remove impurities and ethanol extraction resulting in glycerophospholipid products (referred to as products 3-8). In addition, this demonstrated that there was no significant difference between using freeze-dried samples and concentrated freeze-dried samples or based on the drying method used.

To determine whether porcine is an appropriate source of plasmalogens, soy-derived lecithin products and egg-derived lecithin products were also tested. Unsurprisingly, the plant products were found to have no plasmalogens and therefore are not a good source. The egg-derived products had low levels of plasmalogens but were present, and this low level may be due to the processing steps required since the extraction was different than with the porcine products. When comparing the headgroups found in egg-derived and the porcine, ethanolamine plasmalogens were found to be 97.8% and 98.0% of either raw porcine products, while they were 91.7% of the egg-derived product.

Wu et al were interested in determining the use of porcine brain for plasmalogen supplementation or therapeutic products and whether the manufacturing process may alter the plasmalogen content of the sample. They did mention that a limitation of the results is that the sample size was not large and that going forward, a larger study with more sample batches would be necessary. The authors demonstrated the viability of using porcine brain products for supplying plasmalogens and demonstrated areas of the manufacturing process that appear to reduce levels, such as repeated freeze-thaw cycles. As well, they showed that steps like acetone precipitating, ethanol extraction, freeze-dried concentrated or unconcentrated samples, and drying method that were not found to significantly influence plasmalogen content or composition. This was an interesting finding because the vinyl-ether bond is known to be very unstable and easily oxidized, therefore it is reassuring to know that there are processing methods available that will not deteriorate plasmalogen content. Further work comparing more batches and analyzing additional nutrition components could be useful in optimizing these products.