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.

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In a screening of Iranian plants for antiprotozoal activity, an n-hexane extract of the roots of Salvia sahendica potently inhibited the growth of Plasmodium falciparum K1 strain. Subsequent HPLC-based activity profiling led to the identification of seven known and one new abietane-type diterpenoid. Structure elucidation was achieved by analysis of spectroscopic data including 1D and 2D NMR. The absolute configuration of sahandol (7) and sahandone (8) were assigned by comparison of experimental ECD spectra with calculated ECD data, using time-dependent density functional theory and methanol as the solvent. In vitro biological activity against P. falciparum and Trypanosoma brucei rhodesiense STIB 900 strain and cytotoxicity in rat myoblast (L6) cells were determined. The IC50 values of the compounds ranged from 0.8 µM to over 8.8 µM against P. falciparum, and from 1.8 µM to over 32.3 µM against T. brucei rhodesiense. The cytotoxic IC50 values ranged from 0.5-15.5 µM. Selectivity indices for P. falciparum were 0.1 to 18.2, and 0.1 to 1.2 for T. brucei rhodesiense.

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In a two-microelectrode voltage clamp with Xenopus laevis oocytes, a petroleum ether extract of Acorus calamus rhizomes enhanced the GABA-induced chloride current through GABA A receptors of the α 1 β 2 γ 2S subtype by 277% ± 9.7% (100 μg/mL). β-Asarone (1), (+)-dioxosarcoguaiacol (2), (+)-shyobunone (3), and (+)-preisocalamenediol (4) were subsequently identified as main active principles through HPLC-based activity profiling and targeted isolation. The compounds induced maximum potentiation of the chloride current ranging from 588% ± 126% (EC 50 : 65.3 ± 21.6 μM) (2) to 1200% ± 163% (EC 50 : 171.5 ± 34.6 μM) (1), whereas (−)-isoshyobunone (5) and (−)-acorenone (6) exhibited weak GABA A modulating properties (5: 164% ± 42.9%; EC 50 : 109.4 ± 46.6 μM and 6: 241% ± 23.1%; EC 50 : 34.0 ± 6.7 μM). The relative configuration of 2 was established as 4R*8S*10R* by NOESY experiments and conformational analysis.Acorus calamus L. (Acoraceae), commonly known as "sweet flag", is a polyploidic marsh plant indigenous to Asia and is now distributed along trade routes all over the northern hemisphere. 1 The aromatic rhizome has been widely used as an herbal remedy. It contains 1.7-9.3% of a volatile oil composed of monoterpenes, sesquiterpenes, and phenylpropanoids. The most characteristic constituent of the oil is β-asarone, even though Europe PMC Funders GroupAuthor Manuscript J Nat Prod. Author manuscript; available in PMC 2011 October 24. Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts its concentration may vary considerably (96% in the tetraploidic form found in eastern and tropical southern Asia, 5% in the triploidic form found in Europe, Himalayan, and temperate Indian regions, and 0% in the diploidic variety growing from North America to Siberia). [1][2][3][4] In European folk medicine, A. calamus rhizomes have been mainly used as "Amarum aromaticum" to alleviate gastrointestinal ailments such as acute and chronic dyspepsia, gastritis and gastric ulcer, intestinal colic, and anorexia. 5,6 Ayurvedic medicine and traditional Chinese medicine (TCM) use the drug preferably to treat central nervous system (CNS) related diseases such as epilepsy, insanity, mental weakness, or insomnia. 7-9 Several in vivo studies support a sedative and tranquillizing action of the essential oil and of ethanolic and aqueous extracts of A. calamus. [10][11][12] Up to now, the underlying mechanism of action has remained elusive despite various investigations, even though the pharmacological effect could be mainly attributed to α-asarone and β-asarone. 11,[13][14][15] GABA A receptors are pentameric ligand-gated chloride ion channels that are activated by GABA, the major inhibitory neurotransmitter in the CNS. Most likely more than 11 different receptor subtypes, assembled from five varying subunits, exist in the human brain. These are involved in distinct neuronal circuits and are targeted by numerous classes of drugs such as benzodiazepines, barbiturates, and some general anesthetics. The most abundant GABA...

An ethyl acetate extract of Biota orientalis leaves potentiated GABA-induced control current by 92.6% ± 22.5% when tested at 100 μg/mL in Xenopus laevis oocytes expressing GABA(A) receptors (α₁β₂γ(2S) subtype) in two-microelectrode voltage clamp measurements. HPLC-based activity profiling was used to identify isopimaric acid (4) and sandaracopimaric acid (5) as the compounds largely responsible for the activity. Sandaracopimaradienolal (3) was characterized as a new natural product. Compounds 4 and 5 were investigated for GABA(A) receptor subtype selectivity at the subtypes α₁β₁γ(2S), α₁β₂γ(2S), α₁β₃γ(2S), α₂β₂γ(2S), α₃β₂γ(2S), and α₅β₂γ(2S). Sandaracopimaric acid (5) was significantly more potent than isopimaric acid (4) at the GABA(A) receptor subtypes α₁β₁γ(2S), α₂β₂γ(2S), and α₅β₂γ(2S) (EC₅₀4: 289.5 ± 82.0, 364.8 ± 85.0, and 317.0 ± 83.7 μM vs EC₅₀5: 48.1 ± 13.4, 31.2 ± 4.8, and 40.7 ± 14.7 μM). The highest efficiency was reached by 4 and 5 on α₂- and α₃-containing receptor subtypes. In the open field test, ip administration of 5 induced a dose-dependent decrease of locomotor activity in a range of 3 to 30 mg/kg body weight in mice. No significant anxiolytic-like activity was observed in doses between 1 and 30 mg/kg body weight in mice.

A new dihydroisocoumarin was isolated from a dichloromethane extract of Haloxylon scoparium with the aid of a functional assay with Xenopus oocytes transiently expressing GABA(A) receptors of defined subunit composition (alpha(1)beta(2)gamma(2S)). Compound 1 induced a maximum potentiation of the chloride currents by 144.6 +/- 35.3% with an EC(50) of 140.2 +/- 51.2 muM.