New amide alkaloids from the roots of Piper nigrum

Two pairs of bioactive cyclohexene alkaloid enantiomers from the roots of Piper nigrum

Two pairs of cyclohexene amide alkaloid enantiomers were obtained from the root of Piper nigrum. Their plane structures were established by NMR and HRESIMS spectra. The absolute configurations of 1a/1b and 2a/2b were determined by the comparison between the experimental and calculated electronic circular dichroism (ECD) spectra. All identified compounds were tested for inhibitory effects on acetylcholinesterase (AChE) in vitro. Notably, compounds 1b and 2b showed strong inhibitory effects on AChE and the interaction between proteins and compounds was discussed by molecular docking studies.

Involvement of Both Extrinsic and Intrinsic Apoptotic Pathways in Tridecylpyrrolidine-Diol Derivative-Induced Apoptosis In Vitro

Despite the decreasing trend in mortality from colorectal cancer, this disease still remains the third most common cause of death from cancer. In the present study, we investigated the antiproliferative and pro-apoptotic effects of (2S,3S,4R)-2-tridecylpyrrolidine-3,4-diol hydrochloride on colon cancer cells (Caco-2 and HCT116). The antiproliferative effect and IC₅₀ values were determined by the MTT and BrdU assays. Flow cytometry, qRT-PCR and Western blot were used to study the cellular and molecular mechanisms involved in the induction of apoptotic pathways. Colon cancer cell migration was monitored by the scratch assay. Concentration-dependent cytotoxic and antiproliferative effects on both cell lines, with IC₅₀ values of 3.2 ± 0.1 μmol/L (MTT) vs. 6.46 ± 2.84 μmol/L (BrdU) for HCT116 and 2.17 ± 1.5 μmol/L (MTT) vs. 1.59 ± 0.72 μmol/L (BrdU), for Caco-2 were observed. The results showed that tridecylpyrrolidine-induced apoptosis was associated with the externalization of phosphatidylserine, reduced mitochondrial membrane potential (MMP) accompanied by the activation of casp-3/7, the cleavage of PARP and casp-8, the overexpression of TNF-α and FasL and the dysregulation of Bcl-2 family proteins. Inhibition of the migration of treated cells across the wound area was detected. Taken together, our data show that the anticancer effects of tridecylpyrrolidine analogues in colon cancer cells are mediated by antiproliferative activity, the induction of both extrinsic and intrinsic apoptotic pathways and the inhibition of cell migration.

Anti-inflammatory activity and cytotoxicity against ovarian cancer cell lines by amide alkaloids and piperic esters isolated from Piper longum fruits: In vitro assessments and molecular docking simulation

Three new amide alkaloids, piperlongumamides D-F (14, 19, and 32); a new piperic ester, piperlongumester A (45); and two new natural compounds, methyl (2E,4Z)-5-(1,3-benzodioxol-5-yl)penta-2,4-dienoate (46) and trans-piperolein B ester (47), along with 41 known compounds were isolated from the fruits of Piper longum L. Their structures were identified by analyzing spectroscopic data, including mass spectrometry, 1D, and 2D NMR data. The anti-inflammatory and cytotoxic activities of all isolated compounds (1-47) were evaluated. Compounds 3, 6, and 19 inhibited nitric oxide production with IC₅₀ values of 16.1 ± 0.94, 14.5 ± 0.57, and 27.3 ± 1.11 μM, respectively, whereas compound 1 exhibited strong cytotoxic activity toward three ovarian cancer cell lines A2780, TOV-112D, and SK-OV3, with IC₅₀ values of 6.7 ± 0.77, 5.8 ± 0.29, and 48.3 ± 0.40 μM, respectively. Molecular docking simulations were performed to identify the interaction and binding mechanisms of these active metabolites with proteins related to inflammation and cancer.

The terminal enzymatic step in piperine biosynthesis is co-localized with the product piperine in specialized cells of black pepper (Piper nigrum L.)

Piperine (1-piperoyl piperidine) is responsible for the pungent perception of dried black pepper (Piper nigrum) fruits and essentially contributes to the aromatic properties of this spice in combination with a blend of terpenoids. The final step in piperine biosynthesis involves piperine synthase (PS), which catalyzes the reaction of piperoyl CoA and piperidine to the biologically active and pungent amide. Nevertheless, experimental data on the cellular localization of piperine and the complete biosynthetic pathway are missing. Not only co-localization of enzymes and products, but also potential transport of piperamides to the sink organs is a possible alternative. This work, which includes purification of the native enzyme, immunolocalization, laser microdissection, fluorescence microscopy, and electron microscopy combined with liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS), provides experimental evidence that piperine and PS are co-localized in specialized cells of the black pepper fruit perisperm. PS accumulates during early stages of fruit development and its level declines before the fruits are fully mature. The product piperine is co-localized to PS and can be monitored at the cellular level by its strong bluish fluorescence. Rising piperine levels during fruit maturation are consistent with the increasing numbers of fluorescent cells within the perisperm. Signal intensities of individual laser-dissected cells when monitored by LC-ESI-MS/MS indicate molar concentrations of this alkaloid. Significant levels of piperine and additional piperamides were also detected in cells distributed in the cortex of black pepper roots. In summary, the data provide comprehensive experimental evidence of and insights into cell-specific biosynthesis and storage of piperidine alkaloids, specific and characteristic for the Piperaceae. By a combination of fluorescence microscopy and LC-MS/MS analysis we localized the major piperidine alkaloids to specific cells of the fruit perisperm and the root cortex. Immunolocalization of native piperine and piperamide synthases shows that enzymes are co-localized with high concentrations of products in these idioblasts.

Synthesis and Characterization of Tween-20 Capped Biosynthesized Silver Nanoparticles for Anticancer and Antimicrobial Property

The Vitrus vinifera fruit extract was used to make silver nanoparticles (AgNPs) utilizing a green chemical technique. The biosynthesized Tween-20/Vitrus vinifera-AgNPs were observed by UV-Vis spectrophotometry. Fourier transform infrared spectroscopy, scanning transmission electron microscopy, selected area electron diffraction, and energy-dispersive X-ray spectroscopy were used to characterize the physiochemical properties. The spherical form of AgNPs was confirmed by transmission electron microscopy. The peaks in the Tween-20/Vitrus vinifera-AgNPs have an average crystallite size that is found to be 46 nm according to powder X-ray diffraction examination. Biosynthesized AgNPs had a significant effect on bone osteosarcoma MG63 cells with 55% inhibition, respectively, using MTT assay. The effective dangerous concentration of Tween-20/Vitrus vinifera with AgNP nanoparticles was less harmful to MG63 cells. The results of antibacterial activity showed that Tween-20/Vitrus vinifera-AgNPs effectively inhibited Eggerthella lenta and Staphylococcus epidermis bacteria.

Lathyrane and Jatrophane Diterpenoids from Euphorbia helioscopia Evaluated for Cytotoxicity against a Paclitaxel-Resistant A549 Human Lung Cancer Cell Line

A phytochemical investigation on the aerial parts of Euphorbia helioscopia resulted in the isolation of 27 macrocyclic diterpenoids, including three previously unreported lathyrane derivatives, euphohelioscopoids A-C (1-3). Their structures were elucidated by spectroscopic data interpretation. Three jatrophanes, euphoscopin C (4), euphorbiapene D (6), and euphoheliosnoid A (5), showed cytotoxicity against a paclitaxel-resistant A549 human lung cancer cell line with IC₅₀ values of 6.9, 7.2, and 9.5 μM, respectively, but were inactive against the parent A549 human lung cancer cell line (IC₅₀ > 10 μM). It was found that jatrophanes with a benzoyloxy or a nicotinoyloxy substituent at C-7 showed more potent cytotoxic activity than their analogues containing acetyloxy and hydroxy groups at this position.

High-Content Screening Pipeline for Natural Products Targeting Oncogenic Signaling in Melanoma

The incidence of melanoma, the most fatal dermatological cancer, has dramatically increased over the last few decades. Modern targeted therapy with kinase inhibitors induces potent clinical responses, but drug resistance quickly develops. Combination therapy improves treatment outcomes. Therefore, novel inhibitors targeting aberrant proliferative signaling in melanoma via the MAPK/ERK and PI3K/AKT pathways are urgently needed. Biosensors were combined that report on ERK/AKT activity with image-based high-content screening and HPLC-based activity profiling. An in-house library of 2576 plant extracts was screened on two melanoma cell lines with different oncogenic mutations leading to pathological ERK/AKT activity. Out of 140 plant extract hits, 44 were selected for HPLC activity profiling. Active thymol derivatives and piperamides from Arnica montana and Piper nigrum were identified that inhibited pathological ERK and/or AKT activity. The pipeline used enabled an efficient identification of natural products targeting oncogenic signaling in melanoma.

Recent applications of the Wittig reaction in alkaloid synthesis

The Wittig reaction is the chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide (the Wittig reagent) to afford an alkene and triphenylphosphine oxide. Noteworthy, this reaction results in the synthesis of alkenes in a selective and predictable fashion. Thus, it became as one of the keystone of synthetic organic chemistry, especially in the total synthesis of natural products, where the selectivity of a reaction is paramount of importance. A literature survey disclosed the existence of vast numbers of related reports and comprehensive reviews on the applications of this important name reaction in the total synthesis of natural products. However, the aim of this chapter is to underscore, the applications of the Wittig reaction in the total synthesis of one the most important and prevalent classes of natural products, the alkaloids, especially those showing important and diverse biological activities.

1 H and 13 C NMR data, occurrence, biosynthesis, and biological activity of Piper amides

Alkamides are the major and characteristic chemical compounds of the plants belonging to the Piper genus. These compounds are responsible for the flavor of pepper spices and for its broad use in cuisine across many regions of the world. Humans are in contact every day with these substances, which additionally show a broad variety of pharmacological activities, making them an important research target. A large amount of NMR data for these natural products is dispersed throughout literature. Its organization will help those research groups interested in their identification and structural elucidation. This review summarizes the ¹ H and ¹³ C NMR data of 268 Piper amides in a systematic and orderly way, with a discussion on their biological activities, biosynthetic aspects, and NMR analysis of typical and relevant aspects of this information.

Anti-inflammatory and antitumour activity of various extracts and compounds from the fruits of Piper longum L

OBJECTIVES

To explore effective extraction method and to find active constituents, we investigated the biological activity of three extracts and isolated active compounds from the fruits of Piper longum L.

METHODS

Three extracts from the fruits were obtained by reflux, ultrasonic and supercritical fluid extraction, respectively. Active compounds were isolated by the bioassay-guided method. The anti-inflammatory activity, antiproliferation activity and cytotoxicity were evaluated. The apoptosis was detected by Hoechst 33258 staining assay. The relevant proteins were investigated by Western blot assay.

KEY FINDINGS

The anti-inflammatory activity and cytotoxicity of supercritical fluid extract (SE) were stronger than those of the other two extracts. Among all isolated compounds, the anti-inflammatory activity of eight compounds was stronger than that of indomethacin, and compounds 8, 9, 11, 14 and 15 were found to possess anti-inflammatory effect for the first time. Compounds 1, 2, 3 and 14 exhibited significant cytotoxicity against cancer cells. SE and piperine were found to reduce colony formation, inhibit cell migration and promote apoptosis through increasing cleaved PARP and the ratio of Bax/Bcl-2.

CONCLUSIONS

The anti-inflammatory and antitumour effects of SE were better than those of the other two extracts. The compounds responsible for the activity were elucidated. SE and piperine inhibit cell growth through apoptosis.

A systematic review on black pepper (Piper nigrum L.): from folk uses to pharmacological applications

Considered as the "King of spices", black pepper (Piper nigrum L.) is a widely used spice which adds flavor of its own to dishes, and also enhances the taste of other ingredients. Piper nigrum has also been extensively explored for its biological properties and its bioactive phyto-compounds. There is, however, no updated compilation of these available data to provide a complete profile of the medicinal aspects of P. nigrum. This study endeavors to systematically review scientific data on the traditional uses, phytochemical composition, and pharmacological properties of P. nigrum. Information was obtained using a combination of keywords via recognized electronic databases (e.g., Science Direct and Google Scholar). Google search was also used. Books and online materials were also considered, and the literature search was restricted to the English language. The country with the highest number of traditional reports of P. nigrum for both human and veterinary medicine was India, mostly for menstrual and ear-nose-throat disorders in human and gastrointestinal disorders in livestock. The seeds and fruits were mostly used, and the preferred mode of preparation was in powdered form, pills or tablets, and paste. Piper nigrum and its bioactive compounds were also found to possess important pharmacological properties. Antimicrobial activity was recorded against a wide range of pathogens via inhibition of biofilm, bacterial efflux pumps, bacterial swarming, and swimming motilities. Studies also reported its antioxidant effects against a series of reactive oxygen and nitrogen species including the scavenging of superoxide anion, hydrogen peroxide, nitric oxide, DPPH, ABTS, and reducing effect against ferric and molybdenum (VI). Improvement of antioxidant enzymes in vivo has also been reported. Piper nigrum also exhibited anticancer effect against a number of cell lines from breast, colon, cervical, and prostate through different mechanisms including cytotoxicity, apoptosis, autophagy, and interference with signaling pathways. Its antidiabetic property has also been confirmed in vivo as well as hypolipidemic activity as evidenced by decrease in the level of cholesterol, triglycerides, and low-density lipoprotein and increase in high-density lipoprotein. Piper nigrum also has anti-inflammatory, analgesic, anticonvulsant, and neuroprotective effects. The major bioactive compound identified in P. nigrum is piperine although other compounds are also present including piperic acid, piperlonguminine, pellitorine, piperolein B, piperamide, piperettine, and (-)-kusunokinin, which also showed biological potency. Most pharmacological studies were conducted in vitro (n = 60) while only 21 in vivo and 1 clinical trial were performed. Hence, more in vivo experiments using a pharmacokinetic and pharmacokinetic approach would be beneficial. As a conclusive remark, P. nigrum should not only be regarded as "King of spices" but can also be considered as part of the kingdom of medicinal agents, comprising a panoply of bioactive compounds with potential nutraceutical and pharmaceutical applications.

Chiron approach from D-mannitol to access a diastereomer of the reported structure of an acetogenin, an amide alkaloid and a sex pheromone

A short, simple and convenient chiron approach to (3R,4S,5R)-(-)-3,5-dihydroxy-4-decanolide, a hitherto unknown diastereomer of the reported structure of a naturally occurring acetogenin, (+)-polyporolide has been accomplished starting from a commercially available, inexpensive chiral pool molecule D-(+)-mannitol in nine efficient steps. An advanced intermediate synthesized from D-(+)-mannitol in six steps toward this end was further employed successfully to access two different natural products bearing two contiguous stereogenic centers. As a result, first chiron approach to formal total synthesis of an amide alkaloid, (4R,5R,2E)-4,5-dihydroxy-1-(piperidin-1-yl)dec-2-en-1-one and total synthesis of a male sex pheromone in parasitic Hymenoptera, (4R,5R)-(-)-5-hydroxy-4-decanolide have also been achieved.

GLI1 Inhibitors Identified by Target Protein Oriented Natural Products Isolation (TPO-NAPI) with Hedgehog Inhibition

This report describes the development of a target-protein-oriented natural-products-isolation (TPO-NAPI) method for Hedgehog inhibitors and the direct GLI1 inhibitor, 5'- O-methyl-3-hydroxyflemingin A (3), which inhibited hedgehog (Hh) signal transduction and diminished characteristics of cancer stem cells. Eight natural products (including three newly described products) that directly bind to GLI1 were rapidly obtained via the TPO-NAPI method developed using GLI1 protein-immobilized beads. 5'- O-Methyl-3-hydroxyflemingin A (3) inhibited Hh signaling (IC₅₀ 7.3 μM), leading to decreasing production of the Hh target proteins BCL2, PTCH1, and BMI1. 5'- O-Methyl-3-hydroxyflemingin A (3) was cytotoxic to Hh-related cancer cells. CD experiments revealed that 5'- O-methyl-3-hydroxyflemingin A (3) directly bound GLI1 ( K_d = 7.7 μM). Moreover, 5'- O-methyl-3-hydroxyflemingin A (3) diminished cancer stem cell characters of Huh7 such as sphere formation and production of the cancer stem cell marker EpCAM. These results suggest that Hh inhibitors can efficiently suppress the activity of cancer stem cells.

Pellitorine, an extract of Tetradium daniellii, is an antagonist of the ion channel TRPV1

BACKGROUND

Transient Receptor Potential Vanilloid 1 (TRPV1) confers noxious heat and inflammatory pain signals in the peripheral nervous system. Clinical trial of resiniferatoxin from Euphorbia species is successfully aimed at TRPV1 in cancer pain management and heading toward new selective painkiller status that further validates this target for drug discovery efforts. Evodia species, used in traditional medicine for hundreds of years, are a recognised source of different TRPV1 agonists, but no antagonist has yet been reported.

HYPOTHESIS/PURPOSE

In a search for painkiller leads, we noted for the first time a TRPV1 antagonist activity in the fresh fruits of Tetradium daniellii (Benn.) T.G. Hartley (syn. Evodia hupehensis Dode).

METHODS

Through a combination of extraction and purification methods with functional TRPV1-specific Ca²⁺ uptake assays (bioactivity-guided fractionation/isolation/purification); we isolated a new painkiller candidate that is a distant structural homologue of capsiate exovanilloids and endovanilloids such as anandamide, but a putative competitive inhibitor of the TRPV1. Four additional inactive compounds (N-isobutyl-4,5-epoxy-2E-decadienamide, geranylpsoralen, 8-(7',8'-epoxygeranyloxy)psoralen, and xanthotoxol) were also co-purified with pellitorine. Their structures were established by extensive 1D- and 2D-NMR spectroscopic analysis.

RESULTS

¹H- and ¹³C NMR determination of the chemical structure revealed it to be pellitorine, (2E,4E)-N-(2-methylpropyl)deca-2,4-dienamide, which can compete structurally with algesics released in inflammation. In contrast to previous isolates from Evodia species, pellitorine blocked capsaicin-evoked Ca²⁺ uptake with an IC₅₀ of 154 µg/ml (0.69 mM/l). N-Isobutyl-4,5-epoxy-2E-decadienamide and geranylpsoralen, 8-(7',8'-epoxygeranyloxy)psoralen, and xanthotoxol did not affect the TRPV1.

CONCLUSION

This is the first evidence that pellitorine, an aliphatic alkylamide analogue of capsaicin, can serve as an antagonist of the TRPV1 and may inhibit exovanilloid-induced pain.

A new benzophenanthridine alkaloid and other bioactive constituents from the stem bark of Zanthoxylum heitzii

Heitziquinone (7), a new benzophenanthridine alkaloid, together with five known compounds; isoarnottianamide (5), rhoifoline B (6), isobauerenol (8), 6-hydroxypellitorine (9) and sylvamide (10), were isolated as minor compounds from the hexane extract of stem bark from Zanthoxylum heitzii. Four previously reported compounds (1-4) were found, as well. Compounds 5 and 7 were both found to exist as 4:1 mixtures of two atropisomers. The structures were elucidated by 1D and 2D NMR spectroscopy and by mass spectrometry. Compounds 5-10 were identified for the first time in this species, and they are all rare natural compounds. Pellitorine (4), one of the main compounds from the hexane bark extract, was found to be responsible for the brine shrimp larvae toxicity (LC50 37 μM, 8 μg/ml) of the crude extract (LC50 24 μg/ml). Low cytotoxicity against a macrophage cell line was observed.

Fungal plasma membrane H⁺-ATPase inhibitory activity of o-hydroxybenzylated flavanones and chalcones from Uvaria chamae P. Beauv

In our ongoing efforts of finding natural fungicides to fight food and feed spoilage during production and storage, the antifungal potential of Ghanaian Uvaria chamae P. Beauv. was investigated, with emphasis on plant metabolites targeting the fungal plasma membrane (PM) H(+)-ATPase. Ethyl acetate extract of U. chamae was subjected to high-resolution fungal PM H(+)-ATPase inhibition screening followed by structural elucidation by high-performance liquid chromatography-high-resolution mass spectrometry-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-HRMS-SPE-NMR). This led to identification of a series of uncommon o-hydroxybenzylated flavanones and chalcones, i.e., chamanetin (8), isochamanetin (9), isouvaretin (10), uvaretin (11), dichamanetin (12), and diuvaretin (15). Preparative-scale isolation of the active metabolites allowed determination of IC50 values for inhibition of the PM H(+)-ATPase, and growth inhibition of Saccharomyces cerevisiae and Candida albicans. These revealed a strong correlation between o-hydroxybenzyl substituents and PM H(+)-ATPase activity, with dichamanetin being the most potent compound, but showing moderate activity in the fungal growth inhibition assays.

(E)-α,β-unsaturated amides from tertiary amines, olefins and CO via Pd/Cu-catalyzed aerobic oxidative N-dealkylation

A novel Pd/Cu-catalyzed chemoselective aerobic oxidative N-dealkylation/carbonylation reaction has been developed for the efficient and straightforward construction of synthetically useful and bioactive (E)-α,β-unsaturated amide derivatives.

Microwave-assisted synthesis of N-isobutyl-4,5-epoxy-2(E)-decenamide

A new and efficient synthesis of a naturally occurring amide alkaloid, N-isobutyl-4,5-epoxy-2(E)-decenamide isolated from the roots of Piper nigrum has been described involving a total of nine steps. Octanal and 2-bromoacetic acid have been used as the starting materials.

Anti-HBV active constituents from Piper longum

In the screening search for Hepatitis B virus inhibitory agents from medicinal plants, the ethanol extract of Piper longum Linn. was found to possess superior anti-HBV activity in vitro. Bioassay-guided fractionation coupled with repeated purification resulted in the isolation of four new compounds, involving two new glycosides longumosides A (1) and B (2) and two new amide alkaloids erythro-1-[1-oxo-9(3,4-methylenedioxyphenyl)-8,9-dihydroxy-2E-nonenyl]-piperidine (3), threo-1-[1-oxo-9(3,4-methylenedioxyphenyl)-8,9-dihydroxy-2E-nonenyl]-piperidine (4), as well as two compounds 3β,4α-dihydroxy-2-piperidinone (5), 5,6-dihydro-2(1H)-pyridinone (6) from natural source for the first time. The structures of the four new compounds were determined by extensive analyses of the MS, IR, 1D and 2D NMR data. Besides, the compounds 2-6, together with the known compounds 7-11 obtained previously, were assayed for their anti-HBV activity by using Hep G 2.2.15 cell line in vitro. Results suggested the compound piperine (7) possessed remarkable inhibitory HBV activity, against the secretion of hepatitis B virus surface antigen (HBsAg) and hepatitis B virus e antigen (HBeAg) with the Selectivity Index (SI) values of 15.7 and 16.8, respectively.

Coupling of a high-resolution monoamine oxidase-A inhibitor assay and HPLC-SPE-NMR for advanced bioactivity profiling of plant extracts

INTRODUCTION

Depression is a mental disease causing large personal and socio-economic problems, and new improved drugs are therefore needed. Selective monoamine oxidase A (MAO-A) inhibitors are potential anti-depressants, but discovering new MAO-A inhibitors from natural sources by bioassay-guided approaches are a lengthy and time-consuming process. New analytical technologies that allow simultaneously chemical and biological screening of extracts are therefore urgently needed.

METHOD

In the present study we describe coupling of a photometric microplate-based high-resolution MAO-A inhibitor assay with a hyphenated system consisting of high-performance liquid chromatography, solid-phase extraction and tube transfer nuclear magnetic resonance (HPLC-SPE-ttNMR). The standard compound clorgyline, and an extract of black pepper (Piper nigrum L.), representing a complex plant matrix, were used for proof-of-concept.

RESULTS

The work with clorgyline showed that the microplate-based high-resolution assay produced MAO-A inhibition profiles that easily allowed detection of submicrogram amounts of this selective MAO-A inhibitor. Furthermore, the HPLC-SPE-ttNMR/high-resolution MAO-A inhibition assay platform allowed identification of piperine and two piperine analogues as the main MAO-A inhibitors in the black pepper petroleum ether extract.

CONCLUSION

The HPLC-SPE-ttNMR/high-resolution MAO-A inhibition assay platform is a powerful tool for fast and efficient identification of new MAO-A inhibitors from complex extracts, and promise future advancement in the search for new anti-depressants from natural sources.

Structural and sensory characterization of key pungent and tingling compounds from black pepper (Piper nigrum L.)

To gain a more comprehensive knowledge on whether, besides the well-known piperine, other compounds are responsible for the pungent and tingling oral impression imparted by black pepper, an ethanol extract prepared from black pepper (Piper nigrum L.) was screened for its key sensory-active nonvolatiles by application of taste dilution analysis (TDA). Purification of the compounds perceived with the highest sensory impact, followed by LC-MS and 1D/2D NMR experiments as well as synthesis, led to the structure determination of 25 key pungent and tingling phytochemicals, among which the eight amides 1-(octadeca-2E,4E,13Z-trienyl)piperidine, 1-(octadeca-2E,4E,13Z-trienyl)pyrrolidine, (2E,4E,13Z)-N-isobutyl-octadeca-2,4,13-trienamide, 1-(octadeca-2E,4E,12Z-trienoyl)-pyrrolidine, 1-(eicosa-2E,4E,15Z-trienyl)piperidine, 1-(eicosa-2E,4E,15Z-trienyl)pyrrolidine, (2E,4E,15Z)-N-isobutyl-eicosa-2,4,15-trienamide, and 1-(eicosa-2E,4E,14Z-trienoyl)-pyrrolidine were not yet reported in literature. Sensory studies by means of a modified half-tongue test revealed recognition thresholds ranging from 3.0 to 1150.2 nmol/cm² for pungency and from 520.6 to 2162.1 nmol/cm² for the tingling orosensation depending on their chemical structure.

Antimicrobial, antileishmanial and cytotoxic compounds from Piper chaba

The petroleum ether and chloroform extracts of the root of Piper chaba showed antimicrobial, antileishmanial and cytotoxic activities. Further bioactivity-guided fractionation led to the isolation of Bornyl piperate (1), piperlonguminine (2) and piperine (3). This is the first report of isolation of compounds (1) and (2) from P. chaba. It was observed that the isolated compounds (1 and 2) showed potent antifungal activity when compared with standard drug Nystatin, and significant cytotoxic activity with the IC₅₀ values of 0.76 and 0.83 µg mL⁻¹, respectively. These compounds were also found to have weak antibacterial and antileishmanial activities. This is the first report about the antileishmanial activity of Piper isolates.

Inhibitory Effects of Black Pepper (Piper Nigrum) Extracts and Compounds on Human Tumor Cell Proliferation, Cyclooxygenase Enzymes, Lipid Peroxidation and Nuclear Transcription Factor-kappa-B

Black pepper ( Piper nigrum) and hot pepper ( Capsicum spp.) are widely used in traditional medicines. Although hot Capsicum spp. extracts and its active principles, capsaicinoids, have been linked with anticancer and antiinflammatory activities, whether black pepper and its active principle exhibit similar activities is not known. In this study, we have evaluated the antioxidant, antiinflammatory and anticancer activities of extracts and compounds from black pepper by using proinflammatory transcription factor NF-κB, COX-1 and -2 enzymes, human tumor cell proliferation and lipid peroxidation (LPO). The capsaicinoids, the alkylamides, isolated from the hot pepper Scotch Bonnet were also used to compare the bioactivities of alkylamides and piperine from black pepper. All compounds derived from black pepper suppressed TNF-induced NF-κB activation, but alkyl amides, compound 4 from black pepper and 5 from hot pepper, were most effective. The human cancer cell proliferation inhibitory activities of piperine and alklyl amides in Capsicum and black pepper were dose dependant. The inhibitory concentrations 50% (IC50) of the alklylamides were in the range 13-200 μg/mL. The extracts of black pepper at 200 μg/mL and its compounds at 25 μg/mL inhibited LPO by 45-85%, COX enzymes by 31-80% and cancer cells proliferation by 3.5-86.8%. Overall, these results suggest that black pepper and its constituents like hot pepper, exhibit antiinflammatory, antioxidant and anticancer activities.

New amide alkaloid from the aerial part of Piper capense L.f. (Piperaceae)

Together with apigenine dimethylether and piperchabamide A, a new amide alkaloid, Kaousine and the Z form of antiepilepsirine were isolated from the aerial part of Piper capense L.f (Piperaceae). Their structures were elucidated by spectrometric methods and their in vitro antiparasitic activities were evaluated on Plasmodium falciparum.

HPLC-based activity profiling: discovery of piperine as a positive GABA(A) receptor modulator targeting a benzodiazepine-independent binding site

A plant extract library was screened for GABA(A) receptor activity making use of a two-microelectrode voltage clamp assay on Xenopus laevis oocytes. An ethyl acetate extract of black pepper fruits [Piper nigrum L. (Piperaceae) 100 microg/mL] potentiated GABA-induced chloride currents through GABA(A) receptors (composed of alpha(1), beta(2), and gamma(2S) subunits) by 169.1 +/- 2.4%. With the aid of an HPLC-based activity profiling approach, piperine (5) was identified as the main active compound, together with 12 structurally related less active or inactive piperamides (1-4, 6-13). Identification was achieved by on-line high-resolution mass spectrometry and off-line microprobe 1D and 2D NMR spectroscopy, using only milligram amounts of extract. Compound 5 induced a maximum potentiation of the chloride currents by 301.9 +/- 26.5% with an EC(50) of 52.4 +/- 9.4 microM. A comparison of the modulatory activity of 5 and other naturally occurring piperamides enabled insights into structural features critical for GABA(A) receptor modulation. The stimulation of chloride currents through GABA(A) receptors by compound 5 was not antagonized by flumazenil (10 microM). These data show that piperine (5) represents a new scaffold of positive allosteric GABA(A) receptor modulators targeting a benzodiazepine-independent binding site.

First stereoselective total synthesis and anticancer activity of new amide alkaloids of roots of pepper

The first stereoselective total synthesis of new natural amide alkaloids 1-3 have been achieved from commercially available starting materials. Wittig olefination, Sharpless asymmetric dihydroxylation, epoxidation, a trans regioselective opening of 2,3-epoxy alcohol, Horner-Wadsworth-Emmons (HWE) olefination and amide coupling are the key steps. The amide alkaloids 1-3 are evaluated for their anticancer activity against colon (HT-29), breast (MCF-7) and lung (A-549) human cancer cell lines for the first time.

A new amide alkaloid from the leaves of Piper sarmentosum

A new amide alkaloid, N-(3',4',5'-trimethoxy-cis-cinnamoyl)pyrrolidine (1), named sarmentomicine was isolated from the ethanol extract of the leaves of Malayan Piper sarmentosum, together with two known phenylpropanoids. Their structures were elucidated on the basis of spectroscopic analysis.

Antifungal amides from Piper scutifolium and Piper hoffmanseggianum

Chromatographic fractionation of a dichloromethane extract from the leaves of Piper scutifolium yielded two new isobutyl amides, scutifoliamide A ( 1) and scutifoliamide B ( 2), together with the known compounds piperolactam C ( 3), piperovatine ( 4), piperlonguminine ( 5), corcovadine ( 6), isopiperlonguminine ( 7), and isocorcovadine ( 8). From the dichloromethane extract from the leaves of P. hoffmannseggianum two new isobutyl amides, hoffmannseggiamide A ( 9) and hoffmannseggiamide B ( 10), were obtained together with the known compounds isopiperlonguminine ( 7) and isocorcovadine ( 8), sitosterol, and stigmasterol. The structures of the new compounds were established on the basis of spectroscopic data analysis. The inhibitory activity of compounds 1-10 against the growth of the fungi Cladosporium sphaerospermum and C. cladosporioides was determined by bioautography.

Antidepressant-like effects of piperine and its derivative, antiepilepsirine

In the present study, antidepressant-like effects of piperine (PIP) and its derivative, antiepilepsirine (AES), were investigated in two depressive models: forced swimming test (FST) and tail suspension test (TST). To further explore the mechanisms underlying their antidepressant-like activities, the brain monoamine levels and monoamine oxidase A and B (MAO-A and MAO-B) activities were also determined. The research results for the first time indicated that after two weeks of chronic administration, PIP and AES at doses of 10-20 mg/kg significantly reduced the duration of immobility in both FST and TST, without accompanying changes in locomotor activity in the open-field test. But at the dose of 80 mg/kg, the antidepressant activity of both PIP and AES returned to the control level in the TST and FST. In the monoamine assay, chronic AES administration significantly elevated the dopamine level in striatum, hypothalamus and hippocampus, and also increased the serotonin level in the hypothalamus and hippocampus. In contrast, chronic treatment of PIP only enhanced the serotonin level in the hypothalamus and hippocampus but did not influence the dopamine level. Moreover, both PIP and AES showed no effects on level of noradrenaline in these brain regions. The MAO activity assay also indicated that PIP and AES showed a minor MAO inhibitory activity. In the present study, we demonstrated that the antidepressant-like effects of PIP and AES might depend on the augmentation of the neurotransmitter synthesis or the reduction of the neurotransmitter reuptake. Antidepressant properties of PIP were supposed to be mediated via the regulation of serotonergic system, whereas the mechanisms of antidepressant action of AES might be due to its dual regulation of both serotonergic and dopaminergic systems.

Antidepressant like effects of piperine in chronic mild stress treated mice and its possible mechanisms

In this study, we investigated the antidepressant-like effect of piperine in mice exposed to chronic mild stress (CMS) procedure. Repeated administration of piperine for 14 days at the doses of 2.5, 5 and 10 mg/kg reversed the CMS-induced changes in sucrose consumption, plasma corticosterone level and open field activity. Furthermore, the decreased proliferation of hippocampal progenitor cells was ameliorated and the level of brain-derived neurotrophic factor (BDNF) in hippocampus of CMS stressed mice was up-regulated by piperine treatment in the same time course. In addition, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactic dehydrogenase (LDH) assays showed that piperine (6.25-25 microM) or fluoxetine (FLU, 1 microM) dose-dependently protected primary cultured hippocampal neurons from the lesion induced by 10 microM corticosterone (CORT). Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the messenger ribonucleic acid (mRNA) level of BDNF in cultured neurons. Treatment with piperine (6.25-25 microM) for 72 h reversed the CORT-induced reduction of BDNF mRNA expression in cultured hippocampal neurons. In summary, up-regulation of the progenitor cell proliferation of hippocampus and cytoprotective activity might be mechanisms involved in the antidepressant-like effect of piperine, which may be closely related to the elevation of hippocampal BDNF level.