Isolation and structure elucidation of phenolic compounds from longan (Dimocarpus longan Lour.) seed by high-performance liquid chromatography-electrospray ionization mass spectrometry.

High-performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI-MS) analysis revealed the phenolics profile of longan (Dimocarpus longan Lour.) seed. Gallic acid, ellagic acid, monogalloyl-glucose, monogalloyl-diglucose, digalloyl-diglucose, penta- to heptagalloyl-glucose, ellagic acid-pentose conjugate, galloyl-HHDP (Hexahydroxydiphenoyl)-glucopyranose, pentagalloy-HHDP-glucopyranose, procyanidin A-type dimer, procyanidin B2 and quercetin-3-O-rhamnoside were found to be present in longan seed along with a number of, as yet, unknown compounds. The results illustrate the rich array of phenolic compounds in longan seeds which could be utilized as health-beneficial bioactive compounds rather than just discarded as waste.