Phytochemical Screening and Bioactive Properties of Juglans regia L. Pollen

Abstract

Pollen is one of the major by-products of the walnut tree, yet it is poorly investigated. Thus, the aim of this study was to investigate the total phenolics, flavonoids, antioxidant, anticancer potential, and polyphenol profile of pollen obtained from male Juglans regia flowers. A total of 24 phenolic compounds were identified in Juglans regia pollen and all of them were reported for the first time for this raw material. The content of polyphenols was 408.03 mg/100 g dry weight (dw) and the most abundant components were quercetin 3-O-sophoroside and 4′,5,7-trihydroxy-3,6-dimethoxyflavone-7-O-beta-D-glucoside. The concentration of these compounds, as well as the total content of polyphenols and flavonoids, strongly determined the antioxidant and cytotoxic activity of Juglans regia pollen. Antioxidant action using the ABTS and CUPRAC methods had the values of 3.35 and 0.32 mmol TE/g dw, respectively. In turn, in the tests of chelating ability of ferrous ion, O2•− and OH− radical scavenging activity, of which the results were expressed as IC50, the values were equal to 335.01, 459.31, and 92.89 µg/mL, respectively. Among the six cancer cell lines, the strongest effect was demonstrated for Caco-2 (140.65 µg/mL) and MCF-7 (140.98 µg/mL) cells. The results provide valuable and previously unpublished data on the polyphenol composition and biological potential of Juglans regia pollen.

Chemical Profiling, Bioactive Properties, and Anticancer and Antimicrobial Potential of Juglans regia L. Leaves

“…In turn, the ability to copper ion reduction (CUPRAC) was assessed in the present study for the first time. Compared to the works evaluating the value of this parameter for other morphological parts of the J. regia tree, the estimated value for flowers was 2.9 times lower (3.33 mmol TE/g dw), while for pollen it was 3.6 times higher (0.32 mmol TE/g dw) than in this research [ 11 , 12 ].…”

“…Statistical analysis showed strong correlations between these cell lines and groups, as well as individual polyphenolic compounds (TPC vs. MCF-7, r > −0.999, p < 0.05; TFC vs. DLD-1, r > 0.998, p < 0.05) (see Table S2 ). Such a relationship has already been reported, among others, in works on other morphological parts of the walnut tree, such as seeds [ 21 ], green husk [ 25 ], root bark [ 26 ], flowers [ 11 ], or pollen [ 12 ]. The presented results are extremely interesting in the context of the search for new sources of compounds effective in the prevention and treatment of cancer.…”

“…The available literature data indicate that at least part of the observed antioxidant activity of plant preparations may be due to the presence of polyphenolic compounds [ 10 , 11 , 12 ]. Our analyses showed strong correlations between antioxidant activity and selected groups of polyphenolic compounds (TPC vs. CUPRAC, r > 0.999, p < 0.01; TFC vs. CUPRAC, r > 0.998, p < 0.05) (see Table S1 ).…”

“…Their presence has been detected in J. regia leaves by several authors [ 22 , 44 , 45 ]. Constituents 4 , 33, and 40 remain not fully characterized, however, they were already observed in our previous studies on the pollen and male flowers of walnut [ 11 , 12 ]. Peaks 5 – 7 , 9 , 11 were determined as coumarine derivatives.…”

“…In turn, the woody shells serve as a source of energy for heating, an abrasive agents for cleaning and polishing metals, plastics, as a filter medium for separating oil, hazardous materials, and heavy metals [ 2 , 10 ]. Żurek et al (2022 a,b) showed that both flowers and pollen from a walnut growing in the Subcarpathian region (Poland) have strong antioxidant, anti-microbial, and anti-carcinogenic potential and, thus, can be used as nutraceuticals or for food enrichment [ 11 , 12 ]. Additionally, Pycia et al (2022) confirmed that walnut flowers may be an interesting functional additive to wheat bread, which showed an increased antioxidant potential [ 13 ].…”