Optimization of an Ultra-Sonication Extraction Method for Major Compounds Found in Mondia whitei Using Design of Experiment

Abstract

Optimum extraction conditions are vital in quality control methods to enable accurate quantification of the compounds of interest. An ultra-sonication method was developed for the extraction of seven major compounds found in Mondia whitei. Extraction temperature, time, power, frequency, percentage of ethanol in water and solvent to sample ratio were screened to access their significance on the percentage recovery of the compounds of interest. These parameters were screened using Descriptive screening design. Extraction temperature, solvent to sample ratio and the interaction between temperature and percentage ethanol in water were found to have a significant effect on the response. These parameters were then optimized using central composite design. The optimum conditions were found to be 66.1% ethanol in water, 70 °C temperature and 3 mL: 5 mg solvent to sample ratio. This method was successfully applied in the development of a quality control method for the seven compounds in Mondia whitei samples.

Keywords: Mondia whitei; central composite design; descriptive screening design; extraction; ultra-sonication.

Figure 1

Pareto chart showing the effects of the critical quality parameters on the response.

Figure 2

Surface and contour plots showing percentage recovery as function of the effects temperature and solvent ratio (S:S) while keeping percentage ethanol constant (a); effects of percentage ethanol and solvent ratio (S:S) while keeping temperature constant (b); and effects of percentage ethanol and temperature while keeping solvent ratio constant (c).

Figure 3

Surface and contour plots showing percentage recovery as function of the effects temperature and solvent ratio while keeping percentage ethanol constant (a); effects of percentage ethanol and solvent ratio while keeping temperature constant (b); and effects of percentage ethanol and temperature while keeping solvent ratio constant (c).

Figure 4

The optimum conditions predicted using the Minitab v18 software (State College, PA, USA).

Figure 5

Chromatogram representing the separation of the Mondia whitei roots powder spiked with the compounds of interest under optimised conditions by gradient elution mode; at 0 min 25% B, 2 min 40% B, 3 min 65% B, 4 min 100% B with a run time of 6.5 min. Injection volume of 5 µL, flow rate of 1.3 mL min⁻¹ and temperature of 25 °C.

Figure 6

Typical chromatogram of separation of the C 1–7 under optimised conditions by gradient elution mode; at 0 min 25% B, 2 min 40% B, 3 min 65% B, 4 min 100% B with a run time of 6.5 min. Injection volume of 5 µL, flow rate of 1.3 mL min⁻¹ and temperature of 25 °C.