Effect of flavonoids from various Mediterranean plants on enzymatic activity of intestinal carboxylesterase

Antihyperglycemic Effect of Rhamnus alaternus L. Aqueous Extract in Streptozotocin-induced Diabetic Rats

BACKGROUND

Traditionally, the aerial parts of Rhamnus alaternus L. have been widely used in Mediterranean countries, including Morocco, to cure diabetes.

AIM

This study aimed to evaluate the antidiabetic effect of Rhamnus alaternus aqueous extract in streptozotocin(STZ)-induced diabetic rats.

OBJECTIVE

This work aimed to evaluate the antihyperglycemic effect of Rhamnus alaternus aqueous extract (RAAE) in normal and diabetic rats. Then the phytochemical composition, antioxidant capacity, and potential toxicity of RAAE were also assessed.

METHODS

The effects of acute (6 h) and subchronic (7 days) oral administration of RAAE (20 mg/kg) on blood glucose levels and lipid profiles were evaluated in normal and diabetic rats. Besides, a preliminary phytochemical screening, quantification of phenolic, flavonoid, and tannin contents as well as the antioxidant activity, using the DPPH method, were evaluated. Additionally, the toxicity of the aqueous extract (5 mg/kg) was also studied and the LD50 value was determined.

RESULTS

RAAE (20 mg/kg) over 7 days of oral administration significantly decreased the blood glucose levels both in normal and diabetic rats. In diabetic rats, this extract also improved oral glucose tolerance. In addition, RAAE possessed significant antioxidant activity. According to preliminary phytochemical research, RAAE contains several chemical compounds, including alkaloids, polyphenols, flavonoids, cyanidins, anthraquinones, and sterols. On the other hand, the quantitative phytochemical study of the aqueous extract revealed a considerable amount of total phenolic compounds (497.93 ± 3.38 mg GAE/1g of RAAE), flavonoids (100.42 ± 0.32 mg RE/ g of RAAE), and tannins (14.32 ± 0.37 mg CE/1g of RAAE).

CONCLUSION

We conclude that RAAE exerts a significant antihyperglycemic effect in STZ-induced diabetic rats at a low dose. Indeed, more research is still required to support the use of this plant in the Moroccan population's diabetes care.

Screening of Rhamnus Purpurea (Edgew.) Leaves for Antimicrobial, Antioxidant, and Cytotoxic Potential

Exploring new antimicrobial and cytotoxic drugs has been one of the most active areas of research. Rhamnus purpurea (Edgew.) buckthorn (Rhamnaceae) is a wild shrub traditionally used in Pakistan for the treatment of various ailments including cancer and infectious diseases. The aim of this study is to find novel antimicrobial and cytotoxic agents of plant origin. The crude methanol extract and full range of fractions of R. purpurea leaves were screened for the said activities using in vitro antimicrobial, antioxidant, and cytotoxic models following standard protocols. The antimicrobial activity was evaluated using the agar well diffusion method, while the antioxidant activity was assessed with 1,1-diphenyl-2-picryl hydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. The cytotoxic effect was investigated against the human cancer cell lines i.e. Caco-2 (gut), A549 (lung), HepG2 (liver), and MDA-MB-231 (breast) by MTS assay. In addition, toxicity studies were conducted on renal and alveolar primary epithelial cells (HRPTEpiC and HPAEpiC, respectively). Phytochemical investigation showed the presence of secondary metabolites such as alkaloids, saponins, tannins, glycosides, phenols, carbohydrates, proteins, and flavonoids. The n-hexane and chloroform fractions showed significant activity against Staphylococcus aureus (MIC 0.60 and 0.68 mg/mL, respectively), Salmonella typhi (MIC 0.48 and 0.45 mg/mL, respectively), and Bacillus subtilis (MIC 0.54 and 0.76 mg/mL, respectively). Among fungal strains, crude methanol and chloroform fractions exhibited significant activity against Fusarium solani (MIC 0.53 and 0.44 mg/mL, respectively) and Aspergillus niger (MIC 0.47 and 0.42 mg/mL, respectively). The crude methanol, n-hexane and chloroform fractions revealed the highest antioxidant activity at 1000 μg/mL, compared to that of ascorbic acid. The n-hexane fraction showed a significant cytotoxic effect against Caco-2, A549, and HepG2 cell lines with IC50 values of 5.65 ± 0.88, 5.50 ± 0.90, and 4.95 ± 1.0 μg/mL, respectively. Similarly, the chloroform fraction depicted significant activity against Caco-2, A549, and HepG2 cell lines with IC50 values of 4.55 ± 1.25, 4.65 ± 1.55, and 2.85 ± 0.98 μg/mL, respectively. The crude methanol extract and almost all fractions exhibited the highest selectivity index (>2.0) for Caco-2, A549, and HepG2 cancer cell lines, providing safety data for this study. The results showed that R. purpurea leaves have excellent antimicrobial, antioxidant, and cytotoxic potential and warrant further studies to search for novel compounds for the said activities.

Rhamnusalaternus Plant: Extraction of Bioactive Fractions and Evaluation of Their Pharmacological and Phytochemical Properties

Rhamnus alaternus, is a wild-growing shrub, belonging to the Rhamnaceae family. Widely distributed in the Mediterranean basin, R. alaternus is used in the usual medicine in numerous countries, mostly Tunisia, Algeria, Morocco, Spain, France, Italy, and Croatia. A large number of disorders-including dermatological complications, diabetes, hepatitis, and goiter problems-can be treated by the various parts of R. alaternus (i.e., roots, bark, berries, and leaves). Several bioactive compounds were isolated from R. alaternus, including flavonoids, anthocyanins, and anthraquinones, and showed several effects such as antioxidant, antihyperlipidemic, antigenotoxic, antimutagenic, antimicrobial, and antiproliferative. This review summarizes the updated information concerning the botanical description, distribution, extraction processes applied on R. alaternus, and its ethnopharmacology, toxicity, phytochemistry, and pharmacological effects.

Modeling and optimizing microwave-assisted extraction of antioxidants from Thymbra Spicata L. and characterization of their phenolic constituents

Response surface methodology was used for modeling and optimizing microwave-assisted extraction of antioxidants from Thymbra spicata L. as a factor of temperature, extraction time, solvent concentration, and solvent-to-solid ratio. The prepared extracts showed maximum antioxidant properties, including total phenolic content (TPC), total antioxidant capacity (TAC), and radical scavenging activity (RSA) at the optimum operating conditions. All models calculated for the three responses that are TPC, TAC, and RSA were noteworthy (p < 0.0001) and showed a significant relationship between the response and independent parameters. There was a close relationship between the experimental and the predicted values obtained using the proposed method. The phenolic antioxidant profile of Thymbra spicata L. extract was characterized with the UPLC-PDA-ESI-MS/MS system and rosmarinic acid was found as a major component (1089.2 ± 10.9 mg/100 g-DS). In the future, this optimized and modeled MAE method can be applied in food and pharmaceutical industries to effectively extract antioxidants from edible Thymbra spicata L. plant.

Flavonoids as human carboxylesterase 2 inhibitors: Inhibition potentials and molecular docking simulations

In our search for natural human carboxylesterase 2 (hCE 2) inhibitors from natural products, we investigated inhibitory effects and mechanisms of flavonoids (1-16) against hCE 2. The results demonstrated that kurarinone (1), baicalein (2), 2-[(2'-(1-hydroxy-1-methylethyl)-7'-(3-methyl-2-butenyl)-2',3'-dihydrobenzofuran)-5-yl]-7-hydroxy-8-(3-methyl-2-butenyl)chroman-4-one (5), luteolin (6), kushenol X (9), and kushenol C (11) displayed significantly inhibitory effects against hCE 2 with IC₅₀ values of 1.46 ± 0.43, 5.22 ± 0.89, 1.13 ± 0.19, 9.78 ± 0.98, 3.05 ± 0.46, and 2.61 ± 0.52 μM, respectively. Compounds 1, 5, 6, 9, and 11 were all uncompetitive inhibitors with Ki values of 1.73, 1.59, 16.89, 1.72, and 0.79 μM, respectively, and their Km values ranged from 2.08 μM to 5.41 μM. Furthermore, molecular docking was conducted for investigating mechanisms of compounds 1, 5, 6, 9, and 11 with hCE 2. These results suggested that compounds 1, 5, 6, 9, and 11 could be served as lead compounds for the development of novel hCE 2 inhibitors.

Artemisia campestris L.: review on taxonomical aspects, cytogeography, biological activities and bioactive compounds

Artemisia campestris L. (Asteraceae) is a polymorphic species that consists of many subspecies and varieties. It is known for its medicinal, pharmacological, and culinary properties. This review is undertaken with the aim to highlight some aspects of this plant, specifically the taxonomy, the cytogeography, the phytochemistry with an emphasis on the structure-activity relationship (SAR) of the main bioactive compounds of A. campestris L. in addition to its biological properties and the food control properties. The bibliographic data compiled in this review allowed the revision of 146 papers, by using different databases and scientific engines, such as Scopus, ScienceDirect, Pubmed, and google scholar. The taxonomic analysis has embedded A. campestris L. in the tribe Anthemideae, and the genus Artemisia L. Also many subtaxa have been identified, and a subspecific classification of this species has been established on the basis of its botanical characters. The cytogenetic findings evidenced that A.campestris L. is prevailed by the chromosome number x = 9, with a polyploidization degree ranging from diploidy to hexaploidy according to the geographical distribution of the plant populations, while the genome size seems to be proportional to the ploidy level, suggesting an adaptive trait of the cytotypes to new environments. This plant is rich in polyphenols, flavonoids, and terpenic compounds, which substantiate the bioactivities attributed to its extracts and essential oil. Hence, the SAR of the main bioactive compounds of A. campestris L., mainly the prominent flavonoids, phenolic acids, and terpenes revealed a tight link between specific chemical entities of the bioactive compound and the respective biological activity. Many biological activities were approached in this review, mainly the antioxidant, antivenom, antidiabetic, antihyperlipidemic, anti-inflammatory, antihypertensive, anti-leishmaniasis, antinociceptive, wound healing, and analgesic activities in addition to the hepatoprotective, nephroprotective, neuroprotective, and gastroprotective actions. Finally, the food preservative ability of the extracts and essential oil obtained from A.campestris L. have been fully discussed. The present review contributes to the literature, by bringing more clarifications about the different aspects of A.campestris L., like taxonomy, cytogeography and biological interests of this species. The SAR approach of some constituents that occur in A.campestris L., gives a solid support that can be used to explore the bioactivity of components isolated from this species, while the preservative properties of this plant can be usefully exploited for the agrifood sector.

Antihyperlipidemic effect of a Rhamnus alaternus leaf extract in Triton-induced hyperlipidemic rats and human HepG2 cells

The Mediterranean buckthorn, Rhamnus alaternus L., is a plant used in traditional medicine in Mediterranean countries. We aimed at characterizing its phenolic compounds and explore potential antihyperlipidemic activity of this plant. The profile of phenolic compounds in R. alaternus leaf crude methanolic extract (CME) and its liquid-liquid extraction-derived fractions were analyzed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS²). Effects of CME on: circulating lipids in rats with Triton WR-1339-induced hyperlipidemia, intracellular lipid accumulation and expression of genes of fatty acid metabolism in human hepatoma HepG2 cells, and adipogenesis in the 3T3-L1 murine adipocyte cell model were assessed. The HPLC/ESI-MS² analytical profile revealed a total of fifteen compounds, of which eleven were identified. Oral CME administration decreased blood levels of cholesterol and triacylglycerols in hyperlipidemic rats (by 60% and 70%, respectively, at 200 mg CME/kg). In HepG2 cells, CME exposure dose-dependently decreased intracellular lipids and up-regulated gene expression of carnitine palmitoyltransferase 1 involved in fatty acid oxidation. In the 3T3-L1 model, CME favored preadipocyte proliferation and adipogenesis, pointing to positive effects on adipose tissue expandability. These results suggest novel uses of R. alaternus by showing that its leaves are rich in flavonoids and flavonoid derivatives with an antihyperlipidemic effect in vivo and in hepatic cells.

Isolation and identification of new anthraquinones from Rhamnus alaternus L and evaluation of their free radical scavenging activity

From the butanolic and the ethyl acetate extracts of Rhamnus alaternus L root bark and leaves, three new anthraquinone glycosides, alaternosides A-C (1,4,6,8 tetrahydroxy-3 methyl anthraquinone 1-O-ß-D-glucopyranosyl-4,6-di-O-α-L-rhamnopyranoside (1); 1,2,6,8 tetrahydroxy-3 methyl anthraquinone 8-O-ß-D-glucopyranoside (2) and 1, 6 dihydroxy-3 methyl 6 [2'-Me (heptoxy)] anthraquinone (3)) were isolated and elucidated together with the two known anthraquinone glycosides, Physcion-8-O-rutinoside (4) and emodin-6-O-α-L-rhamnoside (5) as well as with the known kaempferol-7-methylether (6), β-sitosterol (7) and β-sitosterol-3-O-glycoside (8). Their chemical structures were elucidated using spectroscopic methods (1D-, 2D-NMR and FAB-MS). Free radical scavenging activity of the isolated compounds was evaluated by their ability to scavenge DPPH^. free radicals. Compounds (3), (4) and (6) showed the highest activity with IC₅₀ values of 9.46, 27.68 and 2.35 μg/mL, respectively.

Liver injury following small intestinal ischemia reperfusion in rats is attenuated by Pistacia lentiscus oil: antioxidant and anti-inflammatory effects

CONTEXT

Intestinal ischemia-reperfusion (IIR) not only leads to severe intestine damage but also induced subsequent destruction of remote organs.

OBJECTIVE

We investigated the protective effect of Pistascia lentiscus L. (Anacardiaceae) oil on IIR.

MATERIALS AND METHODS

Wistar rats were divided into three groups: sham, intestinal IR and P. lentiscus pretreatment (n = 18 each). In the pretreatment group, oil was administered 1 h before induction of warm ischemia.

RESULTS

IIR led to severe liver damage manifested as a significant (p < .05) increase of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Pistacia lentiscus oil decreased the visible intestinal damage, as well as a significant decrease in serum AST and ALT levels. In addition, Pistacia lentiscus reduce liver injury, as evidenced by the decrease in liver tissue myeloperoxidase activity and lipoperoxidation (MDA) level.

CONCLUSION

Pistascia lentiscus attenuates liver injury induced by IIR, attributable to the antioxidant and anti-inflammatory effect.

Medicinal plants of the family Caryophyllaceae: a review of ethno-medicinal uses and pharmacological properties

Several species of the family Caryophyllaceae are widely used by many ethnic communities as traditional medicine throughout the world. The highest number of plants of the family are used in Chinese traditional medicine. The ethnopharmacologial studies of this family indicate that plants of the family possess anticancer, antibacterial, antifungal, antiviral, antioxidant, and anti-inflammatory properties. Other miscellaneous properties reported are ribosome inactivation properties, inhibition of prostatic enlargement in rats, and inhibition of intestinal enzyme carboxyelasterase in rats, cerebro-protective activity, and antiobesity in rats. Few reviews have been published yet, providing information regarding medicinal plants of the family and their biomedical properties. All published reviews have focused either on a particular taxa or a few species. The present review is focused on the traditional medicinal uses of the plants of the family Caryophyllaceae along with phytochemical and pharmacological studies of the family. A study of the literature revealed significant traditional medicinal importance of the family. Major chemical constituents of Caryophyllceae are saponins, Phytoecdysteroids, benzenoids, phenyl propanoids, and nitrogen containing compounds. The most important property of plants of the family is anticancer activity and is shown by the large number of plant species studied. This review of traditional medicinal and pharmacological uses of plants of the family, provide a ground for future research in the family.

Insights into the transcriptomics of polyphagy: Bemisia tabaci adaptability to phenylpropanoids involves coordinated expression of defense and metabolic genes

The whitefly Bemisia tabaci is a major generalist agricultural pest of field and horticultural crops world-wide. Despite its importance, the molecular bases of defense mechanisms in B. tabaci against major plant secondary defense compounds, such as the phenylpropanoids, remain unknown. Our experimental system utilized transgenic Nicotiana tabacum plants constitutively expressing the PAP1/AtMYB75 transcription factor which activates relatively specifically the phenylpropanoid/flavonoids biosynthetic pathway. Our study used suppression subtractive hybridization (SSH) and cDNA microarray approaches to compare gene expression between B. tabaci adults subjected to wild-type or transgenic plants for 6 h. A total of 2880 clones from the SSH libraries were sequenced. Both the SSH and cDNA microarray analyses indicated a complex interaction between B. tabaci and secondary defense metabolites produced by the phenylpropanoids/flavonoids pathway, involving enhanced expression of detoxification, immunity, oxidative stress and general stress related genes as well as general metabolism and ribosomal genes. Quantitative real-time PCR revealed significant changes in the expression of several of these genes in response to feeding on artificial diet containing the flavonoids quercetin. The elevated transcriptional activity was not accompanied by reduced reproductive performance, indicating high adaptability of B. tabaci to this large group of plant secondary defense metabolites.

Effect of acute administration of Pistacia lentiscus L. essential oil on rat cerebral cortex following transient bilateral common carotid artery occlusion

BACKGROUND

Ischemia/reperfusion leads to inflammation and oxidative stress which damages membrane highly polyunsaturated fatty acids (HPUFAs) and eventually induces neuronal death. This study evaluates the effect of the administration of Pistacia lentiscus L. essential oil (E.O.), a mixture of terpenes and sesquiterpenes, on modifications of fatty acid profile and endocannabinoid (eCB) congener concentrations induced by transient bilateral common carotid artery occlusion (BCCAO) in the rat frontal cortex and plasma.

METHODS

Adult Wistar rats underwent BCCAO for 20 min followed by 30 min reperfusion (BCCAO/R). 6 hours before surgery, rats, randomly assigned to four groups, were gavaged either with E.O. (200 mg/0.45 ml of sunflower oil as vehicle) or with the vehicle alone.

RESULTS

BCCAO/R triggered in frontal cortex a decrease of docosahexaenoic acid (DHA), the membrane highly polyunsaturated fatty acid most susceptible to oxidation. Pre-treatment with E.O. prevented this change and led further to decreased levels of the enzyme cyclooxygenase-2 (COX-2), as assessed by Western Blot. In plasma, only after BCCAO/R, E.O. administration increased both the ratio of DHA-to-its precursor, eicosapentaenoic acid (EPA), and levels of palmytoylethanolamide (PEA) and oleoylethanolamide (OEA).

CONCLUSIONS

Acute treatment with E.O. before BCCAO/R elicits changes both in the frontal cortex, where the BCCAO/R-induced decrease of DHA is apparently prevented and COX-2 expression decreases, and in plasma, where PEA and OEA levels and DHA biosynthesis increase. It is suggested that the increase of PEA and OEA plasma levels may induce DHA biosynthesis via peroxisome proliferator-activated receptor (PPAR) alpha activation, protecting brain tissue from ischemia/reperfusion injury.

Antiproliferative, antioxidant, and antimutagenic activities of flavonoid-enriched extracts from (Tunisian) Rhamnus alaternus L.: combination with the phytochemical composition

A pronounced antiproliferative effect on human leukemia K562 cells was shown with flavonoid-enriched extracts from Rhamnus alaternus roots and leaves, with, respectively, IC(50) values of 165 and 210.73 microg/mL. High DPPH radical-scavenging activity (7.21 and 18.84 microg/mL, respectively) and antioxidative effects using the xanthine oxidase assay (IC(50) values of 83.33 and 103.96 microg/mL, respectively) were detected in the presence of the two tested extracts. Although no mutagenic effect was observed when using the Salmonella typhimurium assay system with TA1535 and TA100 strains, the two tested extracts exhibited a high-level protection toward the direct mutagen, sodium azide-induced response.

Comparative evaluation of various total antioxidant capacity assays applied to phenolic compounds with the CUPRAC assay

It would be desirable to establish and standardize methods that can measure the total antioxidant capacity level directly from vegetable extracts containing phenolics. Antioxidant capacity assays may be broadly classified as electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The majority of HAT assays are kinetics-based, and involve a competitive reaction scheme in which antioxidant and substrate compete for peroxyl radicals thermally generated through the decomposition of azo compounds. ET-based assays measure the capacity of an antioxidant in the reduction of an oxidant, which changes colour when reduced. ET assays include the ABTS/TEAC, CUPRAC, DPPH, Folin-Ciocalteu and FRAP methods, each using different chromogenic redox reagents with different standard potentials. This review intends to offer a critical evaluation of existing antioxidant assays applied to phenolics, and reports the development by our research group of a simple and low-cost antioxidant capacity assay for dietary polyphenols, vitamins C and E, and human serum antioxidants, utilizing the copper(II)-neocuproine reagent as the chromogenic oxidizing agent, which we haved named the CUPRAC (cupric ion reducing antioxidant capacity) method. This method offers distinct advantages over other ET-based assays, namely the selection of working pH at physiological pH (as opposed to the Folin and FRAP methods, which work at alkaline and acidic pHs, respectively), applicability to both hydrophilic and lipophilic antioxidants (unlike Folin and DPPH), completion of the redox reactions for most common flavonoids (unlike FRAP), selective oxidation of antioxidant compounds without affecting sugars and citric acid commonly contained in foodstuffs and the capability to assay -SH bearing antioxidants (unlike FRAP). Other similar ET-based antioxidant assays that we have developed or modified for phenolics are the Fe(III)- and Ce(IV)-reducing capacity methods.