In this study, the allelopathic properties of Medicago sativa on different weeds were investigated under in vitro conditions. The compounds involved in the autotoxicity of M. sativa were analyzed using high-performance liquid chromatography. The extracts of all concentrations inhibited the growth of the calluses of Digitaria ciliaris, Chenopodium album, Amaranthus lividus, Portulaca oleracea, and Commelina communis. Six allelopathic compounds in alfalfa were identified and quantified, and the most predominant phenolic compounds were salicylic acid and p-hydroxybenzoic acid. Various concentrations (10⁻², 10⁻³, and 10⁻⁵ M) of all the tested phenolic compounds exerted inhibitory effects on callus fresh weight. Rutin, salicylic acid, scopoletin, and quercetin significantly inhibited alfalfa seed germination. Of the seven identified saponins, medicagenic acid saponins exhibited the highest autotoxic effect and significantly lowered seed germination rate. Principal component analysis showed that the phenolic compounds and saponin composition significantly contributed to the different variables. The highly phytotoxic properties of the alfalfa-derived phenolic compounds and saponins indicate that these phytochemicals can be a potential source of bioherbicides.

Plant phytochemical accumulation is influenced by various external factors that change with the seasons (e.g., harvesting time). Atractylodes japonica, an important medicinal plant rich in bioactive compounds, is used to treat several human diseases. We analyzed the influence of harvesting time on phenolic compound concentration and antioxidant activity of A. japonica roots. We investigated the correlation between phenolic compound and minerals contents and antioxidant activity in different harvests. Total phenolic and flavonoid contents varied significantly with the harvesting time. Liquid chromatography–mass spectrometry/mass spectrometry (LC–MS/MS) analysis revealed significant changes in the concentration of various phenolics between harvests. The content of different types of phenolics were significantly higher in the samples collected in October. Among them, chlorogenic acids (133,833.30 µg/g dry weight of root extract) were the most dominant phytochemical compounds detected. Samples harvested in October had higher concentrations of flavonoids, including rutin, orientin, vitexin, and apigenin. Roots harvested in October had a significantly higher (p < 0.05) antioxidant activity than that of those harvested later. Root mineral concentrations also varied with the harvest time. The analysis revealed that macro elements such as Ca ad Mg contents were significantly increased with delaying harvesting time, whereas a different trend was observed for the microelements including Fe, Cu, Al, and As contents in the October harvest. We also found a significant relationship between antioxidant activity and phenolic compound content. The most abundant minerals (Ca, Mg, Mn, Fe, and Al) correlated positively with the antioxidant activity indicating that these elements and compounds may be associated with the A. japonica antioxidant potential. Furthermore, A. japonica root extracts inhibited NIH/3T3 cellular proliferation in a season- and dose-dependent manner. Hence, harvesting time influenced the antioxidant properties and phenolic compound accumulation of A. japonica roots. These results indicate that the harvesting time is essential for obtaining the specific phytochemicals.

This study aimed at investigating the Lycium chinense Miller leaf extract mineral and phenolic compound profiles as well as antioxidant and antimicrobial potential. We determined the leaf extract mineral composition, identified its major mineral components, and quantified secondary metabolites. We also measured the leaf extract antioxidant potential and found that it varies in a concentration-dependent manner. We observed a significant and higher positive correlation between DPPH and ABTS assays compared with the total phenolic and flavonoid content. Furthermore, our assay results positively correlated with several observed acids, indicating their strong association with the L. chinense antioxidant potential. Our cytotoxic assay revealed weak toxicity at higher tested concentrations. Our MIC assay showed that the 80% methanol extract effectively inhibited the growth of Escherichia coli Castellani and Chalmers (ATCC35150). The 625-ppm leaf extract completely suppressed the growth of Staphylococcus aureus Rosenbach (ATCC13150), Bacillus cereus (ATCC 14579), and Helicobacter pylori (ATCC43504). These results allow us to understand the indigenous medicinal value of L. chinense. Our study suggests that the L. chinense leaf extract phenolic compounds possess a good antioxidant activity against free radicals and are effective antimicrobial agents. Finally, the presence and high level of diverse minerals suggest the potential of L. chinense for nutraceutical and functional food applications.

In this study, we investigated the allelopathic effect of Secale cereale cultivars on different weeds that grow in the cultivated fields of Perilla frutescens. Two S. cereale cultivars, Paldong and Singhi, were used to test the allelopathic effect on in vitro grown Digitaria ciliaris, Chenopodium album, Amaranthus lividus, Portulaca oleracea, Pinellia ternata and Commelina communis. The results indicated that S. cereale extracts affect callus growth of weeds in terms of fresh weight and percentage of growth inhibition. The inhibitory effects of both S. cereale cultivars combined with grass cover extracts were higher than using grass weeds alone. Concentrations of all identified phenolic compounds were significantly higher in the leaves extracts of Paldong compared to Singhi. Particularly, syringic acid in leaves extract of the Paldong cultivar were 12.87-fold higher than in the Singhi cultivar. The other predominant phenolic compounds such as salicylic acid, p-coumaric acid, vanillic acid, and p-hydroxybenzoic acids were 3.30, 4.63, 3.11, and 1.28 times higher, respectively, in the leaves extracts of Paldong compared to Singhi. Principal component analysis (PCA) results indicated that the composition of phenolic compounds was significantly related to cultivar types and plant parts used. In addition, biomass increase caused increased weed inhibitory capacity of S. cereale both in tillage and no-tillage regimes. These results suggest that the biomass of cover crops negatively influenced weed density.