Extraction of polyphenols from Clinacanthus nutans Lindau (C. nutans) by vacuum solvent-free microwave extraction (V-SFME)

Clinacanthus nutans Lindau (C. nutans) is a popular medicinal herb plant in Asia regions such as Malaysia, Indonesia, Thailand and China for its high polyphenols content. Various conventional extraction techniques have been use to extract bioactive compounds in C. nutans, however, the methods have limitations such as usage of organic solvent, time-consuming and low extraction yield. In this study, polyphenols content from C. nutans leaves extracted by solvent-free microwave extraction (SFME) in a vacuum condition (V-SFME) and at ambient pressure (SFME) to investigate the effect of vacuum on the extraction of polyphenols. Energy density or irradiation power per unit of sample volume is used instead of applied microwave power to determine actual energy absorbed by the microwave extraction. Effect of process parameter on the polyphenol contents: energy density of 0.073, 0.078 and 0.108 W/ml in 5, 10 and 15 min with 6 ml/g of solvent-to-feed (S/F) ratio was studied. The highest total phenol content (TPC) was obtained at 0.073 W/ml, 6 ml/g of S/F ratio and 5 min of extraction time with TPC of 24.08 +/- 0.51 mg GAE/g DW at temperature of 79 degrees C. Results demonstrated that the TPC of C. nutans was higher when extracted under vacuum pressure compared to TPC at ambient pressure. The results suggest that V-SFME method using water under vacuum state appears as the most efficient and green technique for the extraction of polyphenols from C. nutans extract in shorter time with no use any of organic solvent to produce reasonably high TPC.

Automated summary

In this study, solvent-free microwave extraction (SFME) was used to extract polyphenols from Clinacanthus nutans Lindau, showing that extraction under vacuum pressure resulted in higher polyphenol content compared to ambient pressure extraction. This study demonstrates that vacuum conditions are beneficial for polyphenol extraction from C. nutans.