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A comprehensive analysis of the responses of Nigella sativa L. to elevated zinc concentrations was assessed in pot experiments. Zn excess supply did not affect the germination but drastically reduced radicle elongation. A concentration-dependent reduction in all growth parameters, yield, and yield components was observed. With the increasing Zn concentrations, total lipid contents decreased and changes in fatty composition toward the production of saturated ones were underscored. Despite the reduction in the seeds essential oil yield, a redirection of the terpene metabolism toward the synthesis of oxygenated compounds has been evidenced. A significant increase in the total phenols and flavonoids contents concomitant with improved antioxidant activities has also been found. Collectively, these results highlight the possible use of N. sativa L. in phytoremediation applications, on the one hand, and that Zn excess could represent an excellent alternative to improve the nutritional attributes of this important species, on the other hand.

Introduction Rosa species are known by their richness in bioactive compounds useful in cosmetic, perfumery, food and phytotherapy. These metabolites are influenced by several factors accordingly affecting the plant properties in different environments. Objective Exploration of polyphenolic composition and antioxidant activity of stem extracts from Rosa moschata Herrm., R. canina L. and R. sempervirens L. growing in different northern areas in Tunisia. Methods Phytochemical composition was carried out by means of high‐performance liquid chromatography diode‐array detector (HPLC‐DAD) and HPLC‐DAD‐ESI‐MS (electrospray ionisation mass spectrometry). Antioxidant activity was measured using the DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) radical scavenging assay, the FRAP (ferric reducing antioxidant power) test, the TEAC (Trolox equivalent antioxidant capacity) and the ORAC (oxygen radical absorbance capacity) assays. Results Rosa stem profiles were dominated by flavonols but qualitative variation was recorded between sections (Caninae and Synstylae). Aromadendrin‐O‐hexoside‐deoxyhexoside, quercitrin and quercetin 3‐O‐glucoside were identified as the major compounds of R. sempervirens, R. moschata and R. canina, respectively. Quantitative differences were found between species, provenances and extracts either for the individual compounds or for the total phenolic contents. This variability was also highlighted in Rosa scavenger ability results. The highest mean values were recorded by methanolic extracts of R. moschata from Bizerte (TEAC and FRAP) and R. canina for DPPH. However, for ORAC assay, the most active extract was obtained by ethyl acetate from stems of R. canina. Conclusion Results allow concluding that stems of R. sempervirens, R. moschata and R. canina could present a new natural residual source of bioactive phytochemicals, to be employed as additives in pharmaceutical products or in cosmetic and food preparations.