Malek Besbes Hlila

Phenolic composition, antioxidant and anti-acetylcholinesterase activities of the Tunisian Scabiosa arenaria

Abstract Context: There is a need for the discovery of novel natural antioxidants and acetylcholinesterase inhibitors (AChEIs) that are safe and effective at a global level. This is the first study on antioxidant and anti-acethylcholinesterase activity of Scabiosa arenaria Forssk (Dipsacaceae). Objective: The antioxidant potential and anti-acetylcholinesterase (AChE) activity of S. arenaria were investigated. Material and methods: The crude, ethyl acetate (EtOAc), butanol (n-BuOH) and water extracts prepared from flowers, fruits and stems and leaves of S. arenaria were tested to determine their total polyphenol content (TPC), total flavonoid content (TFC), total condensed tannin content (CTC) and their antioxidant activity by using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), reducing power and β-carotene bleaching inhibition activity. Anti-AChE activity was also determined. Results: EtOAc and n-BuOH fractions of fruits had both the highest (TPC) (269.09 mg gallic acid equivalents/g dry weight). The crude extract of stems and leaves had the highest TFC (10.9 mg quercetin equivalent/g dry weight). The n-BuOH fraction of stems and leaves had the highest CTC (489.75 mg catechin equivalents/g dry weight). The EtOAc fraction of flowers exhibit a higher activity in each antioxidant system with a special attention for DPPH assay (IC50 = 0.017 mg/mL) and reducing power (EC50 = 0.02 mg/mL). The EtOAc and n-BuOH fractions of stems and leaves showed strong inhibition of AChE (IC50 = 0.016 and 0.029 mg/mL, respectively). Discussion and conclusions: These results suggest the potential of S. arenaria as a possible source of novel compounds and as an alternative antioxidant and AChEIs.

α-Glucosidase inhibition by Tunisian Scabiosa arenaria Forssk. extracts.

Recent decades have witnessed a sharp increase in the incidence and prevalence of type 2 diabetes mellitus. One antidiabetic therapeutic approach is to reduce gastrointestinal glucose production and absorption through the inhibition of carbohydrate-digesting enzymes such as α-amylase and α-glucosidase. In this study, crude extracts and their corresponding fractions of flowers, fruits, (stems and leaves) and roots of the endemic North African plant Scabiosa arenaria Forssk. were screened for their ability of α-glucosidase inhibition. It was found that the fruits ethyl acetate (EtOAc), the fruits butanolic (n-BuOH) and the flowers ethyl acetate (EtOAc) fractions inhibited α-glucosidase in a non competitive manner with IC50 values of 0.11±0.09, 0.28±0.04 and 0.221±0.01mg/ml, respectively. RP-HPLC analysis indicated that the major components of these active fractions are flavonoid aglycone, cinnamic acid and its derivatives. This result supports the conclusion that the three studied fractions could be a useful natural source for the development of a novel α-glucosidase inhibitory agent against diabetic complications.

Antimicrobial Activity of Scabiosa arenaria Forssk. Extracts and Pure Compounds Using Bioguided Fractionation

The emergence of multidrug resistant pathogens threatened the clinical efficacy of many existing antibiotics. This situation has been recognized globally as a serious concern and justifies further research to discover antimicrobial agents from natural origins including plant extracts. The aim of our work was to evaluate the antimicrobial activities of Scabiosa arenaria Forssk. extracts and pure compounds using a bioguided fractionation, and try to explain some traditional use of this genus. The best antimicrobial activity‐guided fractionation was obtained by BuOH fractions of flowers, fruits and (stems and leaves) against Escherichia coli, Pseudomonas aeruginosa and Candida albicans with minimum inhibitory concentration (MIC) values from 0.0195 to 5 mg/ml. Escherichia coli was the most affected bug, thus the MIC of fruits BuOH extract showed the best anti‐Escherichia coli activity (MIC = 0.0195 mg/ml), followed by the (stems and leaves) and flowers BuOH extracts; MIC = 0.078 and 0.15 mg/ml, respectively. Furthermore, the subfractions obtained from these three mixed fractions showed also an important antimicrobial activity against the three microorganisms, with MIC values between 0.0195 and 0.312 mg/ml. The fractionation of the aerial part BuOH fraction led to the isolation of oleanolic acid (1) and luteolin 7‐O‐glucopyranoside (2) which are reported here for the first time from S. arenaria. Both compounds showed good antimicrobial activities with MIC values ranging from 170 to 683 μm and 86 to 347 μm, respectively. These results support the use of the Scabiosa genus to inhibit the growth of tested pathogenic bacteria and yeasts which may reduce illnesses associated with their exposure.

Biological properties of Hertia cheirifolia L. flower extracts and effect of the nopol on α-glucosidase

In screening for antioxidant and α-glucosidase inhibitors from the extracts of Hertia cheirifolia L. flowers, the petroleum ether extract showed interesting antioxidant activity and inhibitory effect on the activity of α-glucosidase. The fractionation of this extract resulted in the isolation of a compound which is characterized by NMR and ESI-MS as a nopol. The nopol exhibited potent α-glucosidase inhibitory potential with IC50 value of 220μM. The kinetic evaluation indicated that it acts as a non-competitive inhibitor. A molecular docking study proved that the nopol presented a strong affinity with amino acid residues of α-glucosidase.

Chemical Composition, Antioxidant Properties, α-Glucosidase Inhibitory, and Antimicrobial Activity of Essential Oils from Acacia mollissima and Acacia cyclops Cultivated in Tunisia

The genus Acacia is quite large and can be found in the warm subarid and arid parts, but little is known about its chemistry, especially the volatile parts. The volatile oils from fresh flowers of A. mollissima and A. cyclops (growing in Tunisia) obtained by hydrodistillation were analyzed by GC then GC/MS. Eighteen (94.7% of the total oil composition) and 23 (97.4%) compounds were identified in these oils, respectively. (E,E)‐α‐Farnesene (51.5%) and (E)‐cinnamyl alcohol (10.7%) constituted the major compounds of the flower oil of A. mollissima, while nonadecane (29.6%) and caryophyllene oxide (15.9%) were the main constituents of the essential oil of A. cyclops. Antioxidant activity of the isolated oils was studied by varied assays, i.e., 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and 2,2‐azinobis 3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS); the isolated oils showed lowest IC50 (4 – 39 μg/ml) indicating their high antioxidant activity. The α‐glucosidase inhibitor activity was also evaluated and Acacia oils were found to be able to strongly inhibit this enzyme with IC50 values (81 – 89 μg/ml) very close to that of acarbose which was used as positive control. Furthermore, they were tested against five Gram‐positive and Gram‐negative bacteria and one Candida species. Essential oil of A. mollissima was found to be more active than that of A. cyclops, especially against Pseudomonas aeruginosa (MIC = 0.31 mg/ml and MBC = 0.62 mg/ml).

Chemical composition and biological activities of Eruca vesicaria subsp. longirostris essential oils

Abstract Context To date, there are no reports to validate the Tunisian traditional and folklore claims of Eruca vesicaria (L) Cav. subsp. longirostris (Brassicaceae) for the treatment of disease. Objective Investigation of the chemical composition antimicrobial and antioxidant activity of essential oils from Eruca longirostris leaves, stems, roots and fruits. Materials and methods The essential oils of E. longirostris from leaves, stems, roots and fruits were obtained after 4 h of hydrodistillation. Chemical compositions were determined using a combination of GC/FID and GC/MS. The in vitro antimicrobial activity of the volatile constituents of E. longirostris was performed in sterile 96-well microplates against three Gram-positive, four Gram-negative bacteria and one strain as yeast. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration values were reported. Furthermore, the antioxidant activity was evaluated by DPPH and ABTS assays. Results The main compound for fruits, stems and roots was the erucin (96.6%, 85.3% and 83.7%, respectively), while β-elemene (35.7%), hexahydrofarnesylacetone (23.9%), (E)-β-damascone (15.4%), erucin (10.6%) and α-longipinene (9.6%) constituted the major compounds in the essential oil of the leaves. The experimental results showed that in all tests, essential oil of fruits showed the better antioxidant activity than the others. On the other hand, the oils of stems, fruits and roots showed significant antimicrobial activity with MIC values ranging from 0.125 to 0.31 mg/mL against Candida species, Gram-positive and Gram-negative bacteria, mainly Salmonella enterica. Conclusions The present results indicate that essential oils of E. longirostris can be used as a source of erucin.

Characterisation of phenolic antioxidants in Scabiosa arenaria flowers by LC–ESI-MS/MS and NMR

This work describes the bioguided fractionation of the flowers ethyl acetate fraction of Scabiosa arenaria Forssk. (Dipsacaceae).

Phytochemical and Pharmacological Properties of Hertia L. Genus

The genus Hertia L. contains 12 species distributed all over south and North Africa and Southwest Asia. Some species of these plants are used traditionally for pain of stomach and to reduce hyperglycemia. It has been found that the species belonging to this genus possesses a rich phytochemical content and a wide range of pharmacological activities such as acaricidal, spasmolytic, anti-inflammatory, cytotoxic, anthelmintic, antibacterial, antioxidant effects and α-glucosidase inhibition. In an aim to highlight the importance of Hertia, this study evaluated its phytochemical and pharmacological properties.