Review on plant antimicrobials: a mechanistic viewpoint

Microbial resistance to classical antibiotics and its rapid progression have raised serious concern in the treatment of infectious diseases. Recently, many studies have been directed towards finding promising solutions to overcome these problems. Phytochemicals have exerted potential antibacterial activities against sensitive and resistant pathogens via different mechanisms of action. In this review, we have summarized the main antibiotic resistance mechanisms of bacteria and also discussed how phytochemicals belonging to different chemical classes could reverse the antibiotic resistance. Next to containing direct antimicrobial activities, some of them have exerted in vitro synergistic effects when being combined with conventional antibiotics. Considering these facts, it could be stated that phytochemicals represent a valuable source of bioactive compounds with potent antimicrobial activities.

Antibacterial activity of flavonoids and their structure-activity relationship: An update review

Based on World Health Organization reports, resistance of bacteria to well-known antibiotics is a major global health challenge now and in the future. Different strategies have been proposed to tackle this problem including inhibition of multidrug resistance pumps and biofilm formation in bacteria and development of new antibiotics with novel mechanism of action. Flavonoids are a large class of natural compounds, have been extensively studied for their antibacterial activity, and more than 150 articles have been published on this topic since 2005. Over the past decade, some promising results were obtained with the antibacterial activity of flavonoids. In some cases, flavonoids (especially chalcones) showed up to sixfold stronger antibacterial activities than standard drugs in the market. Some synthetic derivatives of flavonoids also exhibited remarkable antibacterial activities with 20- to 80-fold more potent activity than the standard drug against multidrug-resistant Gram-negative and Gram-positive bacteria (including Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus). This review summarizes the ever changing information on antibacterial activity of flavonoids since 2005, with a special focus on the structure-activity relationship and mechanisms of actions of this broad class of natural compounds.

Traditional uses, phytochemistry and pharmacology of asafoetida (Ferula assa-foetida oleo-gum-resin)-a review

The old traditional phytomedicine asafoetida, an oleo-gum-resin obtained from the roots of different Ferula assa-foetida, is used in different countries for various purposes. Asafoetida is not only used as a culinary spice but also traditionally used to treat various diseases, including asthma, gastrointestinal disorders, intestinal parasites, etc. This oleo-gum-resin has been known to possess antifungal, anti-diabetic, anti-inflammatory, anti-mutagenic and antiviral activities. A wide range of chemical compounds including sugars, sesquiterpene coumarins and polysulfides have been isolated from this plant. Recent studies have shown new promising antiviral sesquiterpene coumarins from this old phytomedicine. The present review summarizes the information concerning the traditional uses, phytochemistry and biological activities of asafoetida.

A review of traditional uses, phytochemistry and pharmacology of Portulaca oleracea L

ETHNOPHARMACOLOGICAL RELEVANCE

Portulaca oleracea L. is a widespread medicinal plant that is used not only as an edible plant, but also as a traditional medicine for alleviating a wide spectrum of diseases. It is a well-known plant in the European Traditional Medicine. PA is mentioned by Dioscorides (40-90 CE), with the name of "andrachne".

AIM OF THE REVIEW

In this study, we provide detailed information on botany, traditional uses, phytochemistry, pharmacological uses, pharmacokinetics and safety of P. oleracea.

MATERIALS AND METHODS

An extensive search on electronic databases including PubMed, Web of Science, Google Scholar, ScienceDirect, Scopus, conference papers, local herbal encyclopedias, articles, books (in English, French, Arabic, Persian, etc.) and also a number of unpublished handwritten manuscripts was done to find articles have been published between 1956 and 2015 on pharmacology and phytochemistry of P. oleracea.

RESULTS

P. oleracea has been addressed in De Materia Medica as an astringent, and a remedy for headaches, inflammation of the eyes and other organs, burning of the stomach, erysipela, disorders of the bladder, numbness of the teeth, excessive sexual desire, burning fevers, worms, dysentery, hemorrhoids, eruptions of blood, and bites. Phytochemical investigations revealed that this plant a wide range of secondary metabolites including alkaloids, terpenoids, flavonoids and organic acids. The most important pharmacological activities are renoprotective activities and effects on metabolism. P. oleracea could successfully decrease blood glucose and lipid profile of patients with metabolic syndrome. The safety of P. oleracea has been reported in many clinical trials.

CONCLUSION

Modern pharmacological studies have now proven many traditional uses of P. oleracea, including anti-hyperglycemic and anti-hyperlipidemic, renoprotective and hepatoprotective effects. In addition, in many clinical trials P. oleracea showed no adverse effects and constipation was reported as the most frequent adverse effect.

Perspective on the application of medicinal plants and natural products in wound healing: A mechanistic review

Wound is defined as any injury to the body such as damage to the epidermis of the skin and disturbance to its normal anatomy and function. Since ancient times, the importance of wound healing has been recognized, and many efforts have been made to develop novel wound dressings made of the best material for rapid and effective wound healing. Medicinal plants play a great role in the wound healing process. In recent decades, many studies have focused on the development of novel wound dressings that incorporate medicinal plant extracts or their purified active compounds, which are potential alternatives to conventional wound dressings. Several studies have also investigated the mechanism of action of various herbal medicines in wound healing process. This paper attempts to highlight and review the mechanistic perspective of wound healing mediated by plant-based natural products. The findings showed that herbal medicines act through multiple mechanisms and are involved in various stages of wound healing. Some herbal medicines increase the expression of vascular endothelial growth factor (VEGF) and transforming growth factor-β (TGF-β) which play important role in stimulation of re-epithelialization, angiogenesis, formation of granulation tissue, and collagen fiber deposition. Some other wound dressing containing herbal medicines act as inhibitor of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and inducible nitric oxide synthase (iNOS) protein expression thereby inducing antioxidant and anti-inflammatory properties in various phases of the wound healing process. Besides the growing public interest in traditional and alternative medicine, the use of herbal medicine and natural products for wound healing has many advantages over conventional medicines, including greater effectiveness due to diverse mechanisms of action, antibacterial activity, and safety in long-term wound dressing usage.

Glycyrrhetinic Acid and Its Derivatives: Anti-Cancer and Cancer Chemopreventive Properties, Mechanisms of Action and Structure- Cytotoxic Activity Relationship

The anti-cancer properties of liquorice have been attributed, at least in part, to glycyrrhizin (GL). However, GL is not directly absorbed through the gastrointestinal tract. It is hydrolyzed to 18-β-glycyrrhetinic acid (GA), the pharmacologically active metabolite, by human intestinal microflora. GA exhibits remarkable cytotoxic and anti-tumor properties. The pro-apoptotic targets and mechanisms of action of GA have been extensively studied over the past decade. In addition, GA is an inexpensive and available triterpene with functional groups (COOH and OH) in its structure, which make it an attractive lead compound for medicinal chemists to prepare a large number of analogues. To date, more than 400 cytotoxic derivatives have been prepared on the basis of GA scaffold, including 128 cytotoxic derivatives with IC50 values less than 30 µM. Researchers have also succeeded in synthesizing very potent cytotoxic derivatives with IC50s ≤ 1 µM. Studies have shown that the introduction of a double bound at the C1-C2 position combined with an electronegative functional group, such as CN, CF3 or iodine at C2 position, and the oxidation of the hydroxyl group of C3 to the carbonyl group, significantly increased cytotoxicity. This review describes the cytotoxic and anti-tumor properties of GA and its derivatives, targets and mechanisms of action and provides insight into the structure-activity relationship of GA derivatives.

Investigation of the antibacterial activity and efflux pump inhibitory effect of co-loaded piperine and gentamicin nanoliposomes in methicillin-resistant Staphylococcus aureus

OBJECTIVE

Antibiotic resistance has stimulated the research for developing novel strategies that can prevent bacterial growth. Methicillin-resistant Staphylococcus aureus (MRSA), regarded as one of the most serious antibiotic-resistant bacteria which has been conventionally recognized as a nosocomial pathogen.

MATERIALS AND METHODS

Nanoliposomal formulations of piperine and gentamicin were prepared by dehydration-rehydration (DRV) method and characterized for size, zeta potential and encapsulation efficiency. Antibactericidal activities of liposomal and free forms were evaluated against MRSA ATCC 43300 by the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and fractional inhibitory concentration index (FICI). The time-kill studies were carried out to evaluate the potency of antibacterial agents. The effect of piperine on bacterial efflux pumps was also investigated.

RESULTS

MIC values of gentamicin and piperine were 32 and 100 µg/mL, respectively. Synergetic effects were observed by the combination of gentamicin and piperine and FICI was determined to be 0.5. Following incorporation of gentamicin into liposomal gentamicin and liposomal combination, the MIC values were reduced 16- and 32-fold, respectively. MBC values of gentamicin reduced 4 and 8 times following incorporation into gentamicin and combination liposomes, respectively. In comparison with vancomycin, liposomal combination was more effective in bacterial inhibition and killing. Liposomal combination was the most effective preparations in time-kill study. Our findings indicated that liposomal piperine was able to inhibit the efflux pump sufficiently.

CONCLUSION

The results of this study revealed that liposomal combination is a powerful nano-antibacterial agent to eradicate MRSA infection. This dual-loaded formulation was an effective approach for eradication of MRSA.

The Protective Role of Phenolic Compounds Against Doxorubicin-induced Cardiotoxicity: A Comprehensive Review

Although doxorubicin (DOX) is among the most widely used anticancer agents, its clinical application is hampered owing to its cardiotoxicity. Adjuvant therapy with an antioxidant has been suggested as a promising strategy to reduce DOX-induced adverse effects. In this context, many phenolic compounds have been reported to protect against DOX-induced cardiotoxicity. The cardioprotective effects of phenolic compounds are exerted via multiple mechanisms including inhibition of reactive oxygen species generation, apoptosis, NF-κB, p53, mitochondrial dysfunction, and DNA damage. In this review, we present a summary of the in vitro, in vivo, and clinical findings on the protective mechanisms of phenolic compounds against DOX-induced cardiotoxicity.

Phytochemicals: A Promising Weapon in the Arsenal against Antibiotic-Resistant Bacteria

The extensive usage of antibiotics and the rapid emergence of antimicrobial-resistant microbes (AMR) are becoming important global public health issues. Many solutions to these problems have been proposed, including developing alternative compounds with antimicrobial activities, managing existing antimicrobials, and rapidly detecting AMR pathogens. Among all of them, employing alternative compounds such as phytochemicals alone or in combination with other antibacterial agents appears to be both an effective and safe strategy for battling against these pathogens. The present review summarizes the scientific evidence on the biochemical, pharmacological, and clinical aspects of phytochemicals used to treat microbial pathogenesis. A wide range of commercial products are currently available on the market. Their well-documented clinical efficacy suggests that phytomedicines are valuable sources of new types of antimicrobial agents for future use. Innovative approaches and methodologies for identifying plant-derived products effective against AMR are also proposed in this review.

Biological properties and molecular targets of umbelliprenin--a mini-review

7-Prenyloxycoumarins are a group of secondary metabolites found mainly in plants belonging to the families Rutaceae and Apiaceae. Auraptene, umbelliprenin (UM), and 7-isopentenyloxycoumarin are some examples of prenylated coumarins. UM occurs in various edible plant species including celery, coriander, angelica, lemon, and particularly, Ferula species. Although UM was isolated more than 50 years ago, its biological activities have been studied since the last two decades. Besides anticancer activities, biological activities including anti-inflammatory, antioxidant, and antileishmanial activities have been reported from this natural compound. The present mini-review deals with the biological activities and mechanism of actions reported for UM.

A Randomized Placebo-controlled Double Blind Clinical Trial of Quercetin for Treatment of Oral Lichen Planus

Background and aims. Standard treatment of oral lichen planus (OLP) includes topical or systemic corticosteroids that have many adverse effects. A trend toward alternative natural or herbal drugs has attended recently. This study was conducted to evaluate the effect of quercetin in treatment of erosive-atrophic OLP.

Materials and methods. Thirty patients participated in this randomized clinical trial from April 2010 to June 2010 (Trial Registration Number: NCT01375101). Patients were randomly allocated in two groups. Both groups received the standard treatment (dexamethasone mouthwash and nystatin suspension). Experimental group received oral 250 mg quercetin hydrate capsules (bid) and the control group received placebo capsules. The pain and severity of the lesions were recorded at the initial visit and the follow-ups. All recorded data were analyzed with chi-square, Mann-Whitney, t-test, Wilcoxon and Friedman tests using SPSS 11.5.

Results. There were no significant differences between the two groups in severity of the lesions and pain in the follow-ups.According to the Friedman test, there was a significant reduction in pain (P = 0.01) and severity indices (P = 0.00) in the case group. These differences were not observed in the control group(P = 0.26,SI; and P = 0.86, PI). No adverse effect of quercetin was reported.

Conclusion. According to the results, no significant therapeutic effect can be considered for quercetin in treatment of OLP.

A mechanistic insight into the biological activities of urolithins as gut microbial metabolites of ellagitannins

Urolithins are the gut metabolites produced from ellagitannin-rich foods such as pomegranates, tea, walnuts, as well as strawberries, raspberries, blackberries, and cloudberries. Urolithins are of growing interest due to their various biological activities including cardiovascular protection, anti-inflammatory activity, anticancer properties, antidiabetic activity, and antiaging properties. Several studies mostly based on in vitro and in vivo experiments have investigated the potential mechanisms of urolithins which support the beneficial effects of urolithins in the treatment of several diseases such as Alzheimer's disease, type 2 diabetes mellitus, liver disease, cardiovascular disease, and various cancers. It is now obvious that urolithins can involve several cellular mechanisms including inhibition of MDM2-p53 interaction, modulation of mitogen-activated protein kinase pathway, and suppressing nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activity. Antiaging activity is the most appealing and probably the most important property of urolithin A that has been investigated in depth in recent studies, owing to its unique effects on activation of mitophagy and mitochondrial biogenesis. A recent clinical trial showed that urolithin A is safe up to 2,500 mg/day and can improve mitochondrial biomarkers in elderly patients. Regarding the importance of mitochondria in the pathophysiology of many diseases, urolithins merit further research especially in clinical trials to unravel more aspects of their clinical significance. Besides the nutritional value of urolithins, recent studies proved that urolithins can be used as pharmacological agents to prevent or cure several diseases. Here, we comprehensively review the potential role of urolithins as new therapeutic agents with a special focus on the molecular pathways that have been involved in their biological effects. The pharmacokinetics of urolithins is also included.

Synthesis, biosynthesis and biological activities of galbanic acid - A review

Abstract Context: Galbanic acid (GA) is a biologically active sesquiterpene coumarin from Ferula species (Apiaceae). This compound showed various biological properties including anticancer, cancer chemopreventive, anticoagulant, antiviral, and antileishmanial activities. Objectives: This article is a review on the synthesis, biosynthesis, and biological activities of GA. In addition, we discussed gaps in our knowledge about GA that deserve future research. In this article, we also evaluated the drug-likeness of GA in silico. Methods: All relevant databases were searched for the terms "galbanic acid", "methyl galbanate", "Ferula" and "sesquiterpene coumarin" without limitation, up to May 2013. Information on GA was collected via electronic search using Pubmed, Scopus, Web of Science, and Sciencedirect. All physicochemical parameters used for the prediction of drug-likeness were calculated using MarvinSketch (version 5.11, academic package, ChemAxon). Results: This compound showed various biological properties including anticancer, cancer chemopreventive, anticoagulant, antiviral and antileishmanial activities. GA can inhibit the growth of prostate cancer cells via decreasing androgen receptor abundance. In silico physicochemical studies on GA showed that this compound has drug-like properties, the parameters that are important to predict potential of a compound for being a future drug. Conclusion: GA is a valuable natural product with various biological activities. New discoveries with GA are to be expected.

Sesquiterpene lactones from Ferula oopoda and their cytotoxic properties

Two new sesquiterpene lactones, namely feruhodin A and feruhodin B, together with six known compounds, daucoeudesmanolactone, dehydrooopodin, oopodin, badkhysin, 7-demethylplastochromenol, and scoparone, were isolated from the roots of Ferula oopoda. The structures of these compounds were elucidated by 1D and 2D NMR techniques as well as high-resolution mass spectrometry. Cytotoxic effects of these compounds were evaluated against two human cancer cell lines including MCF7and K562 using the Alamar blue assay. The results showed that dehydrooopodin possessed significant cytotoxic effects with IC₅₀ values of 15 and 5 μM against MCF7 and K562, respectively.

Protective effects of functional foods against Parkinson's disease: A narrative review on pharmacology, phytochemistry, and molecular mechanisms

In Persian Medicine (PM), PD (brain-based tremor) is a known CNS disorder with several therapeutic and preventive options. In their medical textbooks and pharmacopeias, Persian great scientists such as Rhazes (854-925 AD), Avicenna (980-1037 AD), and Jorjani (1042-1136 AD), have discussed pharmacological and nutritional strategies for the prevention, slowing progression, and treatment of PD. In the present study, we surveyed plant- and animal-based foods recommended by PM for the prevention and treatment of CNS-related tremors. In vivo and in-vitro pharmacological evidence supporting the beneficial effects of PM-recommended foods in prevention and alleviating PD, major active phytochemicals along with the relevant mechanisms of action were studied. Several PM plants possess potent antioxidant, antiinflammatory, and PD preventing properties. Garlic and allicin, cabbage and isothiocyanates, chickpea seed and its O-methylated isoflavones biochanin A and formononetin, cinnamon, and cinnamaldehyde, saffron and its crocin, crocetin, and safranal, black cumin and its thymoquinone, black pepper and piperine, pistachio and genistein and daidzein, and resveratrol are among the most effective dietary itemsagainst PD. They act through attenuating neurotoxin-induced memory loss and behavioral impairment, oxidative stress, and dopaminergic cell death. PM-recommended foods can help alleviate PD progression and also discovering and developing new neuroprotective anti-PD pharmaceuticals.

Curcumin-loaded mesoporous silica nanoparticles for drug delivery: synthesis, biological assays and therapeutic potential - a review

Curcumin-loaded mesoporous silica nanoparticles (MSNs) have shown promise as drug delivery systems to address the limited pharmacokinetic characteristics of curcumin. Functionalization with folic acid and PEGylation enhance anticancer activity, biocompatibility, stability, and permeability. Co-delivery with other drugs results in synergistically enhanced cytotoxic activity. Environment-responsive MSNs prevent undesirable drug leakage and increase selectivity towards target tissues. This review summarizes the methods of Cur-loaded MSN synthesis and functionalization and their application in various diseases, and also highlights the potential of Cur-loaded MSNs as a promising drug delivery system.

Evaluation of sedative effects of an intranasal dosage form containing saffron, lettuce seeds and sweet violet in primary chronic insomnia: A randomized, double-dummy, double-blind placebo controlled clinical trial

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Persian Medicine (TPM) has been established as a valuable source of medicinal plants for the treatment of insomnia for thousands of years. Accordingly, oil extracts from plants' parts have been widely used to alleviate central nervous system (CNS) ailments including sleep disorders. A number of preparations have been recommended by TPM for the treatment of insomnia. Among them, an intranasal formulation containing oily macerates of Viola odorata L., Crocus sativus L. and Lactuca sativa L. stands out.

AIM OF THE STUDY

In the present double-dummy, double-blind placebo controlled clinical trial, we aim to evaluate the effectiveness of a combination of violet oil, saffron oil, and lettuce seeds oil nasal drop compared with the placebo (sesame oil).

MATERIALS AND METHODS

Fifty patients with primary chronic insomnia were randomly assigned in TPM-treatment or placebo groups, received either two drops of the herbal oil or placebo into each nostril every noon and evening for 8 weeks. Before the study commencement and after 1, 4 and 8 weeks of treatment, Insomnia Severity Index (ISI) and Pittsburgh Sleep Quality Index (PSQI) questionnaires were completed by all patients. The primary outcome measure was considered as any changes in ISI scores between the first visit and after 8 weeks. Changes in PSQI scores during the study and possible side effects were also assessed. The multicompound herbal oil was standardized using HPLC analysis and contained 0.02 mg/mL crocin and 4 μg/mL isoquercitrin.

RESULTS

Our study revealed a significant reduction in the ISI and PSQI scores from baseline by the study endpoint (P ≤ 0.01). The mean ISI scores in week 8 decreased significantly for the intervention group (P = 0.001) and also the placebo group (P < 0.01) when compared with baseline. Moreover, the use of hypnotic drugs in the intervention group was significantly reduced (P < 0.001), while in the control group was maintained at baseline level.

CONCLUSIONS

It seems that intranasal use of the multi-herbal preparation can be used to improve chronic insomnia and to reduce the dose of conventional hypnotic medications in insomniac patients.

Naphthoquinone Derivatives Isolated from Plants: Recent Advances in Biological Activity

Naturally occurring naphthoquinones (NQs) comprising highly reactive small molecules are the subject of increasing attention due to their promising biological activities such as antioxidant, antimicrobial, apoptosis-inducing activities, and especially anticancer activity. Lapachol, lapachone, and napabucasin belong to the NQs and are in phase II clinical trials for the treatment of many cancers. This review aims to provide a comprehensive and updated overview on the biological activities of several new NQs isolated from different species of plants reported from January 2013 to January 2020, their potential therapeutic applications and their clinical significance.

Thymoquinone abrogates methamphetamine-induced striatal neurotoxicity and hyperlocomotor activity in mice

Background and purpose:

Methamphetamine (METH) abuse has devastating consequences on the nervous system. There are limited therapy choices in METH abuse with reduced effectiveness and elevated recurrence rates. Thymoquinone (TQ), the most bioactive constituent of Nigella sativa seeds exerts neuroprotective effects mainly via antioxidant properties. This study aimed to evaluate the effect of TQ against METH-induced striatal neurotoxicity and hyperlocomotor activity in mice.

Experimental approach:

Our groups of animals received METH (10 mg/kg) four times a day with 2 h intervals. Normal saline or TQ (5, 10, or 20 mg/kg) was injected intraperitoneally 30 min before METH administration. Control and sham groups received vehicle or TQ, respectively. The rectal temperature and behavioral tests including the open field for locomotor activity and rotarod for motor coordination were evaluated. The level of superoxide dismutase (SOD), as well as pathological changes, were also assessed in the striatum region.

Findings/Results:

No significant differences in rectal temperatures were observed among treated groups. Administration of METH increased locomotor activity and did not change motor coordination. TQ co-administration with METH significantly reduced the central and total locomotion and the mean latency to fall off the rotarod in a dose-dependent manner compared with the METH group. TQ also alleviated the METH-induced decrease in the activity of SOD.TQ, especially at the high dose, reduced the METH-induced reactive gliosis level.

Conclusion and implications:

In conclusion, TQ prevents the enhanced locomotor activity, antioxidant impairment, and morphological striatal damage caused by METH in mice. TQ may be a potential candidate for the treatment of specific METH-induced brain disorders or neurological diseases.