Hakimeh Oloumi, Fatemeh Nasibi, Hossein Mozaffari,
Volume 5, Issue 2 (9-2018)
Abstract
Medicinal plants are rich sources of secondary metabolites. Lepidium sativum possess active compounds and secondary metabolites, including polyphenol, anthocyanin, flavonoid compounds, which are of special pharmaceutical and economic importance. Melatonin as bio-stimulator compound has a regulatory role on the amount of secondary metabolites and plant tolerance to environmental stresses. In this study, the effect of exogenous melatonin on secondary metabolites production on Lepidium sativum plants was carried out in a completely randomized design with 5 melatonin treatments (0, 5, 10, 50 and 100 μM) and 3 replications. After applying the treatment, the growth rate and content of the photosynthetic pigments, the leaf water content, as well as the content of flavonoids, anthocyanins and total phenolic compounds were investigated. Seed treatment with melatonin, especially at concentrations of 50 and 100 μM, improved the growth parameters and content of photosynthetic pigments. High levels of melatonin also increased the plant's secondary metabolites, including anthocyanins, carotenoids, and plant phenolic compounds. These effects can confirm the role of melatonin as a growth regulator and its impact on plant growth and resistance.
Parichehr Hanachi, Zahra Adibi, Zahra Gharari, Bahareh Attaran, Roshanak Zarrin Ghalami,
Volume 12, Issue 2 (9-2025)
Abstract
Plant secondary metabolites like phenols and flavonoids neutralize free radicals and are linked to antioxidant and cytotoxic activities. Due to rising drug resistance in pathogens such as Salmonella paratyphi, Bacillus cereus, Escherichia coli, and Staphylococcus aureus, medicinal herbs are increasingly explored for antimicrobial properties. This study evaluated the total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity, and antibacterial effects of Arctium lappa. TPC, TFC, and antioxidant levels were measured using Folin-Ciocalteu, Aluminum chloride, FRAP, and DPPH assays, respectively. Antibacterial activities were assessed by microdilution broth and disc diffusion methods to determine MIC50 and MBC values. Results showed that A. lappa ethanolic extract, prepared with diluted water and the boiling method, had the highest flavonoid content (7.9 ± 0.40 mg/g DW). The leaves and flowers extract, using methanol and the boiling method, had the highest phenolic content (62.13 ± 0.73 mg/g DW) and antioxidant capacity. The ethanolic extract of A. lappa leaves also demonstrated the strongest antibacterial activity, with an MBC of 0.140 mg/mL and an 8 ± 0.4 mm inhibition zone against all tested bacteria. These findings suggest A. lappa bioactive compounds, particularly phenolics and flavonoids, offer promising potential for treating bacterial infections in pharmacognostic applications.
