Abstract
Rich in phenolic compounds, Moringa oleifera leaf extract (ME) exhibits significant antioxidant activity both in vitro and in vivo. ME has already been widely used in fields of medicine, functional food, and cosmetics. Ultrasonic extraction (UE) method has been improved to be one of the most effective ways to extract phenols from M. oleifera leaves. The purpose of this study was to optimize ultrasonic extraction of phenols by response surface methodology (RSM). Four parameters were discussed, such as ethanol concentration, solvent-sample ratio, extraction temperature, and extraction time. Also, purification methods of the crude ME by organic solvent extraction and column chromatography were examined. Antioxidant activities of ME and each fraction were evaluated by DPPH, ABTS, and hydroxy radical-scavenging activities and reducing power. The phenol content of the purified ME reached up to 962.6 mg RE/g, extremely higher than the crude extract 107.22 ± 1.93 mg RE/g. The antioxidant activity of the purified ME was also significantly improved. Furthermore, phenols were identified by using the HPLC-MS method, and the results showed that there were 6 phenolic acids and derivatives and 7 flavonoids in ME. Quercetin-3-O-β-D-glucoside isolated from ME showed excellent DPPH and ABTS radical-scavenging abilities, which were comparable to VC.
Highlights
Moringa oleifera Lam. has been widely used as a nutritional supplement to reduce malnutrition and some ailments [1]
Many extraction methods have been studied for phenolic compounds extraction from M. oleifera, such as ultrasonic extraction (UE), subcritical water/ethanol extraction, and microwave-assisted extraction [9,10,11]. ese are several heat-sensitive hydroxyl-type substituents existing in Moringa oleifera leaf extract (ME), such as kaempferol diglycoside and its acetyl derivatives [12, 13]
The optimization of UE was established for improving the phenolic compounds from M. oleifera leaves
Summary
Moringa oleifera Lam. has been widely used as a nutritional supplement to reduce malnutrition and some ailments [1]. Rich in phenolic acids and avonoids, M. oleifera extract exhibits signi cant antioxidant activity both in vitro and in vivo [3, 4]. Many extraction methods have been studied for phenolic compounds extraction from M. oleifera, such as ultrasonic extraction (UE), subcritical water/ethanol extraction, and microwave-assisted extraction [9,10,11]. Microwave-assisted extraction always employs a temperature higher than 150°C. e UE method has been proved to be the most e ective way to extract phenolic compounds from M. oleifera [3]. It has been reported that there were signi cant di erences in the phenolic pro le, nutritional value, and antioxidant activity of M. oleifera from many di erent cultivars [15, 16]
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