Nutritional Quality of the Walnut Male Inflorescences at Four Flowering Stages

Abstract

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.

Enhanced Recovery of Phenolic and Tocopherolic Compounds from Walnut (Juglans Regia L.) Male Flowers Based on Process Optimization of Ultrasonic Assisted-Extraction: Phytochemical Profile and Biological Activities

“…The best outcomes were detected for 30 min extraction time and 40% water in acetone. For TPC, the highest amount was 2.86 mg GAE/g ( Table 2 ), which was around the content found by Rosa et al [ 40 ], but less than the value of 24.3 mg GAE/g obtained from the same matrix in another study [ 15 ]. There could be many reasons for these discrepancies, as already mentioned, such as the walnut cultivar, the age of the tree, the different flowering stages or the geographic location.…”

“…The content of total flavonoid compounds obtained in our study, 0.98 mg QE/g or 98 mg/100 g dried WMF, conforms to other reported data ( Table 6 ). The maximum TFC content (21.5 ± 0.4 mg rutin equivalents/g WMF) was determined in the flowering stage when the inflorescence is already yellow, in contrast to the TPC, which reached the highest content in the early flowering stage [ 15 ].…”

“…Antioxidant activity has been associated with phenolic content in several studies, with the concentration of polyphenols and flavonoids determining the pharmacological effects of WMF extracts [ 15 ]. This trend was revealed in our study, with a good correlation being established between the total polyphenol quantities and the antioxidant activity ( Table 2 ).…”

“…Walnut male flowers (WMFs) are included in the traditional diets of some Chinese regions, where they are known as longevity foods [ 15 , 16 ]. In traditional medicine, WMFs are used in malaria and rheumatic pain treatments [ 2 ].…”

“…In recent years, several studies have focused on the investigation of the phytochemical profile of WMFs and their biological activities. Rich in carbohydrates, protein, lipids and minerals (potassium, manganese, copper, iron, zinc, calcium, magnesium) [ 15 , 17 ], WMFs represent an interesting vegetal matrix for the development of new food products and bioactive molecule extraction. In one of the first studies on WMFs, a methanolic extract displayed antioxidant, antihypoxic, anti-inflammatory and antidepressive activities in a rodent model [ 18 ].…”