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.
Highlights
The joint presence of compounds of quinone and phenol categories in plant extracts and, the differential content of anthracenediones and 4-tert-butyl-2-phenylphenol, which might be responsible for the chromatic aberration of teak, has been the object of attention in the bibliography [1].Anthracenediones are a class of molecules based on the 9,10-anthracenedione parent (Figure 1a), which–among others–include purpurin (Figure 1a) and those synthesized by the American Cyanamid Laboratories in the late 1970s [2]
Time of year and age of the plant are known to influence the composition [15], the observed differences should be mainly ascribed to differences in both the extractive chemicals and in the extraction process, and to the characterization technique, provided that previous studies on R. tinctorum extracts [36,38,39,40,41] were conducted by HPLC and LC–HRMS and generally focused only on anthraquinones, anthraquinone glycosides and aglycones
The gas chromatography–mass spectrometry (GC–MS) analysis of R. tinctorum hydroalcoholic extracts revealed that, apart from members of the anthraquinone family (19.4%), flavoring phenols similar to those found in oak and guanosine were present
Summary
The joint presence of compounds of quinone and phenol categories in plant extracts and, the differential content of anthracenediones and 4-tert-butyl-2-phenylphenol, which might be responsible for the chromatic aberration of teak (difference between heartwood and sapwood), has been the object of attention in the bibliography [1].Anthracenediones are a class of molecules based on the 9,10-anthracenedione parent (Figure 1a), which–among others–include purpurin (Figure 1a) and those synthesized by the American Cyanamid Laboratories in the late 1970s [2]. The joint presence of compounds of quinone and phenol categories in plant extracts and, the differential content of anthracenediones and 4-tert-butyl-2-phenylphenol, which might be responsible for the chromatic aberration of teak (difference between heartwood and sapwood), has been the object of attention in the bibliography [1]. Mitoxantrone, which has a dihydroxyanthraquinone central chromophore with two symmetrical aminoalkyl side chains (Figure 1a), is considered the biologically most active anthracenedione [3], other anthracenediones have been reported to have antimicrobial activities: for instance, anthraquinone aglycones have been found to have a remarkable in vitro activity. Plants 2021, 10, 1527 Plants 2021, 10, 1527 other anthracenediones have been reported to have antimicrobial activities: for instance, anthraquinone aglycones have been found to have a remarkable in vitro activity aaggaaiinnssttcclliinniiccaallssttrraaiinnssooffddeerrmmaattoopphhyytteess[[44]];;aanntthhrraaqquuiinnoonneeddeerriivvaattiivveesseexxhhiibbiittaannttiiffuunnggaall aaccttiivviittyyaaggaaininssttCCananddidiadaalablibciacnasn(sC(.CP..PR.oRboinb)inB)erBkehrkouhot,uCtr, yCprtyopcotcoccuocscnuesofnoeromfoarnmsa(nSsan(SFaenlicFee)Vliuciel)l.,VTuriicllh.,opThryictohnopmhyetnotnagmroepnhtyatgersop(Chy.Pte.sR(oCb.iPn.) RRo. bBilna)ncRh..,BAlasnpcerhg.,illAusspfeurmgiilgluastufsuFmriegsaetnu.s aFnrdesSenpo.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
