Bioassay-guided isolation of phytotoxins from three salvia species

Authors: DA CRUZ-SILVA, CLAUDIA - Western Paraná State University; Cantrell, Charles; NOBREGA, LUCIA - Western Paraná State University; ALI, ABBAS - University Of Mississippi; DUKE, STEPHEN - University Of Mississippi

Submitted to: Allelopathy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2021
Publication Date: 9/6/2021
Citation: Da Cruz-Silva, C.T., Cantrell, C.L., Nobrega, L.P., Ali, A., Duke, S. 2021. Bioassay-guided isolation of phytotoxins from three salvia species. Allelopathy Journal. 54(1):13-24. https://doi.org/10.26651/allelo.j/2021-54-1-1344.
DOI: https://doi.org/10.26651/allelo.j/2021-54-1-1344

Interpretive Summary: The genus Salvia includes around 900 species distributed throughout the world and is the largest genus in the economically and medicinally important plants of the Lamiaceae family. The secondary compounds of Salvia species have been extensively studied for numerous biological activities. The genus Salvia contains several allelopathic species and extracts from three of these species, Salvia miltiorrhiza, S. hispanica and S. columbariae, were tested in this study for phytotoxicity. Although there are several reports of phytotoxins from Salvia, there are no reports of phytotoxins against higher plants from Salvia miltiorrhiza. The abietane diterpenes tanshinone I and tanshinone IIA were identified as the compounds responsible for phytotoxicity.

Technical Abstract: The genus Salvia contains several allelopathic species. Roots and shoots of Salvia miltiorrhiza, S. hispanica and S. columbariae plants were fractionated with hexane, ethyl acetate, and ethanol, and the fractions were tested for phytotoxicity. All fractions of S. hispanica and S. columbariae were insufficiently phytotoxic for further study, whereas the hexane and ethyl acetate fractions of S. miltiorrhiza were sufficiently phytotoxic and were selected for bioassay-guided fractionation and isolation of pure phytotoxic compounds. The abietane diterpenes tanshinone I and tanshinone IIA were identified as the compounds responsible for phytotoxicity of the fractions. Tanshinone I and tanshinone IIA inhibited growth of duckweed (Lemna paucicostata) 50% at concentrations of 113 and 140 µM, respectively, a level of phytotoxicity similar to that of some commercial herbicides in this bioassay. Neither compound was toxic to mosquito (Aedes aegypti) at 125 ppm (ca. 0.435 mM). Although these compounds are red pigments reported to be weak photosensitizers, a cucumber cotyledon assay for this type of activity indicated that this is not the mode of action of these compounds.