Identification and quantification of glycoside flavonoids in the energy crop Albizia julibrissin.

Oxygen radical absorbance capacity (ORAC) values showed that methanolic extracts of Albizia julibrissin foliage displayed antioxidant activity. High performance liquid chromatography (HPLC) and mass spectrometry (MS) techniques were utilized in the identification of the compounds. The analysis confirmed the presence of three compounds in A. julibrissin foliage methanolic extract: an unknown quercetin derivative with mass of 610 Da, hyperoside (quercetin-3-O-galactoside), and quercitrin (quercetin-3-O-rhamnoside). Fast performance liquid chromatography (FPLC) was employed to fractionate the crude A. julibrissin foliage methanolic extract into its individual flavonoid components. The flavonoids were quantified in terms of mass and their respective contribution to the overall ORAC value. Quercetin glycosides accounted for 2.0% of total foliage.

A glycoside flavonoid in Kudzu (Pueraria lobata): identification, quantification, and determination of antioxidant activity.

Kudzu (Pueraria lobata) foliage has been touted as a possible energy crop. High-performance liquid chromatography and mass spectrometry analysis of the methanolic kudzu foliage extracts confirmed the presence of robinin (kaempferol-3-O-robinoside-7-O-rhamnoside). Robinin accounted for 0.65 +/- 0.16% (dry basis) of kudzu biomass. Fast performance liquid chromatography (FPLC) was employed to fractionate robinin from the crude extract. The antioxidant capacity of robinin was evaluated by an oxygen radical absorbance capacity (ORAC) assay. The ORAC values of pure standard were compared with those of the extract fractions. One milligram of the FPLC-fractionated robinin generated an ORAC value of 5.15 +/- 2.00 micromol/mg of Trolox, whereas 1 mg of pure robinin generated an ORAC value of 12.34 +/- 0.45 micromol/mg of Trolox. Because of its antioxidant properties, robinin may be a flavonoid worth extracting prior to energy production.

Extraction of antioxidant compounds from energy crops.

Energy crops offer enormous opportunities for increasing the sustain ability of agriculture and energy production in the United States. Nevertheless, opportunities for sustaining biomass energy production may well hinge on producing energy and extracting high-value products from the same crop. Seven potential energy crops (mimosa, sericea, kudzu, arunzo, switchgrass, velvet bean, and castor) were extracted and assayed for the presence of potentially high-value antioxidant compounds. Of these crops, mimosa and sericea had the highest antioxidant potential and were selected for further study. High-performance liquid chromatography (ultraviolet) and liquid chromatography/mass spectrometry techniques were then utilized to help identify the compounds with high antioxidant potential using extract fractionation, and total phenolics and oxygen radical absorbance capability assays as a guide. These analyses indicate that methanol extracts of mimosa foliage most likely contain quercetin, a flavonol that has been associated with cardio- protection. Future work will concentrate on quantifying the quercetin content of mimosa (likely parts-per-million levels), as well as identifying and quantifying other antioxidants found in energy crops.