Antioxidant activity and phenolic compounds identification of Micromeria inodora (Desf.) Benth. from Western Algeria.

Micromeria inodora (Desf.) Benth. is most studied for the antimicrobial activity of their essential oils; nevertheless there are no reports on the phenolic compounds of this species and their antioxidant activity. In this study, aqueous and organic extracts were assayed for their antioxidant activity. The polyphenol and total flavonoid content, varied between 175.50 and 332.62 mg GAE/g extract and 65.38-86.30 mg catechin equivalent/g extract, respectively. The results of antioxidant activity have shown that all extracts reported an important activity and the ethyl acetate extract showed the stronger effect, higher than some standards molecules. Its IC50 value of scavenging DPPH is 1.5 ± 0.001 µg/mL; ß-Carotene Bleaching assay (BCB) IC50 = 28.1 ± 0.001 µg/mL and the Ferric Reducing Antioxidant Power (FRAP) IC50 = 6.96 ± 0.05 µg/mL. RP-HPLCPDA analysis of phenolic compounds revealed the presence of phenolic acids and flavonoids as: gallic acid, quercetin, rutin, vanillin and naringenin.

In silico evaluation of phenolic compounds as inhibitors of Α-amylase and Α-glucosidase.

The aim of the present study focuses on the molecular docking approach to screen alternative drug that can regulate the hyperglycemia by down-regulating α-glucosidase and α-amylase activity using phenolic compounds: tannic acid (L1), catechin (L2), gallic acid (L3), quercetin (L5) and epicatechin (L6). L1 gives the best docking scores, its interaction with α-amylase and α-glucosidase has the lowest energy score compared to the other complexes and to the acarbose (L4). L1 forms strong five H-donor interactions with residues of active site of α-amylase and three H-donor interactions with α-glucosidase. The in silico evaluation of the unfavorable absorption, distribution, metabolism, and elimination (ADME) properties and drug-likeness revealed that L5 has high absorption compared to tannic acid and to the other compounds. This study revealed for the first time that tannic acid is a functional inhibitor of α-glucosidase and α-amylase activities and can be used as alternative for the regulation of post-prandial hyperglycaemia. Communicated by Ramaswamy Sarma.

Insulinotropic action of Citrullus colocynthis seed extracts in rat pancreatic islets.

The present study aimed to investigate the direct in vitro effects of several distinct Citrullus colocynthis seed extracts on glucose-stimulated insulin release from pancreatic islets isolated from rats. Six extracts were tested, a crude aqueous, defatted aqueous, ethyl acetate, H2O-methanol and n-butanol extract and an extract containing a major component (fraction A) identified by gel chromatography in the ethyl acetate, n-butanol and H2O-methanol extracts. Under selected experimental conditions, the majority of extracts exhibited a positive insulinotropic action, at least when tested in the presence of 8.3 mM D-glucose. The concentration-response correlation observed with distinct extracts revealed the participation of distinct chemical compounds, including compounds with an inhibitory insulinotropic potential, in the modulation of the insulin secretory response to D-glucose. The results of the present study are relevant for further investigations which aim to identify compounds exhibiting positive insulinotropic actions. These agents may be suitable for the treatment of human diabetic subjects.

Phytochemical screening and free radical scavenging activity of Citrullus colocynthis seeds extracts.

OBJECTIVE: To study the phytochemical screening of different extracts from Citrullus colocynthis (C. colocynthis ) seeds extracts and to assess their antioxidant activity on the DPPH free radical scavenging. METHODS: Phytochemical screening, total content of polyphenols and flavonoids of C. colocynthis seeds extracts, including a crude aqueous extract (E1), a defatted aqueous extract (E2), a hydromethanolic extract (HM), an ethyl acetate extract (EA) and a n-butanol extract (n-B) was carried out according to the standard methods and to assess their corresponding effect on the antioxidant activity of this plant. RESULTS: None of these extracts contained detectable amount of alkaloid, quinone, antraquinone, or reducing sugar. Catechic tannins and flavonoids were abundant in E1, HM and EA, whilst terpenoids were abundantly present in E1 and n-B but only weekly in HM. Coumarins were found in E2, EA and n-B. Polyphenols, expressed as gallic acid equivalent, amounted, per 100 g plant matter, to 329, 1002 and 150 mg in EA, HM an E1 respectively. Flavonoids, expressed as catechin equivalent, amounted, per 100 g plant matter to 620, 241 and 94 mg in EA, HM and E1 respectively. Comparable values were found in n-B and E1, with lower values in E2. Quercetin, myricetin and gallic acid were found in the EA and HM extracts by thin layer chromatography, The antioxidative effect of these extracts yielded, when tested at a concentration of 2 000 µg/mL in a 1,1-diphenyl-2-picrylhydrazyl assay, a reducing percentage of 88.8% with EA, 74.5% with HM and 66.2% with E1, and corresponding IC50 of 350, 580 and 500 µg/mL as compared to 1.1 µg/mL for ascorbic acid. CONCLUSIONS: These qualitative and quantitative analytical data document the presence in C. colocynthis extracts of such chemical compounds as flavonoids responsible for the antioxidant activity, as well as other biological activities of this plant.

Protective action of Citrullus colocynthis seed extracts against the deleterious effect of streptozotocin on both in vitro glucose-stimulated insulin release from rat pancreatic islets and in vivo glucose homeostasis.

Citrullus colocynthis extracts improve glucose homeostasis in alloxan- or streptozotocin (STZ)-induced diabetic rats. Little is known, however, regarding the protective effect of these extracts against the ß-cytotoxic action of STZ. In the present study, an H2O-methanol extract was found to suppress the inhibition of glucose-stimulated insulin secretion by STZ in rat-isolated pancreatic islets. Similarly, when an aqueous extract from Citrullus colocynthis seeds was injected daily for 21 days prior to STZ administration, the perturbation of glucose homeostasis otherwise generated by the ß-cytotoxic agent was minimized in rats.

Short- and long-term effects of various Citrullus colocynthis seed extracts in normal and streptozotocin-induced diabetic rats.

In the light of previous findings, the major aim of the present study was to investigate the potential beneficial effects of various Citrullus colocynthis L. seed extracts on such variables as glucose tolerance, body weight gain, pancreas, liver, kidney, testis, epididymal fat and diaphragm muscle weight, as well as serum cholesterol, triglyceride, urea, creatinine, transaminases and alkaline phosphatase concentrations in an animal model of type-1 diabetes mellitus, i.e. streptozotocin-induced diabetic rats. For purpose of comparison, a comparable study was conducted in normal rats. Both the immediate and long-term effects of the plant extracts were assessed in rats injected daily, up to 3 weeks after the start of the experiments. The results of this study reinforce the view that both a crude aqueous extract and a n-butanol extract from the Citrullus colocynthis L. seeds may represent the best candidates in order to eventually identify a component suitable for the treatment of both type-1 and type-2 diabetic subjects.