# Advanced and Potential Methods for Extraction of Bioactive Compounds from Avocado Peel--A Review
## 5 Potential Techniques for Extraction of Bioactive Compounds from Avocado Peel
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**Extraction Method** & **Important Finding** & **Ref.** \\ \hline Enzymatic-assisted extraction & The avocado peel extract treated by peptidase showed higher total phenolics (45.46 mg GAE/g DW) and antioxidant activities (FRAP: 1547.00 \(\upmu\)molTE/g, DPPH: 243.93 \(\upmu\)molTE/g, ABTS assay: 211.96 \(\upmu\)molTE/g) than the methanolic extract. & [70] \\ \hline Total phenolic content (TPC) of avocado peel (296.5–515.1 mg/100 g DM) and TPC of avocado & \\ between TPC of avocado pulp (389.3–663.93 mg/100 g DM). The antioxidant capacity of avocado peel & \\ extract (ABTS: 6.407–20.96 mmol TE/g, DPPH: 9.341–22.85 \(\upmu\)mol TE/g) was & [71] \\ lower than avocado seed extract (ABTS: 14.70–24.54 mmol TE/g, DPPH: \\ 24.78–52.08 \(\upmu\)mol TE/g), but higher than avocado pulp & \\ (ABTS: 3.587–5.748 mmol TE/g, DPPH: 0.635–0.962 \(\upmu\)mol TE/g) and avocado oil & \\ (ABTS: 0.320–0.561 mmol TE/g, DPPH: 0.040–0.351 \(\upmu\)mol TE/g). & \\ \hline Natural deep eutectic solvent (NaDES) extraction & The best solvents used were choline chloride-acetic acid and -lactic acid., The deep eutectic solvents were more efficient than ethanol. The extract contained higher phenolics (92.03 \(\pm\) 2.11 mg GAE/g DAP) and flavonoid content & [48] \\  & (186.01 \(\pm\) 3.27 mg RE/g DAP) than conventional extract with ethanol. & \\ \hline Pressurized liquid extraction & The extraction with pure water (without ethanol) at 100 bar and 40 \({}^{\circ}\)C obtained a high extraction yield (26.8 \(\pm\) 0.9\(\%\)), antioxidant capacity (ABTS: 3350 \(\pm\) 179 \(\upmu\)mol TE/g dry extract, ORAC: 0.14 \(\pm\) 0.01 \(\upmu\)m), total phenol content (505 \(\pm\) 25 mg GAE/g dry extract), and acetylcholinesteraseinehition (33.6 \(\pm\) 2.9 \(\upmu\)g/mL). & [72] \\ \hline \multicolumn{3}{c}{The total phenolic content of avocado peel extract was 158.8 \(\pm\) 25.9 mg GAE/g} \\ \multicolumn{3}{c}{DE—higher than the phenolic content of avocado seed tegument extract} \\ (9.5 \(\pm\) 0.16 mg GAE/g DE) but lower than avocado seed extract (11.9 \(\pm\) 0.05 mg GAE/g DE). The antioxidant capacity of avocado peel extract was & [65] \\  & 1329.4 \(\pm\) 492.1 \(\upmu\)mol TE/g DE of DPPH, 829.8 \(\pm\) 445.4 \(\upmu\)mol TE/g DE of ABTS, and 3215.1 \(\pm\) 668.4 \(\upmu\)mol Fe\({}^{2+}\)/g DE of FRAP. & \\ \hline Supercritical fluid extraction & Avocado peel extract contained phenolic acid, flavonoid, quercetin, and catechchin. & \\  & The production cost is 5.52 USD/kg for stand-alone extraction processes, with & [37] \\  & profit margins of 21.14\(\%\). & \\ \hline \multicolumn{3}{c}{The supercritical fluids extraction increased 14.20–17.14\(\%\) extraction yield but} \\ \multicolumn{3}{c}{decreased catechching concentration on Lorena variety. The optimal conditions} \\ \multicolumn{3}{c}{during supercritical fluids extraction were 60 C, 0.2 mg avocado peel every liter} \\ \multicolumn{3}{c}{of solvent, 30 kHz, and 60 min. The minimum extraction cost was 8.21 USD/kg} \\ \multicolumn{3}{c}{of avocado peel extract.} \\ \hline Aqueous two-phase extraction & The extraction based on polyethylene glycol with 24.9–14.5\(\%\) sodium nitrate and \\  & 12.2–15.5\(\%\) magnesium sulfate recovered more than 82\(\%\) flavonoids, phenols, and condensable tannin from the avocado peel. & [52] \\ \hline Hydrothermal treatment & This extraction was due to increased oligosaccharides and polyphenonics & \\  & recovery. The optimal extraction obtained by 150 \({}^{\circ}\)C with the highest & \\  & oligosaccharide recovery (14.3 g oligosaccharides/100 g avocado peel) and & [74] \\  & antioxidant phenolics recovery (3.48 g gallic acid equivalents/100 g AP and \\  & 10.80 g Trolox equivalents/100 g avocado peel measured with ABTS** assay). & \\ \hline Combination of maceration & The extract was divided into ethanolic extract, liquid phases, and heavy bio-oils. & \\  & and hydrothermal & Ethanolic extract had the highest proanthocyanidins content. The liquid phases & [75] \\  & carbonization & were high in total phenols, flavonoids, and hydroxynamic acids. Heavy bio-oils & \\  & inhibited tyrosinase and elastase activities significantly. & \\ \hline \hline \end{tabular}
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