Table 1.
Extraction of polyphenols from red pitaya.
| Extraction Methods | Compounds | Quantification Methods | Concentrations (Dry Weight) | Reference |
|---|---|---|---|---|
| Freeze-dried fruit pulps were mixed with 80% ethanol (1:2) in an ultrasonic bath in the dark for 30 min at 60 °C followed by centrifugation at 5000× g for 15 min. The supernatant was collected, and ethanol was evaporated by a rotary evaporator. | Phenolics | Folin-Ciocalteu reagent | 48.30 ± 0.10 mg GAE/100 g | [23] |
| Flavonoids | Aluminium chloride method (Catechin was used as a standard) | 31.2 ± 1.30 mg CE/100 g | ||
| Beta-cyanins | McIlvaine buffer method (at 538 nm) | 20.4 ± 1.90 mg BCE/100 g | ||
| A microwave-assisted extraction with different ratios of solid/water, from 1/50–1/150 g/mL, at 600 W for 5–65 min) was used to extract phenolic compounds and beta-cyanins in freeze-dried pulps followed by centrifuged twice at 4000× g for 10 min each time. | Phenolics | HPLC-DAD-ESI/MS | 2.39–10.14 mg/g | [24] |
| Flavonoids | HPLC-DAD | 3.22–5.04 mg/g | ||
| Beta-cyanins | HPLC-DAD | 0.43–1.66 mg/g | ||
| Freeze-dried peels were mixed with different proportions of ethanol (from 30% to 60%) at varied solvent/solid ratios (10:1–30:1) in an ultrasonic bath in the dark for 5–25 min at different temperatures (30–70 °C). | Phenolics | Folin-Ciocalteu reagent | 4.51–8.54 mg GAE/g | [2] |
| Beta-cyanins | McIlvaine buffer method (at 537 nm absorption) | 1.02–1.60 mg BCE/g | ||
| Freeze-dried peels were homogenized with deionized water at pH 5.5, 40 °C for 20 min. The extract was kept in the dark in a refrigerator until analysis. | Phenolics | Folin-Ciocalteu reagent | 35.81 ± 3.11 mg GAE/g | [26] |
| Beta-cyanins | Liquid Chromatography Mass Selective Detector (LCMS) | 15.21 ± 0.04 mg/g | ||
| A comparison of solvent extraction and supercritical fluid extraction was conducted. Oven-dried pitaya peel or flesh (5 g) were extracted with 50 mL ethanol solvent (100%, 90%, 70%, 50%, 30%, 10% and 0%) for 20 min at 25 °C with a magnetic stirrer at 300 RPM followed by filtrated through a Whatman No. 4 paper. Samples (5 g) were treated with a supercritical fluid extraction system with 99.9% purity of CO2 at 2 mL/min flow rate and 10% ethanol solvent (50 mL). The extraction was conducted under 25 MPa pressure and 50 °C. | Phenolics | Folin-Ciocalteu agent | 139 ± 0.41 (peel, 50% ethanol), 105 ± 0.53 (flesh, 50% ethanol), 135.75 (peel, supercritical fluid) and 99.42 (flesh, supercritical fluid) GAE/100 g | [27] |
| Beta-cyanins | McIlvaine buffer method (at 538 nm) | 28.44 ± 1.98 (peel, 50% ethanol), 84.25 ± 0.89 (flesh, 50% ethanol), 24.58 ± 2.16 (peel, supercritical fluid), and 91.20 ± 2.23 (flesh, supercritical fluid) mg/100 mL | ||
| The juice was extracted by a juice extractor and filtered through a hand-held kitchen sieve followed by centrifugation at 3000× g for 10 min at 4 °C. The supernatant was vacuum filtered through a filter paper (F1001, CHMLAB Group) and stored at −20 °C until analysis. | Phenolics | Folin-Ciocalteu agent | 17.80 ± 0.70 mg GAE/100 g | [28] |
| Beta-cyanins | McIlvaine buffer method (at 537 nm) | 0.20 ± 0.01 mg BCE/L | ||
| Freeze-dried red pitaya peel, pulp and seed were mixed in a hydroalcoholic solution at pH 2 to obtain the extracts. The extracts were filtrated, and the solvent was evaporated by vacuum drying under reduced pressure. | Phenolics | Folin-Ciocalteu agent | 294.8 ± 12.9 (peel), 277.6 ± 14.2 (pulp) and 375.1 ± 12.6 (seed) mg GAE/g | [25] |
| Flavonoids | Aluminium chloride method (quercetin was used as a standard) | 193.8 ± 11.7 (peel), 177.4 ± 12.5 (pulp), and 264.4 ± 10.8 (seed) mg QE/g | ||
| Anthocyanin | Modified pH differential method (cyanidin chloride as positive control) | 135.4 ± 9.3 (peel) and 159.7 ± 8.9 (pulp) mg CCE/g | ||
| Oven-dried peels or seeds (0.5 g) were homogenized with 80% methanol (15 mL) on ice for 15 min using Ultra-Turrax homogeniser followed by centrifugation at 4000× g for 15 min at 4 °C. The supernatant was re-extracted twice before store in a freezer at −20 °C and covered with aluminium foil. | Phenolics | Folin-Ciocalteu reagent | 0.18 ± 0.01 and 0.31 ± 0.02 g/100 g | [29] |
| Air-dried seed powder ( <0.85 mm particle-sized) were extracted by using 90% ethanol (1:10) in an Innova 4000 incubator shaker for 24 h at 30 °C and 150 rpm. The extracts were filtrated through Whatman No. 4 filter paper followed by evaporation at 40 °C to remove solvents. | Phenolics | Folin-Ciocalteu reagent | 13.56 ± 2.04 mg/g | [30] |
| Catechin | HPLC | 3.60 ± 2.33 mg/g |