Abstract
Red fruit oil (RFO) is a high-value oil that contains functional compounds, mainly phenolic compounds, providing antioxidant activity. Therefore, an optimal extraction method is essential to recover the RFO and phenolic compounds simultaneously. This research aimed to optimize the ultrasound-assisted extraction (UAE) for oil from red fruit using the Box-Behnken design combined with response surface methodology. The studied UAE factors, including sample-to-solvent ratio (1:3, 1:2, and 1:1 g mL−1), extraction temperature (60, 75, and 90 °C), and pulse duty-cycle (0.20, 0.50, and 0.80 s−1). Analysis of variance revealed that the three studied factors significantly influenced the recovered RFO, while the level of total phenolic compounds in the extracts was defined merely by extraction temperature (p < 0.05). These significant factors were then included in the optimization models (R2 > 0.99, lack-of-fit p > 0.05). The proposed UAE setting by the multiresponse optimization was an extraction temperature of 67 °C, a pulse duty-cycle of 0.50 s−1, and a sample-to-solvent ratio of 1:2.5 g mL−1. Subsequently, the extraction kinetic was evaluated, confirming full recovery at 60 min of extraction time. The developed method was then applied to extract six red fruit clones. Mbarugum clones provided high RFO recovery (9.60%), with an uppermost total phenolic compound of (42.63 mg GAE g−1) among the six red fruit clones. Additionally, the resulting RFO showed eminent antioxidant activities, indicated by excellent values of IC50 DPPH (37.69 mg L−1), IC50 FIC (30.43 mg L−1), FRAP reducing power (63.55 mg AAEA g−1), and IC50 ABTS (93.88 mg L−1). In contrast with a wet rendering method, UAE enhanced the RFO recovery by 53.02%, resulting in a higher level of total phenolic compounds. Henceforth, the proposed UAE method is a promising technique to substitute conventional oil production in the food and pharmaceutical industries.
Highlights
Our research showed that the total phenolic compounds (TPC) levels in Red fruit oil (RFO) by ultrasound-assisted extraction (UAE) were higher than in the wet rendering method (Figure 6)
The negative correlation between TPC and IC50 (DPPH and ABTS) indicated the positive correlation between phenolic content and antiradical scavenging activities. These findings indicated that phenolic compounds contributed significantly toward all antioxidant activities, except the IC50 value of Ferrous ion-chelating (FIC)
A Box-Behnken design combined with response surface methodology and multiresponse optimization was employed to determine the optimum conditions of red fruit oil extraction using UAE
Summary
RFO is valuable due to its nutritional and functional constituents, which expose intense natural antioxidants, including phenolic compounds [3]. A previous studies report, the red fruit extract exhibits a strong scavenge DPPH radical with an IC50 value ranging from 5.25 to 53.47 mg L−1. This value is mainly due to the phenolic compounds in the red fruit extract, which contribute 64.5% of free DPPH radical scavenging [5]. As RFO receives a higher price in the retail market over some oils extracted from sunflower and palm fruit, it is expected that the RFO will provide further benefits related to the antioxidant activity of phenolic compounds contained in the oil
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