Optimization of extraction of phenolics from leaves of Ficus virens

Abstract

In this research, the conditions for extraction of phenolics from leaves of Ficus virens were optimized using response surface methodology (RSM). The extraction abilities of phenolics (EAP) and flavonoids (EAF), the 2,2-diphenyl-1-pierylhydrazyl (DPPH) free-radical scavenging potential, and the ferric reducing/antioxidant power (FRAP) were used as quality indicators. The results of single-factor experiments showed that temperature, ethanol concentration, extraction time, and the number of extraction cycles were the main influencing variables, and these provided key information for the central composite design. The results of RSM fitted well to a second degree polynomial model and more than 98% of the variability was explained. The ideal extraction conditions for EAP, EAF, DPPH free-radical scavenging potential, and FRAP were obtained. Considering the four quality indicators overall, the ideal extraction conditions were 58% ethanol at 57 °C for 37 min with three extraction cycles. At the ideal extraction conditions, the values of EAP, EAF, DPPH free-radical scavenging potential, and FRAP were 5.72%, 3.09%, 58.88 mg ascorbic acid equivalent (AAE)/g dry weight (DW), and 15.86 mg AAE/g DW, respectively. In addition, linear correlations were observed between EAP, EAF, and antioxidant potential.

Fig. 1

Influences of ethanol concentration (a), extraction time (b), extraction temperature (c), and solid-to-solvent ratio (d) on EAP and EAF from leaves of F. virens Data are expressed as mean±SD, n=3. The same letters in the columns indicate no significant difference (Tukey’s test, P>0.05)

Fig. 2

Influences of ethanol concentration (a), extraction time (b), extraction temperature (c), and solid-to-solvent ratio (d) on the DPPH free-radical scavenging potential and FRAP of phenolics from leaves of F. virens Data are expressed as mean±SD, n=3. The same letters in the columns indicate no significant difference (Tukey’s test, P>0.05)

Fig. 3

Effects of the number of extraction cycles on EAP and EAF from leaves of F. virens Data are expressed as mean±SD, n=3. The same letters in the columns indicate no significant difference (Tukey’s test, P>0.05)

Fig. 4

Effects of the number of extraction cycles on the DPPH free-radical scavenging potential and FRAP of phenolics from the leaves of F. virens Data are expressed as mean±SD, n=3. The same letters in the columns indicate no significant difference (Tukey’s test, P>0.05)

Fig. 5

Tri-dimensional response surface contour plots showing the effect of co-variance in ethanol concentration (X ₁)/extraction time (X ₂) (left), ethanol concentration (X ₁)/extraction temperature (X ₃) (middle), and ethanol concentration (X ₁)/number of cycles (X ₄) (right) on the EAP and EAF from leaves of F. virens

Fig. 6

Tri-dimensional response surface contour plots showing the effect of co-variance in ethanol concentration (X ₁)/extraction time (X ₂) (left), ethanol concentration (X ₁)/extraction temperature (X ₃) (middle), and ethanol concentration (X ₁)/number of cycles (X ₄) (right) on the DPPH free-radical scavenging potential and FRAP of polyphenols from leaves of F. virens