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Phenolic acids are potent antioxidants, yet the quantitative structure-activity relationships of phenolic acids remain unclear. The purpose of this study was to establish 3D-QSAR models able to predict phenolic acids with high DPPH• scavenging activity and understand their structure-activity relationships. The model has been established by using a training set of compounds with cross-validated q2 = 0.638/0.855, non-cross-validated r2 = 0.984/0.986, standard error of estimate = 0.236/0.216, and F = 139.126/208.320 for the best CoMFA/CoMSIA models. The predictive ability of the models was validated with the correlation coefficient r2pred = 0.971/0.996 (>0.6) for each model. Additionally, the contour map results suggested that structural characteristics of phenolics acids favorable for the high DPPH• scavenging activity might include: (1) bulky and/or electron-donating substituent groups on the phenol ring; (2) electron-donating groups at the meta-position and/or hydrophobic groups at the meta-/ortho-position; (3) hydrogen-bond donor/electron-donating groups at the ortho-position. The results have been confirmed based on structural analyses of phenolic acids and their DPPH• scavenging data from eight recent publications. The findings may provide deeper insight into the antioxidant mechanisms and provide useful information for selecting phenolic acids for free radical scavenging properties.

Quality control issues overshadow potential health benefits of the edible mushroom Flammulina velutipes, with the detection and isolation of polysaccharides posing particular problems. In this study, multiple-fingerprint analysis was performed using chemometrics to assess polysaccharide quality and antioxidant activity of F. velutipes fruiting bodies from different sources. The authentic source exhibited differences in both oxygen radical absorbance capacity and ferric reducing antioxidant power from foreign sources. IR spectroscopic/HPLC fingerprints of polysaccharide extracts from the authentic source were established and applied to assess the polysaccharide quality of foreign sources. Analysis of IR fingerprints using Pearson correlation coefficient gave correlation coefficient r values of 0.788 and 0.828 for two foreign sources, respectively, indicating distinctness from the authentic source. Analysis of HPLC fingerprints using the supervised method by Traditional Chinese Medicine could not discriminate between sources (r > 0.9), but principal component analysis of IR and HPLC fingerprints distinguished the foreign sources.

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Background and Aims: Stilbenes are an important group of phenolic substances that exist in roots, stems, leaves, skins and seeds. But little work has been performed to characterise the composition of grape root or to measure the antioxidant capacity of several stilbenes with hydroxyl radicals,1,1-diphenyl-2-picrylhydrazyl and nitric oxide free radicals. Methods and Results: Stilbenes were analysed by HPLC-MS/MS, and the radicals scavenging ability was determined by electron paramagnetic resonance. The root contained the highest concentration of stilbenes, followed by the stem and grape skin. The concentration of the following stilbenes increased in the order: piceatannol, δ-viniferin, trans-piceid, trans-resveratrol and ε-viniferin. All stilbenes had a high hydroxyl radical scavenging ability, with the scavenging rate above 50% for stilbenes at a concentration of 5 μmol/L; the same concentration of stilbenes had the lowest scavenging capacity for the nitric oxide free radicals model, with the rate below 50%. Conclusions: Five stilbenes were determined in three grape tissues. The root contained the highest concentration of stilbenes. All stilbenes had radical scavenging ability. The highest antioxidant activity was found in piceatannol. Significance of the Study: The results provide a more detailed tissue-specific profile for where these health-promoting substances can be extracted from in the grape.