Phytotoxic Metabolites from <i>Hyptis</i> Species: Chemical Profiling and Bioherbicide Activity Against <i>Amaranthus</i>

The phytotoxic effects of extracts from <i>Hyptis crenata</i> ( <i><b>Hcre</b></i> ), <i>Hyptis suaveolens</i> ( <i><b>Hsua</b></i> ), <i>Hyptis saxatilis</i> ( <i><b>Hsax</b></i> ), <i>Hyptis campestris</i> ( <i><b>Hcam</b></i> ), and <i>Hyptis brevipes</i> ( <i><b>Hbre</b></i> ) were evaluated against three <i>Amaranthus</i> weed species under controlled germination chamber conditions. Extracts <i><b>Hcre</b></i> , <i><b>Hsua</b></i> and <i><b>Hsax</b></i> inhibited seed germination by 85-93% relative to the control and markedly suppressed radicle and hypocotyl growth in <i>Amaranthus viridis</i> and <i>Amaranthus hybridus</i> in Petri dish assays. At 200 ppm, <i><b>Hcre</b></i> and <i><b>Hsax</b></i> reduced radicle and hypocotyl lengths by up to 90% in both species, comparable to the effects of commercial herbicides Sencor and Sulfentrazone. Multivariate analyses, including PCA, PLS-DA, and molecular networking based on LC-MS/MS data, enabled the annotation of compounds associated with phytotoxicity. A total of 56 metabolites were identified, including terpenoids, flavonoids, α-pyrones, carbohydrate derivatives, and polyketides, using both an in-house database and the GNPS platform. Terpenoids were the predominant class, with abietane-type diterpenes as the most abundant subgroup, exhibiting strong correlations with the observed biological activity.