Biosynthesis of the flavonoid naringenin in plants and bacteria is commonly catalysed by a type III polyketide synthase (PKS) using one p-coumaroyl-CoA and three malonyl-CoA molecules as substrates. Here, we report a fungal non-ribosomal peptide synthetase -polyketide synthase (NRPS-PKS) hybrid FnsA for the naringenin formation. Feeding experiments with isotope-labelled precursors demonstrate that FnsA accepts not only p-coumaric acid (p-CA), but also p-hydroxybenzoic acid (p-HBA) as starter units, with three or four malonyl-CoA molecules for elongation, respectively. In vitro assays and MS/MS analysis prove that both p-CA and p-HBA are firstly activated by the adenylation domain of FnsA. Phylogenetic analysis reveals that the PKS portion of FnsA shares high sequence homology with type I PKSs. Refactoring the biosynthetic pathway in yeast with the involvement of fnsA provides an alternative approach for the production of flavonoids such as isorhamnetin and acacetin.

In this study, response surface methodology was employed to optimize the ultrasound‐assisted extraction (UAE) process of perilla seed meal polysaccharides (PSMP). The optimal conditions for UAE of PSMP were: liquid–solid ratio of 26.00 mL/g, ultrasonic temperature of 43.00 °C, ultrasonic time of 52.00 min, and ultrasonic power of 229.00 W, the optimal conditions lead to an yield of 6.137 ± 0.062%. The structural characteristics of molecular weight, compositional monosaccharides, and glycosidic linkages were determined by size exclusion chromatography with multiangle light scattering, gas chromatography‐mass spectrometry, Fourier‐transfer infrared spectroscopy, and nuclear magnetic resonance detections. Scanning electron microscopy analysis showed that many holes were formed on the surface of PSM after UAE. The antioxidant activities of PSMP were investigated using various assays in vitro. The results suggested that PSMP is potential natural resource of antioxidants for medicine and functional foods. Practical Application The selection of raw material perilla seed meal is conducive to the comprehensive utilization of edible resources. With consumer demands for newly developed foods with natural, wholesome ingredients are increasing nowadays. This study provides effective reference for in‐depth research on other medicine‐food dual‐use resources. Ultrasound‐assisted extraction (UAE) is a promising alternative method for hot water reflux extraction (HWRE) of polysaccharides for advantages of high efficiency and energy saving. In this work, the UAE process optimized by response surface methodology is more suitable for industrial application that can effectively decrease total cost of production by reducing the extraction temperature, shortening extraction time, and increasing raw material utilization.

A Box-Behnken design was employed to optimize ultrasound-assisted enzymatic extraction of polysaccharides from perilla leaves. Four independent variables, namely, liquid-to-solid ratio, enzymatic time, enzymatic temperature, and ultrasonic power were investigated. Under the optimal liquid-to-solid ratio of 41:1, enzymatic time of 40 min, enzymatic temperature of 49 °C, and ultrasonic power of 204 W, the experimental polysaccharide yield was 3.84% (n = 3), which was close to the value predicted by response surface methodology (3.9%). Four polysaccharides (PLP1, PLP2, PLP3, and PLP4) were obtained with DEAE-cellulose-52 and Sephadex G-100 chromatography, and their antioxidant activities were investigated with various antioxidant assays in vitro. All the four polysaccharides possessed good antioxidant properties in a concentration-dependent manner, and PLP3 presented the highest antioxidant activity. Thus, the novel polysaccharides extracted from perilla leaves could be promising bioactive macromolecules that can be applied as potential antioxidants in medical and food industries.