The phenolics content and antioxidant activity of walnut (Juglans sigillata Dode) green husks were analysed during different stages of development. Contents of total phenolics and total flavonoids decreased from April 25th to June 7th, then increased during June and July, and decreased again at the beginning of August. Thirteen types of phenolic compounds were identified using HPLC of which juglone had the highest content. Because of seasonal variations, the trends of different phenolic compounds were different. Contents of both total phenolics and total flavonoids were strongly correlated with antioxidant activity; however, compared with totals, less significant correlations were observed between individual phenolic compounds and antioxidant activities.

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The objective of this study was to investigate the effect of storage temperature and time on nutrients, bioactive compounds, and antioxidant activities of walnut male inflorescences. The results showed that the moisture, saccharides, fat, protein, amino acids, ascorbic acid, phenolic and flavonoid compound contents, and antioxidant activities of walnut male inflorescences were markedly influenced by storage temperature, and different degrees of decrease in these parameters were observed during the entire storage period. Moreover, higher storage temperature had a more significant effect on the nutrients, bioactive compounds, and antioxidant activities of walnut male flowers, and the loss rate of these components at 25°C was higher than that determined at 4°C. However, the results also presented that the ash and mineral contents did not appear to be influenced significantly by the storage temperature, and slightly significant changes were observed in crude fiber throughout storage, which indicated that the influence of storage on the individual mineral and crude fiber content was minimal. Based on the findings in this study, in order to maximize nutrients concentration, walnut male inflorescences should be kept at 4°C for <6 days and be consumed as fresh as possible.

Nutrients, bioactive compounds and antioxidant activities of walnut male inflorescences at four flowering stages were analyzed in this study. The results showed that the male inflorescences were rich in carbohydrate, protein and mineral contents, and had antioxidant activities due to high contents of phenolic and flavonoid compounds. The nutritional compositions were varied at four stages. In the first half stage, including early flowering stage (EFS) and flowering stage (FS), the contents of protein, total amino acids, carbohydrates, antioxidants (phenolic, flavonoid and ascorbic acid) and some minerals (phosphorus, zinc and copper) were higher than that of the second half stage, including pollen-scattering stage (PSS) and later pollen-scattering stage (LPSS). Due to high contents of phenolic and flavonoid at EFS, the highest antioxidant activity was also observed at this stage. However, the higher amounts of crude fat, crude fiber and some mineral elements (potassium, iron, manganese, calcium and magnesium) were found in the second half stage. These results could contribute to using walnut male inflorescences as food, as well as developing new food products, and obtaining the bioactive substances from walnut male flowers.