The dual-targeting mechanism of an anti-inflammatory diarylheptanoid from Curcuma zedoaria (Christm.) Roscoe with the capacity for ß2-adrenoreceptor agonism and NLRP3 inhibition.

Chronic obstructive pulmonary disease (COPD) is a common respiratory disease characterized by symptoms of shortness of breath and chronic inflammation. Curcuma zedoaria (Christm.) Roscoe is a well-documented traditional medical herb that is frequently used in the treatment of COPD. Previously, we identified a diarylheptanoid compound (1-(4-hydroxy-5-methoxyphenyl)-7-(4,5-dihydroxyphenyl)-3,5-dihydroxyheptane; abbreviated as HMDD) from this herb that exhibited potent agonistic activity on ß2-adrenergic receptors (ß2 adrenoreceptor) that are present on airway smooth muscle cells. In this work, we used chemically synthesized HMDD compound, and confirmed its bioactivity on ß2 adrenoreceptors. Then by a proteomics study and anti-inflammatory evaluation detections, we found that HMDD downregulated the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) signaling pathway and suppressed the NLRP3 receptor expression in RAW264.7 macrophages and in a COPD model in A549 lung carcinoma cells. HMDD also decreased nitric oxide production levels, and impacted other interleukins and the phosphorylation of NF-κB and ERK pathways. We performed molecular docking of HMDD on ß2 adrenoreceptor and NLRP3 protein models. This work reports the anti-inflammatory effects of HMDD and suggests a dual-targeting mechanism of ß2-adrenoreceptor agonism and NLRP3 inhibition. Such a mechanism scientifically supports the clinical uses of Curcuma zedoaria (Christm.) Roscoe in treating COPD, as it can simultaneously relieve persistent breathlessness and inflammation. HMDD can be considered as a potential non-steroidal anti-inflammatory drug in novel therapy design for the treatment of COPD and other inflammatory diseases.

Development and Characterization of Fluorescent Probes for the G Protein-Coupled Receptor 35.

The orphan G protein-coupled receptor 35 (GPR35) is a potential target for the treatment of pain, inflammation, and metabolic diseases. Although many GPR35 agonists have been discovered, research on functional GPR35 ligands, such as fluorescent probes, is still limited. Herein, we developed a series of GPR35 fluorescent probes by conjugating a BODIPY fluorophore to DQDA, a known GPR35 agonist. All probes exhibited excellent GPR35 agonistic activity and desired spectroscopic properties, as determined by the DMR assay, bioluminescence resonance energy transfer (BRET)-based saturation, and kinetic binding experiments. Notably, compound 15 showed the highest binding potency and the weakest nonspecific BRET binding signal (K d = 3.9 nM). A BRET-based competition binding assay with 15 was also established and used to determine the binding constants and kinetics of unlabeled GPR35 ligands.

Design and synthesis of 2-(2,2-diarylethyl)-cyclamine derivatives as M3 receptor antagonists and functional evaluation on COPD.

Muscarine acetylcholine receptors (mAChRs) regulate a variety of central and peripheral physiological functions and emerge as important therapeutic targets for a number of diseases including chronic obstructive pulmonary disease (COPD). Inspired by two active natural products, we designed and synthesized a series of 2-(2,2-diarylethyl)-cyclamine derivatives for screening M3 mAChR antagonists. On this skeleton, the structural units including N heterocycle, aryl groups and its substituents on aryl were examined and resulted in a clear structure-activity relationships on the M3 mAChR. In general, these 2-(2,2-diarylethyl)-cyclamine derivatives exhibited good to excellent M3 antagonistic potency and receptor selectivity. The most active 5b-C1 had an IC50 value of 3 nM and the most of compound 6 displayed inactivity against histamine H1 receptor closely related to M3. In in vitro and in vivo evaluations of tracheo-relaxation function, some compounds even showed comparable activity to tiotropium bromide, a known blockbuster drug for COPD. Such excellent properties made these novel compounds potential candidates for COPD drug development.

Discovery and characterization of novel ATP citrate lyase inhibitors from natural products by a luminescence-based assay.

ATP citrate lyase (ACLY) is a key enzyme in glucolipid metabolism with therapeutic prospect for treating hyperlipidemia and various cancers. Much effort has been put into discovering ACLY inhibitors. However, current screening approaches have limitations in sensitivity, portability and high-throughput. To develop a general screening assay, we investigated series of conditions affecting the enzymatic reaction based on the ADP-Glo luminescence assay. Bovine serum albumin (0.001%) added triggered strong and stable fluorescence signal. The optimized assay was validated and applied to screen our natural product library. Two novel inhibitors were identified with IC50 values of 3.86 ± 0.62 µM (2) and 15.48 ± 2.51 µM (4). Their aggregations and target specificities were also examined. 2 was characterized as a noncompetitive inhibitor of ACLY, while 4 was a competitive inhibitor of CoA, which was also elucidated by docking studies. In anticancer activity evaluation, 2 with higher inhibition potency did not exhibit anticancer effect, probably owing to its insufficient cell-permeability. 4 showed moderate inhibition in the proliferation of A549 and PC3 cells. This study not only developed a general approach for ACLY inhibitor discovery, but also identified a new scaffold ACLY inhibitor, which could be served as a hit compound in drug design.

Menisperdaurines A-W, structurally diverse isoquinoline alkaloids from Menispermum dauricum and their dopamine D1 receptor activities.

A total of 33 structurally diverse isoquinoline alkaloids were isolated from the rhizomes of Menispermum dauricum, including seventeen benzylisoquinoline analogues (menisperdaurines A-Q, 1-17), five protoberberine analogues (menisperdaurines R-V, 18-22), a quaternary phenanthrene alkaloid (menisperdaurine W, 23) and ten known compounds (24-33). Compound structures, including absolute configurations, were determined by extensive spectroscopic methods, quantum chemical calculations of chemical shifts, and calculated and experimental electronic circular dichroism (ECD) data. Compounds 1-5 were glycosidic benzylisoquinolines with glucose moieties attached at the C-12 position. Compound 8 was the first example that was isolated from the rhizomes of Menispermum dauricum, benzylisoquinoline and an aromatic unit connected by a sugar bridge. Compounds were evaluated for their inhibitory effects on the dopamine D1 receptor. Compounds 1, 8, 21, 24 and 29 showed potent D1 antagonistic activities, with IC50 values ranging from 1.0 to 4.5 µM. Compound 1 exhibited the highest antagonistic activity with an IC50 value of 1.0 ± 0.2 µM.

Ursodesoxycholic acid is an FFA4 agonist and reduces hepatic steatosis via FFA4 signaling.

Ursodeoxycholic acid (UDCA) is a safe bile acid effective in reducing hepatic steatosis in non-alcoholic fatty liver disease (NAFLD). However, the mechanism of action linked to this effect is poorly defined. In the present study, we identified that UDCA acted as a free fatty acid receptor 4 (FFA4) agonist with EC50 of 10.4 ± 0.7 µM, and its activity was determined by dynamic mass redistribution, fluorometric imaging plate reader, inositol monophosphate and bioluminescence resonance energy transfer assays. Moreover, UDCA showed FFA4 selectivity over eleven other G protein-coupled receptors. Real-Time PCR and immunocytochemistry analyses showed that FFA4 was abundantly expressed in human hepatocytes HuH-7 cells. In an in vitro model of NAFLD induced by oleic acid (OA), UDCA downregulated lipid accumulation in HuH-7 cells and suppressed sterol-regulatory element binding protein-1c (SREBP-1c) mRNA expression. This suppression of SREBP-1c was restored when FFA4 expression was knocked down in siRNA assay. In a mouse model of hepatic steatosis, db/db mice were exposed to a high-fat diet (HFD), and treatment of UDCA or docosahexaenoic acid (DHA, an endogenous FFA4 agonist) effectively prevented body weight gain and hepatic fat deposition and reduced triglyceride (TG) levels in serum and liver. This study not only identified a new skeleton of FFA4 agonists, but also demonstrated that FFA4 signal was accounting for the protective effects of UDCA in the NAFLD treatment.

Structure-Activity Relationship Studies of Coumarin-like Diacid Derivatives as Human G Protein-Coupled Receptor-35 (hGPR35) Agonists and a Consequent New Design Principle.

A series of coumarin-like diacid derivatives were designed and synthesized as novel agonists of human G-protein-coupled receptor 35 (hGPR35). Active compounds were characterized to possess one acidic group on both sides of a fused tricyclic aromatic scaffold. Most of them functioned as full agonists selective to hGPR35 and exhibited excellent potency at low nanomolar concentrations. Substitution on the middle ring of the scaffold could effectively regulate compound potency. Structure-activity relationship studies and docking simulation indicated that compounds that carried two acidic groups with a proper special distance and attached to a rigid aromatic scaffold would most likely show a potent agonistic activity on hGPR35. Following this principle, we screened a list of known compounds and some were found to be potent GPR35 agonists, and compound 24 even had an EC50 of 8 nM. Particularly, a dietary supplement pyrroloquinoline quinone (PQQ) was identified as a potent agonist (EC50 = 71.4 nM). To some extent, this principle provides a general strategy to design and recognize GPR35 agonists.

Scocycamides, a Pair of Macrocyclic Dicaffeoylspermidines with Butyrylcholinesterase Inhibition and Antioxidation Activity from the Roots of Scopolia tangutica.

A pair of new macrocyclic spermidine alkaloids, (+)-(S)-scocycamide and (-)-(R)-scocycamide, were isolated from the roots of Scopolia tangutica. Their structures were established by extensive spectroscopic data, electronic circular dichroism analyses, and chemical synthesis. They featured a unique 6/18 fused bicyclic framework with spermidine and catechol units, representing a new subtype of natural spermidine alkaloids. A plausible biosynthetic pathway was also proposed. They inhibited butyrylcholinesterase and exhibited antioxidant capacity, suggesting beneficial constituents against Alzheimer's disease and oxidation.

Synthesis and evaluation of 3-(4-(phenoxymethyl)phenyl)propanoic acid and N-phenylbenzenesulfonamide derivatives as FFA4 agonists.

Free fatty acid receptor 4 (FFA4) has been recognized as an attractive target in metabolic diseases. To find potent and selective FFA4 agonist, 28 compounds of 3-(4-(phenoxymethyl)phenyl)propanoic acid and N-phenylbenzenesulfonamide derivatives were designed and synthesized, featuring OC and SO2-N linkage. For the OC linkage compounds, 1g showed the most potent FFA4 agonistic activity with a pEC50 of 5.81 ± 0.04 and exhibited at least 64-fold selectivity against FFA1. For SO2-N linkage agonists, 2m had a pEC50 of 5.66 ± 0.04 and displayed>46-fold selectivity against FFA1. Among these two series of compounds, 1g was the most potent agonist at FFA4 and the best selectivity against FFA1, demonstrated by docking simulation. Moreover, 1g showed receptor selectivity on other seven GPCRs. In anti-diabetic evaluation, 1g dose-dependently reduced blood glucose, which was better than a clinical phase III drug TAK875. This study provides guidance for FFA4 ligand design and drug optimization.

Isolation and bioactive evaluation of flavonoid glycosides from Lobelia chinensis Lour using two-dimensional liquid chromatography combined with label-free cell phenotypic assays.

Flavonoid glycosides are widespread in herbs and often used as medicines and nutraceuticals because of good bioactivities and low toxicities. However, due to their structural complexity and diversity, isolation of flavonoid glycosides and evaluation of their bioactivities are still highly challenging. To solve this problem, a new method for separation and preparation of novel flavonoid glycosides from Lobelia chinensis Lour (L. chinensis) was developed. To avoid the interference of non-flavonoids, a solid phase extraction method was used to selectively enrich the flavonoids from the total extract. Based on hydrophilic and hydrophobic properties of the flavonoid chemical structure consisting of sugar residue and diphenylpropane (C6C3C6) skeleton, a structure-guided method development strategy was employed to design a 2D-HILIC × RPLC system in the first time. After optimization of chromatographic conditions, high selectivity and symmetric peaks of flavonoids were obtained on a zwitterionic Click XIon column and a polar-modified Atlantis T3 column. Based on these two columns, a 2 D-HILIC × RPLC system was constructed and successfully enlarged from the analytical level to the preparative level. In the first dimension, 20 fractions were obtained with good peak shapes at high sample loading. In the second-dimensional preparation, nine compounds were isolated and identified. Seven of them were novel flavonoid glycosides, lobelitin A-G, and two other known compounds were linatin and diosmin, respectively. Their target activities were evaluated via label-free cell phenotypic assays. Four novel flavonoid glycosides lobelitin A-D were found to have agonistic activities at G protein-coupled receptor 35 (GPR35). These results demonstrated that this method was effective to orthogonally separate flavonoids at the preparative level, especially for novel active flavonoid glycosides. The discovery of flavonoid glycosides with novel agonistic activity on GPR35 also sheds light on the mechanisms of action of L. chinensis relevant to its clinical application.

Discovery of ß2- adrenoceptor agonists in Curcuma zedoaria Rosc using label-free cell phenotypic assay combined with two-dimensional liquid chromatography.

Traditional Chinese Medicines (TCMs) have been widely used in clinical practice, and provided a rich source for discovering new drug leads. However, efficient identification of active molecules responsible for the therapeutic effects of complex TCMs is still highly challenging. Here, we combined label-free cell phenotypic assay with two dimensional liquid chromatography (2DLC) to identify potential ß2-adrenoceptor (ß2-AR) agonists related to anti-asthmatic effect of Curcuma zedoaria Rosc (C.zedoaria), a commonly used TCM. The ethyl acetate extract of C.zedoaria was first fractionated into 26 fractions. Label-free cell phenotypic profiling was then used to locate the active sites. Orthogonal second-dimensional (D2) separation was performed on two fractions displaying agonistic effect at the ß2-AR, combined with screening of the D2 fractions to track the activity. Finally, this approach led to the isolation of three known diarylheptanoids, among which diarylheptanoid b exhibited the most potent agonistic activity with an EC50 value of 5.93 µM. This result was further demonstrated through the chemical synthesis of diarylheptanoid b. It is the first time to discover that diarylheptanoids could activate the ß2-AR, which may be responsible for the anti-asthmatic effect of C.zedoaria observed traditionally and in clinical application. This study also demonstrates the potential of this integrated strategy for identifying active ingredients and determining the basis of therapeutic materials in complex TCMs.

SAR Studies of N-[2-(1H-Tetrazol-5-yl)phenyl]benzamide Derivatives as Potent G Protein-Coupled Receptor-35 Agonists.

G protein-coupled receptor-35 (GPR35) has emerged as a potential target in the treatment of pain and inflammatory and metabolic diseases. We have discovered a series of potent GPR35 agonists based on a coumarin scaffold and found that the introduction of a 1H-tetrazol-5-yl group significantly increased their potency. We designed and synthesized a new series of N-[2-(1H-tetrazol-5-yl)phenyl]benzamide derivatives through a two-step synthetic approach, and characterized their agonistic activities against GPR35 using a dynamic mass redistribution (DMR) assay. N-(5-bromo-2-(1H-tetrazol-5-yl)phenyl)-4-methoxybenzamide (56) and N-(5-bromo-2-(1H-tetrazol-5-yl)phenyl)-2-fluoro-4-methoxybenzamide (63) displayed the highest agonistic potency agonist GPR35 with an EC50 of 0.059 µM and 0.041 µM, respectively. The physicochemical properties of selected compounds were calculated to evaluate their druglikeness, suggesting that compounds 56 and 63 have good druglike properties. Together, N-[2-(1H-tetrazol-5-yl)phenyl]benzamide derivatives are potentially great candidates for developing potent GPR35 agonists.

Chemical Identity and Mechanism of Action and Formation of a Cell Growth Inhibitory Compound from Polycarbonate Flasks.

This paper reports the chemical identity and mechanism of action and formation of a cell growth inhibitory compound leached from some single-use Erlenmeyer polycarbonate shaker flasks under routine cell culture conditions. Single-use cell culture vessels have been increasingly used for the production of biopharmaceuticals; however, they often suffer from issues associated with leachables that may interfere with cell growth and protein stability. Here, high-performance liquid-chromatography preparations and cell proliferation assays led to identification of a compound from the water extracts of some polycarbonate flasks, which exhibited subline- and seeding density-dependent growth inhibition of CHO cells in suspension culture. Mass spectroscopy, nuclear magnetic resonance spectroscopy, and chemical synthesis confirmed that this compound is 3,5-dinitro-bisphenol A. Cell cycle analysis suggests that 3,5-dinitro-bisphenol A arrests CHO-S cells at the G1/Go phase. Dynamic mass redistribution assays showed that 3,5-dinitro-bisphenol A is a weak GPR35 agonist. Analysis of the flask manufacturing process suggests that 3,5-dinitro-bisphenol A is formed via the combination of molding process with γ-sterilization. This is the first report of a cell culture/assay interfering leachable compound that is formed through γ-irradiation-mediated nitric oxide free radical reaction.

Competitive Binding of Organic Dyes between Cucurbiturils and Octa Acid.

Employing six cationic water-soluble organic dye molecules as probes, we have attempted to qualitatively understand the factors that govern the attraction between such molecules and the anionic water-soluble host, octa acid (OA). Examination of the competitive host-guest complexation between cucurbit[8]uril (CB[8]) and OA using absorption and emission spectroscopy revealed that the dye molecules included within CB[8] could be "pulled out" by OA. However, an order of magnitude higher concentration of OA was required to shift the equilibrium toward OA, suggesting that attraction between the anionic host OA and the cationic dye molecules such as cresyl violet perchlorate and methylene blue is weaker than the hydrophobic and cation-dipolar interaction between these dye molecules and CB[8]. The importance of Coulombic attraction between OA and dye molecules is also revealed by monomer-to-dimer conversion upon addition of OA to an aqueous solution of monomeric dye molecules. Under conditions where the dye-to-OA ratio is high, freely dissolved monomeric dye molecules are attracted to the exterior of OA and aggregate as dimers on the exterior wall of OA. On the other hand, at high ratios of OA to dye molecules, the dye molecules adsorb as monomers on the exterior of OA. Thus, the monomer-to-dimer ratio in aqueous solution can be controlled by adjusting the ratio of dye to OA molecules. The results presented are of value in qualitatively understanding the relative binding properties of ionic guests with ionic hosts. Studies are qualitative in nature, and further detailed quantitative studies planned for the future are likely to provide deeper understanding of the interaction between water-soluble dye molecules, OA, and CB.

Cocatalyst-Free Hybrid Ionic Liquid (IL)-Based Porous Materials for Efficient Synthesis of Cyclic Carbonates through a Cooperative Activation Pathway.

Cocatalyst-free ionic liquid (IL)-based porous polymers (Px -Vy -OHz R) functionalized with an intermolecular hydroxyl group were prepared by means of radical copolymerization of 1-butyl-3-vinylimidazolium bromide, (4-vinylphenyl)methanol (VBzOH), and divinylbenzene (DVB) under solvothermal conditions. As the ratio of 4-vinylphenylmethanol in the initial mixture increased, the content of the hydroxyl groups in the polymer increased from 3.35 to 5.35 mmol g-1 and the Brunauer-Emmett-Teller (BET) surface area of the polymer decreased sharply from 365 to 2.5 m2 g-1 . In the carbonation of CO2 and epoxides, the turnover frequency (TOF) of Px -Vy -OHz R increased gradually from 25 to 67 h-1 as the OH ratio increased irrespective of the sharp decrease in BET surface area, which suggests the existence of a cooperative activation effect between OH and ILs. To obtain a high OH content while still maintaining a high BET surface area, hybrid porous materials (SBA-[Vx OHy ]R-n) were prepared by means of copolymerization of 1-ethyl-3-vinylimidazolium bromide and 4-vinylphenylmethanol in the mesopores of SBA-15. SBA-[Vx OHy ]R-n was more active than its polymer counterpart (TOF: 188 versus 71 h-1 ) in the cycloaddition of CO2 with propyl oxide owing to the combined effect of the high BET surface area and the high OH content. The hybridization of mesoporous materials with polymers represents an efficient strategy for the preparation of high-performance solid catalysts for chemical transformations.

Discovery of 2H-Chromen-2-one Derivatives as G Protein-Coupled Receptor-35 Agonists.

A family of 2H-chromen-2-one derivatives were identified as G protein-coupled receptor-35 (GPR35) agonists using dynamic mass redistribution assays in HT-29 cells. The compounds with 1H-tetrazol-5-yl in 3-substituted position displayed higher potency than the corresponding carboxyl analogs, and the hydroxyl group in the 7-position also played an important role in GPR35 agonistic activity. 6-Bromo-7-hydroxy-8-nitro-3-(1H-tetrazol-5-yl)-2H-chromen-2-one (50) was found to be the most potent GPR35 agonist with an EC50 of 5.8 nM. Calculating the physicochemical properties of compounds with moderate to high potency suggested that compounds 30, 50, and 51 showed good druggability. This study provides a novel series of GPR35 agonists, and compound 50 may be a powerful tool to study GPR35.

Spectroscopic and crystallographic investigations of novel BODIPY-derived metal-organic frameworks.

To explore new 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)-derived metal-organic frameworks (MOFs), we employed 2,6-dicarboxyl-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (H2L) as a ligand to successfully synthesize five coordination polymers, namely, {[Zn2(L)2(bpp)]·2H2O·2EtOH}n (1), {[Cd2(L)2(bpp)]·2H2O·EtOH}n (2), {[Cd2(L)(bpe)3(NO3)2]·2H2O·DMF·EtOH}n (3), {[Cd(L)(bpe)0.5(DMF)(H2O)]}n (4), and {[Cd(L)(bpe)0.5]·1.5H2O·DMF}n (5) (bpp = 1,3-bi(4-pyridyl)propane, bpe = 1,2-bi(4-pyridyl)ethane). Except for two 2D-layer coordination polymers 3 and 4, the rest samples exhibit 3D metal-organic frameworks with certain pore sizes, especially MOFs 1 and 5. Spectroscopic and crystallographic investigations demonstrate that the absorption and emission energies of the BODIPY chromophores are sensitive to the coordination modes. Moreover, in case 2, the transition metal centers coordinated with the dicarboxylate ligands L(2-) are capable of forming the two BODIPY units in coplanar arrangements (θ = 37.9°), simultaneously suppressing the uncommon J-dimer absorption band centered at 705 nm with a long tail into the near-infrared region at room temperature. On the other hand, in comparison with the ligand H2L, the emission of monomer-like BODIPY in case 3 is enhanced in the solid state by a considerably long distance between the parallel BODIPY planes (about 14.0 Å).

Ultrasmall single micelle@resin core-shell nanocarriers as efficient cargo loading vehicles for in vivo biomedical applications.

Ultrasmall core-shell nanocarriers (NCs) are believed to be ideal candidates for biological applications, as proved by silica-based core-shell NCs fabricated using a single micelle as a template. Compared with inert silica, polymers with various properties play an essential and ubiquitous role in our daily life. However, the fabrication of polymer-based NCs with ultrasmall particle size (less than 20 nm) is still very limited, which is probably hindered due to the difficulty in handling the polymeric process and the soft nature of most polymers. In this study, we demonstrated the fabrication of ultrasmall single micelle@resin core-shell NCs through a single micelle template method using resorcinol-formaldehyde resins (RFRs) as model polymers. Moreover, the fluorescence properties of the ultrasmall single micelle@resin core-shell NCs could be adjusted from visible light to near-infrared through the incorporation of different dye molecules. The fluorescent single micelle@RFR core-shell NCs show extra-low cytotoxicity and great potential in both in vitro and in vivo bioimaging and photothermal therapy applications.

Polystyrene sulphonic acid resins with enhanced acid strength via macromolecular self-assembly within confined nanospace.

Tightening environmental legislation is driving the chemical industries to develop efficient solid acid catalysts to replace conventional mineral acids. Polystyrene sulphonic acid resins, as some of the most important solid acid catalysts, have been widely studied. However, the influence of the morphology on their acid strength--closely related to the catalytic activity--has seldom been reported. Herein, we demonstrate that the acid strength of polystyrene sulphonic acid resins can be adjusted through their reversible morphology transformation from aggregated to swelling state, mainly driven by the formation and breakage of hydrogen bond interactions among adjacent sulphonic acid groups within the confined nanospace of hollow silica nanospheres. The hybrid solid acid catalyst demonstrates high activity and selectivity in a series of important acid-catalysed reactions. This may offer an efficient strategy to fabricate hybrid solid acid catalysts for green chemical processes.

Nature of supramolecular complexes controlled by the structure of the guest molecules: formation of octa acid based capsuleplex and cavitandplex.

Factors that govern inclusion of organic molecules within octa acid (OA), a synthetic deep cavity cavitand, have been delineated by examining the complexation behavior of a number of organic molecules with varying dimensions and functionalities with OA. The formation of two types of complexes has been noted: the one which we call cavitandplex is a partially open complex in which a part of the guest molecule remains exposed to water, and the other termed capsuleplex is formed through assembly of two OA molecules. In capsuleplex, the guest is protected from water. Generally, guest molecules that possess ionic head groups form cavitandplex, and all others form capsuleplex. Capsuleplex may contain one or two guest molecules within the capsule. Small organic molecules (<10 A in length) may form both 2:1 and 2:2 capsuleplex, while longer ones (>12 A) preferentially form 2:1 capsuleplex. Extensive 1H NMR experiments have been carried out to characterize host-guest complexes. In the absence of the guest, OA tends to aggregate in water. The extent of aggregation depends on the concentration of OA and the presence of salts in solution. We expect the information obtained from this study to be of great value in predicting the nature of complexes with a given guest and facilitating appropriate guest chosen by researchers.