Valorisation of bark lipophilic fractions from three Portuguese Salix species: A systematic study of the chemical composition and inhibitory activity on Escherichia coli

abstract

Salix (Salicaceae) species bark extracts are traditionally consumed due to their anti-inflammatory and analgesic benefits, mainly attributed to phenolic compounds. However, this biomass could be further exploited calling upon other extractive components, namely the lipophilic fraction. Hence, the present study highlights, for the first time, the chemical characterisation and the inhibitory effect of S. viminalis L., S. atrocinerea Brot. and S. fragilis L. bark lipophilic dichloromethane extracts against the Gram-negative bacterium Escherichia coll. Gas chromatography-mass spectrometry allowed the identification and quantification of 63 compounds, from which 36 were reported for the first time in these Salix species, namely 15 aromatic compounds, 4 fatty acids, 4 long chain aliphatic alcohols, 1 diterpene, 4 pentacyclic triterpenes, 4 tocopherols, 3 long chain aliphatic aldehydes and 1 sterol. Long chain aliphatic aldehydes represent the prevalent family, with triacontanal as the major component in S. fragilis L and S. atrocinerea Brot. barks. Additionally, beta-sitosterol was the major component identified in S. viminalis L bark lipophilic extract, followed by lupeol. This last extract exhibited the highest inhibitory effect against E. coli viability, being probably related with these bioactive components. In contrast, aromatic compounds were detected at high abundances in S. atrocinerea Brot. and S. fragilis L. barks, with piceol as the predominant component. These findings can contribute to valorise bark of the three endogenous Portuguese Salix species, based on their chemical composition and biological properties.

keywords

ANTIMICROBIAL ACTIVITY; FATTY-ACIDS; SECONDARY METABOLITES; ALPHA-TOCOPHEROL; CUTICULAR WAXES; IDENTIFICATION; EXTRACT; WOOD; ANTIBACTERIAL; CONSTITUENTS

subject category

Agriculture

authors

Ramos, PAB; Moreirinha, C; Santos, SAO; Almeida, A; Freire, CSR; Silva, AMS; Silvestre, AJD

Groups

G4 - Renewable Materials and Circular Economy

Projects

CICECO - Aveiro Institute of Materials (UID/CTM/50011/2019)

MultiBiorefinery - Multi-purpose strategies for broadband agro-forest and fisheries by-products valorization: a step forward for a truly integrated biorefinery (SAICTPAC/0040/2015)

AgroForWealth - Biorefinação de sub-Produtos agrícolas e florestais: uma estratégia de valorização de recursos para o bem estar social e a sustentabilidade (AGROFORWEALTH)

acknowledgements

The authors acknowledge FCT/MCTES for the financial support to the CICECO-Aveiro Institute of Materials (UID/CTM/50011/2019) and to the QOPNA research unit (UID/QUI/00062/2019), through national funds; co-financing, where applicable, come from FEDER within the PT2020, and also to the Portuguese NMR Network. Patricia Ramos acknowledges the MultiBiorefinery project (POCI-01-0145-FEDER-016403) for the post-doctoral grant. Sonia Santos and Catarina Moreirinha acknowledge the AgroForWealth project (CENTRO-01-0145-FEDER-000001) funded by Centro2020, through FEDER and PT2020 for the contract and the post-doctoral grant, respectively. Carmen Freire also acknowledges FCT/MCTES for a contract under the program Investigador FCT 2012 (IF/01407/2012). The authors also want to acknowledge The Navigator Company and RAIZ for kindly supplying Salix spp. samples.