Glycosidic conjugates of C13 norisoprenoids, monoterpenoids, and cucurbates in Boronia megastigma (Nees)

Megastigmane glycosides from Streblus ilicifolius (S.Vidal) Corner and their anti-inflammatory activity

Twelve undescribed megastigmane glycosides, streilicifolosides A-L (1-12), together with 8 known analogues (13-21) were isolated from the leaves of Streblus ilicifolius (S.Vidal) Corner. Their plannar structures were elucidated using extensive NMR spectroscopic methods (1D and 2D-NMR spectroscopy), and HRESIMS spectroscopic data analyses. The absolute configurations of the undescribed compounds were determined by the glucose-induced shift-trend, calculated and experimental circular dichroism spectroscopy. All the compounds were tested for inhibitory effects on the production of NO in LPS-treated RAW264.7 cells, and streilicifoloside E and platanionoside D exhibited potent anti-inflammatory activity comparable to that of the positive control, with IC₅₀ values of 26.33 and 21.84 μM, respectively. Furthermore, these two compounds markedly decreased the secretion of PGE2 and TNF-α and inhibited the expression of COX‒2, iNOS and NF-κB/p65 in LPS-induced RAW264.7 cells in a dose-dependent manner. In addition, the structure-activity relationships of the isolates were also discussed. The results suggest that streilicifoloside E and platanionoside D could be used as potential candidates for the development of new anti-inflammatory agents.

An LC-MS profiling method reveals a route for apocarotene glycosylation and shows its induction by high light stress in Arabidopsis

Apocarotenoid glycosylation serves as a valve regulating carotenoid homeostasis in plants and may contribute to their response to photo-oxidative stress.

Intraspecific variability in allelopathy of Heracleum mantegazzianum is linked to the metabolic profile of root exudates

BACKGROUND AND AIMS

Allelopathy may drive invasions of some exotic plants, although empirical evidence for this theory remains largely inconclusive. This could be related to the large intraspecific variability of chemically mediated plant-plant interactions, which is poorly studied. This study addressed intraspecific variability in allelopathy of Heracleum mantegazzianum (giant hogweed), an invasive species with a considerable negative impact on native communities and ecosystems.

METHODS

Bioassays were carried out to test the alleopathic effects of H. mantegazzianum root exudates on germination of Arabidopsis thaliana and Plantago lanceolata. Populations of H. mantegazzianum from the Czech Republic were sampled and variation in the phytotoxic effects of the exudates was partitioned between areas, populations within areas, and maternal lines. The composition of the root exudates was determined by metabolic profiling using ultra-high-performance liquid chromatography with time-of-flight mass spectrometry, and the relationships between the metabolic profiles and the effects observed in the bioassays were tested using orthogonal partial least-squares analysis.

KEY RESULTS

Variance partitioning indicated that the highest variance in phytotoxic effects was within populations. The inhibition of germination observed in the bioassay for the co-occurring native species P. lanceolata could be predicted by the metabolic profiles of the root exudates of particular maternal lines. Fifteen compounds associated with this inhibition were tentatively identified.

CONCLUSIONS

The results present strong evidence that intraspecific variability needs to be considered in research on allelopathy, and suggest that metabolic profiling provides an efficient tool for studying chemically mediated plant-plant interactions whenever unknown metabolites are involved.

Accelerated identification of halogenated monoterpenes from Australian specimens of the red algae Plocamium hamatum and Plocamium costatum

Two species of red algae belonging to the genus Plocamium, P. hamatum from Moreton Bay, Queensland, and P. costatum, from Pandalowie Bay, South Australia, were investigated to assess their chemical variation and as potential sources of new halogenated monoterpenes. The hyphenated technique HPLC-UV-MS-SPE-NMR was used to assess the algal extracts and to determine its potential for accelerated identification of halogenated monoterpenes generally. A combination of the hyphenated and traditional chromatographic techniques resulted in the isolation and characterization of a total of 10 halogenated monoterpene metabolites, eight of which are reported for the first time. Their structures, including configurations, were determined through interpretation of their 1D and 2D NMR, mass spectrometric, infrared, and X-ray data. The two species of Plocamium produced different secondary metabolites and contained a significant number of new polyhalogenated monoterpenes. The investigation also showed the hyphenated technique HPLC-UV-MS-SPE-NMR to be useful for preliminary investigation of the chemical content of algal extracts.