N-Alkylamides from Piper longum L. and their stimulative effects on the melanin content and tyrosinase activity in B16 melanoma cells

Abstract

Piper longum L., known as long pepper, is an edible and medicinal plant used as spice and for the treatment of stomach disease and analgesia in traditional Chinese medicine. N-Alkylamides are the major secondary metabolites in this plant. Sixteen known N-alkylamides were isolated from P. longum. Their structures were established on the basis of spectroscopic data and comparison to reported literatures. Among them, five compounds were isolated from this plant for the first time. Ethanol extract, compounds 1, 2, 3, 7 and 11 exhibited potent ability to increase the melanin content and weak stimulative effect on the tyrosinase activity in a concentration-dependent manner. Moreover, compound 2 also presented strong capacity to increase the tyrosinase activity in a concentration-dependent manner. These results indicated that P. longum might be a good natural source of lead compound for skin disorder diseases.     

Pressurized fluid extraction of carotenoids from Haematococcus pluvialis and Dunaliella salina and kavalactones from Piper methysticum

Pressurized fluid extraction (PFE) was examined as an alternative technology for the extraction of carotenoids in the green algae Haematococcus pluvialis and Dunaliella salina and kavalactones in Piper methysticum. The extraction process was optimized by varying the key extraction factors of solvent, sample-solvent ratio, temperature, and time. The selectivity and efficiency of extraction parameters were determined with high performance liquid chromatography (LC) and LC-mass spectrometry (LC-MS). Results showed that PFE utilization of conventional solvents under controlled temperature and pressure in an oxygen and light-free environment could result in the use of less solvent in a shorter period of time. PFE showed higher or equal extraction efficiencies as compared with traditional solvent extractions while maintaining the integrity of chemical components. PFE showed high potential for extraction of natural products and nutraceuticals, particularly labile and light sensitive chemicals.     

Chabamides F and G, two novel dimeric alkaloids from the roots of piper chaba hunter

Two new dimeric alkaloids, chabamide F (1) and chabamide G (2), containing pyrrolidine rings, were isolated from the roots of piper chaba hunter. The structures of 1 and 2 were established on the basis of spectroscopic data, especially 2D NMR and mass spectral data.     

中草药假蒟挥发油的色谱-质谱分析

假药(PipersarmentosumRoxb.),别名荜茇子、蛤蒟、大柄萎、马蹄蒌、假蒟(广东、广西)、钻骨风、叶子藤、芦子藤(云南)。在我国福建、广东、广西、云南、贵州、西藏有分布。云南、广东民间常取其茎叶及果穗治腹胀、腹痛、肠炎腹泻、食欲不振、风湿痛、疝气痛,外用治外伤出血、跌打痨伤、冻疮等。根据《中药大辞典》、《广东中草药》、广州部队《常用中草药手册》记载,假蒟根、叶、果穗温中暖胃,驱风行气,化湿消肿;治腹账腹痛,肠炎腹泻,食欲不振,胃炎,行气通窍,消滞化痰,风湿性关节炎等病症。通过对假药挥发油的色谱-质谱分析鉴定,假蒟挥发油中含有大约55％的细辛脑类化合物。细辛脑能对抗组胺、乙酰胆碱,缓解支气管痉挛起到平喘作用,对咳嗽中枢也有较强的抑制作用;可引起分泌物增加,使浓痰变稀,降低痰液黏滞,易于咳出;有类似氨茶碱松弛支气管平滑肌的作用;还能提高大脑皮质的电刺激阈,抑制电刺激的突触传导及癫痫性电的扩散。     

Pleiocarpumlignan A,a new dineolignan from Piper pleiocarpum Chang ex Tseng

Abstract

The investigation of chemical constituents from the whole plants Piper pleiocarpum Chang ex Tseng resulted in the isolation of one new dineolignan, pleiocarpumlignan A (1), along with one known benzoate derivative, trans-2,3-diacetoxy-1-[(benzoy1oxy)methyl]-cyclohexa-4,6-diene (2), and two known neolignans (3–4) as (±)-trans-dehydrodiisoeugenol (3), (7R,8R,3′S)-△^8′-3′,6′-dihydro-3′-methoxy-3,4-methylenedioxy-6′-oxo-8,3′,7,O,4′-lignan (4). Their structures were elucidated through extensive spectroscopic analyses including 1D, 2D NMR, HR-ESI-MS, and by comparison with the literature. All compounds (1–4) were firstly isolated from Piper pleiocarpum Chang ex Tseng. The ¹³C NMR spectra of 2 were completely assigned for the first time. Cytotoxic activities of these isolated compounds against five human cancer cell lines (including A-549, SMMC-7721, HL-60, MCF-7, and SW-480) were evaluated.     

Circadian variation and in vitro cytotoxic activity evaluation of volatile compounds from leaves of Piper regnellii (Miq) C. DC. var. regnellii (C. DC.) Yunck (Piperaceae)

Aiming detection of circadian variation in the chemical composition of volatiles from Piper regnellii, the leaves were collected during four different periods (8, 12, 16 and 20 h) in the same day. After extraction by hydrodistillation and GC/MS analysis, no significant variation was observed for the main compounds: germacrene D (45.6 ± 1.5–51.4 ± 3.1%), α–chamigrene (8.9 ± 1.3–11.3 ± 2.7%) and β–caryophyllene (8.2 ± 0.9–9.5 ± 0.3%). Evaluation of in vitro cytotoxicity against several cancer and non-tumourigenic cells indicated promising activity, especially to HeLa (human cervical carcinoma) with IC₅₀ ranging from 11 ± 3 to 17 ± 3 μg/mL. The obtained volatile oils were pooled and subjected to fractionation to afford pure β-caryophyllene, α-chamigrene and germacrene D, being this last compound the more active against HeLa cells with IC₅₀ of 7 ± 1 μg/mL (34 ± 5 μM). Therefore, the predominance of germacrene D in all analysed oils could justify, at least in part, the activity observed for the volatile compounds from P. regnellii leaves.     

Development of an LC‐MS/MS method for quantification of kadsurenone in rat plasma and its application to a pharmacokinetic study

A sensitive and rapid LC‐MS/MS method was developed and validated for the determination of kadsurenone in rat plasma using lysionotin as the internal standard (IS). The analytes were extracted from rat plasma with acetonitrile and separated on a SB‐C₁₈ column (50 × 2.1 mm, i.d.; 1.8 µm) at 30 °C. Elution was achieved with a mobile phase consisting of methanol–water–formic acid (65:35:0.1, v/v/v) at a flow rate of 0.30 mL/min. Detection and quantification for analytes were performed by mass spectrometry in the multiple reaction monitoring mode with positive electrospray ionization m/z at 357.1 → 178.1 for kadsurenone, and m/z 345.1 → 315.1 for IS. Calibration curves were linear over a concentration range of 4.88–1464 ng/mL with a lower limit of quantification of 4.88 ng/mL. The intra‐ and inter‐day accuracies and precisions were <8.9%. The LC‐MS/MS assay was successfully applied for oral pharmacokinetic evaluation of kadsurenone using the rat as an animal model. Copyright © 2013 John Wiley & Sons, Ltd.     

First mechanosynthesis of piperlotines A,C, and derivatives through solvent-free Horner–Wadsworth–Emmons reaction

Piperlotines are natural products characterized by an α,β-unsaturated amide moiety. These compounds found wide applications in Medicinal Chemistry like antibacterials, cytotoxic agents, anticoagulants, among others. To date, diverse methods of synthesis have been reported for piperlotines, but involving the use of catalysts, hazard reagents, anhydrous media or coupling reagents. Thus, in this work, we developed a greener method of synthesis of piperlotines A, C, and derivatives, through mechanochemical activation under solvent-free conditions. The reaction of a β-amidophosphonate, K₂CO₃, and an aromatic aldehyde afforded target compounds in moderate to good yields (46–77%), in an open atmosphere by grinding. It is worth to mention that this mechanochemical process was under thermodynamic control because just E isomer was isolated for every reaction. Moreover, synthesized piperlotines have been predicted by means of chemoinformatic analysis as potential therapeutic agents for the treatment of arthritis or cancer.     

Biodereplication of Antiplasmodial Extracts: Application of the Amazonian Medicinal Plant Piper coruscans Kunth

Improved methodological tools to hasten antimalarial drug discovery remain of interest, especially when considering natural products as a source of drug candidates. We propose a biodereplication method combining the classical dereplication approach with the early detection of potential antiplasmodial compounds in crude extracts. Heme binding is used as a surrogate of the antiplasmodial activity and is monitored by mass spectrometry in a biomimetic assay. Molecular networking and automated annotation of targeted mass through data mining were followed by mass-guided compound isolation by taking advantage of the versatility and finely tunable selectivity offered by centrifugal partition chromatography. This biodereplication workflow was applied to an ethanolic extract of the Amazonian medicinal plant Piper coruscans Kunth (Piperaceae) showing an IC₅₀ of 1.36 µg/mL on the 3D7 Plasmodium falciparum strain. It resulted in the isolation of twelve compounds designated as potential antiplasmodial compounds by the biodereplication workflow. Two chalcones, aurentiacin (1) and cardamonin (3), with IC₅₀ values of 2.25 and 5.5 µM, respectively, can be considered to bear the antiplasmodial activity of the extract, with the latter not relying on a heme-binding mechanism. This biodereplication method constitutes a rapid, efficient, and robust technique to identify potential antimalarial compounds in complex extracts such as plant extracts.     

Molecular Docking and Dynamics Simulation of Natural Compounds from Betel Leaves (Piper betle L.) for Investigating the Potential Inhibition of Alpha-Amylase and Alpha-Glucosidase of Type 2 Diabetes

Piper betle L. is widely distributed and commonly used medicinally important herb. It can also be used as a medication for type 2 diabetes patients. In this study, compounds of P. betle were screened to investigate the inhibitory action of alpha-amylase and alpha-glucosidase against type 2 diabetes through molecular docking, molecular dynamics simulation, and ADMET (absorption, distribution, metabolism, excretion, and toxicity) analysis. The molecule apigenin-7-O-glucoside showed the highest binding affinity among 123 (one hundred twenty-three) tested compounds. This compound simultaneously bound with the two-target proteins alpha-amylase and alpha-glucosidase, with high molecular mechanics-generalized born surface area (MM/GBSA) values (ΔG Bind = −45.02 kcal mol⁻¹ for alpha-amylase and −38.288 for alpha-glucosidase) compared with control inhibitor acarbose, which had binding affinities of −36.796 kcal mol⁻¹ for alpha-amylase and −29.622 kcal mol⁻¹ for alpha-glucosidase. The apigenin-7-O-glucoside was revealed to be the most stable molecule with the highest binding free energy through molecular dynamics simulation, indicating that it could compete with the inhibitors’ native ligand. Based on ADMET analysis, this phytochemical exhibited a wide range of physicochemical, pharmacokinetic, and drug-like qualities and had no significant side effects, making them prospective drug candidates for type 2 diabetes. Additional in vitro, in vivo, and clinical investigations are needed to determine the precise efficacy of drugs.