Phytotoxic Potential of Zanthoxylum affine and Its Major Compound Linarin as a Possible Natural Herbicide

Abstract

Four compounds, the flavone linarin (1), the triterpene lupenone (2), the tocopherol (vitamin E, 3), and the new natural alkaloid 1,2,3,4-tetrahydro-1,1-dimethyl-6,7-isoquinolindiol (affineine, 4), were the major natural products isolated from Zanthoxylum affine (syn. Zanthoxylum fagara, Rutaceae). Compound 1 is highly abundant in this plant and was isolated as a white precipitate obtained from the acetone and methanol extracts. The structure of these four compounds was established by 1D and 2D NMR spectroscopy including 1H, 13C, DEPT, COSY, HSQC, and HMBC experiments. The hexane, acetone, and methanol extracts, as well as 1, were evaluated for their potential phytotoxic effects in pre- and post-emergent assays, as well as to identify their mechanisms of action. As pre-emergent phytotoxic agents, the hexane, acetone, and methanol extracts inhibited germination and residual growth (root and stem elongation) of Lactuca sativa (lettuce) and Lolium perenne (perennial ryegrass). As post-emergent agents, they inhibited dry biomass. Compound 1 acts as a pre-emergent herbicide, by inhibiting germination, seed respiration, residual seedling growth and, notably, root hair development. Furthermore, 1 inhibited the synthesis of ATP and the electron transport chain of isolated spinach chloroplasts; in this way, it behaves as a Hill reaction inhibitor. The site of inhibition was located at the donor site of PSII from the oxygen evolving complex to QA, thus acting as a multisite compound. These results suggest that compound 1 can be used as a lead for a potential green herbicide with different targets.

Perspective: present pesticide discovery paradigms promote the evolution of resistance – learn from nature and prioritize multi‐target site inhibitor design

“…It is apparent from the new compounds recently released that insufficient thought and effort has been given to the active discovery of multi‐target site acting pesticides. Although there are many known cases of multi‐target‐site action, a search on the Web of Science separately using the keywords ‘multisite’ and ‘multitarget’ (with and without hyphenation), opposite (separately) the keywords herbicide, fungicide, insecticide and pesticide came up with few relevant references for such compounds, along with the suggestion of mixing old multi‐target fungicides with the newer ones …”

“…The compound linarin also has enhanced toxic effects due to multi‐target action. When used pre‐emergence it inhibits seed respiration, germination, root and root hair growth, unrelated to its inhibition of the donor side of photosystem II . Likewise, allosamidin, a pseudotrisaccharide metabolite from a Streptomyces inhibits both insect chitinase as well as insect (but not human) OfHex1, a b‐N‐acetyl‐D‐hexosaminidase, as evidenced from molecular docking …”

Linarin, a Glycosylated Flavonoid, with Potential Therapeutic Attributes: A Comprehensive Review

“…(Campanulaceae) [66], Ginkgo biloba L. (Ginkgoaceae) [67], Bombax malabaricum DC. (Malvaceae) [68], Avena sativa L.(Poaceae) [69], Thalictrum aquilegiifolium L. [70], and Coptis chinensis Franch [71] (Ranunculaceae), Zanthoxylum affine Kunth (Rutaceae) [72] and Lippia rubella (Moldenke) T.R.S.Silva & Salimena (Verbenaceae) [73].…”

“…(Ranunculaceae family) were assessed via HPLC-MS and LN was identified as the main compounds [71]. Moreover, Rios et al (2018) identified LN in the hexane, acetone, and methanolic extracts of Zanthoxylum affine Kunth (Rutaceae) aerial parts, whilst HPLC−Q-TOF-MS was employed with water and methanol as the solvent systems [72].…”

Phytochemical Characterization of Ethanolic Extracts of the Leaves of Zanthoxylum Caribaeum Lam and Evaluation of Antimicrobial Activity Against Burkholderia Glumae

“…Z. Monophyllum contains metabolites with biological activity against fungi affecting humans such as Aspergillus terreus, Aspergillus flavus, Penicillium digitatum, Penicillium funiculosum, Penicillium citinum, Paecilomyces and Candida albicans [11]. Finally, due the phytotoxic potential of Zanthoxylum affine has been suggested as a possible natural herbicide [12]. Despite the remarkable use of Z. caribeaum and its wide presence in different regions of Norte de Santander, there is a lack of studies related to its phytochemical composition and biological activity that allow in the future the development of medicines or compounds for the control of pathogens that affect the population or crop plants such as Burkholderia glumae, which causes bacterial panicle blight (BPB) in rice crops [13].…”