Journal Article

Polyphenol-Rich Larix decidua Bark Extract with Antimicrobial Activity against Respiratory-Tract Pathogens: A Novel Bioactive Ingredient with Potential Pharmaceutical and Nutraceutical Applications

Peron, Gregorio, Faggian, Marta, Dall’Acqua, Stefano, Castagliuolo, Ignazio, Bernabè, Giulia, Francescato, Stefano, Ferrari, Sara, Baratto, Gianni

2021

Overview

Larch (Larix decidua) bark is a sawmill waste, traditionally used for antiseptic, expectorant and dermatological (wound healing, eczema, psoriasis) purposes. In this work, we developed a food-grade dry larch bark extract (LBE) from sawmill by-products using hydro-alcoholic extraction. The antibacterial activity of LBE was evaluated against respiratory-tract pathogens, i.e., Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa and Haemophilus influenza, and it was compared to that of grapefruit seed extract (GSE), a commercially available raw material commonly proposed as antibacterial ingredient for over-the-counter products. Procyanidins (PACs) and other polyphenols contents in LBE were determined by HPLC-FLD-MS and HPLC-DAD-MSn, respectively. The antimicrobial activity of LBE and GSE was assessed using the micro-plate dilution technique in concentration range of 2–200 µg/mL, and the safety of these dosages was assessed in cellular and animal models. LBE showed considerable contents of PACs (15% w/w; especially B-type) and other polyphenols (3.8% w/w), among which the characteristic spiropolyphenols larixinol and epilarixinol were identified, together with the flavonoids isoquercitrin and rutin, already reported as growth inhibitors of different respiratory-tract pathogens. LBE showed higher antimicrobial activity compared to GSE, demonstrated by a growth inhibition range of 10–40% towards five of six strains tested, compared to 10–15% of GSE. These results suggest that LBE may represent a natural and sustainable source of active compounds with antibacterial activity for pharmaceutical and nutraceutical applications.

• Publisher: MDPI AG,MDPI
• Subject: Animal models / Animals / Antibacterial activity / Antibiotics / Antimicrobial activity / antimicrobial agent / Antimicrobial agents / Bacterial infections / Bark / Chromatography / Cytotoxicity / Dilution / Eczema / Flavonoids / Functional foods & nutraceuticals / Grapefruit / green extraction / High-performance liquid chromatography / Humidity / Influenza / Klebsiella / Laboratories / Larix decidua / Larix decidua bark extract / Liquid chromatography / Mass spectrometry / Pathogens / Pharmaceuticals / Plant extracts / Polyphenols / Procyanidins / Pseudomonas aeruginosa / Psoriasis / Respiratory tract / Rutin / Scientific imaging / Skin diseases / Staphylococcus infections / Streptococcus infections / Wound healing