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United States Department of Agriculture

Agricultural Research Service

Title: Phytochemical Methods for the Extraction and Analysis of Seed Coat Flavonoids from Common Bean (Phaseolis Vulgaris L.)

Authors
item Beninger, Clifford
item Hosfield, George
item Nair, M - MICHIGAN STATE UNIVERSITY

Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Proceedings
Publication Acceptance Date: March 1, 1997
Publication Date: N/A

Interpretive Summary: Dry bean seed coat color is determined by the presence and relative amounts of pigment forming compounds known as flavonoids and anthocyanins. These compounds are under the control of eight genes in the common bean. Some flavonoids and anthocyanins are antioxidant compounds and may protect against cancer. Other flavonoids and anthocyanins interact with protein and dstarch in the seed and make beans hard-to-cook and indigestible. Plant breeders need to know which compounds are associated with the specific seed coat color genes in order to genetically enhance the beneficial compounds and remove the harmful compounds. We conducted an experiment to identify flavonoids from stocks with a common genetic background but which differed from each other in seed coat color due to only recessive substitutions of one or more of the eight color determining genes. The stocks investigated were: mineral brown, mat soft brown, yellow brown, buffy citrine, dark brown violet, mat black, shiny black, and gray-white. Unknown flavonoids A, B, and C were common to mineral brown, mat soft brown, yellow-brown, and buffy citrine. Unknowns A and B were absent in the dark-seeded lines such as mat black, shiny black, and dark brown violet. The black and dark brown violet lines contained anthocyanins while these were absent in all other genotypes. No flavonoids or anthocyanins were detected in the gray-white genotype. Unknown compound A was isolated, purified and identified as a flavonoid alcohol. This research will provide information to bean breeders so that they can make sound breeding judgements regarding bean seed coat flavonoids. In the future, breeders may enhance or eliminate these metabolically active and pharmacologically interesting compounds from bean populations.

Technical Abstract: There is a renewed interest in the study of bean seed coat flavonoid compounds. This interest is prompted by uncertainty about the function of flavonoids within the bean seed coat and how the compounds interact with others in the whole bean. For example it is unclear which flavonoids are responsible for the wide range of color in bean seeds, or how the interaction of flavonoids with seed macromolecules affects after-darkening and indigestibility. Flavonoids from beans may also be a source of antioxidants. We conducted an experiment to identify flavonoids from bean stocks that share a common genetic background, but that differed from each other in seed coat color due only to recessive allelic substitutions at the color determining loci. The genetic stocks investigated were: mineral brown, mat soft brown yellow brown, buffy citrine, dark brown violet, mat black, shiny black, and gray-white. Seed coats were removed from cotyledons sby soaking seed in 50 ml of water (30 min. to 5 hr. depending on the genotype). Removed seed coats were freeze dried, ground to a 40 u particle size and were then extracted sequentially with ethyl acetate, methanol and methanol:water as solvent systems. A sample of each dried extract was spotted on silica gel thin layer chromatography plates with chloroform: methanol (3:1) solvent system. Unknown phenolic compounds A,B, and C were common to mineral brown, mat soft brown, yellow-brown, and buffy citrine. Unknown B was absent in mat black, shiny black, and dark brown violet. The black and dark brown violet lines contained anthocyanins but these were absent in all other genotypes. No flavonoids or anthocyanins were detected in the gray-white genotype. Unknown compound A was fractionated purified and identifed as a dihydroflavonol.

Last Modified: 9/22/2014
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