Isolation, Identification, and Characterization of Phosphate-Solubilizing Bacteria from Tunisian Soils.

Soil microorganisms play an important role in maintaining natural ecological balance through active participation in carbon, nitrogen, sulfur, and phosphorous cycles. Phosphate-solubilizing bacteria (PSB) are of high importance in the rhizosphere, enhancing the solubilization of inorganic phosphorus complexes into soluble forms available for plant nutrition. The investigation of this species of bacteria is of major interest in agriculture, as they can be used as biofertilizers for crops. In the present study, 28 isolates of PSB were obtained after the phosphate enrichment of soil samples from five Tunisian regions. Five PSB species were identified by 16S rRNA gene sequencing including Pseudomonas fluorescens, P. putida, and P. taiwanensis, Stenotrophomonas maltophilia, and Pantoea agglomerans. Solid and liquid Pikovskaya's (PVK) and National Botanical Research Institute's (NBRIP) media containing insoluble tricalcium phosphate were used for the evaluation of the phosphate solubilization ability of the bacterial isolates by two methods: visual evaluation of the solubilization zone around colonies (halo) and determination of solubilized phosphates in liquid medium by the colorimetric method of the vanado-molybdate yellow. Based on the results of the halo method, the isolate of each species that showed the higher phosphate solubilization index was selected for evaluation of phosphate solubilization by the colorimetric method. In the liquid media, the bacterial isolates showed phosphate solubilization ranging from 535.70 to 618.57 µg mL-1 in the NBRIP medium, and 374.20 to 544.28 µg mL-1 in the PVK medium, with the highest values produced by P. fluorescens. The best phosphate solubilization ability and higher reduction in broth pH, which indicates higher organic acid production, were achieved in NBRIP broth for most of the PSB. Strong correlations were observed between the average capability of PSB to solubilize phosphates and both the pH and total phosphorous content in the soil. The production of the hormone indole acetic acid (IAA), which can promote plant growth, was observed for all five PSB species. Among them, P. fluorescens obtained from the forest soil of northern Tunisia showed the highest production of IAA (50.4 ± 0.9 µg mL-1).

Antioxidant Properties, Phytoactive Compounds and Potential Protective Action of Salvia officinalis Flowers Against Combined Gastro-Intestinal Ulcer and Diarrhea Experimentally Induced in Rat.

The present study was conducted to investigate the protective action of Salvia officinalis flowers aqueous extract (SOFAE) against combined gastro-intestinal (GI) disorders-induced by ethanol and castor oil administration in rats. Adult male Wistar rats were divided into seven groups of ten each and various doses of SOFAE (50, 100, and 200 mg kg-1, b.w., p.o.) and sulfasalazine (100 mg kg-1, b.w., p.o.) were daily administrated during 15 days. After, animals were intoxicated with a single oral administration of ethanol (4 g kg-1, b.w., p.o.) and castor oil (5 mL kg-1, b.w., p.o.). We found that SOFAE contains several phytoactive compounds with a strong ABTS scavenging ability. In vivo, we showed that SOFAE protected against EtOH/CO-induced macroscopic and histological alterations in GI tract accompanied by intestinal fluid accumulation and gastric juice decrease. SOFAE significantly counteracted lipoperoxydation increase and reversed the depletion of both enzymatic and non-enzymatic antioxidants. More importantly, SOFAE significantly reduced the levels of inflammatory markers (CRP and ALP) in plasma and mucosal GI tract. In conclusion, our data clearly indicate that the SOFAE exerted a potential protective effect against EtOH-induced peptic ulcer combined with CO-induced diarrhea in rats. These effects could be associated with its antioxidant and anti-inflammatory properties.

Antioxidant Properties of Salvia officinalis Decoction Extract and Mechanism of Its Protective Effects on Ethanol-Induced Liver and Kidney Injuries.

This study assessed the hepato- and nephroprotective effects of Salvia officinalis flowers decoction extract (SODE) against ethanol (EtOH)-induced oxidative stress in rats as well as the possible mechanism implicated in such protection. Animals were divided into four groups: control, EtOH, and EtOH+SODE. Wistar rats were pretreated with SODE (50, 100, and 200 mg/kg, body weight [b.w.], p.o.) for 15 days and intoxicated during 2 h by acute oral administration of EtOH (4 g/kg, b.w.) 60 min after the last dose of SODE. We found that SODE pretreatment, in vivo, protected against EtOH-induced liver and kidney injuries evident by plasma transaminases activity and preservation of the hepatic tissue structure. Compared with the control group, the animals treated with the SODE showed a significant decrease (68.81 ± 6.89-50.65 ± 3.97 UI/L) of alanine aminotransferase (ALT) and aspartate aminotransferase (AST; 144.38 ± 6.58-113.64 ± 8.03 UI/L) in a dose-dependent manner. By contrast, the plant extract significantly and dose dependently increased (0.175 ± 0.077-0.302 ± 0.011 mmol/L) the uric acid. The SODE counteracted EtOH-induced liver and kidney lipoperoxidation, preserved sulfhydryl groups (-SH) and glutathione reduced (GSH) contents. Our extract prevented the depletion of antioxidant enzyme activities such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx). We also showed that acute alcohol administration increased tissue and plasma hydrogen peroxide (H2O2), calcium and free iron levels. Of interest, SODE pretreatment reversed all EtOH-induced disturbances in intracellular mediators. More importantly, SODE treatment significantly protected against alcohol-induced inflammation by reducing C-reactive protein (CRP) and alkaline phosphatase (ALP) activities in plasma. It was concluded that the SODE exerted a potential protective effect against EtOH-induced inflammation and oxidative stress in the rat organs. This study recommends that the consumption of sage flowers is useful for patients who suffer from hepato- and nephrotoxicity.

Comparative Studies of Phytochemical Screening, HPLC-PDA-ESI-MS/MS-LC/HR-ESI-MS Analysis, Antioxidant Capacity and in Vitro Fermentation of Officinal Sage (Salvia officinalis L.) Cultivated in Different Biotopes of Northwestern Tunisia.

We aimed in the present study to investigate the chemical composition, the antioxidant capacities as well as the in vitro fermentation properties of Salvia officinalis leaves aqueous extract (SOLAE) grown in four regions of northwestern Tunisia. Our data firstly indicated a spatial variation (P<0.05) in condensed tannins, total lipids, polyphenols and flavonoids contents. The HPLC-PDA-ESI-MS/MS-LC/HR-ESI-MS technique allowed to the identification of 13 phenolic compounds and showed that protocatechuic acid is the major constituent of the plant leaves grown in Tabarka, Ain Draham and Testour. The SOLAE of the plant grown in Tabarka presents the most potent scavenging activity against DPPH radical and had the highest percentage of inhibition. More importantly, we found in the present study that the digestibility of dry matter and in vitro fermentation showed a significant variation between the regions and the animal species. Also, we showed a very positive correlation between antioxidant properties and phenolic compounds contents. In conclusion, we suggest that SOLAE had potential beneficial effects owing in part to its antioxidant and ROS scavenging activities. Therefore, S. officinalis can be proposed as an additive food for animals' nutrition and health.