Chung-Hung Chan

Microwave-assisted extractions of active ingredients from plants

Microwave-assisted extraction (MAE) is widely employed in the analysis and the extraction of active compounds from plants. This review summarizes the research done during the last decade on the MAE of active ingredients from plants. Advances and modifications to improve the performance of MAE are presented and discussed in detail. Modified MAE such as vacuum microwave-assisted extraction (VMAE), nitrogen-protected microwave-assisted extraction (NPMAE), ultrasonic microwave-assisted extraction (UMAE), dynamic microwave-assisted extraction (DMAE) and other advancements in MAE are also detailed in this article. In addition, the microwave extraction procedures and the important parameters influencing its performance are also included, together with the advantages and the drawbacks of each MAE techniques.

Modeling and Prediction of Extraction Profile for Microwave-Assisted Extraction Based on Absorbed Microwave Energy

A modeling technique based on absorbed microwave energy was proposed to model microwave-assisted extraction (MAE) of antioxidant compounds from cocoa (Theobroma cacao L.) leaves. By adapting suitable extraction model at the basis of microwave energy absorbed during extraction, the model can be developed to predict extraction profile of MAE at various microwave irradiation power (100-600 W) and solvent loading (100-300 ml). Verification with experimental data confirmed that the prediction was accurate in capturing the extraction profile of MAE (R-square value greater than 0.87). Besides, the predicted yields from the model showed good agreement with the experimental results with less than 10% deviation observed. Furthermore, suitable extraction times to ensure high extraction yield at various MAE conditions can be estimated based on absorbed microwave energy. The estimation is feasible as more than 85% of active compounds can be extracted when compared with the conventional extraction technique.

A Brief Review on Anti Diabetic Plants: Global Distribution, Active Ingredients, Extraction Techniques and Acting Mechanisms

A study has been conducted with the aim to provide researchers with general information on anti diabetic extracts based on relevant research articles collected from 34 reliable medical journals. The study showed that Asian and African continents have 56% and 17% share of the worldwide distribution of therapeutic herbal plants, respectively. In Asia, India and China are the leading countries in herbal plants research, and there has been an increase in medicinal research on plants extract for diabetes treatment since 1995 in these regions. The information collected shows that plant leaves are about 20% more favorable for storing active ingredients, as compared to other parts of herbal plants. A brief review on the extraction techniques for the mentioned parts is also included. Furthermore, the acting mechanisms for the anti diabetic activity were described, and the related active ingredients were identified. The findings reveal that most of the anti diabetic research is focused on the alteration of glucose metabolism to prevent diabetes.

Extraction of bioactives from Orthosiphon stamineus using microwave and ultrasound-assisted techniques: Process optimization and scale up

This work demonstrated the optimization and scale up of microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) of bioactive compounds from Orthosiphon stamineus using energy-based parameters such as absorbed power density and absorbed energy density (APD-AED) and response surface methodology (RSM). The intensive optimum conditions of MAE obtained at 80% EtOH, 50mL/g, APD of 0.35W/mL, AED of 250J/mL can be used to determine the optimum conditions of the scale-dependent parameters i.e. microwave power and treatment time at various extraction scales (100-300mL solvent loading). The yields of the up scaled conditions were consistent with less than 8% discrepancy and they were about 91-98% of the Soxhlet extraction yield. By adapting APD-AED method in the case of UAE, the intensive optimum conditions of the extraction, i.e. 70% EtOH, 30mL/g, APD of 0.22W/mL, AED of 450J/mL are able to achieve similar scale up results.

Assessment of Various Pretreatment and Extraction Methods for the Extraction of Bioactive Compounds from Orthosiphon Stamineus Leaf via Microstructures Analysis

Abstract The impacts of various methods such as mechanical grinding, ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), and also sample pretreatments using acid and alkali on the microstructure of plant sample were studied for the extraction of bioactive compounds from Orthosiphon stamineus leaf. From scanning electron microscopy (SEM) analysis of the extracted sample, UAE and MAE induced significant disruption on glandular trichomes structure, which is the main site for biosynthesis of plant secondary metabolites. This improves the diffusion of bioactive compound and resulted in approximately 86–95 % of the total extraction yield quantified by conventional Soxhlet extraction. Chemical pretreatments generally imparted weaker microstructures disruption thus slight improvement on the extraction yields was observed. In this case, acid reagent is more suitable for the pretreatment as the presence of alkali decomposes the bioactive compounds. In a nutshell, the performance of an extraction strongly depends on its degree of disruption on the plant sample microstructure.

Chapter 15 – An Energy-Based Approach to Scale Up Microwave-Assisted Extraction of Plant Bioactives

Abstract Optimization and modeling techniques based on energy-based parameters enable scale up of microwave-assisted extraction (MAE) of plant-derived bioactive compounds. Energy-based parameters, namely absorbed power density (APD) and absorbed energy density (AED), are able to characterize the extraction kinetics of MAE in predicting the extraction profiles and the optimum conditions at various conditions particularly at larger scale operations. The objective of this chapter is to demonstrate the scale-up of MAE using APD and AED parameters. In this chapter, the associated theory, the optimization technique, as well as the modeling technique, are elucidated. This chapter also discusses the applications of APD and AED in equipment design, operational flexibility, and adaptability for various types of plant extraction with the aim to commercialize the MAE.