Optimization of ultrasound assisted extraction of ergosterol from Agaricus bisporus L
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abstract
Mushrooms are appreciated worldwide, not only for their nutritional value and exquisite flavor and
texture, but also for their medicinal properties. There is scientific evidence demonstrating the benefits
of mushrooms ingestion due to their richness in bioactive compounds such as mycosterols, in
particular ergosterol [1]. Agaricus bisporus L. is the most consumed mushroom worldwide presenting
a high content of ergosterol, which represents 90% of its sterol fraction [2]. Thus, it is an interesting
matrix to obtain ergosterol, a molecule with a high commercial value. According to literature,
ergosterol concentration can vary between 3 and 9 mg per g of dried mushroom. Traditional methods
such as maceration and soxhlet extraction are being replaced by emerging methodologies such as
ultrasound assisted extraction in order to decrease the used solvent amount, the extraction time and,
of course, increasing the extraction yield [3]. In the present work, A. bisporus was extraction solvent
type (hexane and ethanol), ultrasound amplitude (50%, 75% and 100%) and sonication time (5 min,
10 min and 15 min). Moreover, in order to decrease the process complexity, it was evaluated the
pertinence of the saponification step. Ethanol proved to be the best solvent to extract higher levels of
ergosterol (671.5 ± 0.5 mg/100 g dw, at 75% amplitude for 15 min), once hexane was only able to
extract 152.2 ± 0.2 mg/100 g dw, in the same conditions. Nevertheless, the hexane extract showed
higher purity (11%) when compared with the ethanol counterpart (4%). Furthermore, in the case of
the ethanolic extract, the saponification step increased its purity to 21%, while for the hexane extract
the purity was similar; in fact, hexane presents higher selectivity for the lipophilic compounds
comparatively with ethanol. Overall, ultrasound assisted extraction proved to be an efficient
technology to maximize ergosterol extraction yield, but other emerging technologies such as
microwave assisted extraction can be applied with foreseen interesting results.
