Rhaponticum acaule (L) DC essential oil: chemical composition, in vitro antioxidant and enzyme inhibition properties.

BACKGROUND: α-glucosidase is a therapeutic target for diabetes mellitus (DM) and α-glucosidase inhibitors play a vital role in the treatments for the disease. Furthermore, xanthine oxidase (XO) is a key enzyme that catalyzes hypoxanthine and xanthine to uric acid which at high levels can lead to hyperuricemia which is an important cause of gout. Pancreatic lipase (PL) secreted into the duodenum plays a key role in the digestion and absorption of fats. For its importance in lipid digestion, PL represents an attractive target for obesity prevention. METHODS: The flowers essential oil of Rhaponticum acaule (L) DC (R. acaule) was characterized using gas chromatography-mass spectrometry (GC-MS). The antioxidant activities of R. acaule essential oil (RaEO) were also determined using 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), reducing power, phosphomolybdenum, and DNA nicking assays. The inhibitory power of RaEO against α-glucosidase, xanthine oxidase and pancreatic lipase was evaluated. Enzyme kinetic studies using Michaelis-Menten and the derived Lineweaver-Burk (LB) plots were performed to understand the possible mechanism of inhibition exercised by the components of this essential oil. RESULTS: The result revealed the presence of 26 compounds (97.4%). The main constituents include germacrene D (49.2%), methyl eugenol (8.3%), (E)-ß-ionone (6.2%), ß-caryophyllene (5.7%), (E,E)-α-farnesene (4.2%), bicyclogermacrene (4.1%) and (Z)-α-bisabolene (3.7%). The kinetic inhibition study showed that the essential oil demonstrated a strong α-glucosidase inhibiton and it was a mixed inhibitor. On the other hand, our results evidenced that this oil exhibited important xanthine oxidase inhibitory effect, behaving as a non-competitive inhibitor. The essential oil inhibited the turkey pancreatic lipase, with maximum inhibition of 80% achieved at 2 mg/mL. Furthermore, the inhibition of turkey pancreatic lipase by RaEO was an irreversible one. CONCLUSION: The results revealed that the RaEO is a new promising potential source of antioxidant compounds, endowed with good practical applications for human health.

Phytochemical analysis and biological activities of Hertia cheirifolia L. roots extracts.

OBJECTIVE: To test the antioxidant, antimicrobial and α-glucosidase inhibitory activities of the roots extracts from Hertia cheirifolia (H. cheirifolia) L. METHODS: Total phenolics and total flavonoids content of the different extracts were determined by colorimetric methods and reverse phase high-performance liquid chromatography (RP-HPLC) was performed to identify various chemical components. The different extracts were evaluated for antioxidant activities by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis-3-ethylenebenzothiozoline-6-sulfonic acid (ABTS+) and ß-carotene bleaching tests and α-glucosidase inhibitory properties. The antimicrobial activity was carried out in vitro by the broth dilution method. RESULTS: Trans-cinnamic acid, rutin hydrate, naringin and quercetin were the main compounds of the ethyl acetate extract from H. cheirifolia L. This extract has significant scavenging activity to decrease free radicals especially for DPPH and ABTS radicals. As well as, the ethyl acetate extract exhibited an antimicrobial property against bacterial strains. Bacillus licheniformis and Salmonella enterica were the most sensitive strains with minimum inhibitory concentration values of 0.156 mg/mL. CONCLUSION: The ethyl acetate extract was found to be selectively antioxidant and antimicrobial.

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

OBJECTIVES: This work describes the bioguided fractionation of the flower's ethyl acetate fraction of Scabiosa arenaria Forssk. (Dipsacaceae). METHODS: The identification of the pure compound isolated has been studied by mono-dimensional NMR experiments. The mixture of phenolic compounds was analysed by LC-ESI-MS/MS. The antioxidant activity has been evaluated by the 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. KEY FINDINGS: The bioguided fractionation of the flower's ethyl acetate fraction of Scabiosa arenaria led to the isolation of a pure compound: luteolin. The mixture of three phenolic compounds was identified as: 1, 4-O-dicaffeoylquinic acid, apigenin 7-O-glucoside and luteolin-7-O-glucoside. Two of which are reported here for the first time in Scabiosa genus. Luteolin had the highest antioxidant activity with an IC50 value of 0.02 ± 0.007 mg/ml, followed by the three phenolic compounds with an IC50 value of 0.025 ± 0.008 mg/ml. CONCLUSIONS: The results of the present work indicate that S. arenaria flower's ethyl acetate extract could be used as natural antioxidant agents in food preservation and human health.

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.