A sedge plant as the source of Kangaroo Island propolis rich in prenylated p-coumarate ester and stilbenes

AbstractPropolis samples from Kangaroo Island, South Australia, were investigated for chemical constituents using high-field nuclear magnetic resonance spectral profiling. A type of propolis was found containing a high proportion of prenylated hydroxystilbenes. Subsequently, the botanical origin of this type of propolis was identified using a beehive propolis depletion method and analysis of flora. Ligurian honey bees, Apis mellifera ligustica Spinola, were found to produce propolis from resin exuded by the Australian native sedge plant Lepidosperma sp. Montebello (Cyperaceae). The plants, commonly known as sword sedge, were found to have resin that matched with the propolis samples identified as the most abundant propolis type on the island containing C- and O-prenylated tetrahydroxystilbenes (pTHOS) in addition to a small amount of prenylated p-coumarate. The isolation of five pTHOS not previously characterized are reported: (E)-4-(3-methyl-2-buten-1-yl)-3,4′,5-trihydroxy-3′-methoxystilbene, (E)-2,4-bis(3-methyl-2-buten-1-yl)-3,3′,4′,5-tetrahydroxystilbene, (E)-2-(3-methyl-2-buten-1-yl)-3-(3-methyl-2-butenyloxy)-3′,4′,5-trihydroxystilbene, (E)-2,6-bis(3-methyl-2-buten-1-yl)-3,3′,5,5′-tetrahydroxystilbene and (E)-2,6-bis(3-methyl-2-buten-1-yl)-3,4′,5-trihydroxy-3′-methoxystilbene. A National Cancer Institute 60 human cell line anticancer screen of three of these compounds showed growth inhibitory activity. The large Australasian genus Lepidosperma is identified as a valuable resource for the isolation of substances with medicinal potential

A sedge plant as the source of Kangaroo Island propolis rich in prenylated p-coumarate ester and stilbenes

Propolis samples from Kangaroo Island, South Australia, were investigated for chemical constituents using high-field nuclear magnetic resonance spectral profiling. A type of propolis was found containing a high proportion of prenylated hydroxystilbenes. Subsequently, the botanical origin of this type of propolis was identified using a beehive propolis depletion method and analysis of flora. Ligurian honey bees, Apis mellifera ligustica Spinola, were found to produce propolis from resin exuded by the Australian native sedge plant Lepidosperma sp. Montebello (Cyperaceae). The plants, commonly known as sword sedge, were found to have resin that matched with the propolis samples identified as the most abundant propolis type on the island containing C- and O-prenylated tetrahydroxystilbenes (pTHOS) in addition to a small amount of prenylated p-coumarate. The isolation of five pTHOS not previously characterized are reported: (E)-4-(3-methyl-2-buten-1-yl)-3,40,5-trihydroxy-30-methoxystilbene, (E)-2,4-bis(3-methyl-2-buten-1-yl)-3,30,40,5-tetrahydroxystilbene, (E)-2-(3-methyl-2-buten-1-yl)-3-(3-methyl-2-butenyloxy)-30,40,5-trihydroxystilbene, (E)-2,6-bis(3-methyl-2-buten-1-yl)-3,30,5,50-tetrahydroxystilbene and (E)-2,6-bis(3-methyl-2-buten-1-yl)-3,40,5-trihydroxy-30-methoxystilbene. A National Cancer Institute 60 human cell line anticancer screen of three of these compounds showed growth inhibitory activity. The large Australasian genus Lepidosperma is identified as a valuable resource for the isolation of substances with medicinal potential

trans-4-Amino-2-methylbut-2-enoic acid (2-MeTACA) and (±)-trans-2-aminomethylcyclopropanecarboxylic acid ((±)-TAMP) can differentiate rat ρ3 from human ρ1 and ρ2 recombinant GABA(C) receptors

1. This study investigated the effects of a number of GABA analogues on rat ρ3 GABA(C) receptors expressed in Xenopus oocytes using 2-electrode voltage clamp methods. 2. The potency order of agonists was muscimol (EC(50)=1.9±0.1 μM) (+)-trans-3-aminocyclopentanecarboxylic acids ((+)-TACP; EC(50)=2.7±0.9 μM) trans-4-aminocrotonic acid (TACA; EC(50)=3.8±0.3 μM) GABA (EC(50)=4.0±0.3 μM) > thiomuscimol (EC(50)=24.8±2.6 μM) > (±)-cis-2-aminomethylcyclopropane-carboxylic acid ((±)-CAMP; EC(50)=52.6±8.7 μM) > cis-4-aminocrotonic acid (CACA; EC(50)=139.4±5.2 μM). 3. The potency order of antagonists was (±)-trans-2-aminomethylcyclopropanecarboxylic acid ((±)-TAMP; K(B)=4.8±1.8 μM) (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA; K(B)=4.8±0.8 μM) > (piperidin-4-yl)methylphosphinic acid (P4MPA; K(B)=10.2±2.3 μM) 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP; K(B)=10.2±0.3  μM) imidazole-4-acetic acid (I4AA; K(B)=12.6±2.7 μM) > 3-aminopropylphosphonic acid (3-APA; K(B)=35.8±13.5 μM). 4. trans-4-Amino-2-methylbut-2-enoic acid (2-MeTACA; 300 μM) had no effect as an agonist or an antagonist indicating that the C2 methyl substituent is sterically interacting with the ligand-binding site of rat ρ3 GABA(C) receptors. 5. 2-MeTACA affects ρ1 and ρ2 but not ρ3 GABA(C) receptors. In contrast, (±)-TAMP is a partial agonist at ρ1 and ρ2 GABA(C) receptors, while at rat ρ3 GABA(C) receptors it is an antagonist. Thus, 2-MeTACA and (±)-TAMP could be important pharmacological tools because they may functionally differentiate between ρ1, ρ2 and ρ3 GABA(C) receptors in vitro

Guanidino Acids Act as q1 GABA C Receptor Antagonists

Abstract GABA C receptors play a role in myopia, memory-related disorders and circadian rhythms signifying a need to develop potent and selective agents for this class of receptors. Guanidino analogs related to glycine, b-alanine and taurine were evaluated at human q 1 GABA C receptors expressed in Xenopus oocytes using 2-electrode voltage clamp methods. Of the 12 analogs tested, 8 analogs were active as antagonists and the remaining were inactive. (S)-2-Guanidinopropionic acid (IC 50 = 2.2 lM) and guanidinoacetic acid (IC 50 = 5.4 lM; K B = 7.75 lM [pK B = 5.11 ± 0.06]) were the most potent being competitive antagonists at this receptor. In contrast, the b-alanine and GABA guanidino analogs showed reduced activity, indicating the distance between the carboxyl carbon and terminal nitrogen of the guanidino group is critical for activity. Substituting the C2-position of guanidinoacetic acid with various alkyl groups reduced activity indicating that steric effects may impact on activity. The results of this study contribute to the structure-activity-relationship profile required in developing novel therapeutic agents

Ginkgolide B and bilobalide block the pore of the 5-HT3 receptor at a location that overlaps the picrotoxin binding site

Extracts from the Ginkgo biloba tree are widely used as herbal medicines, and include bilobalide (BB) and ginkgolides A and B (GA and GB). Here we examine their effects on human 5-HT3A and 5-HT3AB receptors, and compare these to the effects of the structurally related compounds picrotin (PTN) and picrotoxinin (PXN), the two components of picrotoxin (PTX), a known channel blocker of 5-HT3, nACh and GABAA receptors. The compounds inhibited 5-HT-induced responses of 5-HT3 receptors expressed in Xenopus oocytes, with IC50 values of 470 μM (BB), 730 μM (GB), 470 μM (PTN), 11 μM (PXN) and >1 mM (GA) in 5-HT3A receptors, and 3.1 mM (BB), 3.9 mM (GB), 2.7 mM (PTN), 62 μM (PXN) and >1 mM (GA) in 5-HT3AB receptors. Radioligand binding on receptors expressed in HEK 293 cells showed none of the compounds displaced the specific 5-HT3 receptor antagonist [3H]granisetron, confirming that they do not act at the agonist binding site. Inhibition by GB at 5-HT3A receptors is weakly use-dependent, and recovery is activity dependent, indicating channel block. To further probe their site of action at 5-HT3A receptors, BB and GB were applied alone or in combination with PXN, and the results fitted to a mathematical model; the data revealed partially overlapping sites of action. We conclude that BB and GB block the channel of the 5-HT3A receptor. Thus these compounds have comparable, although less potent, behaviour than at some other Cys-loop receptors, demonstrating their actions are conserved across the family