Figures (3)  Tables (5)

    • Figure 1. 

      Comparison of yield and total phenolic content of the extracts from cocoa bean shells using different extraction techniques using water as a solvent. CBS, cocoa bean shells; db, dry basis; GAE, gallic acid equivalent; HE, heating-aided extraction; ME, microwave-aided extraction; MUE, ordered microwave-ultrasound-aided extraction; UE, ultrasound-aided extraction; UME, ordered ultrasound-microwave-aided extraction. Data followed by the same lowercase letter (for yield) or uppercase letter (for total phenolic content) are not significantly different (p > 0.05).

    • Figure 2. 

      Comparison of yield and total phenolic content of the extracts from cocoa bean shells using different extraction solvents using UME as an extraction technique. AA, acetic acid (0.3 mL in 100 mL water); CA, citric acid (1 g in 40 mL water); CBS, cocoa bean shell; ChCl, choline chloride solution (1 g in 40 mL water); ChCl–AA, the mixture of ChCl and AA (ratio of 1:2, v/v); ChCl-CA, the mixture of ChCl and CA (ratio of 2:1, v/v); ChCl–G, the mixture of ChCl and G (ratio of 5:2, v/v); ChCl–G–W, the mixture of ChCl, G, and water (ratio of 5:2:5, v/v/v); ChCl-LA, the mixture of ChCl and LA (ratio of 1:3, v/v); db, dry basis; G, glucose solution (1 g/40 mL water); G–AA, the mixture of G, AA, and water (ratio of 1:5:3, v/v/v); GAE, gallic acid equivalent; G–CA, the mixture of G, CA, and water (ratio of 1:5:3, v/v/v); G–LA, the mixture of G, LA, and water (ratio of 1:5:3, v/v/v); LA, lactic acid (1 mL in 40 mL water); NaOAc–AA, the mixture of NaOAc, AA, and water (ratio of 1:3:4, v/v/v); NaOAc–CA, the mixture of NaOAc, CA, and water (ratio of 1:3:4, v/v/v); NaOAc, sodium acetate solution (1 g in 40 mL water); NaOAc–LA, the mixture of NaOAc, LA, and water (ratio of 1:3:4, v/v/v); UME, ordered ultrasound-microwave-aided extraction; W, water. Data followed by the same lowercase letter (for yield) or uppercase letter (for total phenolic content) are not significantly different (p > 0.05).

    • Figure 3. 

      Response surface plots showing the effects of process variables on extracting yield (a)−(f) and total phenolic content (g)−(l): (a) and (g) effects of LSR and STi at constant STe (55 °C) and MTi (20 min); (b) and (h) effects of LSR and STe at constant STi (45 min) and MTi (20 min); (c) and (i) effects of LSR and MTi at constant STi (45 min) and STe (55 °C); (d) and (j) effects of STi and STe at constant LSR (50 mL g−1) and MTi (20 min); (e) and (k) effects of STi and MTi at constant LSR (50 mL g−1) and STe (55 °C); (f) and (l) effects of STe and MTi at constant LSR (50 mL g−1) and STi (45 min). Abbreviations: LSR, liquid-solid ratio (mL g−1); STi, sonication time (min); STe, sonication temperature (°C); MTi, microwave time (min).

    • Independent variables Abbreviation Symbol Levels
      −1 0 1
      Liquid-solid ratio (mL g−1) LSR X1 30 50 70
      Sonication time (min) STi X2 25 45 65
      Sonication temperature (°C) STe X3 35 55 75
      Microwave time (min) MTi X4 10 20 30
      Dependent variables
      Yield (%, dry basis) Y1
      Total phenolic content (mg gallic
      acid equivalent g−1 dried cocoa
      bean shells)      		 Y2

      Table 1. 

      Independent and dependent variables in the Box–Behnken design for extracting phenolic compounds from cocoa bean shells.

    • # Independent variables Dependent variables
      Coded Actual Yield
      (%, db)      		 Total phenolic content
      (mg GAE g−1 dried CBS)
      X1 X2 X3 X4 X1 X2 X3 X4 Observed2 Estimated Observed2 Estimated
      1 0 0 0 0 50 45 55 20 28.5 ± 0.2 29.8 14.3 ± 0.4 14.1
      2 1 1 0 0 70 65 55 20 19.0 ± 0.4 19.6 10.9 ± 0.4 11.2
      3 1 0 0 1 70 45 55 30 17.4 ± 0.5 16.4 9.09 ± 0.10 8.67
      4 0 0 0 0 50 45 55 20 30.3 ± 0.1 29.8 14.8 ± 0.6 14.1
      5 0 0 −1 −1 50 45 35 10 24.4 ± 1.4 24.3 12.7 ± 0.4 13.3
      6 −1 1 0 0 30 65 55 20 22.8 ± 0.8 24.5 10.0 ± 0.6 10.4
      7 0 1 0 1 50 65 55 30 15.7 ± 0.2 15.1 6.48 ± 0.09 6.41
      8 0 −1 0 1 50 25 55 30 18.5 ± 0.1 20.0 8.50 ± 0.69 9.16
      9 1 0 0 −1 70 45 55 10 24.2 ± 0.3 24.4 12.8 ± 0.5 12.6
      10 0 −1 1 0 50 25 75 20 24.7 ± 0.4 25.7 12.3 ± 0.4 12.5
      11 1 0 −1 0 70 45 35 20 22.7 ± 0.4 23.9 13.2 ± 0.2 13.5
      12 0 1 1 0 50 65 75 20 18.8 ± 0.2 19.0 9.40 ± 0.35 9.90
      13 0 −1 0 −1 50 25 55 10 24.7 ± 0.6 25.0 13.1 ± 0.8 12.6
      14 1 0 1 0 70 45 75 20 20.4 ± 0.5 21.6 11.6 ± 0.4 11.7
      15 −1 0 −1 0 30 45 35 20 26.2 ± 0.9 24.8 12.2 ± 0.6 11.6
      16 0 1 −1 0 50 65 35 20 25.0 ± 0.4 24.8 12.8 ± 0.6 12.8
      17 0 0 −1 1 50 45 35 30 19.4 ± 0.2 19.3 9.02 ± 0.49 8.83
      18 0 1 0 −1 50 65 55 10 25.8 ± 0.6 24.1 13.4 ± 0.2 12.2
      19 −1 0 1 0 30 45 75 20 24.4 ± 0.1 23.0 10.7 ± 0.2 9.80
      20 0 0 1 −1 50 45 75 10 24.7 ± 0.3 24.3 11.2 ± 0.3 11.7
      21 0 0 1 1 50 45 75 30 15.7 ± 0.4 15.3 7.33 ± 0.20 6.89
      22 −1 −1 0 0 30 25 55 20 24.8 ± 0.6 23.7 11.0 ± 0.6 10.8
      23 −1 0 0 −1 30 45 55 10 22.9 ± 0.9 24.6 10.7 ± 0.1 11.4
      24 −1 0 0 1 30 45 55 30 18.0 ± 0.4 18.5 5.52 ± 0.21 5.99
      25 0 −1 −1 0 50 25 35 20 23.5 ± 1.1 24.0 13.5 ± 0.2 13.3
      26 1 −1 0 0 70 25 55 20 28.6 ± 0.3 26.3 14.1 ± 0.3 13.9
      27 0 0 0 0 50 45 55 20 31.9 ± 0.5 29.8 14.9 ± 0.3 14.1
      28 0 0 0 0 50 45 55 20 30.1 ± 0.6 29.8 13.0 ± 0.5 14.1
      29 0 0 0 0 50 45 55 20 28.3 ± 0.9 29.8 13.4 ± 0.6 14.1
      1 X1, liquid-solid ratio (mL g−1); X2, sonication time (min); X3, sonication temperature (°C); X4, microwave time (min); CBS, cocoa bean shells. 2 Mean of triplicate determination.

      Table 2. 

      Design matrix and result of Box–Behnken design for extracting phenolic compounds from cocoa bean shells1.

    • Source Yield Total phenolic content
      Sum of squares df Mean square F-value p-value Sum of squares df Mean square F-value p-value
      Model 505 14 36.1 14.0 < 0.0001 160 14 11.4 18.4 < 0.0001
      X1 3.93 1 3.93 1.52 0.238 11.3 1 11.3 18.1 0.0008
      X2 25.8 1 25.8 10.0 0.007 7.38 1 7.38 11.9 0.004
      X3 12.5 1 12.5 4.86 0.045 9.80 1 9.80 15.8 0.001
      X4 147 1 147 57.1 < 0.0001 64.5 1 64.5 103.7 < 0.0001
      X1X2 14.1 1 14.1 5.45 0.035 1.27 1 1.27 2.04 0.175
      X1X3 0.066 1 0.066 0.026 0.875 0.0004 1 0.0004 0.0006 0.981
      X1X4 0.900 1 0.900 0.349 0.564 0.549 1 0.549 0.883 0.363
      X2X3 13.8 1 13.8 5.35 0.036 1.12 1 1.12 1.81 0.200
      X2X4 3.97 1 3.97 1.54 0.235 1.40 1 1.40 2.25 0.156
      X3X4 3.93 1 3.93 1.52 0.238 0.019 1 0.019 0.031 0.863
      X12 64.9 1 64.9 25.2 0.0002 13.9 1 13.9 22.4 0.0003
      X22 62.7 1 62.7 24.3 0.0002 6.59 1 6.59 10.6 0.006
      X32 73.0 1 73.0 28.3 0.0001 5.65 1 5.65 9.08 0.009
      X42 208 1 208 80.9 < 0.0001 56.4 1 56.4 90.7 < 0.0001
      Residual 36.1 14 2.58 8.70 14 0.622
      Lack-of-Fit 27.6 10 2.76 1.29 0.435 5.75 10 0.575 0.778 0.661
      Pure Error 8.56 4 2.14 2.96 4 0.739
      Cor Total 541 28 168 28
      R² 0.933 0.948
      Adjusted R² 0.867 0.897
      1 X1, liquid-solid ratio (mL g−1); X2, sonication time (min); X3, sonication temperature (°C); X4, microwave time (min).

      Table 3. 

      Analysis of variance for regression model of extracting bioactive compounds from cocoa bean shells1.

    • HE UME-S UME-W
      Yield 6.36 ± 0.11a 31.7 ± 1.8c 19.9 ±1.2b
      TPC 4.52 ± 0.26a 14.7 ± 0.3c 10.7 ±0.6b
      TFC 4.14 ± 0.20a 9.90 ± 0.44c 7.73 ± 0.27b
      DPPH 14.3 ± 1.0a 23.4 ± 1.2c 18.8 ± 0.8b
      ABTS 19.8 ± 1.7a 31.7 ± 2.1c 26.2 ± 1.3b
      Caffeic acid3 0.090 ± 0.009a 0.197 ± 0.043b 0.184 ± 0.016b
      Hydroxybenzoic acid3 7.73 ± 0.80a 8.59 ± 0.40a 7.81 ± 0.57a
      Protocatechuic acid3 1.96 ± 0.02a 4.05 ± 0.25c 3.28 ± 0.07b
      Catechin3 3.12 ± 0.62a 4.61 ± 0.24b 4.32 ± 0.37b
      Inhibition zone against S. aureus4 1.22 ± 0.03a 1.85 ± 0.05b 1.30 ± 0.05a
      Inhibition zone against E. coli nd nd nd
      1 HE, heating-aided extraction; UME-S, ordered ultrasound-microwave-aided extraction under optimized conditions using the mixture of sodium acetate, citric acid, and water (ratio of 1:3:4, v/v/v) as extraction solvent; UME-W, ordered ultrasound-microwave-aided extraction under optimized conditions using water as extraction solvent. 2 ABTS, ABTS radical scavenging assay (mg Trolox equivalent g−1 dried CBS); DPPH, DPPH radical scavenging assay (mg Trolox equivalent g−1 dried CBS); TFC, total flavonoid content (mg rutin equivalent g−1 dried CBS); TPC, total phenolic content (mg gallic acid equivalent g−1 dried CBS); Yield, yield (%, dry basis). 3 The unit of these compounds is µg component g−1 dried CBS. 4 The unit of inhibition zone is cm; the inhibition zone of the positive control (30 g C6H7KO2 in 50 mL water) against S. aureus is 1.28 ± 0.03 cm. 5 Data followed by the same superscript in the same row are not significantly different (p > 0.05).

      Table 4. 

      Yield, total phenolic content, total flavonoid content, antioxidant activity, chemical components qualified by UPLC–MS/MS, and inhibition zone of phenolic extract from cocoa bean shells1,2,5.

    • # Name of putative compounds MW (g mol−1) MF HE UME-S UME-W
      RT (min) PA (%) RT (min) PA (%) RT (min) PA (%)
      1 2,2-dimethoxybutane 118 C6H14O2 3.70 80.8 3.69 30.9 3.70 13.0
      2 Undecane 156 C11H24 15.0 19.2 15.0 5.06 15.0 1.45
      3 2H-cyclohepta[b]furan-2-one, 6-[1-(acetyloxy)-3-oxobutyl]-3,
      3a,4,7,8,8a-hexahydro-7-methyl-3-methylene-      		 306 C17H22O5 nd 30.8 0.700 nd
      4 Cyclo(L-prolyl-L-valine) 196 C10H16N2O2 nd 33.2 1.54 33.2 1.15
      5 Caffeine 194 C8H10N4O2 nd 33.8 61.8 33.8 84.4
      1 HE, heating-aided extraction; UME-S, ordered ultrasound-microwave-aided extraction under optimized conditions using the mixture of sodium acetate, citric acid, and water (ratio of 1:3:4, v/v/v) as extraction solvent; UME-W, ordered ultrasound-microwave-aided extraction under optimized conditions using water as extraction solvent. 2 MW, molecular weight; MF, molecular formula; nd, not detected; RT, retention time; PA, peak area.

      Table 5. 

      Components detected in phenolic extracts from cocoa bean shells by GC–MS/MS1,2.