Antioxidant activity and high-performance liquid chromatographic analysis of phenolic compounds during in vitro callus culture of Plantago ovata Forsk. and effect of exogenous additives on accumulation of phenolic compounds.

BACKGROUND: Plantago ovata, commonly called psyllium, is known to be a rich source of polyphenolic compounds. The present study was aimed at determining polyphenol content and studying their antioxidant activities in P. ovata during in vitro callus culture. An attempt was also made to enhance polyphenol content using external additives. The role of PAL gene in polyphenol accumulation was also studied. RESULTS: The study indicated the presence of significant amounts of polyphenols, including flavonoids, in P. ovata callus. A gradual increase in polyphenol and flavonoid content was observed up to the third passage (63 days) of callus culture, which declined at the next passage. The third-passage callus showed highest antioxidant activity. High-performance liquid chromatographic results indicated the presence of high amounts of gallic acid and rutin in P. ovata calli; however, other polyphenols were also present but to a lesser extent. Additive supplementation was effective in enhancing polyphenol production and in increasing antioxidant activity in P. ovata callus. CONCLUSION: The present research reported accumulation of polyphenols in callus culture of P. ovata, which could be applied to isolation of polyphenols for various beneficial purposes. It also indicated enhancement in the production of several polyphenols and also an increase in antioxidant activity in the additive-treated callus.

Cross-adaptation to cadmium stress in Plantago ovata by pre-exposure to low dose of gamma rays: Effects on metallothionein and metal content.

PURPOSE: To investigate the effects of gamma pre-exposure on cadmium accumulation in Plantago ovata seedlings. Metallothionein (MT) localization was also studied following Cadmium (Cd) treatment in P. ovata. MATERIALS AND METHODS: DNA damage was determined by alkaline comet assay. MT gene and protein expression were studied by real-time polymerase chain reaction and flow cytometry, respectively, in root and shoot tissues. Metal accumulation (Cd, zinc [Zn], iron [Fe]) was evaluated by Atomic Absorption Spectroscopy. RESULTS: Cd treatment decreased seed germination rate, biomass and free radical scavenging activity and increased DNA damage in a dose-dependent manner. When P. ovata seeds were pre- exposed to 5 Gy gamma dose (prior to Cd treatment) seed germination rate, biomass and free radical scavenging activity increased significantly. MT genes (PoMT1, PoMT2 and PoMT3) and MT protein expression enhanced when 5 Gy gamma-irradiated seeds were grown in Cd containing medium and Cd accumulation also increased in a dose-dependent manner. CONCLUSIONS: Higher Cd accumulation in P. ovata seedlings may be attributed to the upregulation of PoMT genes in gamma pretreated seedlings. Localization of metallothionein in cytosol and nucleus indicated its positive role against Cd-mediated cytotoxic and genotoxic effects.

Alterations in transcriptome and proteome on metallothioneins following oxidative stress induced by sublethal doses of cadmium and gamma rays in Plantago ovata.

PURPOSE: To study the oxidative stress-induced changes by sublethal doses of cadmium chloride (CdCl2) and gamma irradiation, two redox-inducing agents, on metallothionein (MT) gene and protein expression in Plantago ovata Forsk (P. ovata). MATERIALS AND METHODS: Chlorophyll content was estimated to study the stress response in P. ovata seedlings following exposure to gamma irradiation and CdCl2. Lipid peroxidation and proline content, two oxidative stress markers, were also studied. The level of metallothionein gene and protein expression was further investigated using polymerase chain reaction (PCR), reverse transcription-PCR (RT-PCR), immunocytochemistry and flow cytometry. RESULTS: Three MT genes of P. ovata namely PoMT 1, PoMT 2 and PoMT 3 were isolated, sequenced and characterized and their expressions were found to be altered in the case of both oxidative stresses in a dose-dependent and tissue-specific manner. The results were in agreement with the observations from immunocytochemistry and FACS analysis. CONCLUSIONS: The results suggest that both gamma irradiation and CdCl2 alter redox balance in P. ovata. The metallothionein gene may play an important role in metal tolerance and stress balance. It is conjectured that the stress-mediated imbalance is maintained by altered MT gene and protein expression.