Honokiol, magnolol and its monoacetyl derivative show strong anti-fungal effect on Fusarium isolates of clinical relevance

Abstract

The antifungal activity of magnolol and honokiol, two naturally occurring hydroxylated biphenyls, and of their synthetic derivatives was evaluated on a collection of representative isolates of Fusarium oxysporum , F . solani and F . verticillioides of clinical and ecological concern. The tested compounds were proposed as a ‘natural’ alternative to conventional fungicides, even though a larger range of concentrations (5–400 μg/ml) was applied. The activity of magnolol and honokiol was compared with that of terbinafine (0.1–10 μg/ml), and fluconazole (1–50 μg/ml), two fungicides widely used in treating fungal infections on humans. Magnolol showed similar fungicidal activity compared to fluconazole, whereas honokiol was more effective in inhibiting mycelium growth compared to this fungicide on all tested clinical Fusarium spp. isolates. Compared to terbinafine, honokiol showed similar antifungal activity when tested on clinical F . solani isolates, whereas magnolol was less effective at all selected concentrations (5–400 μg/ml). The different position of the phenol-OH group, as well as its protection, explain different in vitro activities between magnolol, honokiol, and their derivatives. Furthermore, magnolol showed mycelium dry weight reduction at a concentration of 0.5 mM when tested on a set of agricultural isolates of Fusaria , leading to complete inhibition of some of them. Magnolol and honokiol are proposed as efficient and safe candidates for treating clinically relevant Fusaria .

Transcriptomic Insights into the Antifungal Effects of Magnolol on the Growth and Mycotoxin Production of Alternaria alternata

“…[ 9 , 10 ] and Fusarium spp. [ 7 , 9 , 29 ]. The mycelial extending and biomass weight of A. alternata in our work could be strongly inhibited by up to 93.5% and 88.3% with the treatment of magnolol only at 25 μM.…”

“…A number of plant extracts are considered to exert brilliant antifungal activities, including some naturally occurring polyphenols. Among the polyphenols, magnolol, extracted from the traditional Chinese herb Magnolia officinalis , showed strong antifungal activities against Fusarium species [ 7 ], Candida isolates [ 8 ], Magnaporthe grisea [ 9 ], Penicillium expansum as well as A. alternata [ 10 ]. However, little is known on its inhibitory effects against Alternaria toxins, especially AOH and AME.…”

Pharmacology, Toxicity, Bioavailability, and Formulation of Magnolol: An Update

“…The results revealed that MG had similar bactericidal activity compared with fluconazole, whereas honokiol had a better effect of inhibiting the mycelium growth compared to this fungicide. Compared to terbinafine, honokiol exhibited similar antifungal activity, whereas MG was less effective at all selected concentrations ( Oufensou et al, 2019 ).…”

“…The isomers MG (5,5′-diallyl-2,2′-dihydroxybiphenyl) and honokiol (3,5′-diallyl-4,2′dihydroxybiphenyl) are biphenyl-type neolignans. They have been recognized as the principal active components of magnolia bark extract, usually accounted for 1-10% of dry bark, depending on the Magnolia species (officinalis or obovata) and extraction method (Sarrica et al, 2018;Oufensou et al, 2019;Łata et al, 2020). Talarek et al reviewed the chemistry, bioavailability, and The studies about MG's toxicity have been done, suggesting that MG has no genotoxicity and mutagenic toxicity (Saito et al, 2006).…”

Prenylated Trans-Cinnamic Esters and Ethers against Clinical Fusarium spp.: Repositioning of Natural Compounds in Antimicrobial Discovery

“…In a previous article reporting the activity of natural phenols against clinical Fusarium spp., we observed that the percentage of growth inhibition measured in liquid medium (Vogel’s) and solid (PDA) was comparable [ 50 ]. To achieve full solubilisation of compounds 1 – 13 at 0.5 mM, the preliminary screening was carried out with a sustainable solid medium based on gellan/water, where each compound was solubilized in a 0.1% water/gellan solution.…”