Abstract
SUMMARYMoringa stenopetala is a multipurpose plant having high nutritional and medicinal values. The aim of this study is to evaluate the effect of time and temperature of ultrasound-assisted extraction on bioactive compounds and antioxidant activities of M. stenopetala leaf extract. The ultrasound-assisted extraction took place at each of 30, 40 and 50 °C for 10, 20 and 30 min. The study also included the analysis of the interaction effects of time and temperature on the total phenolic content, total flavonoid content, antioxidant activity (ABTS and DPPH assay), FRAP and chelating activity. The highest total phenolic content, expressed in mg gallic acid equivalents per g dry mass, was 46.6 and total flavonoid content, expressed in mg catechin equivalents per g dry mass, was 20.4 at 40 °C for 20 min. Under the same conditions, the highest antioxidant activities evaluated by DPPH, ABTS and FRAP, expressed in mg Trolox equivalents per g dry mass, were 336.5, 581.8 and 133.3 respectively, and chelating activity, expressed in mg EDTA equivalents per g dry mass, was 28.4. The lowest amounts of bioactive compounds and antioxidant activities were observable when the extraction occurred at 50 °C for 30 min, followed by the extraction at lower temperature (30 °C) for shorter time (10 min). The morphological analysis of the residues obtained after extraction using scanning electron microscope indicated that there was a higher ultrasonic destruction of the structural components of the sample at longer extraction time. Therefore, ultrasound-assisted extraction at a temperature of 40 °C for 20 min is the best time-temperature combination to extract bioactive compounds from M. stenopetala leaves.
Highlights
Moringa stenopetala, often referred to as the African moringa tree, is a multipurpose tree with nutritional and medicinal values, used as oil source or for water clarification [1,2,3]
The maceration extraction gave higher total phenolic content (TPC) and total flavonoid content (TFC) than the ultrasound-assisted extraction at 30 °C for 10 min and 50 °C for 30 min (Table 1), which might be due to the insufficient extraction time or to the possible destruction of the extracted TPC and TFC because of longer exposure to the ultrasound at higher temperature, respectively
Even if conventional extraction technique has comparable yield of TPC and TFC to some time and temperature combinations of ultrasound-assisted extraction, the time of the extraction was too short compared to maceration extraction that took 24 h
Summary
Often referred to as the African moringa tree, is a multipurpose tree with nutritional and medicinal values, used as oil source or for water clarification [1,2,3]. The antioxidant activity of M. stenopetala leaf extract is far superior to the antioxidant activity of M. oleifera leaf extract [8] This plant is a potential source of natural antioxidants [8,10] that serve as anti-inflammatory [11], anti-atherosclerotic [12,13], antihypertensive agents as well as for the prevention and treatment of haematological and hepatorenal disorders [14]. Because of these numerous medicinal benefits and nutritional values, this plant can be popularized and promoted for the development of various food and pharmaceutical products
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