Flavonoid content in fresh, home-processed, and light-exposed onions and in dehydrated commercial onion products.

Onion plants synthesize flavonoids as protection against damage by UV radiation and by intracellular hydrogen peroxide. Because flavonoids also exhibit health-promoting effects in humans, a need exists to measure their content in onions and in processed onion products. To contribute to the knowledge about the levels of onion flavonoids, HPLC and LC-MS were used to measure levels of seven quercetin and isorhamnetin glucosides in four Korean commercial onion bulb varieties and their distribution within the onion, in scales of field-grown onions exposed to home processing or to fluorescent light and in 16 commercial dehydrated onion products sold in the United States.

Analysis by HPLC and LC/MS of pungent piperamides in commercial black, white, green, and red whole and ground peppercorns.

Pepper plants accumulate pungent bioactive alkaloids called piperamides. To facilitate studies in this area, high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry methods were developed and used to measure the following piperamides in 10 commercial whole (peppercorns) and in 10 ground, black, white, green, and red peppers: piperanine, piperdardine, piperine, piperlonguminine, and piperettine. Structural identification of individual compounds in extracts was performed by associating the HPLC peak of each compound with the corresponding mass spectrum.