Mucosal and blood-brain barrier transport kinetics of the plant N-alkylamide spilanthol using in vitro and in vivo models

Comprehensive review of the phytochemistry, pharmacology, pharmacokinetics, and toxicology of alkamides (2016-2022)

Alkamides refer to a class of natural active small-molecule products composed of fatty acids and amine groups. These compounds are widely distributed in plants, and their unique structures and various pharmacological activities have caught the attention of scholars. This review provides a collection of literatures related to the phytochemistry, pharmacological effects, pharmacokinetics, and toxicity of alkamides published in 2016-2022 and their summary to provide references for further development of this class of ingredients. A total of 234 components (including chiral isomers) were summarized, pharmacological activities, such as anti-inflammatory, antitumor, antidiabetic, analgesic, neuroprotective, insecticidal, antioxidant, and antibacterial, and miscellaneous properties of alkamides were discussed. In addition, the pharmacokinetic characteristics and toxicity of alkamides were reviewed. However, information on the pharmacological mechanisms of the action, drug safety, and pharmacokinetics of alkamides is limited and thus requires further investigation and evaluation.

Pharmacological Characteristics of the Hydroethanolic Extract of Acmella oleracea (L) R. K. Jansen Flowers: ADME/Tox In Silico and In Vivo Antihypertensive and Chronic Toxicity Evaluation

Acmella oleracea (L.) R. K. Jansen, popularly known as jambu in Northern Brazil, is widely used in folk medicine and local cuisine. Its consumption in different ways reinforces the need for safety assessments. In this study, the major compounds found in the hydroethanolic extract of A. oleracea flowers (EHFAO) were characterized by ultra-performance liquid mass spectrometry (UHPLC-ESI-QTOF-MS/MS). The effects of oral administration of 100/mg/kg of EHFAO extract over 60 days in male spontaneously hypertensive (SHR) and Wistar (WR) rats and the in silico ADME/Tox predictions, lipophilicity, and water solubility were accomplished for the compounds identified. Spilanthol was detected as the foremost major compound at a concentration of 97.7%, followed by 1.53% scopoletin and 0.77% d-limonene. The treatment with EHFAO did not alter the animals´ weight over the studied period. Moderate alterations were observed solely in the hepatic enzymes AST (WR = 97 UI/L and SHR = 150 UI/L ∗ p < 0.05) and ALT (WR = 55 UI/L and SHR = 95 UI/L ∗ p < 0.05), while no relevant histopathological alterations were found. The in-silico study confirmed the in vivo findings, as the identified compounds were considered highly bioactive orally, due to their drug similarity profiles, adequate lipid solubility, bioavailability, and pharmacokinetics. Therefore, the chronic treatment with EHFAO was found safe at the concentration of 100/mg/kg, with no interference in the blood pressure levels neither appreciable toxic effects.

Chemical composition of the lipophilic compounds from the rind and pith of papyrus (Cyperus papyrus L.) stems

Papyrus (Cyperus papyrus L.) is a sedge plant with a high rate of biomass productivity that represents an interesting raw material to produce chemicals, materials and fuels, which are currently still obtained from fossil resources, in the context of a lignocellulosic biorefinery. In this work, the content and chemical composition of the lipids present in papyrus stems were thoroughly studied. For this, the papyrus stems were separated into the rind and the pith. The lipid content accounted for 4.1% in the rind and 4.9% in the pith (based on dry matter). The main compounds identified in both parts of the papyrus stem were hydrocarbons, n-fatty acids, 2-hydroxyfatty acids, alcohols, alkylamides, mono- and diglycerides, steroids (sterols, ketones, hydrocarbons, esters and glycosides), tocopherols, tocopherol esters, phytol, phytol esters, alkyl ferulates, ω-carboxyalkyl ferulates (and their monoglycerides), and acylglycerol glycosides. The rind presented a predominance of n-fatty acids (6790 mg/kg; that represented 28.6% of all identified compounds), steroid compounds (6255 mg/kg; 26.3%), phytol and phytol esters (4985 mg/kg; 21.0%), and isoprenoid hydrocarbons, namely phytadiene and squalene (2660 mg/kg; 11.2%), while the most abundant lipids in the pith were steroids (8600 mg/kg; 44.4% of all identified compounds) and fatty acids (6245 mg/kg; 32.2%). Due to the great diversity and significant abundance of the compounds identified in papyrus, it can be considered as a potential raw material for biorefineries to obtain valuable phytochemicals of interest to various industrial sectors.

A Review of the Chemistry and Biological Activities of Acmella oleracea ("jambù", Asteraceae), with a View to the Development of Bioinsecticides and Acaricides

Human pathologies, environmental pollution, and resistance phenomena caused by the intensive use of chemical pesticides have shifted the attention of the agrochemical industries towards eco-friendly insecticides and acaricides. Acmella oleracea (L.) R. K. Jansen (jambù) is a plant native to South America, widely distributed and cultivated in many countries due to its numerous pharmacological properties. This review analyzes literature about the plant, its uses, and current knowledge regarding insecticidal and acaricidal activity. Acmella oleracea has proven to be a potential pesticide candidate against several key arthropod pest and vector species. This property is inherent to its essential oil and plant extract, which contain spilanthol, the main representative of N-alkylamides. As a result, there is a scientific basis for the industrial exploitation of jambù in the preparation of green insecticides. However, studies related to its toxicity towards non-target species and those aimed at formulating and developing marketable products are lacking.

Proangiogenic Effect of Affinin and an Ethanolic Extract from Heliopsis longipes Roots: Ex Vivo and In Vivo Evidence

Angiogenesis, the formation of new blood vessels, underlies tissue development and repair. Some medicinal plant-derived compounds can modulate the angiogenic response. Heliopsis longipes, a Mexican medicinal plant, is widely used because of its effects on pain and inflammation. The main bioactive phytochemicals from H. longipes roots are alkamides, where affinin is the most abundant. Scientific studies show various medical effects of organic extracts of H. longipes roots and affinin that share some molecular pathways with the angiogenesis process, with the vasodilation mechanism of action being the most recent. This study investigates whether pure affinin and the ethanolic extract from Heliopsis longipes roots (HLEE) promote angiogenesis. Using the aortic ring rat assay (ex vivo method) and the direct in vivo angiogenesis assay, where angioreactors were implanted in CD1 female mice, showed that affinin and the HLEE increased vascular growth in a dose-dependent manner in both bioassays. This is the first study showing the proangiogenic effect of H. longipes. Further studies should focus on the mechanism of action and its possible therapeutic use in diseases characterized by insufficient angiogenesis.

The Acute and Chronic Cognitive and Cerebral Blood-Flow Effects of Nepalese Pepper (Zanthoxylum armatum DC.) Extract-A Randomized, Double-Blind, Placebo-Controlled Study in Healthy Humans

Background: Zanthoxylum armatum DC. (ZA) is a traditional Asian culinary spice and medicinal compound, which is rich in monoterpenes and hydroxy α-sanshool. Mechanistic interactions with the monoamine, cholinergic and cannabinoid neurotransmission systems, as well as transient receptor potential (TRP) and potassium ion channels, may predispose ZA to modulate human brain function. Objectives: To investigate the effects of a single dose and 56-days supplementation with a lipid extract of ZA on cognitive function, mood and cerebral blood-flow (CBF) parameters in the pre-frontal cortex during cognitive task performance. Design: Double-blind, randomized, parallel groups study with N = 82 healthy males and females between the ages of 30 and 55 years. Assessments were undertaken pre-dose and at 1, 3 and 5 hours post-dose on the first (Day 1) and last (Day 56) days of supplementation. Results: A single dose of ZA (Day 1) resulted in acute improvements on a 'Speed of Attention' factor and the Rapid Visual Information Processing (RVIP) task, in comparison to placebo. However, following ZA participants were less accurate on the name-to-face recall task. After 56 days of ZA consumption (Day 56), speed was enhanced on a global 'Speed of Performance' measure, comprising data from all of the timed tasks in the computerized battery. Participants also completed more correct Serial 3s Subtractions at the 3 hours assessment and were less mentally fatigued throughout the day than participants consuming placebo. These effects were complemented on both Day 1 and Day 56 by modulation of CBF parameters, as assessed by Near Infrared Spectroscopy (NIRS). The primary finding here was a reduced hemodynamic response during the RVIP task. Conclusion: ZA improves aspects of cognitive performance, in particular the speed of performing tasks, in healthy humans and results in concomitant reductions in hemodynamic responses in the frontal cortex during task performance. The findings suggest an increase in neural efficiency following ZA.

Spilanthol from Traditionally Used Spilanthes acmella Enhances AMPK and Ameliorates Obesity in Mice Fed High-Fat Diet

Spilanthol (SP) is a bioactive compound found in Spilanthes acmella, giving the flowers and leaves a spicy taste. Studies found that phyto-ingredients stored in spice plants act against obesity-related diseases. SP has antimicrobial, anti-inflammatory, and analgesic properties, but the effects on obesity are not yet known. We investigated the effects of SP in differentiated adipocytes (3T3-L1 cells) and mice fed a high-fat diet (HFD). SP significantly inhibited intracellular lipid accumulation and significantly reduced the expression of lipogenesis-related proteins, including acetyl-CoA carboxylase (ACC) and fatty-acid synthase (FAS). In contrast, SP increased the expression of carnitine palmitoyltransferase (CPT)1 and AMP-activated protein kinase (AMPK) in adipocytes. However, SP suppressed the levels of cyclooxygenase-2 (COX-2), phospho-p38 (pp38), and phospho-JNK (c-Jun N-terminal kinase) (pJNK) in LPS (lipopolysaccharide)-stimulated murine pre-adipocytes. SP administered to HFD-induced obese mice via intraperitoneal injections twice a week for 10 weeks decreased body weight gain, visceral adipose tissue weight, and adipocyte size. SP inhibited lipogenic proteins FAS and ACC, and suppressed adipogenic transcription factors, enhancing lipolysis and AMPK protein expression in the liver. SP has anti-obesity effects, upregulating AMPK to attenuate lipogenic and adipogenic transcription factors.

Acmella oleracea (L) R. K. Jansen Reproductive Toxicity in Zebrafish: An In Vivo and In Silico Assessment

The plant species Acmella oleracea L. is used in the north of Brazil for the treatment of a range of illnesses, such as tuberculosis, flu, cough, and rheumatism and as an anti-inflammatory agent; besides, hydroethanolic formulations with this species are popularly used as a female aphrodisiac agent. However, currently, there are no studies performed evaluating its effect on embryonic development. Hence, this research aimed to evaluate the effects of the hydroethanolic extract of A. oleracea (EHFAo) on the reproductive performance (parental) and embryonic development (F1 generation) of zebrafish, at concentrations of 50, 100, and 200 μg/L. Histopathology of parental gonads after 21 days of exposure to EHFAo reveals few alterations in the ovaries and testes, not impairing the reproduction; an increase of eggs deposition was observed in animals treated with EHFAo at the highest concentrations. Nevertheless, concerning the embryonic development of F1, teratogenic effects were observed including tail deformation, cardiac and yolk edema, scoliosis, and growth retardation; these alterations were more prominent in the groups born from progenitors exposed to the highest concentrations (100 and 200 μg/L.); but only the occurrence of yolk and cardiac edema had a statistically significant difference when compared to the control group. The chromatographic analysis shows that spilanthol (affinin) was the primary compound found in the EHFAo. Hence, in silico assessment was performed to evaluate the pharmacokinetic and toxicological properties of this molecule and 37 metabolites derived from it. Overall, our data show that the treatment caused no detrimental changes in progenitors regarding their gonads or fertility but caused some potentially teratogenic activity in embryos, which may be due to the action of spilanthol's metabolites M3, M6, M7, M8, M16, M28, and M31.

Interaction of Plant Extracts with Central Nervous System Receptors

Background: Plant extracts have been used in traditional medicine for the treatment of various maladies including neurological diseases. Several central nervous system receptors have been demonstrated to interact with plant extracts and components affecting the pharmacology and thereby potentially playing a role in human disease and treatment. For instance, extracts from Hypericum perforatum (St. John’s wort) targeted several CNS receptors. Similarly, extracts from Piper nigrum, Stephania cambodica, and Styphnolobium japonicum exerted inhibition of agonist-induced activity of the human neurokinin-1 receptor. Methods: Different methods have been established for receptor binding and functional assays based on radioactive and fluorescence-labeled ligands in cell lines and primary cell cultures. Behavioral studies of the effect of plant extracts have been conducted in rodents. Plant extracts have further been subjected to mood and cognition studies in humans. Results: Mechanisms of action at molecular and cellular levels have been elucidated for medicinal plants in support of standardization of herbal products and identification of active extract compounds. In several studies, plant extracts demonstrated affinity to a number of CNS receptors in parallel indicating the complexity of this interaction. In vivo studies showed modifications of CNS receptor affinity and behavioral responses in animal models after treatment with medicinal herbs. Certain plant extracts demonstrated neuroprotection and enhanced cognitive performance, respectively, when evaluated in humans. Noteworthy, the penetration of plant extracts and their protective effect on the blood-brain-barrier are discussed. Conclusion: The affinity of plant extracts and their isolated compounds for CNS receptors indicates an important role for medicinal plants in the treatment of neurological disorders. Moreover, studies in animal and human models have confirmed a scientific basis for the application of medicinal herbs. However, additional investigations related to plant extracts and their isolated compounds, as well as their application in animal models and the conducting of clinical trials, are required.

Affinin (Spilanthol), Isolated from Heliopsis longipes, Induces Vasodilation via Activation of Gasotransmitters and Prostacyclin Signaling Pathways

Heliopsis longipes roots have been widely used in Mexican traditional medicine to relieve pain, mainly, toothaches. Previous studies have shown that affinin, the major alkamide of these roots, induces potent antinociceptive and anti-inflammatory activities. However, the effect of H. longipes root extracts and affinin on the cardiovascular system have not been investigated so far. In the present study, we demonstrated that the dichloromethane and ethanolic extracts of H. longipes roots, and affinin, isolated from these roots, produce a concentration-dependent vasodilation of rat aorta. Affinin-induced vasorelaxation was partly dependent on the presence of endothelium and was significantly blocked in the presence of inhibitors of NO, H₂S, and CO synthesis (NG-nitro-l-arginine methyl ester (l-NAME), dl-propargylglycine (PAG), and chromium mesoporphyrin (CrMP), respectively); K⁺ channel blockers (glibenclamide (Gli) and tetraethyl ammonium (TEA)), and guanylate cyclase and cyclooxygenase inhibitors (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and indomethacin (INDO), respectively). Our results demonstrate, for the first time, that affinin induces vasodilation by mechanisms that involve gasotransmitters, and prostacyclin signaling pathways. These findings indicate that this natural alkamide has therapeutic potential in the treatment of cardiovascular diseases.

Quantitative In Vitro and In Vivo Evaluation of Intestinal and Blood-Brain Barrier Transport Kinetics of the Plant N-Alkylamide Pellitorine

Objective. To evaluate the gut mucosa and blood-brain barrier (BBB) pharmacokinetic permeability properties of the plant N-alkylamide pellitorine. Methods. Pure pellitorine and an Anacyclus pyrethrum extract were used to investigate the permeation of pellitorine through (1) a Caco-2 cell monolayer, (2) the rat gut after oral administration, and (3) the BBB in mice after intravenous and intracerebroventricular administration. A validated bioanalytical UPLC-MS(2) method was used to quantify pellitorine. Results. Pellitorine was able to cross the Caco-2 cell monolayer from the apical-to-basolateral and from the basolateral-to-apical side with apparent permeability coefficients between 0.6 · 10(-5) and 4.8 · 10(-5) cm/h and between 0.3 · 10(-5) and 5.8 · 10(-5) cm/h, respectively. In rats, a serum elimination rate constant of 0.3 h(-1) was obtained. Intravenous injection of pellitorine in mice resulted in a rapid and high permeation of pellitorine through the BBB with a unidirectional influx rate constant of 153 μL/(g·min). In particular, 97% of pellitorine reached the brain tissue, while only 3% remained in the brain capillaries. An efflux transfer constant of 0.05 min(-1) was obtained. Conclusion. Pellitorine shows a good gut permeation and rapidly permeates the BBB once in the blood, indicating a possible role in the treatment of central nervous system diseases.