Potential allelopathic interferenceofMelilotus neapolitanametabolites on three coexisting species of Mediterranean herbaceous plant community

Abstract

This study is focused on the allelopathic interference of Melilotus neapolitana, an annual stenomediterranean species frequently occurring in the herbaceous plant community of the Mediterranean macchia, on three coexisting species of the Mediterranean herbaceous plant community. The ethereal and methanol extracts of the plant led to the isolation of 11 allelochemicals: coumarin, cis-and trans-melilotoside, the dihydromelilotoside, seven flavone glycosides, as well as the inactive b-sitosterol, a C13-norterpene glucoside and a polyphenol. All the structures have been elucidated on the basis of their spectroscopic features. The organic extracts and all the pure compounds have been assayed for their allelopathic activity on three coexisting species, Petrorhagia velutina, Dactylis hispanica, and Phleum subulatum. The cluster analysis has shown a clear structure-activity relationship, by evidencing four main groups of compounds with a specific effect patterns. Coumarin, the most abundant compound both in the plant extracts and soil, is found to be highly phytotoxic on all the tested species. As for the flavone glycosides, it is shown that aglycones play an important role due to their bioactivity.

NMR‐based metabolomics and bioassays to study phytotoxic extracts and putative phytotoxins from Mediterranean plant species

“…In the 1 H‐NMR spectrum (Figure ), two doublets at δ H 6.50 and 8.06 ( J = 9.6 Hz), along with further four signals at δ H 7.39, 7.42, 7.64, 7.70, were attributed to coumarin. The presence of two couples of doublets at δ H 6.07/6.79 ( J = 11.4 Hz) and δ H 6.51/7.86 ( J = 16.8 Hz) as well as the heterocorrelations evidenced in the HSQC, H2BC, and HMBC experiments indicated the presence of cis ‐ and trans ‐melilotosides …”

“…Metabolic profiling of M. neapolitana evidenced coumarin and related compounds as the main constituent of the extracts. In the 1 H‐NMR spectrum (Figure ), two doublets at δ H 6.50 and 8.06 ( J = 9.6 Hz), along with further four signals at δ H 7.39, 7.42, 7.64, 7.70, were attributed to coumarin.…”

“…The Mediterranean ecosystem, indeed, is characterised by strong environmental conditions (e.g. climatic stress and disturbance abiotic and biotic factors), that elicit the plant production of natural active compounds, some of which are known to be involved in specific allelopathic interaction …”

Kaempferol Glycosides from Lobularia maritima and Their Potential Role in Plant Interactions

“…Results evidenced the relationship between the distribution pattern observed in the field and the phytotoxic effect of coumarin, the most abundant metabolite isolated [10].…”

“…Recently, Macias et al [23], in a review on the use of natural products for weed control, reported the most recent advances in allelopathy on flavonoids (glycosides and aglycones). Very few articles have appeared on the phytotoxic effects of flavone glycosides, their structure -activity relationships, and their different species-specific effects [10] [24].…”