Three new kavalactone dimers from Piper methysticum (kava)

Abstract

Three new dimeric kavalactones, designated as diyangonins A–C (1–3), along with two known analogs were isolated from the roots of Piper methysticum. Their structures were elucidated by means of extensive analysis of their 1D, 2D NMR, and mass spectroscopic data. All these dimers possess a skeleton featuring a cyclobutane ring connecting two kavalactone units in head-to-tail or head-to-head mode. Compounds 1–5 were evaluated for their cytotoxic activities against human tumor cell lines.     

Extracts and kavalactones of Piper methysticum G. Forst (kava-kava) inhibit P-glycoprotein in vitro.

Root extracts from kava-kava (Piper methysticum G. Forst) are clinically used for the treatment of anxiety and restlessness. Due to reported cases of liver toxicity, kava-kava extracts were withdrawn from the market in several countries in 2002. Because the efflux transporter P-glycoprotein (P-gp) is involved in the absorption, distribution, and excretion of many drugs and often participates in drug-drug interactions, we studied the effect of a crude kava extract and the main kavalactones kavain, dihydrokavain, methysticin, dihydromethysticin, yangonin, and desmethoxyyangonin on the P-gp-mediated efflux of calcein-acetoxymethylester in the P-gp-overexpressing cell line P388/dx and the corresponding cell line P388. The crude extract and the kavalactones showed a moderate to potent inhibitory activity with f2) (concentration needed to double baseline fluorescence) values of 170 microg/ml and 17 to 90 microM, respectively. The f2 value of yangonin could not be determined due to its higher lipophilicity. In conclusion, our results for the first time demonstrate P-gp-inhibitory activity of kava-kava and its components in vitro.     

In vitro antioxidant activity of three Piper species

Reactive oxygen species are known to play a role in numerous pathological conditions, and antioxidants from plant sources have been of great help in modulating this effect. This study assesses the methanolic extracts of the leaves of three Piper species (Piper guineense Schum and Thonn., Piper nigrum L. and Piper umbellatum L.) (Piperaceae) for their polyphenolic concentration and free radical scavenging activity. The Folin-Ciocalteu method was used to assess the polyphenolic concentration while the reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide radical, hydroxyl radical, nitric oxide scavenging and metal chelating activities were employed in studying the radical scavenging activity of the extracts. All three spices exhibited a marked polyphenolic concentration and dose dependent free radical scavenging activity. The free polyphenolic concentration of the three spices was in the order P. umbellatum (15.9 +/- 1.9 mg/g) > P. guineense (12.6 +/- 0.3 mg/g) > P. nigrum (9.8 +/- 0.8). The three Piper extracts exhibited a 79.8-89.9% scavenging effect on DPPH, an 85.1-97.9% scavenging effect on nitric oxide at a dose level of 10 mg/ml and a 47.1-51.6% scavenging effect on superoxide radical at a dose level of 8 mg/ml extraction. Piper extracts also exhibited a 57-76.1% scavenging effect on hydroxyl radical at 5 mg/ml, a 0.4-0.6 reducing power and an 88.3-93.9% metal chelating activity at a dose level of 8 mg/ml of extract. Thus, these Piper species can play a role in the modulation of free radical induced disorders.     

In vitro antioxidant activity of some Teucrium species (Lamiaceae)

The chemical composition and antioxidant activity of different extracts (diethyl ether, ethyl acetate and n-butanol) obtained from Teucrium species (T. chamaedrys, T. montanum, T. polium) were investigated in this work. Phytochemical screening of the plant extracts proved the presence of flavonoids luteolin, apigenin and/or diosmetin. The chemical composition of extracts was evaluated by HPLC and spectrophotometry. Antioxidant activities of the extracts were evaluated using three complementary in vitro assays: inhibition of DPPH (1,1-diphenyl-2-picrylhydrazyl) radical, inhibition of hydroxyl radicals and protection of beta-carotene-linoleic acid model system. In the first two assays, strong inhibitory activity was shown by T. montanum and T. chamaedrys extracts. In the beta-carotene-linoleic acid model system, extracts from T. polium showed remarkable activity. These findings demonstrated that Teucrium species possess free radical and hydroxyl radical scavenging activity as well as antioxidant activity in vitro.     

On the anti-inflammatory activity of some substituted phenolic compounds

Some substituted dihydroxybenzenes have been examined for suppression of the yeast-induced inflammatory reaction in the rat paw. This anti-inflammatory activity is greatest in those compounds derived from resorcinol and in particular the halogenated 5-methylresorcinols. The significance of the internuclear distance between the hydroxyl groups in the meta-position to each other in resorcinol and the importance of the enhanced activity due to the halogen atom(s) is discussed. In this series the toxicity and activity could not be divorced.     

Enhanced cognitive performance and cheerful mood by standardized extracts of Piper methysticum (Kava-kava)

The acute effects of the herbal anxiolytic Kava-kava (Piper methysticum G. Forster) on emotional reactivity and cognitive performance were investigated in a double-blind randomized placebo-controlled trial involving healthy volunteers. Subjects' reports of mood change were assessed with the state-trait-cheerfulness-inventory, which measures the three concepts of cheerfulness, seriousness and bad mood as both traits and states. Cognitive performance was examined with the Sperling partial report and the Sternberg item recognition task, which were used as an index for visual attention and short-term memory processing. The intake of a single dose of Kava extract (300 mg; p.o.) led to an increase in state cheerfulness, while the phytopharmacon did not influence state seriousness and bad mood. The mood-elevating effects of Kava were most prominent in trait cheerful subjects, indicating that trait cheerfulness moderated the drug-induced increase in cheerful mood. Furthermore, Kava improved the accuracy and the speed of performing the partial report and the item recognition task, indicative of a beneficial effect of the phytopharmacon on visual attention and short-term memory retrieval, respectively. Thus, unlike conventional benzodiazepine-type anxiolytics, which tend to impair cognitive performance and to increase the occurrence of negative affective states, Kava is a potent anxiolytic agent, which, additionally, can facilitate cognitive functioning and can increase positive affectivity related to exhilaration.     

Drug absorption in vitro model: filter-immobilized artificial membranes. 2. Studies of the permeability properties of lactones in Piper methysticum Forst.

The assessment of transport properties of 23 drug and natural product molecules was made using the in vitro model based on filter-immobilized artificial membranes (filter-IAM), assembled from phosphatidylcholine in dodecane, in buffer solutions at pH 7.4. Five of the compounds were lactones extracted from the roots of the kava-kava plant. Experiments were designed to test the effects of stirring (0–600 rpm) during assays and the effects of varying the assay times (2–15 h). The highly mobile kava lactones permeated in the order dihydromethisticin (40)>yangonin (37)>kavain (34)>methisticin (32)>desmethoxyyangonin (26), the numbers in parentheses being the measured effective permeabilities in units of 10⁻⁶ cm/s. By comparison, commercial drugs ranked: phenazopyridine (35)>testosterone (19)>propranolol (13)>ketoconazole (6.3)>piroxicam (2.2)>caffeine (1.7)>metoprolol (0.8)>terbutaline (0.01). In addition to permeability measurements, membrane retention of compounds was determined. Yangonin, desmethoxyyangonin, ketoconazole, and phenazopyridine were more than 60% retained by the artificial membranes containing phospholipids. Stirring during assay significantly increased the observed permeabilities for highly mobile molecules, but had minimal impact on the poorly permeable molecules. The influence of hydrogen bonding was explored by determining permeabilities using filters coated with dodecane free of phospholipids. In the filter-IAM method, concentrations were determined by microtitre plate UV spectrophotometry and by LC–MS. Higher-throughput was achieved with direct UV by the use of 96-well microtitre plate formats and with LC–MS by the use of cassette dosing (five-in-one).     

Safety review of kava (Piper methysticum) by the Natural Standard Research Collaboration

This systematic review discusses the proposed uses, dosing parameters, adverse effects, toxicology, interactions and mechanism of action of kava. The widespread concern regarding the potential hepatotoxicity of kava is discussed. A recommendation is made to consolidate and analyse available reports and to continue postmarket surveillance in an international repository to prevent duplicates and promote collection of thorough details at the time of each report so that any association with kava is clearly defined.     

Safety review of kava (Piper methysticum) by the Natural Standard Research Collaboration

This systematic review discusses the proposed uses, dosing parameters, adverse effects, toxicology, interactions and mechanism of action of kava. The widespread concern regarding the potential hepatotoxicity of kava is discussed. A recommendation is made to consolidate and analyse available reports and to continue postmarket surveillance in an international repository to prevent duplicates and promote collection of thorough details at the time of each report so that any association with kava is clearly defined.     

Pressurized liquid extraction of phenolic compounds from Anatolia propolis and their radical scavenging capacities

Propolis samples from important honey producing locations of Anatolia namely; Bingol (BG), Rize (RZ), Tekirdag (TK) and Van (VN), were evaluated for their antiradical capacities, total phenolic contents and individual phenolic compounds which was recovered by means of pressurized liquid extraction (PLE). Several extraction parameters of PLE such as; temperature, pressure, solvent type, extraction time and cell size were investigated for their effects on the extraction performances. The results showed that, 40 °C, 1500 psi, Ethanol:water:HCl; (70:25:5, v/v/v) containing 0.1% tert-butylhydroquinone (tBHQ) as solvent, three extraction cycles within 15 min, and a cell size of 11 mL was the most favorable PLE operating conditions. Results of the tests performed to designate the success of the polyphenol analysis showed that the recovery was in the range of 97.2% and 99.7%.Major phenolic compounds in all samples were found to be gallocatechin (GCT), catechin (CT), epicatechin gallate (ECTG), caffeic acid (CA), chlorogenic acid (ChA), and myricetin (Myr). ChA level of BG propolis was 4.5, 3 and 23 times higher than that of RZ, TK and VN region, respectively. Antiradical tests showed that all propolis samples have superior antiradical capacities up to 500 mg Trolox equivalent activity per gram of extract.     

Electrospray high performance liquid chromatography-mass spectrometry in phytochemical analysis of kava (Piper methysticum) extract

HPLC coupled with electrospray (ES) MS was used to study a chloroform extract from kava roots ( PIPER METHYSTICUM). A total of thirteen kavalactones and flavokavains were identified. Seven major kavalactones, methysticin, dihydromethysticin, kavain, 7,8-dihydrokavain, 5,6-dehydrokavain, 5,6-dehydromethysticin and yangonin, were easily recognized in the extract by their [M + H] (+) or [M + Na] (+) ions, UV spectra, and retention times, compared with those of standard compounds. Six minor constituents were isolated as our own reference compounds. These constituents were identified by their [M + H] (+) or [M + Na] (+) ions, UV spectra and NMR data as 11 -hydroxy-12-methoxydihydrokavain, 7,8-dihydro-5-hydroxy-kavain, 11,12-dimethoxydihydrokavain, and flavokavains A, B and C. HPLC-ES-MS appears to be a suitable technique for identification of kavalactones and kavachalcones in the kava extract. The method also provides direct guidance for identification of other trace constituents from kava extracts.