Harnessing thermal spring water and hydrophobic eutectic solvent for galactoglucomannans, glucans and phenolics recovery from Evernia prunastri and their potential biological applications

Abstract

Lichens produce polysaccharides scarcely studied, in addition to secondary metabolites, that can exhibit high bioactivity. The aim of this work is to evaluate the efficiency of subcritical water extraction using thermal spring water and hydrophobic eutectic solvent for the extraction of these compounds. Subcritical water extraction of E. prunastri compounds was performed between 150 and 190 °C with distilled or with thermal spring water, combined or not with eutectic solvent men:lau as modifier. The biochemical composition of the polysaccharide extracts from each process (P-D for distilled water, P-T for thermal spring water, P-DM and P-TM when the eutectic was added) and of the soluble liquid extracts free from the precipitated polysaccharides (E-D, E-T, E-DM and E-TM) was analyzed as well as their antioxidant capacity and biological activity against herpes viruses. After purification through resin of E-T170 and E-TM150, extracts with an antioxidant activity of 1.38 and 1.78 g Trolox eq./ g of extract were obtained. Polysaccharides were identified as galactoglucomannans and glucans by NMR analysis. All polysaccharides were formulated in films, however, those extracted with thermal water presented much better viscoelastic properties than those extracted with distilled water. P-T-170 °C and P-TM-150 °C were non-irritating according to Skinethic® test but did not exhibit protective activity against HSV-1 and HSV-2 viruses. E-T170 °C presented a slightly higher antiviral activity (around 40 % protection) with low cytotoxicity. In addition, the films' physical and mechanical properties suggest potential for biomedical applications, especially in topical or mucosal delivery systems-ISblue project | Ref. ANR-17-EURE-0015Xunta de Galicia | Ref. ED431C 2022/08Xunta de Galicia | Ref. ED431G 2023/06Xunta de Galicia | Ref. ED431F 2020/01FCT/MCTES | Ref. 2024.01202.BDFundação para a Ciência e a Tecnologia | Ref. 2023.14718.TENURE.016Fundação para a Ciência e a Tecnologia | Ref. UIDP/04378/2020Fundação para a Ciência e a Tecnologia | Ref. UIDB/04378/2020UCIBIO | Ref. LA/P/0140/2020Agencia Estatal de Investigación | Ref. RYC2018-024454-