Solid-state microwave disruption technique for the extraction of bioactive compounds from Orthosiphon stamineus (Java tea) / See Tiam You

See , Tiam You (2024) Solid-state microwave disruption technique for the extraction of bioactive compounds from Orthosiphon stamineus (Java tea) / See Tiam You. PhD thesis, Universiti Malaya.

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Abstract

Natural products that can be extracted from herbal plant leaves with pharmaceutical effect tend to be less harmful and have less or no side effect as compared to synthetic drugs. Extraction of herbal plant leaves involved lengthy drying time and is energy intensive. Hence, fresh and dried Orthosiphon stamineus (Java tea) leaves which contains medicinal values was processed into herbal tea to reduce the processing time and energy consumption while preserving its bioactive compounds over a prolong storage period. In this work, a solvent free biomass disruption process using microwave which is named as solid-state microwave disruption (SSMD) was established. Microwave process not only can achieve higher drying efficiency but also can disrupt cell plant for better elution process of bioactive compounds. A simple elution process was employed to elute the bioactive compounds and the total amount of bioactive compound of eupatorin, 3’- hydroxy-5,6,7,4’-tetramethoxyflavone and sinensetin obtained was used to illustrate the performance of SSMD. The microwave method was optimized and modelled using modified energy parameters method of absorbed energy density (AED) and absorbed power density (APD). The optimum extraction yield of 6.61 mg/g obtained by SSMD is comparable with those obtained by ultrasonic assisted extracion (UAE), microwaveassisted extraction (MAE) and Soxhlet extraction (SE) at 6.47 mg/g, 6.59 mg/g and 6.90 mg/g, respectively. It was found that for both fresh and dried Java tea leaves, the irradiated microwave flux was able to penetrate the biomass’s plant cell wall and interact with the intracellular moisture within the plant cell. As the moisture reacted with microwave, more plant cell disrupted with reduced moisture content. The microwave method was optimized and modelled. The model gives an accurate prediction and successfully optimized the degree of disruption. The extraction yield of SSMD-elution for both fresh and dried samples was more than 95% of SE yield. However, the fresh sample required shorter overall heating time as compared to that of the dried sample. Moreover, SSMD shortened the traditional long drying process which normally required more than 24 hours. In addition, the SSMD process was scaled-up using the energy-based parameter for both fresh and dried sample. The large scale process (5 times larger) shows that the model has good predictability and the optimum condition obtained can be scaled up. The scale up process further highlighted the feasibility of SSMD such as time saving in overall drying, disruption and extraction process. On the other hand, the simple SSMD process eases the selection of solvent, space saving and lower solvent consumption. Also, the simple optimization and modelling process using energy based method confirm the application of SSMD in bioactive compound extraction and also for herbal tea processing. The solvent free disruption and extraction process is established via modelling and optimization study which would contribute greatly to the development of pharmaceutical and food processing industrial.

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