Effect of Growing Area on Total Polyphenols, Flavonoids, Tannins and Antimicrobial Activity in Quercus suber L. Acorn Oil

Abstract

The investigation was conducted on oil extracted from mature acorns of Quercus suber L. harvested from three different Tunisian sites. The content of total polyphenols, tannins and flavonoides were determined. Antimicrobial activities were also evaluated. Antimicrobial activity of this oil was tested against: Escherichia Coli, Bacillus subtilis and Candida albicans. Gentamicin and amphotericin B were respectively used as a positive reference for bacteria and fungi. Discs without samples were used as a negative control. Fixed oil of cork oak acorn was extracted by the soxhlet apparatus. The oil content, expressed as dry weight, ranged from 0.9 to 2.02%. Fixed oil extracted from acorns of cork oak showed a high amount of total polyphenols 18.93 mg GAE/g. Amounts of flavonoids and tannins were also important. The results showed a significant antimicrobial effect against B. subtilis and C. albicans with inhibition diameter of 10.6 mm and 9.8 mm, respectively.

Acorn (Quercus spp.) Consumption in Algeria

“…The other species present in Algeria are slightly consumed due to their important tannin content, while, none of the informants reported consuming Quercus faginea acorns because of their pronounced bitter and high astringent taste (Kaya and Kamalak 2012; Miranda et al 2017). Despite the pronounced astringent taste of some acorns, several studies have been conducted on the health benefits of tannins present in oak fruits (Kaya and Kamalak 2012; Mezni et al 2021; Stiti, Mezni and Zarroug 2022).…”

“…Several studies attest to the nutritional and therapeutic benefits of acorns; indeed, acorns contain carbohydrates, proteins, and fat, presenting a higher nutritional value. In addition, acorns are rich in unsaturated fatty acids, known for their health-beneficial effects (Taib, Bouyazza and Lyoussi 2020), acorns also contain secondary metabolites compounds such as tannins, polyphenols, and vitamins (C, A, and E), which are important in the human diet as an important source of antioxidants (Mezni et al 2021). Furthermore, acorns have also been recorded to be used against hemorrhoids, diabetes, and heart diseases as a remedy in Mediterranean traditional medicine, due to their several biological activities such as antimicrobial, antiulcerogenic, anthelmintic, and anti-inflammatory (Gezici and Sekeroglu 2019; Martins et al 2020; Vinha et al 2020).…”

“…Lately, it has been noted that acorn-based goods production has increased in number and diversity; acorn-based products are proposed in biscuits (Pasqualone et al 2019), coffee substitutes (Díaz-Rojas et al 2019), chocolate (Marc et al 2021), and vegetable oil (Taib, Bouyazza and Lyoussi 2020, Mezni et al 2021); in Algeria, the use of acorn flour as a substitute for wheat flour could reduce dependency on imported wheat (Algeria is one of the biggest wheat importers worldwide) and promote more sustainable and self-sufficient food programs. Moreover, the production of acorn-based goods can generate new economic opportunities, especially for rural population where oak forests are abundant (Dahmani-Megrerouche 2002; FAO 2021).…”