Abstract
The present study was conducted to optimize extraction process for defatted pitaya seed extract (DPSE) adopting response surface methodology (RSM). A five-level central composite design was used to optimize total phenolic content (TPC), total flavonoid content (TFC), ferric reducing antioxidant power (FRAP), and 2,2′-azino-bis (3-ethylbenzothizoline-6-sulfonic acid (ABTS) activities. The independent variables included extraction time (30–60 min), extraction temperature (40–80 °C) and ethanol concentration (60%–80%). Results showed that the quadratic polynomial equations for all models were significant at (p < 0.05), with non-significant lack of fit at p > 0.05 and R2 of more than 0.90. The optimized extraction parameters were established as follows: extraction time of 45 min, extraction temperature of 70 °C and ethanol concentration of 80%. Under these conditions, the recovery of TPC, TFC, and antioxidant activity based on FRAP and ABTS were 128.58 ± 1.61 mg gallic acid equivalent (GAE)/g sample, 9.805 ± 0.69 mg quercetin equivalent (QE)/g sample, 1.23 ± 0.03 mM Fe2+/g sample, and 91.62% ± 0.15, respectively. Ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF/MS) analysis identified seven chemical compounds with flavonoids constituting major composition of the DPSE.
Highlights
Pitaya, Hylocereus polyrhizus, or commonly known as dragon fruit in English or ‘Buah Naga’ inMalay, is oblong in shape with scaly structures on its outer peels
The final predictive equations generated by the software were expressed in terms of coded factors as shown in Equations (1)–(4) where the empirical correlation between time of extraction (A) temperatures (B) and ethanol concentrations (C) were established: Y(TPC) = + 109.53 + 2.66A + 17.60B + 9.23C − 13.83AB − 0.36AC − 3.96BC − 9.04A2 − 7.93B2 + 4.22C2 (1)
Antioxidant activity was based on Ferric Reducing Antioxidant Power (FRAP) and ABTS from Defatted Pitaya Seed Extract (DPSE) by analyzing the interaction effects between the independent variables
Summary
Hylocereus polyrhizus, or commonly known as dragon fruit in English or ‘Buah Naga’ in. Malay, is oblong in shape with scaly structures on its outer peels. It belongs to the family, Cactacae from the genus Hylocereous. Pitaya originates from Central and Northern South America and presently has become a recent fruit crop of interest being cultivated in Malaysia, Thailand, Vietnam, Australia, Taiwan, and other regions around the world. Other than appealing appearance of the fruit, pitaya has recently gained much attraction due to its high dietary contents [1,2]. The flesh of the fruit is tasty and sugary with numerous tiny and grainy black seeds. Seed oil from pitaya fruit has been successfully extracted and reported to be potentially
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