Total Monomeric Anthocyanin, Total Phenolic Content and Antioxidant Activity of Extracts from Eggplant (Solanum Melongena L.) Peel Using Ultrasonic Treatments

Abstract

Eggplant peel is a less studied source in terms of bioactive compound extraction from industrial residues, although its high content of anthocyanin and phenolic compounds is known. The method described here uses three different solvents, namely ethanol, methanol and 2-propanol, for phenol, anthocyanin and antioxidant activity extraction. The extraction yields of total monomeric anthocyanin (TMA), total phenolic compound (TPC) and antioxidant activity (AA) from eggplant peel were optimized by varying the frequency, temperature and time of ultrasonic treatment. The influence of interactions between process parameters on extraction efficiency was also studied. The highest concentrations achieved were 7.842 g/100g in the case of TPC (2-propanol, 45 kHz, 60°C for 40 min), 2,275 mg/kg in the case of TMA (methanol, 45 kHz, 50°C for 50 min) and 10.18 μM Trolox/kg in the case of AA (methanol, 0 kHz, 60°C for 20 min). The suitable parameters to achieve the highest concentration of antioxidants were determined for each solvent as follows: ethanol -28.8 kHz, 67.1°C and 49.5 min; methanol -45 kHz, 50°C and 53.75 min; and 2-propanol -30.6 kHz, 70°C and 60 min. PRACTICAL APPLICATIONSThis study presents a significant improvement in eggplant peel extraction using ultrasonic-assisted extraction of bioactive compounds. During ultrasonication, the extraction of bioactive compounds in eggplant peel increases because the solvent has been energized. The ultrasound-assisted extraction of bioactive compounds is a fast, economical and green alternative to the current techniques used in the extraction industry.

Extraction and characterization of bioactive compounds from eggplant peel using ultrasound – assisted extraction

“…Among the extraction solvents, acidified methanol was the most efficient solvent for extraction of anthocyanins from eggplant peel, followed by acidified ethanol and acetone. These data are agreeing with results reported by many authors (Dranca and Oroian, 2015;Boulekbache-Maklhouf et al, 2013). Similarly to Todaro et al (2009) who reported that ethanolic extract obtained from eggplant peel contains five anthocyanins with the major ones were delphinidin-3-rutinoside followed by delphinidin-3-rutinoside-5-glucoside, cyanidin-3-glucoside, delphinidin-3-glucoside and petunidin-3-rutinoside, we found the same anthocyanins profile (Figure 2), but the major was delphinidin-3-glucoside, followed by delphinidin-3-rutinoside, cyanidin-3-glucoside, petunidin-3-rutinoside and delphinidin-3-rutinozid-5-glucoside (Figure 2).…”

“…The eggplant peel methanolic extract has a profile which contains six anthocyanins presented in Figure1. The major ones were delphinidin-3-rutinoside followed by delphinidin-3-glucoside, cyanidin-3-rutinoside, delphinidin-3-rutinoside-5glucoside, malvidin-3-rutinoside-5-glucoside and petunidin-3-rutinoside as previously reported by many authors (Wu and Prior, 2005;Dranca and Oroian, 2015;Zaro et al, 2014). In a study conducted by Koponen et al (2007), used HPLC-DAD detection for analysis of anthocyanins from whole eggplant fruit using 80% aqueous methanol containing 2% of HCl in the extractions and it has identified delphinidin-3-glucoside and delphinidin-3-rutinoside as predominant anthocyanins.…”

“…All the eggplant peel extracts displayed the same anthocyanins content profile, where the delphinidin-3-rutinoside was the major anthocyanin found in the eggplant extracts (Todaro et al, 2009;Zaro et al, 2014;Dranca and Oroian, 2015;Ferarsa et al, 2018). Also, in this study, the effect of solvents extraction on the anthocyanins profile was investigated.…”

“…Different solvents have been used for the extraction of polyphenols from the eggplant peel powder. The extraction yield and the antioxidant activity of the natural extracts depended on the solvent used for the extraction (Dranca et al, 2015(Dranca et al, , 2016. The extraction of phenolic compounds from eggplant peel was performed using an ultrasonic treatment and three different solvents (methanol, ethanol and acetone) at 40˚C for 30 minutes.…”

Ultrasound-Assisted Extraction of Polyphenols from Crude Pollen

“…The increase of temperature may decrease the surface tension and the viscosity, which will promote the solvent penetration into the matrix and improve the extraction process [33,34]. Our results were in agreement with those reported in the case of polyphenol extraction from wild sage [35], bioactive compounds from aromatic plants [36], polyhenols and anthocyanin from eggplant [14,37] and polyphenols from propolis [21]. Table 2 shows the influence of time on the extraction yield, TPC and TFC.…”