# Phytochemistry and Allelopathic Properties of Invasive Heracleum sosnowskyi Aqueous Extracts Against Lettuce (Lactuca sativa L.), Perennial Ryegrass (Lolium perenne L.), Timothy (Phleum pratense L.) and White Clover (Trifolium repens L.)

## TL;DR

This study identifies harmful chemicals in the invasive plant Heracleum sosnowskyi that inhibit the growth of several native plants, offering insights into natural herbicide development.

## Contribution

The paper reveals specific phytotoxic compounds in H. sosnowskyi and quantifies their inhibitory effects on native plant species.

## Key findings

- Flower and leaf extracts of H. sosnowskyi strongly inhibited the growth of timothy and white clover seedlings.
- Furanocoumarins and flavonoids were identified as key allelopathic compounds in the plant extracts.
- The highest concentrations of extracts caused up to 100% suppression of seedling growth in tested species.

## Abstract

Heracleum sosnowskyi is considered to be a dangerous invasive plant species that has successfully naturalized within a variety of plant communities across numerous countries. As a result of its superior competitiveness, the alien species is able to displace the indigenous species from their native habitats, thus changing the ecosystems and decreasing biodiversity. The phytochemicals present in the H. sosnowskyi aqueous extracts were revealed using GC/MS and HPLC/DAD/TOF techniques. Isopsoralen, methoxsalen, (iso)pimpinellin and/or bergapten were determined to be major compounds in the leaf, inflorescence and root extracts. Glutaric, quinic, linolenic, (iso)chlorogenic and other polyphenolic acids were identified in the extracts. Furthermore, a number of furanocoumarins, including hermandiol, bakuchicin, candinols (A and C) and candibirin F, and coumarins, umbelliferone and yunngnins (A and B), were identified in the roots. Additionally, the presence of flavonoids, including astragalin, quercetin 7,3,4-trimethyl ether, nicotiflorin and rutin, has been detected in the flower and leaf extracts. Allelopathic effects of H. sosnowskyi aqueous extracts were tested on four model plants, lettuce (Lactuca sativa L.) and three native Lithuanian meadow herbs, perennial ryegrass (Lolium perenne L.), timothy (Phleum pratense L.) and white clover (Trifolium repens L.), using the Petri dish method. H. sosnowskyi flower and leaf extracts demonstrated the strongest inhibitory effects on the germination and growth of the tested plant seeds. At the highest relative concentrations, 0.5 and 1.0, extracts of Sosnowsky’s hogweed inflorescences inhibited timothy seedling growth by 95.47% (from 19.64 ± 2.57 mm to 0.89 ± 0.73 mm) and 100%, respectively. The leaf extracts exhibited the strongest inhibitory effects on white clover seedlings. The highest relative concentrations tested (0.5 and 1.0) suppressed clover seedling growth by 94.66% (from 41.22 ± 2.53 mm to 2.20 ± 0.63 mm) and 100%, respectively. Additionally, the germination rate and vigor index of model plants were assessed. The research is of significance for the regulation and monitoring of the spreading of aggressive H. sosnowskyi plants. Moreover, it is important for the development of natural herbicides based on active phytotoxic compounds from these plants.