Abstract
Flavonoids are polyphenolic structures, a class of secondary plant metabolites with low-molecular weights, and are commonly found in plants. They have diverse chemical structures, and as of recently, the prenylated derivates have been reported to show improved biological activities. Most flavonoids are highly polar and unsuitable for gas chromatographic analyses. Derivatization (e.g., silylation) is commonly used to make them amenable to gas chromatography by altering their physico-chemical properties. Although highly effective, derivatization techniques introduce extra preparation steps and use hazardous chemicals. Continuous flow with microfluidics combined with the power of 4IR technologies, such as 3D printing and automation, can be used/adopted to address such limitations. The aim of this study was to automate derivatization (specifically silylation) by developing 3D-printed microfluidic devices in which derivatization will occur, focusing on flavonoid compounds.
Microfluidic devices of 40 × 40 mm and 30 × 20 mm dimensions with ± 1 mm ID channels were designed, and 3D printed using clear polypropylene. Quercetin and other flavonoids (referred to as, TED 4, TED 13, and ZTF 1016) isolated from plant extracts were silylated with N-tert-Butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA) at room temperature both in batch and in continuous flow. An optimal combined flow rate of 200 μL/min was used, and a residence time of ≈ 3 mins was observed. All the samples were analyzed using Fourier transformation infrared spectroscopy (FTIR), gas chromatography flame ionization detection (GC-FID), gas chromatography tandem mass spectrometry (GC-MS/MS), and high-resolution mass spectrometry (HR-MS), and the batch and flow results were compared for all derivatized samples.
All the characterization techniques showed comparable results for quercetin both in batch and flow. Interestingly, the HR-MS results showed that the flow method was up to ≈25 times more efficient than the batch method for quercetin samples. In the derivatized TED 13 samples, the flavonoid was completely derivatized in the flow method when compared to the batch where the
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reaction was incomplete. Similar results were observed for ZTF 1016, where the flow method resulted in a four times derivatized compound compared to batch, where the compound was only derivatized once. In conclusion, an alternative natural product derivatization method has been demonstrated and proved more efficient than the traditional batch method.