Kristiaan Demeyer

Seasonal, gender and regional variations in total phenolic, flavonoid, and condensed tannins contents and in antioxidant properties from Pistacia atlantica ssp. leaves

Abstract Context: The widespread use of Pistacia atlantica Desf. ssp. (Anacardiaceae) in traditional medicine can be partly attributed to the content of its secondary metabolites, in particular, the phenolic compounds. Objective: The effects of harvest period, growing region and gender on the phenolic compounds, flavonoids and condensed tannins contents were studied, as well as on the antioxidant activities of P. atlantica leaves in order to provide a scientific basis for optimal collection. Materials and methods: Leaves were collected monthly from April to October 2010 in two Algerian sites. The powdered leaves were used for preparing the ethyl acetate extract. Contents of total phenolics (TPC), flavonoids (FC) and condensed tannins (CTC) were determined spectrophotometrically. Antioxidant activity was evaluated through radical scavenging activity (RSA) of 2,2-diphenyl-1-picrylhydrazyl (250 μM) and the reducing power capacity (RPC) determination by K3Fe(CN)6 (1%). Results: The TPC was found to vary from 79 ± 13 to 259 ± 8 mg gallic acid equivalents/g of dry weight (DW) during the study period. The RSA and RPC varied between 262 ± 18 and 675 ± 21 mg Ascorbic Acid Equivalent (AAE)/g DW, and from 259 ± 16 to 983 ± 20 mg AAE/g DW, respectively. A seasonal pattern was observed consisting of a decrease in TPC content and RPC from spring to autumn. The FC, CTC and RSA did not show a seasonal pattern. Discussion and conclusion: Our findings showed that secondary metabolite content and antioxidant activities of P. atlantica leaves were more influenced by harvest time and growing region than by gender.

Polyphenolic contents, antioxidant activities and UPLC–ESI–MS analysis of Haplophyllum tuberculatum A. Juss leaves extracts

The aim of this study is to determine the phytochemical profile, the total polyphenolic contents and the antioxidant activities of Haplophyllum tuberculatum leaves extracts. The most active extracts were analyzed by ultra-high performance liquid chromatography coupled to electrospray ionization mass spectrometry. Antioxidant activities were screened by the 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) test and measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azinobis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and β-carotene bleaching inhibition assays. Phytochemical screening of the extracts revealed the presence of various secondary metabolites. The ethyl acetate extract was the richest extract in phenolics and flavonoids with 262mg gallic acid equivalents/g and 99.1mg quercetin equivalent/g of dry weight, respectively. The same extract showed an important scavenging effect on DPPH, ABTS and β-carotene/linoleic acid with IC50 of 0.020mg/mL, 0.029mg/mL and 0.022mg/mL, respectively. The correlations between the antioxidant capacities and the polyphenolic content were ranging between 0.889 and 0.256 and occasionally found to be significant. The UPLC-ESI-MS analysis showed the presence of polyphenolic and alkaloid compounds. Arabelline, majidine, dictamine and a qudsine derivative are found for the first time in H. tuberculatum. The results indicate that polyphenolic and alkaloid compounds may be major contributors to the antioxidant activity of these extracts.

Determination of optimal extraction conditions for phenolic compounds from Pistacia atlantica leaves using the response surface methodology

The response surface methodology in combination with a Box–Behnken experimental design was performed to optimize the extraction conditions, resulting in a maximum yield of the total phenolic content (TPC) from the leaves of Pistacia atlantica. The ranges of the examined independent variables (factors), i.e. extraction time (24–72 hours), liquid-to-solid ratio (30 : 1–50 : 1 ml solvent per g dry leaf) and extraction temperature (35–55 °C), were identified by preliminary experiments. Quadratic polynomial regression models were fitted through the experimental results. They showed acceptable coefficients of multiple determinations. From the models, the liquid-to-solid ratio was found to have the most influence on the extraction of TPC. The optimum extraction conditions were found to be 72 h extraction time and 50 : 1 ml g−1 liquid-to-solid ratio. For the extraction temperature, rather high values (about 50 °C) were found to be the best. Using the optimized conditions, the TPC varied from 256 to 306 mg gallic acid equivalents per g dry leaf in different sample types.

Identification of some Bioactive Metabolites in a Fractionated Methanol Extract from Ipomoea aquatica (Aerial Parts) through TLC, HPLC, UPLC-ESI-QTOF-MS and LC-SPE-NMR Fingerprints Analyses

INTRODUCTION The plant species Ipomoea aquatica contains various bioactive constituents, e.g. phenols and flavonoids, which have several medical uses. All previous studies were executed in Asia; however, no reports are available from Africa, and the secondary metabolites of this plant species from Africa are still unknown. OBJECTIVE The present study aims finding suitable conditions to identify the bioactive compounds from different fractions. METHODOLOGY Chromatographic fingerprint profiles of different fractions were developed using high-performance liquid chromatography (HPLC) and then these conditions were transferred to thin-layer chromatography (TLC). Subsequently, the chemical structure of some bioactive compounds was elucidated using ultra-performance liquid chromatography-quadrupole time of flight-tandem mass spectrometry (UPLC-QTOF-MS) and liquid chromatography-solid phase extraction-nuclear magnetic resonance (LC-SPE-NMR) spectroscopy. RESULTS The HPLC fingerprints, developed on two coupled Chromolith RP-18e columns, using a gradient mobile phase (methanol/water/trifluoroacetic acid, 5:95:0.05, v/v/v), showed more peaks than the TLC profile. The TLC fingerprint allows the identification of the types of chemical constituents, e.g. flavonoids. Two flavonoids (nicotiflorin and ramnazin-3-O-rutinoside) and two phenolic compounds (dihydroxybenzoic acid pentoside and di-pentoside) were tentatively identified by QTOF-MS, while NMR confirmed the structure of rutin and nicotiflorin. CONCLUSION The HPLC and TLC results showed that HPLC fingerprints give more and better separated peaks, but TLC helped in determining the class of the active compounds in some fractions. Bioactive constituents were identified as well using MS and NMR analyses. Two flavonoids and two phenolic compounds were tentatively identified in this species for the first time, to the best of our knowledge. Copyright

Potentially antidiabetic and antihypertensive compounds identified from Pistacia atlantica leaf extracts by LC fingerprinting

Graphical abstract Figure. No caption available. HighlightsIn vitro evaluation of antidiabetic and antihypertensive activities of Pistacia atlantica.Effect of the growing region and gender on the &agr;‐amylase, &agr;‐glucosidase and ACE‐I inhibitory activities of P. atlantica leave extracts.Potentially antidiabetic and antihypertensive compounds indicated from fingerprints using PLS.Identify contributions of the individual phenolic compounds in P. atlantica leaves to the &agr;‐amylase, &agr;‐glucosidase and ACE‐I inhibitory activities. ABSTRACT The objective of this paper is to evaluate the variations in the ability of Pistacia atlantica leaves to inhibit enzymes linked to type 2 diabetes (&agr;‐amylase and &agr;‐glucosidase) and to hypertension (angiotensin converting enzyme‐I (ACE‐I)), depending on harvesting month, gender and growing region, as well as to identify the peaks in chromatographic fingerprints that potentially correspond to components with enzymatic inhibitory activities. In this study, LC fingerprints of P. atlantica leave extracts were developed. Peaks which were probably responsible for the anti‐amylase, anti‐glucosidase and anti‐ACE‐I activities were assigned. For the latter purpose, the relevant information was extracted, linking the chromatographic fingerprints with the activities using a linear multivariate calibration technique, i.e., Partial Least Squares (PLS) regression. Prior to the construction of the models, the fingerprints are aligned using a warping method, called Correlation Optimized Warping (COW). Besides COW, different other data pretreatment methods were applied and compared. Our findings revealed that the influence of the growing region and gender on the &agr;‐amylase, &agr;‐glucosidase and ACE‐I inhibitory activities of P. atlantica leaves was less important than the harvest time. Thirteen common peaks were selected from the chromatograms and used as a dataset to model the biological activities. The peaks potentially responsible for the biological activity of the samples were indicated by studying the regression coefficients of the models. Seven peaks corresponding to possibly anti‐amylase compounds were found, while 6 peaks were considered important for inhibiting the &agr;‐glucosidase activity. Furthermore, the regression coefficients of the hypertension model indicated eight peaks as being important for inhibiting the ACE‐I activity. The contributions of individual phenolic compounds of P. atlantica leaves to the &agr;‐amylase, &agr;‐glucosidase and ACE‐I inhibitory activities were also identified. This investigation showed that the extract of P. atlantica leaves provides a rational basis for the isolation and development of antidiabetic and antihypertensive agents.