The occurrence and accumulation of d-pinitol in fenugreek (Trigonella foenum graecum L.)

Abstract

This article presents changes in concentrations of d-pinitol (and other cyclitols as well as low molecular weight carbohydrates) in vegetative and reproductive organs of fenugreek (Trigonella foenumgraecum L.) during an entire plant growing period. d-Pinitol was the major cyclitol in all tested organs, representing 43–94% of total cyclitols and 2–77% of total soluble carbohydrates. The highest concentration of d-pinitol was found in pods (14–23 mg g−1 of dry weight, DW), lower in leaves and stems (5–20 and 9–10 mg g−1 DW, respectively), and the lowest in maturing seeds (2–5 mg g−1 DW). Although maturing seeds accumulate α-d-galactosides of d-pinitol (galactosyl pinitols, up to 6.6 mg g−1 DW), the major storage sugars were raffinose family oligosaccharides (RFOs, 65.37 mg g−1 DW). Both RFOs and galactosyl pinitols are hydrolyzed during seed germination, releasing sucrose and d-pinitol, respectively. Accumulation of free galactose was not detected. Owing to the high concentration of d-pinitol (up to 23.70 mg g−1 DW) and low concentration of soluble sugars, developing pods seem to be the best source of d-pinitol.