| Alfalfa and red clover cause bloat and have high extent of proteolysis in the silo and rumen. Flavonoids and related polyphenols may alleviate these nutritional problems. However, an increased understanding of polyphenol methods of analysis is required in order to manipulate forage quality by altering phenolic composition.; Gravimetric methods based on precipitation of flavonoids by polyvalent cations have an advantage over others methods because they do not require standards. Trivalent ytterbium forms insoluble chelates with flavonoids. Ytterbium completely precipitated quercetin, rutin and taxifolin. At neutral pH, ytterbium partially precipitated catechin, naringenin, phoretin and phloridzin and their precipitation was increased at higher pH. Variables such as pH and composition of the solvent, and ytterbium to flavonoid ratio, can be manipulated in order to optimize precipitation.; Two phenylpropanoid compounds (trans-clovamide and phaselic acid) were isolated from leaves of red clover (Marathon), and are substrates for polyphenol oxidase. This enzyme was purified using a combination of temperature-induced phase partitioning in Triton X-114, ammonium sulfate fractionation and size exclusion chromatography. The optimum temperature for maximum activity was 52°C, and the best storage temperature was −20°C. An isoenzyme isolated by size exclusion chromatography had an activity of 148.8 abs/mg of protein, and a molecular weight of about 57 kDa. The lower extent of proteolysis of red clover silage compared to alfalfa is explained by polyphenol oxidase and phenylpropanoid substrates.; A novel anthocyanin, cyanidin 3–O-(6′ ′-O-(acetyl)-2′′-O-(β-D-glucuronyl)-β-D-glucopyranoside), was isolated from the red epidemis of alfalfa (Medicago sativa L.), Redline cultivar. A previously described anthocyanin, cyanidin 3-O-(2 ′′O-(β-D-glucuronyl)-β-glucopyranoside, was also isolated. The structures of three other anthocyanins were partially identified. Anthocyanins were incorporated into Redline by recurrent selection. Anthocyanins are biosynthetically related to polymeric flavonoids. These results suggest that non-bloating alfalfa can be produced by similar recurrent selection if the polymers can be detected in unique phenotypes. |
