Process optimization of microwave-assisted extraction of bioactive molecules from avocado seeds

Avocado seeds are an agroindustrial residue produced largely by avocado processing industries, which is accumulated in high quantities because it has low reuse due to its poor revalorization. The optimization of Microwave-Assisted Extraction (MAE) of bioactive compounds with high antioxidant capacity from avocado seeds were studied in the present work for the first time. Applying two experimental designs, using acetone 70 % and ethanol, the optimal conditions of extraction were found: 72.18 °C for 19.01 min and 71.64 °C for 14.69 min with 58.51 % of ethanol, respectively, to obtain extracts with highest antioxidant activity. The optimized extracts obtained with acetone and ethanol showed a high polyphenolic content (307.09 ± 14.16 and 254.40 ± 16.36 mg GAE/g extract) and high antioxidant activity measured by DPPH (266.56 ± 2.76 and 221.69 ± 20.12 mg ET/g extract), ABTS (607.28 ± 4.71 and 516.34 ± 11.81 mg ET/g extract) and ORAC (475.55 ± 47.82 and 495.25 ± 14.52 mg ET/g extract), proving MAE as a better technique than those previously reported for avocado seeds. Fiber residues obtained after MAE showed bonded phenolics compounds with relevant antioxidant activity, those obtained with ethanol. HPLC-ESI-MS analysis showed the presence of 20 different identified compounds, including phenolic acids, procyanidins dimer B and trimer A and B in different isomers forms, catechin, epicatechin and perseitol. MAE is a green, energy efficient and rapid tool for extractions of bioactive components from avocado seedswithout affecting their antioxidant activities representing an attractive alternative protocol in traditional herbal industry and medicine.