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A novel technique based on dynamic microwave-assisted extraction (DMAE) coupled on-line with high-performance liquid chromatography (HPLC) through a flow injection interface has been developed for determination of andrographolide and dehydroandrographolide in Andrographis paniculata Nees. A TM(010) microwave resonance cavity built in the laboratory was applied to concentrating the microwave energy. An extraction vessel was placed in microwave irradiation zone. The extraction was performed in a recirculating system. When a number of extraction cycles were completed, the fractional extract (20muL) was driven to the analytical column by 65% aqueous methanol and was measured by diode array detector (DAD) at 225nm. The optimized extraction conditions are follows: extraction solvent 60% aqueous methanol; microwave forward power 80W; extraction time 6min; extraction solvent flow-rate 1.0mLmin(-1). The detection and quantification limits obtained are 0.5 and 1.7microgmL(-1) for andrographolide and 0.6 and 1.9microgmL(-1) for dehydroandrographolide, respectively. The within-day and between-day precision (RSD) are 2.1% and 3.7% for andrographolide and 1.7% and 4.1% for dehydroandrographolide, respectively. Mean recoveries for andrographolide and dehydroandrographolide are 97.7% and 98.7%, respectively. Compared with ultrasonic extraction used in the Chinese pharmacopoeia, the proposed method was demonstrated to obtain higher extraction yield in a shorter time. In addition, only small quantities of solvent (5mL) and sample (10mg) were required.

In order to stabilize the whole wheat flour and extend its shelf life, microwave was employed to heat the wheat bran to inactivate the lipase in this paper. The effects of microwave heating of wheat bran on the lipase activities, gluten properties, dough properties and storage stability of the stabilized whole wheat flour, and the quality of steamed bread made of stabilized whole wheat flour were investigated. Furthermore, molecular docking was applied to interpret the mechanism. The results showed that microwave can reduce lipase activity, maintain the quality of whole wheat flour dough and steamed bread, and retard rancidity. The molecular docking results displayed that the conformation of the amino acids chains near the lipase catalytic center changed, which made the substrate difficult to enter the catalytic center and prevented the hydrolysis of the fat substrate. [ABSTRACT FROM AUTHOR]

Highlights: [•] Different extraction methods affected the antioxidant activity differently. [•] Power was the key parameter in ultrasonic and microwave extraction. [•] Powers of 300W and 600W were two critical points in microwave extraction. [•] Sevag reagent combined with H2O2 was best for protein and pigment removal. [ABSTRACT FROM AUTHOR]

Abstract: An apparatus for extraction of flavonoids from Herba Epimedii has been constructed which utilizes a microwave technique for heating in a dynamic mode. A TM010 microwave resonance cavity was applied to concentrate the microwave energy; the power needed to achieve efficient extraction was significantly reduced. The method has been compared with other extraction methods, such as pressurized microwave-assisted extraction (PMAE), ultrasonic extraction (UE), heat reflux extraction (RE) and Soxhlet extraction (SOX). The four flavonoids in extract were identified by HPLC–MS. The influence of extraction parameters on the extraction yield of flavonoids has been evaluated by comparison with the peak areas of HPLC-DAD spectra in the different extraction methods. The results showed that the extraction yield of flavonoids in Herba Epimedii obtained by dynamic microwave-assisted extraction (DMAE) was higher than that obtained by UE, RE and SOX, and the extraction time is dramatically reduced. The extraction yield obtained by DMAE is similar to that obtained by PMAE. But the flavonoids in Herba Epimedii would not decompose easily when increasing the extraction time in DMAE. This is the benefit of dynamic extraction system which can transfer the analytes extracted from the sample matrix with flowed fresh solvent to the out of extraction vessel. [Copyright &y& Elsevier]