Search

A challenge in recent years has been the rational use of forest and agriculture residues for the production of bio-fuel, biochemical, and other bioproducts. In this study, potentially useful compounds from pyrolytic lignins were identified by HPLC-MS/MS and untargeted metabolomics. The metabolites identified were 2-(4-allyl-2-methoxyphenoxy)-1-(4-hydroxy-3-methoxyphenyl)-1-propanol, benzyl benzoate, fisetinidol, phenyllactic acid, 2-phenylpropionic acid, 6,3'-dimethoxyflavone, and vanillin. The 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH), trolox equivalent antioxidant capacity (TEAC), and total phenolics content (TPC) per gram of pyrolytic lignin ranged from 14 to 503 mg ascorbic acid equivalents, 35 to 277 mg trolox equivalents, and 0.42 to 50 mg gallic acid equivalents, respectively. A very significant correlation was observed between the DPPH and TPC ( r = 0.8663, p ≤ 0.0001), TEAC and TPC ( r = 0.8044, p ≤ 0.0001), and DPPH and TEAC ( r = 0.8851, p ≤ 0.0001). The polyphenolic compounds in the pyrolytic lignins which are responsible for radical scavenging activity and antioxidant properties can be readily profiled with HPLC-MS/MS combined with untargeted metabolomics. The results also suggest that DPPH, TEAC, and TPC assays are suitable methods for the measurement of antioxidant activity in a variety of pyrolytic lignins. These data show that the pyrolytic lignins can be considered as promising sources of natural antioxidants and value-added chemicals.

Antioxidant efficacy of defatted almond whole seed, brown skin, and green shell cover extracts was evaluated by monitoring inhibition of human low-density lipoprotein (LDL) oxidation, inhibition of DNA scission, and metal ion chelation activities. The total phenolic contents of ethanolic extracts of brown skin and green shell cover of almond were 10 and 9 times higher than that of the whole seed, respectively. Brown skin extract at 50 ppm effectively inhibited copper-induced oxidation of human LDL cholesterol compared to whole seed and green shell cover extracts, which reached the same level of efficacy at 200 ppm. Green shell cover extract at 50 ppm level completely arrested peroxyl radical-induced DNA scission, whereas 100 ppm of brown skin and whole seed extracts was required for similar efficiencies. All three almond extracts exhibited excellent metal ion chelation efficacies. High-performance liquid chromatographic (HPLC) analysis revealed the presence of quercetin, isorhamnetin, quercitrin, kaempferol 3-O-rutinoside, isorhamnetin 3-O-glucoside, and morin as the major flavonoids in all extracts.

Maple syrup of four grades (extra-light, light, medium, and dark) of the 2007 crop was provided by three local (St. Joseph's Island, Ontario, Canada) producers. Twenty-four phenolic compounds were isolated from a medium-grade syrup and identified on the basis of spectral and chemical evidence. They were (a) benzoic acid and several hydroxylated and methoxylated derivatives (gallic acid, 1-O-galloyl-β-d-glucose, γ-resorcylic acid); (b) cinnamic acid derivatives (p-coumaric acid, 4-methoxycinnamic acid, caffeic acid, ferulic acid, sinapic acid, and the ester chlorogenic acid); (c) flavonoids, the flavanols catechin and epicatechin, and the flavonols kaempferol and its 3-O-β-d-glucoside, 3-O-β-d-galactoside, quercetin and its 3-O-β-d-glucoside, 3-O-β-L-rhamnoside and 3-O-rhamnoglucoside (rutin). Traces obtained at 280 and 350 nm in HPLC runs of the ethyl acetate-soluble fractions of eight samples indicated the presence of many more phenolic substances, most at very low concentration with some varibilities in peak heights, but not in retention times, among the syrups. In view of the well-established antioxidant activity these substances possess, it is suggested that it is the complexity of the mixture rather than any one compound that may serve to counter the unhealthful presence of the high concentration of sugars in the syrup. [ABSTRACT FROM AUTHOR]