Federica Menichini

Natural Products as α-Amylase and α-Glucosidase Inhibitors and their Hypoglycaemic Potential in the Treatment of Diabetes: An Update

The inhibition of alpha-glucosidase and alpha-amylase, enzymes involved in the digestion of carbohydrates, can significantly reduce the post-prandial increase of blood glucose and therefore can be an important strategy in the management of blood glucose level in type 2 diabetic and borderline patients. Currently, there is renewed interest in plant-based medicines and functional foods modulating physiological effects in the prevention and cure of diabetes and obesity. The plant kingdom is a wide field to search for natural effective oral hypoglycaemic agents that have slight or no side effects. More than ca. 1200 plant species have been recorded to be used empirically worldwide for their alleged hypoglycaemic activity. Therefore, natural alpha-glucosidase and alpha-amylase inhibitors from plant sources offer an attractive strategy for the control of hyperglycaemia. This article reviews recent data on plant extracts and isolated natural compounds that are being tested for their hypglycaemic activity, highlights ongoing research and considers the future persepctives.

In vivo anti-inflammatory and in vitro antioxidant activities of Mediterranean dietary plants.

Five hydroalcoholic extracts of edible plants from Calabria region (Italy) used in local traditional medicine for the treatment of inflammatory diseases were evaluated for their in vivo topical anti-inflammatory activity (inhibition of croton oil-induced ear oedema in mice) and in vitro antioxidant and antiradical properties (inhibition of linoleic acid oxidation and bovine brain liposomes peroxidation, DPPH radical scavenging). All the extracts showed an anti-inflammatory effect: 300 microg/cm(2) provoked oedema reductions ranging from 21 to 27%. All the extracts exerted also radical scavenging and/or antioxidant properties, the most active plant being Mentha aquatica L. (Lamiaceae) which contained the highest amount of phenolics (337 mg/g) and of flavonoids (15.75 mg/g). Moreover, the content and the composition of sterols were assessed by GC-MS in the examined plants Borago officinalis L. (Boraginaceae) contained the highest number of sterols.

Biological and Pharmacological Activities of Iridoids: Recent Developments

Iridoids represent a large group of cyclopenta[c]pyran monoterpenoids that occur wide-spread in nature, mainly in dicotyledonous plant families like Apocynaceae, Scrophulariaceae, Diervillaceae, Lamiaceae, Loganiaceae and Rubiaceae. Recently, more extensive studies revealed that iridoids exhibit a wide range of bioactivity, such as neuroprotective, antinflammatory and immunomodulator, hepatoprotective and cardioprotective effects. Anticancer, antioxidant, antimicrobic, hypoglycaemic, hypolipidemic, choleretic, antispasmodic and purgative properties were also reported. The aim of the present review is to discuss the recent developments on biological and pharmacological activities of iridoids, supporting the new therapeutic possibilities for the use of these compounds.

Natural Products and their Derivatives as Cholinesterase Inhibitors in the Treatment of Neurodegenerative Disorders: An Update

Alzheimers disease (AD) is the most common form of neurodegenerative disorders. If more effective therapies than the ones currently available are not developed that either prevent AD or other neurodegenerative or block progression of the diseases in its very early stages, the economic and societal cost of caring for AD patients will be devastating. Besides the neuropathologic hallmarks of the diseases, namely neurofibrillary tangles and AD neuritic plaques, the disease is characterized neurochemically by a consistent deficit in cholinergic neurotransmission, particularly affecting cholinergic neurons in basal forebrain. AD and other forms of dementia could be treated by the use of agents which restore the level of acetylcholine through inhibition of both two major forms of cholinesterase: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Moreover, the inhibition of AChE holds a key role not only to enhance cholinergic transmission in the brain but also to reduce the aggregation of beta-amyloid and the formation of the neurotoxic fibrils in AD. Following this view, in recent years, an increased interest has emerged directed to finding drugs able to inhibit both of these events. This review summarizes and highlights recent advances in current knowledge on natural products as cholinesterase inhibitors and how these compounds have also served as the starting points for semi-synthetic analogs with improved properties.

Antiproliferative effects of essential oils and their major constituents in human renal adenocarcinoma and amelanotic melanoma cells

Abstract.  Objectives: The purpose of this study was to evaluate cytotoxic activity of Platycladus orientalis, Prangos asperula and Cupressus sempervirens ssp. pyramidalis essential oils and to identify active components involved in inhibition of population growth of human cancer cell lines. Materials and methods: Essential oils were obtained by hydrodistillation and were analysed by gas chromatography and gas chromatography coupled to mass spectrometry. Antiproliferative activity was tested on amelanotic melanoma C32 cells and on renal cell adenocarcinoma cells, using the sulphorhodamine B assay. Results: Cupressus sempervirens ssp. pyramidalis leaf oil exerted the highest cytotoxic activity with an IC50 value of 104.90 µg/mL against C32, followed by activity of P. orientalis and P. asperula on the renal adenocarcinoma cell line (IC50 of 121.93 and 139.17 µg/mL, respectively). P. orientalis essential oil was also active against amelanotic melanoma with an IC50 of 330.04 µg/mL. Three identified terpenes, linalool, β‐caryophyllene and α‐cedrol, were found to be active on both cell lines tested. Conclusions: Our findings provide novel insights into the field of cytotoxic properties of essential oils. This study provided evidence on how cytotoxic activity of the oils is not always related to their major constituents, except for lower activity found in both cell lines for α‐cedrol. Interestingly, β‐caryophyllene and linalool exhibited comparable IC50 values to the commercial drug vinblastine on the ACHN cell line. This opens a new field of investigation to discover mechanisms responsible for the observed activity.

In vitro inhibitory activities of plants used in Lebanon traditional medicine against angiotensin converting enzyme (ACE) and digestive enzymes related to diabetes

AIM OF THE STUDY In recent years the use of medicinal plants has been growing worldwide and this is particularly true in Lebanon. In the present investigation we report the inhibitory activity against digestive enzymes related to diabetes and angiotensin converting enzyme (ACE) of extracts of nine plant species collected in Lebanon, where they have a traditional use against diabetes. MATERIALS AND METHODS In order to evaluate if the extraction procedure could influence the activity we decided to perform different extractions with methanol, n-hexane and chloroform of Calamintha origanifolia, Satureja thymbra, Prangos asperula, Sideritis perfoliata, Asperula glomerata, Hyssopus officinalis, Erythraea centaurium, Marrubium radiatum and Salvia acetabulosa and test each of them. RESULTS AND CONCLUSIONS Marrubium radiatum and Salvia acetabulosa methanol extracts exerted the highest activity against alpha-amylase (IC(50) 61.1 and 91.2 microg/ml, respectively) and alpha-glucosidase (IC(50) 68.8 and 76.9 microg/ml, respectively). The same extracts exhibited a strong inhibitory activity against ACE with IC(50) of 72.7 and 52.7 microg/ml, respectively. The results support the traditional use of some the species examined.

Antiproliferative activity against human tumor cell lines and toxicity test on Mediterranean dietary plants.

Sixteen edible plants from Southern Italy were evaluated for their in vitro antiproliferative properties, using the sulforodamine B (SRB) assay, on four human cancer cell lines: breast cancer MCF-7, prostate cancer LNCaP, amelanotic melanoma C32 and renal adenocarcinoma ACHN. After 48 h of incubation the most antiproliferative plant extract was Cynara cardunculus ssp. cardunculus on C32 and ACHN cell lines with IC(50) of 21 and 18 microg/ml, respectively. Mentha aquatica showed a selective antiproliferative activity on breast cancer while significant activity was exerted by Cichorium intybus on melanoma. These species contained the highest amount of phenolics. The acute toxicity of the hydroalcohol extracts from all the plants were evaluated by using the Microtox acute toxicity test. This bacterial test measures the decrease in light emission from the marine luminescent Vibrio fischeri bacteria when exposed to organic extracts. This inhibition test was revealed to be highly sensitive, cost effective and easy to operate, requiring just 15 min to predict the sample toxicity. All the extracts analyzed resulted to give values very less than a limit of 20% value, demonstrating so an irrelevant toxicity for the human health. In contrast, Echium vulgare and Malva sylvestris showed bioluminescence inhibition values of 19.42% and 17.32%, respectively, just under the established limit.

Biological Potential and Structure-Activity Relationships of Most Recently Developed Vascular Disrupting Agents: An Overview of New Derivatives of Natural Combretastatin A-4

Tumor blood vessels are an important emerging target for anti-cancer therapy. The antimitotic agent combretastatin A-4 (CA-4), a cis-stilbene natural product isolated from the South African tree Combretum caffrum Kuntze, is the lead compound of a new class of anti-cancer drugs that target tumor vasculature. CA-4 inhibits tubulin polymerization by interacting at the colchicine binding site on tubulin. This alters the morphology of endothelial cells and causes vascular shutdown and regression of tumor vasculature. Some tubulin-binding vascular-disrupting agents (VDAs) are currently in clinical trials for cancer therapy. As a consequence of the potential favorable applications of these compounds, several analogs projected to induce rapid and selective vascular shutdown in tumors have been synthesized during the last few years. Many of these molecules have already been tested for their effects on tubulin polymerization as well as for their antiproliferative activity and other biological properties, and possible mechanisms of action have been investigated. The aim of the present review is to offer an overview of most recently developed combretastatin derivatives, focusing on biological effects exerted by these compounds. The published data about new analogs are presented and compared, and a detailed investigation of structure-activity relationships is described.

Acetylcholinesterase and butyrylcholinesterase inhibition of ethanolic extract and monoterpenes from Pimpinella anisoides V Brig. (Apiaceae)

Ethanolic extract from the fruits of Pimpinella anisoides, an aromatic plant and a spice, exhibited activity against AChE and BChE, with IC(50) values of 227.5 and 362.1 microg/ml, respectively. The most abundant constituents of the extract were trans-anethole, (+)-limonene and (+)-sabinene. trans-Anethole exhibited the highest activity against AChE and BChE with IC(50) values of 134.7 and 209.6 microg/ml, respectively. The bicyclic monoterpene (+)-sabinene exhibited a promising activity against AChE (IC(50) of 176.5 microg/ml) and BChE (IC(50) of 218.6 microg/ml).

Salvia leriifolia Benth (Lamiaceae) extract demonstrates in vitro antioxidant properties and cholinesterase inhibitory activity

The object of the present study was to investigate the in vitro antioxidant properties and cholinesterase inhibitory activity of Salvia leriifolia Benth extracts and fractions. The functional role of herbs and spices and their constituents is a hot topic in food-related plant research. Salvia species have been used since ancient times in folk medicine for cognitive brain function and have been subjected to extensive research. Thus, we hypothesize that S leriifolia, because of its functional properties, would be a good candidate to use as a nutraceutical product for improving memory in the elderly or patients affected by Alzheimer disease (ad). To test this hypothesis, we examined the cholinesterase inhibitory activity using the modified colorimetric Ellmans method against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The n-hexane exhibited the highest activity, with inhibitory concentration 50% (IC(50)) values of 0.59 and 0.21 mg/mL, for AChE and BChE, respectively. This extract was fractionated, and 9 of these fractions (A-I) were obtained and tested. Fraction G, characterized by the presence of sesquiterpenes as major components, was the most active against AChE (IC(50) = 0.05 mg/mL). Because oxidative stress is a critical event in the pathogenesis of AD, we decided to screen the antioxidant activity (AA) using 2,2-diphenyl-1-picrylhydrazyl test, β-carotene bleaching test, and bovine brain peroxidation (thiobarbituric acid) assay. The ethyl acetate extract showed the highest activity, with IC(50) values of 2 and 33 μg/mL on β-carotene bleaching test and thiobarbituric acid test, respectively. These results suggest potential health benefits of S leriifolia extracts. However, this finding requires additional investigation in vivo.