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Paulownia leaves and flowers have been used to prepare medicinal tea in traditional Chinese medicine; however, there has been no scientific validation of bioactive compounds so far. A systematic study is presented to establish a suitable drying protocol for leaf and flower tissues that may be useful in preserving bioactive compounds and retaining high antioxidant capacity. Additionally, a suitable drying protocol is commercially imperative for improving the shelf life of these tissues. In this study, P. elongata and P. fortunei juvenile leaves and flowers at two stages (pre- and post-anthesis stages) were subjected to five drying treatments to study the drying characteristics and were analyzed for total polyphenols, total flavonoids, and antioxidant capacity. Oven drying, sun drying, shade drying, freeze drying, and microwave drying were the five drying methods that were used to evaluate their efficacy on the drying characteristics and antioxidant potential. Fresh and dried tissues were analyzed for total polyphenols, total flavonoids, total tannins, total catechins, total monomeric anthocyanins, and total antioxidant capacity. A strong correlation was observed between the moisture content and total polyphenols (the lower the moisture content, the lower the polyphenols). Sun drying was the best method for Paulownia tissues based on color retention, moisture content, overall cost effectiveness, time, and antioxidant capacity. Shade drying was the second-best method based on the same parameters. No significant differences were observed between P. elongata and P. fortunei tissues in their total antioxidant capacity. Leaves and flowers at the pre-anthesis stage (stage 6) registered a higher level of total polyphenols, flavonoids, tannins, catechins, and resultant antioxidant capacity in comparison with flowers at stage 9 (the post-anthesis stage). Monomeric anthocyanins were highest in P. elongata flowers at stage 6. A strong correlation was observed between moisture content and the antioxidant levels of Paulownia tissues. Full article

The volatile composition of Paulownia Shan tong (Fortunei × Tomentosa) essential oil isolated by steam distillation (yielding 0.013% v/w) from flowers (forestry wastes) was investigated by gas chromatography–mass spectrometry. Thirty-one components were identified, with 3-acetoxy-7, 8-epoxylanostan-11-ol (38.16%), β-monoolein (14.4%), lycopene, 1,2-dihydro-1-hydroxy- (10.21%), and 9,12-octadecadienoic acid, 2-phenyl-1,3-dioxan-5-yl ester (9.21%) as main compounds. In addition, molecular docking was employed to identify potential protein targets for the 31 quantified essential oil components. Inhibition of these targets is typically associated with antibacterial or antioxidant properties. Molecular docking revealed that six of these components, namely, 13-heptadecyn-1-ol, ascabiol, geranylgeraniol, anethole, and quinol dimethyl ether, outperformed the native ligand (hypoxanthine) of xanthine oxidase in terms of theoretical binding affinity, therefore implying a significant in silico inhibitory potential against xanthine oxidase. These findings suggest that the essential oil extracted from Paulownia Shan tong flowers could be valuable for developing protein-targeted antioxidant compounds with applications in the food, pharmaceutical, and cosmetic industries. Full article

The flavonoid-rich extract from Paulownia fortunei flowers (EPF) has been reported to prevent obesity and other lipid metabolism disease. However, the mechanism of its protective effects is not yet clear. The objective of this study was to investigate molecular factors involved in the hypoglycemic and hypolipidemic effects of EPF in obese mice fed a high-fat diet (HFD). Male h ICR (Institute of Cancer Research) mice were fed a HFD containing or not containing the EPF (50 or 100 mg/kg) for eight weeks. EPF reduced body weight gain, lipid accumulation in livers and levels of lipid, glucose and insulin in plasma as well as reduced insulin resistance as compared with the HFD group. EPF significantly decreased serum aminotransferase activity of the HFD group. We observed that EPF administration significantly increased the level of AMP-activated kinase (AMPK) phosphorylation and prevented fat deposits in livers and HepG2 cells, but these effects were blocked by compound C (an AMPK inhibitor). The protective effects of EPF were probably associated with the decrease in HMGCR, SREBP-1c and FAS expressions and the increase in CPT1 and phosphor-IRS-1 expressions. Our results suggest that EPF might be a potential natural candidate for the treatment and/or prevention of overweight and hepatic and metabolic-related alterations induced by HFD. Full article