Table 1.
Extraction methods used by other authors to extract anthocyanins from onions.
| Publication Year | Extraction Method | Anthocyanins Analyzed 1 | Onion Variety | Total Anthocyanins Measured (mg g−1) | Reference |
|---|---|---|---|---|---|
| 2020 | Homogenization (1 min), sonication (30 min), and centrifugation. The supernatant residue was re-extracted twice | 1, 2, 3, 4, 5, 6, 7 | Honeysuckle red onions and sweet Italian red onions | Honeysuckle 0.103 ± 2.206 Sweet Italian 0.086 ± 1.843 |
[25] |
| 2019 | Centrifugation at 3214 g. The supernatant residue was re-extracted until the samples turned colourless | 1, 2, 4, 5 | Red onion | 0.056 | [26] |
| 2018 | Sonication at 60 °C for 1 h | Total anthocyanins measured by colourimetric methods | Red onions from eight different cultivars | 0.02 ± 0.01–0.12 ± 0.01 | [27] |
| 2018 | Three different methods: maceration (24 h), percolation (8 h), reflux and Soxhlet method (2 h). The extractions were repeated three times | 1, 4, 5, 8 | Bima Brebes and Maja Cipanas | Maceration: 1.463 ± 0.013 and 1.181 ± 0.008 Percolation: 0.328 ± 0.010 and 0.597 ± 0.015 Reflux: 1.415 ± 0.08 and 1.449 ± 0.013 Soxhlet: 0.218 ± 0.021 and 0.342 ± 0.022 |
[28] |
| 2017 | Sonication in an ultrasonic bath at 4 °C for 24 h | 1, 4, 11, 12, 13 | Dark-red onion cultivar ‘Xiu Qiu’ and white onion cultivar ‘Ring Master’ | Xiu Qui: 0.3587 ± 0.0054 Ring Master: 0.0142 ± 0.0087 |
[29] |
| 2013 | Extraction at 4 °C, overnight or for 2 h | Total anthocyanins measured by colourimetric methods | Red onion | 0.9966 | [30] |
| 2012 | The extraction was carried out on a rotary shaker overnight (15 h; 400 rpm) at room temperature | 1, 4, 9, 14 | Red onion Pier-C and Red onion Pearl | Red onion Pier-C: 0.0777 ± 0.0038 Red onion Pearl: 0.1895 ± 0.0363 |
[11] |
| 2011 | Centrifugation at 1200 rpm (3 min) and agitation (15 min). Each homogenate was extracted three |
1, 2, 4, 5, 6 | Red onion “Vermelha da Povoa” |
0.059 | [31] |
| 2011 | Shaking (15 min) and centrifugation. Two additional extractions were performed for each sample | 1, 2, 4, 5, 6 | Red onion “Vermelha da Povoa” |
0.003 ± 0.016 | [32] |
| 2010 | Incubating (1 h) at room temperature with alternative shaking and subsequently centrifuged at 4000 rpm for 15 min at 28 °C. Two additional extractions were performed |
1, 2, 4, 5, 6, 9, 10, 15 | Red Onion Vermelha da Povoa, improved Vermelha da Povoa and Red Creole |
Vermelha da Povoa: 0.057 ± 0.018 Improved Vermelha: 0.128 ± 0.046 Red Creole: 0.286 ± 0.08 |
[14] |
1. Compounds analyzed: 1. cyanidin 3-O-glucoside, 2. cyanidin 3-O-laminaribioside, 3. delphinidin 3,5-O-diglucoside, 4. cyanidin 3-O-(6″-malonoylglucoside), 5. cyanidin 3-O-(6″-malonoyl-laminaribioside), 6. Peonidin 3-O-malonoylglucoside, 7. cyanidin 3-O-(malonoyl)-(acetyl)-glucoside, 8. cyanidin 3-O-arabinoside, 9. cyanidin 3-O-(3″-malonilglucósido), 10. pedonidina 3-O-glucósido, 11. delphinidin 3-O-diglucoside, 12. delphinidin 3-O-glucoside, 13. delphinidin aglycon, 14. cyanidin 3-O-(malonyl)diglucoside, 15. cyanidin 3-O-dimalonylaminaribioside.