Grains, leaves, sheaths, glumes and stalks of sorghum varieties were
analyzed for total phenols, condensed tannins, flavan-4-ols, anthocyanins and in
vitro antioxidant activity. Black sorghum bran was used to evaluate the
effectiveness of organic acids and enzymes on extractability of phenols.
Flavonoid profiles of grains and non-grain tissues were determined and
characterized using HPLC-PDA and HPLC-ESI-MSn.
The presence of a pigmented testa and spreader genes (B1B2S) is a
predictor for polymeric flavonoids (tannins) but not for simple phenols such as
flavan-4-ols, 3-deoxyanthocyanins, flavones and flavanones. Simple flavonoids
increased antioxidant capacity of sorghum, and were present in all sorghum
except for the white pericarp sorghums that did not have flavanones. The "red
turning into black" gene increased phenols in Type I sorghum.
The leaves, sheath and glumes of sorghum had higher levels of phenols (78-600 times more), with in vitro antioxidant properties than commonly seen in
grains. Pigmentation of plant components increased levels of 3-
deoxyanthocyanins but not flavones nor flavanones. The leaves of biomass
sorghum, Collier variety, had 3.4 times more 3-deoxyanthocyanins than the
leaves of Tx430 Black x Sumac which had the highest levels (1810 ?g/g) of 3-
deoxyanthocyanins among the leaves.
The use of 1% HCl/ethanol provides a possible food grade substitute
solvent for 1%HCl/methanol in the extraction of phenolic compounds from
sorghum. All enzymes evaluated broke down bran particles forming a gel-like
material which had increased phenols and antioxidant activities but not 3-
deoxyanthocyanins as revealed by HPLC analysis. Microscopy examination
showed the gel matrix rich in fiber and can possibly be used for nutraceutical
applications. Careful understanding of enzyme activities is necessary for
effective extraction of 3-deoxyanthocyanins from sorghum.
Sorghum leaves, sheaths and glumes are excellent sources of bioactive
compounds, up to 600 times more than the grains of some varieties. Sorghum
with the "red turning to black genes" is a potential source of 3-
deoxyanthocyanins and flavan-4-ols. With the trend towards sorghum as
biomass for ethanol production, plant breeders must select special traits aimed
at developing enhanced desired functionality such as antioxidant potential and
other healthy attributes with application in food, pharmaceutical/nutraceutical
and cosmetic industries.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-560 |
| Date | 2009 May 1900 |
| Creators | Njongmeta, Nenge Lynda A. |
| Contributors | Rooney, Llyod W. |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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