Changes in the structure of soybean triglycerides during maturation

Abstract

Soybeans of the Hawkeye variety were picked at eleven periods from 30 to 111 days after flowering and extracted with chloroform-methanol. The triglyceride fraction of five pickings, selected 35 to 91 days after flowering (when synthesis of lipid was most active), were isolated by silicic acid thin layer chromatography (TLC) and species composition determined using argentation TLC and lipase hydrolysis. The triglyceride content of the total lipid increased from 6.5% at 30 days after flowering to 85% in the mature bean (111 days). The major changes in fatty acid composition of the triglycerides occurred during the first 52 days after flowering. During this period linolenic acid decreased from 34.2% to 11.7%, the percentages of linoleic and oleic acids increased, stearic remained fairly constant and palmitic decreased slightly. Large quantitative changes occurred in the molecular species of the triglycerides of the bean during maturation; some triglycerides containing linolenic acid could not be detected approximately 66 days after flowering. Although changes occurred in the percentage and amount of each triglyceride species, the positional distribution of fatty acids remained virtually unchanged throughout maturation. Linolenic acid was distributed fairly uniformly between the β-position and the α-positions, linoleate favored esterification in the β-position, and oleate the α-positions. Most of the stearic and palmitic acids were esterified in the α-positions. The consistency of the positional arrangement of the fatty acids indicated that the mode of glyceride synthesis was established very early during maturation and molecular species composition was controlled by the fatty acids available for synthesis.

Analysis of Acyl Fluxes through Multiple Pathways of Triacylglycerol Synthesis in Developing Soybean Embryos

“…TAG FA composition and molecular species distribution are shown in Table I and Figure 1B, respectively. The TAG molecular species analysis is similar to that reported for 35 to 40 d after flowering field-grown soybeans (Roehm and Privett, 1970).…”

Triacylglycerol profiling by using chromatographic techniques

“…where S, M, D, and T denote saturated-, monoenoic-, dienoic-, and trienoic-acyl residues [165,[170][171][172]. The position of the residue in the TG molecule is only indicative and does not follow the stereospecific numbering convention of TGs.…”

“…TGs are separated according to the overall degree of unsaturation of the constituent FAs [170,171]. where S, M, D, and T denote saturated-, monoenoic-, dienoic-, and trienoic-acyl residues [165,[170][171][172].…”

Acúmulo de substâncias de reserva em grãos de soja. I: matéria seca, óleo e ácidos graxos

“…ROEHN & PRIVETT (1970) The dynamks of dry mattei and lipids accumulation in seeds of ten cultivara of soybeans during the pod fílling stage was studied. Samples were taken at in-* tervals of seven days until maturity during 1978/79 and 1979/80, respectively.…”