Optimization and modeling of microwaveassisted extraction of active compounds from cocoa leaves

Transcription

1 Malaysian Palm Oil Board From the SelectedWorks of Chung-Hung Chan 2013 Optimization and modeling of microwaveassisted extraction of active compounds from cocoa leaves Chung-Hung Chan, C.-H Chan, University of Malaya Available at:

2 Viva Presentation Ph.D. (Engineering) OPTIMIZATION AND MODELING OF MICROWAVE-ASSISTED EXTRACTION OF ACTIVE COMPOUNDS FROM COCOA LEAVES Chan, Chung Hung (KHA ) Supervised by Dr. Rozita Yusoff Dr. Ngoh Gek Cheng 31 st Aug 2013 Dean Meeting Room, Level 4 Engineering Tower, Faculty of Engineering 1

3 Table of Contents 1. Background 2. Objectives 3. Methodology 4. Results & Discussion 5. Conclusions 5. Novelty & Contributions 6. Applications 7. List of Publications 2 2

4 Diabetes Diabetes Atlas [1] 439 millions adults with diabetes by 2030 Malaysia: top 10 for diabetes prevalence Medications Natural product Synthetic drug Example of natural occurring anti diabetic compounds Quercetin derivatives - stimulate insulin and regenerate pancreatic islets Catechin compounds - oxidize glucose [1] Shaw, J.E., R.A. Sicree, and P.Z. Zimmet, Global estimates of the prevalence of diabetes for 2010 and Diabetes Research and Clinical Practice, (1): p

5 Source of Flavonoids Cocoa (Theobroma Cacao L.) Leaves Fig. 1: Cocoa leaves Cultivated globally Available in Malaysia disposed of during pruning Contain catechin compounds Leaf is the most favorable storage site for anti diabetic compounds [2] [2] Chan, C.-H., R. Yusoff, and G.-C. Ngoh, A brief review on anti diabetic plants: Global distribution, active ingredients, extraction techniques and acting mechanisms. Phcog. Rev., (11): p

6 Microwave-Assisted Extraction MAE - Promising technique for medicinal plant research [3] localized heating Fast extraction Low solvent consumption Suitable for polar compounds State of the Art: Optimum MAE conditions Restricted to specific extractor Hardly applied at larger scales No standardized optimization strategy Kinetic models No predictive capability Heavily dependent on exp. data Difficult to predict extraction behavior for different extractor Lack of significant PARAMETERS to describe MAE process [3] Mandal, V., Y. Mohan, and S. Hemalatha, Microwave assisted extraction - An innovative and promising extraction tool for medicinal plant research. Pharmacognosy Reviews, (1): p

7 Objectives Feasibility study of MAE for cocoa leaves extraction 1. To explore potential anti diabetic compounds in cocoa leaves & to optimize the MAE. Quantification of Main anti diabetic compounds Optimization of MAE based on RSM-BBD Comparison with conventional Soxhlet extraction 2. To study MAE kinetics. Modeling using empirical model to study the effect of operating parameters: 1. Particle sizes of sample 2. Solvent to feed ratio Yield Washing step Diffusion step 3. Microwave Power 4. Solvent loading Time 6 Fig. 2: Typical MAE curve

8 Objectives (Cont..) Methods for Modeling & Optimization of MAE 3. To study the feasibility of the absorbed microwave power as a new parameter for MAE. APD predictive method 3. To develop MAE kinetic model with incorporation of the absorbed microwave energy during extraction. AED modeling method 4. To standardize MAE optimization procedure for plant extraction using the absorbed microwave power and energy. APD-AED optimization method 7

9 MAE procedures Drying & Grinding MAE by domestic oven Filtration Yield (mg/g) mass of active compounds in extract (mg) mass of sample(g) Fig. 3: Extraction procedure of MAE HPLC-MS analysis

10 Results & Discussion Obj. 1 Quantification of main anti-diabetic compounds in cocoa leaves & Optimization of MAE 1. Main anti-diabetic compounds in cocoa leaves: Rutin ( mg/g) (-)-Epicatechin ( mg/g) Isoquercitrin ( mg/g) Comparable to red onion & green tea 2. Optimization of MAE Single factor exp.: 85% (v/v) aqueous EtOH RSM-BBD: Table 1: Box-Behnken design (BBD) Factor Unit Low level High level X 1 : Microwave power W X 2 : Extraction time min 5 15 X 3 : Solvent to feed ratio ml/g

11 Results & Discussion Obj total yield total yield B: S/F A: Power C: time Fig. 4: Response surface curves B: S/F Optimum MAE condition: 50 ml/g, 156 W and 18 min Table 2: Predicted and actual yields Extraction yields Total extraction yields(mg/g) Predicted 6.95 Experimental 6.93 ±

12 Results & Discussion Obj Comparison with conventional Soxhlet extraction Table 3: MAE vs. Soxhlet yields Technique Total extraction yields MAE: 85% EtOH, 50 ml/g, 156 W and 18 min 6.93 ± 0.06 SX : 100% EtOH, 100 ml/g and 6 hr 7.09 ± 0.20 MAE Soxhlet Ruptured cells Shrinking cells Formation of pits Fig. 5: Scanning electron micrographs (SEM) of extracted sample

13 Results & Discussion Obj. 2 To study MAE kinetics 1. Effect of particle size 2. Effect of S/F ratio < 0.25 mm > 0.25 mm Average leaf thickness = 0.25 mm 20 ml/g 50 ml/g 80 ml/g Total extraction yields (mg/g) improved washing step Extraction time (min) Fig. 6: Effect of particle size on MAE kinetics Total extraction yields (mg/g) enhance equilibrium extraction yield Extraction time (min) Fig. 7: Effect of S/F ratio on MAE kinetics 12

14 Results & Discussion Obj Effect of microwave power (P) 4. Effect of solvent loading (V) Based on nominal power density of 1 W/ml improves diffusion step and shorten extraction time Inconsistent extraction time High V gives high rate of heating (shorter time) Total extraction yields (mg/g) Extraction time (min) Microwave power (W) Total extraction yields (mg/g) Extraction time (min) Solvent loading (ml) Fig. 8: Effect of P on MAE kinetics Fig. 9: Effect of V on MAE kinetics 13

15 Results & Discussion Obj. 3 To study the feasibility of the absorbed microwave power as a new parameter for MAE 1. Introduction to Absorbed Power Density (APD) Increase with P Absorbed power (W) APD 200 Solvent loading (ml) 150 Increase with V Fig. 10: Absorbed power under influence of solvent loading and nominal microwave power Nominal microwave power (W) NEW PARAMETER APD Absorbed microwave power in the extraction solvent per unit solvent volume (W/ml) APD Indicates the interaction between microwave irradiation power & solvent loading 14

16 Results & Discussion Obj Effect of APD on MAE kinetics 1. The MAE favors low APD value (< 0.5 W/ml) 13 APD characterizes the MAE kinetics Total yield (mg/g) g, 100 W, 100 ml 2 g, 200 W, 100 ml 2 g, 300 W, 100 ml 2 g, 450 W, 100 ml 2 g, 600 W, 200 ml 3 g, 150 W, 150 ml 4 g, 200 W, 200 ml 5 g, 250 W, 250 ml 6 g, 300 W, 300 ml optimum extraction time region Extraction time (min) APD (W/ml) 2.5 Fig. 11: Significances of APD on MAE kinetics 2. High APD gives short extraction time but with slightly lower yield 15

17 Results & Discussion Obj APD predictive method Correlation between OETR and APD Correlation based on Exp. Data: Extraction time (min) Incomplete extraction Optimum extraction time region Overheating region Power ( W) Solvent loading (100ml) Prediction of optimum extraction time based on APD value: Various Power Larger scale extraction APD (W/ml) Fig. 12: APD predictive method 16

18 Results & Discussion Obj. 4 To develop MAE kinetic model with incorporation of the absorbed microwave energy during extraction. 1. Absorbed energy density (AED) Modeling method i. Adapt selected model in AED basis ii. iii. Yield f (time) Yield f ( AED) Determine the model parameter (f) using Exp. Data Convert the formulated AED model into time basis Yield f ( AED) Yield f ( APD time) New Parameter AED Absorbed microwave energy per unit solvent volume (J/ml) during extraction AED = APD x t Predict extraction profile of MAE at various P and V based on APD 17

19 Results & Discussion Obj Prediction of MAE curves using the adapted model ml, 200 W (0.43 W/ml) R-square = ml, 300 W (0.93 W/ml) R-square = 0.97 Y/Ysat 0.8 Y Ysat exp( t) Y/Ysat 0.7 Extraction model b (1) k (min -1 ) Predicted by AED model Curve fitting by original film Percentage difference (%) ml, 200 W (0.25 W/ml) Extraction time (min) R-square = Y Ysat exp( t) Extraction model b (1) k (min -1 ) Predicted by AED model Curve fitting by original film Percentage difference (%) ml, 300 W (0.42 W/ml) Extraction time (min) R-square = Y/Ysat Y Ysat exp( t) Extraction model b (1) k (min -1 ) Predicted by AED model Curve fitting by original film Percentage difference (%) Extraction time (min) Y/Ysat 0.8 Y Ysat exp( t) 0.7 Extraction model b (1) k (min -1 ) Predicted by AED model Curve fitting by original film Percentage difference (%) Extraction time (min) Fig. 13: Prediction of MAE curves using AED extraction model 18

20 Results & Discussion Obj Effect of AED on MAE process Extraction yield (mg/g) steady diffusion equilibrium extraction W Energy required to reach equilibrium AED (J/ml) overheating 2 g, 100 W, 100 ml 2 g, 200 W, 100 ml 2 g, 300 W, 100 ml 2 g, 600 W, 100 ml 4 g, 200 W, 200 ml 5 g, 250 W, 250 ml 6 g, 300 W, 300 ml temperature profile Fig. 14: Diffusive extraction stages of MAE under influence of AED AED indicates the extraction stages of MAE Temperature ( o C) 19

21 Results & Discussion Obj. 5 To standardize MAE optimization procedure for plant extraction using the absorbed microwave power and energy. 1. APD-AED Optimization Method Specify prior to the optimization of mechanism 2 1. Extraction solvent 2. S/F ratio (constant volume) 3. Particle size of sample No interaction Mechanism 1 Penetration of solvent to plant matrix Rate limiting Mechanism 2 Rupturing of plant cells RSM optimization 1. Power 2. Time Interaction Single factor Exp. 1. APD 2. AED No interaction Mechanism 3 Elution of compounds into solvent Fig. 15: APD-AED optimization strategy 20

22 Results & Discussion Obj Optimization based on APD & AED Intensive optimum conditions (S/F, APD, AED) 50 ml/g, 0.3 W/ml, 300 J/ml Table 4: Application of intensive optimum parameters for scaling up purpose Scale of extraction Optimum condition Recovery of compounds 2 g 50 ml/g, 156 W, 18 min (RSM) ml/g, 150 W, 16.7 min g 50 ml/g, 200 W, 15.6 min g 50 ml/g, 220 W, 14.7 min g 50 ml/g, 220 W, 18.5 min g 50 ml/g, 260 W, 16.1 min 98.3 Consistent extraction yields 21

23 Results & Discussion Obj Performance regimes of MAE under various APD & AED APD (W/ml) Diffusive extraction Equlibrium region Excessive thermal exposure 0.35 Incomplete extraction Overheating Overheating Overpower microwave heating 0.25 Incomplete extraction Incomplete extraction Optimum extraction Incomplete extraction Overheating Incomplete extraction Optimum microwave heating Underpower microwave heating Fig. 16: Performance regimes of MAE AED (J/ml) 22

24 Conclusions 1. Cocoa leaves - potential source of anti diabetic compounds. 2. Absorbed power density (APD) can be used to replace microwave irradiation power in MAE study as it can characterize the extraction kinetics of MAE. 3. Absorbed energy density (AED) can be used to replace extraction time in MAE study as it indicates the progress of MAE to reach equilibrium extraction. 4. Intensive optimum MAE conditions (S/F, APD, AED) are the intrinsic criteria for optimum extraction. 23

25 Novelty & Contributions 1. Confirms the potential of cocoa leaves as potential anti diabetic plants 2. Introduces APD and AED as new MAE parameters 3. Devises viable methods to model MAE process at varying extraction scale APD predictive method AED modeling method 4. Standardizes and develops optimization method for MAE APD-AED optimization method 24

26 Applications Reproduction of extraction using different microwave extractor Intensive parameters serve as references when attempting new extraction APD/AED Methods Prediction of extraction behavior of MAE using lesser experimental data Scaling up of MAE 25

27 REFERENCES 1. Chan, C.-H., Yusoff, R., & Ngoh, G.-C. (2013). Modeling and prediction of extraction profile for microwave-assisted extraction based on absorbed microwave energy. Food Chemistry, 140(1 2), Chan, C.-H., Yusoff, R., & Ngoh, G.-C. (2012). A brief review on anti diabetic plants: Global distribution, active ingredients, extraction techniques and acting mechanisms. Phcog. Rev., 6(11), Chan, C.-H., Yusoff, R., Ngoh, G.-C., & Kung, F. W.-L. (2011). Microwave-assisted extractions of active ingredients from plants. Journal of Chromatography A, 1218(37), Chan, C.-H., Yusoff, R., & Ngoh, G.-C. (2014). Optimization of microwave-assisted extraction based on absorbed microwave power and energy. Chemical Engineering Science, 111(0), Chan, C.-H., Yusoff, R., & Ngoh, G.-C. (2014). Modeling and kinetics study of conventional and assisted batch solvent extraction. Chemical Engineering Research and Design, 92(6),