Enantiomer-Selective Characterization of the Adsorption, Dissipation, and Phytotoxicity of the Plant Monoterpene Pulegone in Soils

Abstract

Plant monoterpenes have received attention for their ecological functions and as potential surrogates for synthetic herbicides, but very little is known about the processes that govern their behavior in the soil environment, and even less about the possible enantioselectivity in the functions and environmental behavior of chiral monoterpenes. We characterized the adsorption and dissipation of the two enantiomers of the chiral monoterpene pulegone in different soils, and their phytotoxicity to different plant species through Petri dish and soil bioassays. R- and S-pulegone displayed a low-to-moderate non-enantioselective adsorption on the soils that involved weak interaction mechanisms. Soil incubation experiments indicated that, once in the soil, R- and S-pulegone are expected to suffer rapid volatilization and scarcely enantioselective, biodegradation losses. In Petri dishes, the phytotoxicity of pulegone and its enantioselectivity to Lactuca sativa, Hordeum vulgare, and Eruca sativa was species-dependent. Lactuca sativa was the most sensitive species and showed higher susceptibility to S- than to R-pulegone. Biodegradation and volatilization losses greatly reduced the phytotoxic activity of S-pulegone applied to soil, but the addition of a highly-adsorptive organoclay stabilized the monoterpene and increased its phytotoxic effect. Stabilization by adsorption may represent an important mechanism by which the bioactivity of plant monoterpenes in soils can be increased.

The Essential Oil of Petroselinum crispum (Mill) Fuss Seeds from Peru: Phytotoxic Activity and In Silico Evaluation on the Target Enzyme of the Glyphosate Herbicide

“…On the other hand, certain volatile terpenes have demonstrated phytotoxic activity against L. sativa seeds including: 1,8-cineole, sabinene, and α-pinene from Vitex agnus-castus [ 27 ]; p-cymene, γ-terpinene, thymol, carvacrol, and borneol from Thymus eigii [ 28 ]; pulegone [ 29 ], β-pinene, δ 3 -carene, and limonene from Heterothalamus psiadioides [ 30 ]; α-pinene, γ-terpinene, and p-cymene from Eucalyptus grandis [ 31 ]; α-pinene, and β-pinene from Pinus brutia [ 32 ]; eucalyptol, linalool and β-myrcene from Artemisia absinthium [ 33 ]; and 1,8-cineole, β-phellandrene, α-pinene from Majorana hortensis [ 34 ]. Several of these volatile compounds were reported in the GC-MS analysis ( Table 1 ) but in low percentages, except for β-phellandrene which might synergize with the phytotoxic effect.…”

Chemical Evaluation, Phytotoxic Potential, and In Silico Study of Essential Oils from Leaves of Guatteria schomburgkiana Mart. and Xylopia frutescens Aubl. (Annonaceae) from the Brazilian Amazon

“…In addition, the synergistic and/or antagonistic effects of the volatile components in the samples may contribute to their biological activities [ 91 , 92 , 93 , 94 ]. According to Galán-Pérez et al [ 95 ], monoterpenes are potent inhibitors of the germination and growth of several plant species. In addition, the authors note that oxygenated monoterpenes have greater water solubility and inhibitory activity than hydrocarbon monoterpenes.…”

Soil Effects on the Bioactivity of Hydroxycoumarins as Plant Allelochemicals

“…Disregarding the processes to which allelochemicals are subjected in the soil may result in incorrect predictions of their actual activities [ 21 , 22 , 23 ]. For example, several studies have shown that putative allelochemicals presenting great phytotoxic activity in water or artificial substrates displayed lower or no activity in natural soils [ 18 , 24 , 25 , 26 ].…”