Optimization of Ultrasound-Assisted Extraction of Phenolic Compounds from Black Locust (Robiniae Pseudoacaciae) Flowers and Comparison with Conventional Methods

Abstract

The aim of this study was to optimize the ultrasound-assisted extraction of phenolic compounds from black locust (Robiniae pseudoacaciae) flowers using central composite design. The ethanol concentration (33–67%), extraction temperature (33–67 °C), and extraction time (17–33 min) were analyzed as the factors that impact the total phenolic content. The liquid-to-solid ratio of 10 cm3 g−1 was the same during extractions. The optimal conditions were found to be 59 °C, 60% (v/v) ethanol, and extraction time of 30 min. The total phenolic content (TPC = 3.12 gGAE 100 g−1 dry plant material) and antioxidant activity (IC50 = 120.5 µg cm−3) of the extract obtained by ultrasound-assisted extraction were compared with those obtained by maceration (TPC = 2.54 gGAE 100 g−1 dry plant material, IC50 = 150.6 µg cm−3) and Soxhlet extraction (TPC = 3.22 gGAE 100 g−1 dry plant material, IC50 = 204.2 µg cm−3). The ultrasound-assisted extraction gave higher total phenolic content and better antioxidant activity for shorter extraction time so that it represents the technique of choice for the extraction of phenolic compounds. The obtained extract, as the source of antioxidants, can be applied in the pharmaceutical and food industries.

Antioxidant Activity of Polyphenolic Plant Extracts

“…The results showed that extraction time had the greatest influence on the total polyphenolic content, followed by the extraction temperature and ethanol concentration [40]. The optimal extraction conditions were 60% (v/v) ethanol, 59 • C, and 30 min at the liquid-to-solid ratio of 10 cm 3 g −1 [40]. Moreover, the UAE gave a higher yield of polyphenols than the maceration and Soxhlet extraction [40].…”

“…The most common of such "green methods" are microwave assisted (MAE), ultrasound assisted (UAE), pulsed electric field assisted, and enzyme assisted extractions, infrared irradiation (IR), pressurized liquid and supercritical fluid extractions [39]. Gajic et al [40] investigated the optimal conditions for isolating polyphenols from black locust (Robiniae pseudoacaciae) flowers using UAE. The results showed that extraction time had the greatest influence on the total polyphenolic content, followed by the extraction temperature and ethanol concentration [40].…”

“…Gajic et al [40] investigated the optimal conditions for isolating polyphenols from black locust (Robiniae pseudoacaciae) flowers using UAE. The results showed that extraction time had the greatest influence on the total polyphenolic content, followed by the extraction temperature and ethanol concentration [40]. The optimal extraction conditions were 60% (v/v) ethanol, 59 • C, and 30 min at the liquid-to-solid ratio of 10 cm 3 g −1 [40].…”

“…The optimal extraction conditions were 60% (v/v) ethanol, 59 • C, and 30 min at the liquid-to-solid ratio of 10 cm 3 g −1 [40]. Moreover, the UAE gave a higher yield of polyphenols than the maceration and Soxhlet extraction [40]. The main polyphenols found in the extract were rutin, epigallocatechin, ferulic acid, and quercetin [40].…”

Optimization of Ultrasound-Assisted Extraction Condition for Phenolic Compounds, Antioxidant Activity, and Epigallocatechin Gallate in Lipid-Extracted Microalgae

“…The significance of each coefficient was determined using the f -test and p-value. According to the results, the model was highly significant when the computed f -value was greater than the tabulated f -value and the probability value was low (p < 0.05) [25]. ANOVA showed that the model's f -values were 9.09 and 5.28 for the TPC and AA, respectively, with probability (p < 0.001), implying there was only a 0.1% chance that this large f -value occurred because of noise and the model was remarkably significant and can be used for subsequent optimization designs.…”