Quantification of Total Folate, Folate Species and Polyglutamyl Folate Distribution in Winged Beans (Psophocarus tetragonolobus (L) DC) from Different Cultivars and Growth Stages by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry.

Abstract

Winged beans are an important natural source of some micronutrients. This paper presents the first complete characterization of folate derivatives including polyglutamyl 5-methyltetrahydrofolate (5-CH3-H4PteGlun), folate species and total folate accumulating in pods and immature seeds of winged beans from 9 cultivars and 7 growth stages. 5-CH3-H4PteGlun and folate species were determined with a UHPLC-MS/MS method. Accurate determination of 5-CH3-H4PteGlun and folate species was optimized and validated according to EMA guidelines including method selectivity, sensitivity, linearity, accuracy, precision, matrix effect and carry-over. The level of total folate is in the range of 73-200 μg/100 g in the pods and 33-61 μg/100 g in the immature seeds. The predominant folate species in winged beans is 5-CH3-H4PteGlu1. 5-CH3-H4PteGlu5 is the major polyglutamyl folate derivative. The level of total folate is increased about 4 fold with advancing maturity. For pods, the chain length is increased with growth which shifts from 5-CH3-H4PteGlu1 in the early stage to 5-CH3-H4PteGlu5 and 5-CH3-H4PteGlu6 in the 7th stage. Our findings demonstrate that winged beans are good source of folate. The validated UHPLC-MS/MS method allows for the determination of 5-CH3-H4PteGlun and folate species from other vegetable matrices.