Obtaining antioxidant compounds from the endophytic fungus Diaporthe schini using heat- and ultrasound-assisted extraction

Abstract

Ultrasound-assisted extraction (UAE) of antioxidant compounds from Diaporthe schini biomass using ethanol as solvent was performed and the results were compared with heat-assisted extraction (HAE; conventional technique). Ultrasound intensity (17–85 W cm−2) and pulse cycle (0.50–1.00) were evaluated according to a Central Composite Rotatable Design (CCRD) to obtain the highest extraction yield. The HAE was studied at 30 and 50 °C. In the validation condition (85 W cm−2 and 0.93) of the UAE the extraction yield and antioxidant capacity (DPPH) were 22.30 ± 0.47% and 91.35 ± 0.27%, respectively. The best extraction yield (8.34 ± 0.38%) and antioxidant activity (91.32 ± 0.98%) of the HAE were observed at 50 ºC. The GC/MS analysis of the UAE extracts showed the presence of methyl 9,12 octadecadienoate (Z, Z)-, ethyl ester of hexadecanoic acid, ethyl octadec-9-enoate, and 1,4-diaza-2,5-dioxo-3-isobutyl bicyclo[4.3.0]nonane, which could be responsible for the antioxidant activity observed. This study was the first attempt to optimize the UAE parameters for the antioxidant compounds extraction from Diaporthe schini. UAE improved the extraction yield and reduced the extraction time in relation to HAE.