Process optimization for green synthesis of silver nanoparticles using Rubus discolor leaves extract and its biological activities against multi-drug resistant bacteria and cancer cells.

Multi-drug resistant (MDR) bacteria are considered a serious public health threat. Also, increasing rate of resistance to anticancer drugs, as well as their toxicity, is another point of concern. Therefore, the new antibacterial and anticancer agents are always needed. The synthesizing silver nanoparticles (AgNPs) using medicinal plants, is an effective approach for developing novel antibacterial and anticancer agents. Rubus discolor, a native species of the Caucasus region, produces leaves that are typically discarded as a by-product of raspberry production. The present study has focused on optimizing the green synthesis of AgNPs using R. discolor leaves extract through response surface methodology. The optimal values for AgNPs synthesis were an AgNO3 concentration of 7.11 mM, a time of 17.83 h, a temperature of 56.51 °C, and an extract percentage of 29.22. The production of AgNPs was confirmed using UV-visible spectroscopy (λmax at 456.01 nm). TEM analysis revealed well-dispersed AgNPs (an average size of 37 nm). The XRD analysis confirmed the crystalline structure. The EDX detected a strong peak at 3 keV corresponded to Ag. The zeta potential value (- 44.2 mV) indicated the stability of nanoparticles. FT-IR spectra showed the presence of various functional groups from plant compounds, which play an important role in the capping and bio-reduction processes. The AgNPs revealed impressive antibacterial activities against MDR Escherichia coli and Pseudomonas aeruginosa (MIC ranging from 0.93 to 3.75 mg ml-1). The phytochemical analysis indicated the presence of phenolics, tannins, and flavonoids on the surface of AgNPs. They also showed significant cytotoxic effects on A431, MCF-7, and HepG2 cells (IC50 values ranging from 11 to 49.1 µg ml-l).

Isolation and structure elucidation of the compounds from Teucrium hyrcanicum L. and the investigation of cytotoxicity, antioxidant activity, and protective effect on hydrogen peroxide-induced oxidative stress.

BACKGROUND: Teucrium hyrcanicum L. (family Lamiaceae) is widely distributed in the North and Northwest of Iran. It has been used in the form of tea, tonic, and tincture for the treatment of various diseases such as cough, rheumatism, and fever. METHODS: In this study, the total phenolic and flavonoid contents, antioxidant and cytotoxic activities of methanol extract and different fractions of T. hyrcanicum were measured. Furthermore, the potential ability of T. hyrcanicum to protect against H2O2-induced oxidative stress was tested on the NIH3T3 cell line. Then, the isolation and structure elucidation of the compounds were performed on the most potent fractions. Finally, the quantification of isolated compounds in methanol extract (ME) was done by the HPLC method. Isolated phytochemicals were assessed for the cytotoxic and antioxidant activities. RESULTS: The results indicated that the methanol fraction (MF) had the highest amount of phenolic and flavonoid contents (69.36 mg GAE/g extract and 68.95 mg QE/g extract). The highest radical scavenging activities were observed from MF and ME (IC50 44.32 and 61.12 µg.ml-1, respectively). The best cytotoxicity was obtained by ethyl acetate fraction (EF) against A431 and MCF7 cell lines (IC50 values of 235.4and 326.6 µg.ml-1, respectively). The pretreatment with MF exerts the highest reduction in malondialdehyde (MDA) formation (IC50 2.51 µM, p < 0.001) compared to the H2O2 group (5.77 µM). Also, MF significantly inhibited H2O2-induced Glutathione (GSH) oxidation (p < 0.001). Furthermore, two phenolic compounds, acteoside and quercetin, were isolated and identified in MF and EF, respectively. The IC50 values of acteoside and quercetin in the DPPH assay were 7.19 and 5.56 µg.ml-1, respectively. Both quercetin and acteoside significantly reduced the MDA formation and inhibited GSH oxidation, which was comparable with BHA (as a standard antioxidant) (p < 0.05). Acteoside demonstrated significant cytotoxicity against all tested cell lines (IC50 = 32 to 145 µg.ml-1). The HPLC quantification of isolated compounds revealed that the quantity of acteoside and quercetin in ME were 93.31 and 16.87 µg.mg-1, respectively. CONCLUSION: The isolated compounds (quercetin and acteoside) had significant antioxidant activities and revealed a protective effect on H2O2-induced oxidative stress which was comparable with BHA.

Investigation of phenolic compounds and antioxidant activity of leaves extracts from seventeen cultivars of Iranian olive (Olea europaea L.).

The leaves of seventeen cultivars of olive growing in the north of Iran were investigated for total phenol content and antioxidant activity. The identification and quantification of main phenolic compounds were performed by reverse phase high performance liquid chromatography with diode array detector. The cultivars Kalamon, Gordal, and Coratina contained the highest concentration of phenolic compounds (190.65 ± 0.03, 184.72 ± 0.001, and 155.91 ± 0.06 mg GAE/g extract, respectively). The maximum radical scavenging activities were found in Gordal, Coratina, and Kalamon extracts (IC50 20.66, 22.95, and 26.74 µg ml-1, respectively). The extracts of Mishen, Fishomi, and Arbequina (1971.37 ± 0.007, 1794.57 ± 0.001, and 1760.57 ± 0.005 µmol Fe II/g dried extract, respectively) showed highest antioxidant activity in FRAP assay. The identification analysis demonstrated the present of vanillin, rutin, luteolin 7-O-glucoside, oleuropein, and quercetin. The highest oleuropein concentrations were detected in cultivars Mishen, Beleidi, Kalamon, and Roghani while it was not detected in cultivars Conservolea, Amigdalolia, Leccino, and Fishomi.