Moringa oleifera leaves: could solvent and extraction method affect phenolic composition and bioactivities?

This study was carried out to evaluate the effect of extraction methods (direct maceration (DM) and successive maceration (SM)) and solvents (dichloromethane (DCM), ethyl acetate (EAc), butanol (But), and aqueous extraction (Aqu)) on the phenolic composition and biological activities of Moringa oleifera leaves cultivated for the first time in Tunisia. Total polyphenol content (TPC), total flavonoid content (TFC) and LC-MS analysis were performed for all extracts. Antioxidant potential by DPPH, metal chelating, and FRAP assays, antibacterial activity against Staphylococcus aureus (ATCC 29213) and Escherichia coli (ATCC 25922) by the minimum inhibitory concentration method (MIC) and cytotoxic properties against lung cancer cells (A549), were determined. Phenolic compounds and biological activities of M. oleifera leaves depend on the method and the solvent used for the extraction of these bioactive substances. The But extract prepared by SM method exhibited the highest amounts of TPC (103.06 ± 0.5 mg GAE/g DE) and showed the strongest potential antioxidant (CI50 = 0.26 mg/mL on DPPH test), antibacterial (MIC = 250 µg/mL) and cytotoxic activities (GI50 = 69.9 µg/mL). LC-MS analysis showed that 28 phenolic compounds of 33 tested standards were found in M. oleifera leaves. The But extract obtained by SM method exhibited the highest amounts of rutin, quercetin and syringic acid.

Bioactive flavones isolated from Tunisian Artemisia campestris L. Leaves.

Four flavones were isolated from dried leaves of Artemisia campestris L. 2',4',5,7-tetrahydroxy-5',6-dimethoxyflavone, eupatilin and dimethoxycentaureidin were reported for the first time in this species whereas cirsiliol was previously identified but it was isolated for the first time. Their structures were elucidated by spectroscopic methods, including 1D and 2D NMR experiments and mass spectrometry analysis. In addition, all isolated flavones were evaluated for their antioxidant, anti-inflammatory, anti-superoxide dismutase, anti-xanthine oxidase and cytotoxic activities. The results showed that all isolated compounds exhibited potent anti-xanthine oxidase activity with IC50 ranging from 3.3 to 6.8 µM, which was higher than that of the control compound allopurinol (8.2 ± 0.6 µM). In addition, cirsiliol was found to be the most cytotoxic against OVCAR-3, IGROV-1and HCT-116 cell lines at 15µM, with inhibition percentage values of 53.7, 48.8 and 40.9%, respectively. All compounds also showed weak to moderate anti-inflammatory and anti-superoxide dismutase activities.

Antioxidant and antitumor activities of Artemisia campestris and Thymelaea hirsuta from southern Tunisia.

The essential oil of Artemisia campestris and the ethanol-water, hexane and water extracts of A. campestris and Thymelaea hirsuta collected in southern of Tunisia were investigated for their antioxidant (DPPH, ABTS and beta-carotene methods) and antitumor growth inhibition of human colon cancer HT-29 cells using MTT test activities. All the A. campestris extracts tested at high concentrations (100 µg/ml) showed activity ranging from 19.5% for essential oil to 64.4% of negative control growth for infusion extract, except the hexane extract. With T. hirsuta, all the extracts tested (hexane and ethanol-water), except the infusion extract, also exhibited antitumor activity (58.2% and 65.5% of control growth respectively). The ethanol-water and infusion extracts of A. campestris showed higher antioxidant activity, polyphenol and flavonoid contents than those of T. hirsuta. These results show that there is a positive correlation between the antitumor activity and the antioxidant activity, and of these two activities and with the levels of polyphenols and flavonoids. The essential oil and the other extracts of A. campestris, which exhibited significant antitumor activity against the HT-29 cells deserve further research into the chemoprevention and treatment of colon cancer.

Composition and intraspecific chemical variability of the essential oil from Artemisia herba-alba growing wild in a Tunisian arid zone.

The intraspecific chemical variability of essential oils (50 samples) isolated from the aerial parts of Artemisia herba-alba Asso growing wild in the arid zone of Southeastern Tunisia was investigated. Analysis by GC (RI) and GC/MS allowed the identification of 54 essential oil components. The main compounds were ß-thujone and α-thujone, followed by 1,8-cineole, camphor, chrysanthenone, trans-sabinyl acetate, trans-pinocarveol, and borneol. Chemometric analysis (k-means clustering and PCA) led to the partitioning into three groups. The composition of two thirds of the samples was dominated by α-thujone or ß-thujone. Therefore, it could be expected that wild plants of A. herba-alba randomly harvested in the area of Kirchaou and transplanted by local farmers for the cultivation in arid zones of Southern Tunisia produce an essential oil belonging to the α-thujone/ß-thujone chemotype and containing also 1,8-cineole, camphor, and trans-sabinyl acetate at appreciable amounts.