Activity of Anthracenediones and Flavoring Phenols in Hydromethanolic Extracts of Rubia tinctorum against Grapevine Phytopathogenic Fungi

Abstract

In this work, the chemical composition of Rubia tinctorum root hydromethanolic extract was analyzed by GC–MS, and over 50 constituents were identified. The main phytochemicals were alizarin-related anthraquinones and flavoring phenol compounds. The antifungal activity of this extract, alone and in combination with chitosan oligomers (COS) or with stevioside, was evaluated against the pathogenic taxa Diplodia seriata, Dothiorella viticola and Neofusicoccum parvum, responsible for the so-called Botryosphaeria dieback of grapevine. In vitro mycelial growth inhibition tests showed remarkable activity for the pure extract, with EC50 and EC90 values as low as 66 and 88 μg·mL−1, respectively. Nonetheless, enhanced activity was attained upon the formation of conjugate complexes with COS or with stevioside, with synergy factors of up to 5.4 and 3.3, respectively, resulting in EC50 and EC90 values as low as 22 and 56 μg·mL−1, respectively. The conjugate with the best performance (COS–R. tinctorum extract) was then assayed ex situ on autoclaved grapevine wood against D. seriata, confirming its antifungal behavior on this plant material. Finally, the same conjugate was evaluated in greenhouse assays on grafted grapevine plants artificially inoculated with the three aforementioned fungal species, resulting in a significant reduction in the infection rate in all cases. This natural antifungal compound represents a promising alternative for developing sustainable control methods against grapevine trunk diseases.

Holm Oak (Quercus ilex subsp. ballota (Desf.) Samp.) Bark Aqueous Ammonia Extract for the Control of Invasive Forest Pathogens

“…It is known to have active oxygen-scavenging activities, preventing oxidative damage. Concerning its fungicidal action, also reported for other supraene-rich natural products (summarized in Table S2 [ 48 , 49 , 50 , 51 ]), it is known that the intracellular accumulation of squalene disrupts fungal cell membranes, possibly by forming squalene vesicles that weaken fungal cells by extracting essential membrane lipid components [ 52 ]. In fact, the mechanism of action of terbinafine and other antifungal drugs is based on the inhibition of squalene peroxidase, resulting in the aforementioned squalene accumulation [ 53 ].…”

Characterization and Antimicrobial Activity of a Halophyte from the Asturian Coast (Spain): Limonium binervosum (G.E.Sm.) C.E.Salmon

“…Equipment calibration was conducted using test mixture 2 for apolar capillary columns according to Grob (Supelco 86501) and PFTBA tuning standards. Compound identification was carried out using the NIST11 library [ 78 ].…”

Lignin–Chitosan Nanocarriers for the Delivery of Bioactive Natural Products against Wood-Decay Phytopathogens

“…The bioactive constituents present in each of the extracts, characterized by gas chromatography-mass spectroscopy (GC-MS), have been reported in previous works [19][20][21].…”

“…Extracts of R. tinctorum and S. marianum were obtained in a methanol:water mixture (1:1 v/v) according to the previously reported procedure [20,21]. In short, the dried samples were mixed with the hydromethanolic medium in a 1:20 (w/v) ratio and heated in a water bath at 50 • C for 30 min, followed by 5 min of sonication.…”

“…Simmons [18]. As an alternative, this work proposes the use of plant extracts for which inhibitory concentrations below 1000 ppm against Botryosphaeriaceae species have been previously reported by our group, such as Rubia tinctorum L., Silybum marianum (L.) Gaertn., Urtica dioica L., or Equisetum arvense L. [19][20][21], and which have proven effective for pruning wound protection applications. These products of natural origin would be suitable for use in organic or conventional agriculture (in fact, the latter two are 'basic substances' under the EU plant protection products regulation, Article 23 of (EC) No 1107/2009).…”