Structure of piperlonguminine, an alkaloid of piper longum linn.

Phytochemistry of the genus Piper

Abstract: The secondary metabolites isolated from Piper species for the period 1907 to June 1996 have been reviewed. Nearly six hundred chemical constituents belonging to different classes of bioactive compounds are listed together with their source(s) and references. © 1997 Elsevier Science Ltd

Polyphenols and alkaloids from piper species

Abstract: Thirty eight compounds of different types have been isolated from twelve Piper species. The ether extract of the leaves of P. aduncum yielded eleven compounds, out of which 2,6-dimethoxy-4-(2-propenyl)phenol was isolated for the first time from the genus Piper and 2-acetoxy-1,3-dimethoxy-5-(2-propenyl)benzene is a new compound. The petrol extract of the stems and leaves of P. attenuatum furnished a novel long chain alcohol, 14-benzo 1 , 3 dioxol-5-yl-tetradecan-2-ol. From P. betle, β-sitosteryl palmitate was isolated for the first time from the genus Piper. A novel amide, 3-(3,4-dimethoxyphenyl)propanoyl pyrrole has been obtained from P. brachystachyum. Nerolidol was isolated for the first time from P. falconeri. From the methanol extract of the stems and leaves of P. khasiana, piperlonguminine, piperine, apigenin dimethyl ether and β-sitosterol were obtained. Retrofractamide A was obtained for the first time from P. longum; the structure of (+)-asarinin, isolated from P. longum, was confirmed by X-ray crystallographic studies. Retrofractamide A, apigenin dimethyl ether, tetratriacontanol and tectochrysin were isolated from P. manii. P. pedicellosum furnished β-sitosterol, pellitorine, piperlonguminine, cepharadione A and furacridone, the last compound being isolated for the first time from the genus Piper.

Insecticidal activity of Piper tuberculatum Jacq. extracts: synergistic interaction of piperamides

Abstract: 1 The insecticidal activity of the neotropical pepper Piper tuberculatum Jacq. and its isolated piperamides was studied. Bioassays with the mosquito Aedes atropalpus L. assessed the relative toxicity of the whole extract of Piper tuberculatum and four of the piperamides, which were isolated and identified, then prepared synthetically. 2 The results confirm that P. tuberculatum leaf extracts are as effective as black pepper seed extract and provide an alternative pepper insecticide from a more convenient source, the leaves. 3 Experiments with piperamides showed that the tertiary and quaternary mixtures have greater-than-additive toxicity compared to single compounds or binary mixtures. One of the four amide compounds, 4,5-dihydropiperlonguminine, was the most acutely toxic in mosquito larvae bioassays. 4 A study of piperamide levels from different P. tuberculatum populations in Costa Rica determined that they were relatively homogeneous. Piper tuberculatum from only one of the five sites had higher levels of one piperamide, 4,5-dihydropiperine, in both leaf and stem parts. One explanation for differences in the amide concentrations between populations is that one site is ecologically unique compared to the other four.

Catalytic Hunsdiecker Reaction and One-Pot Catalytic Hunsdiecker–Heck Strategy: Synthesis of α,β-Unsaturated Aromatic Halides, α-(Dihalomethyl)benzenemethanols, 5-Aryl-2,4-pentadienoic acids, Dienoates and Dienamides

Abstract: The reaction of α,β-unsaturated aromatic (or heteroaromatic) carboxylic acids with N-halosuccinimides (1 equiv.) and catalytic tetrabutylammonium trifluoroacetate (0.2 equiv.) in dichloroethane results in facile halodecarboxylation affording the corresponding (E)-halides in good to excellent yields. A similar reaction, but with 2 equiv. of N-halosuccinimides in acetonitrile-water (1:1 v/v) results in the exclusive formation of the corresponding α-(dihalomethyl)benzenemethanols. Furthermore, a one-pot strategy has been developed combining catalytic Hunsdiecker reaction (using tetrabutylammonium trifluoroacetate in dichloroethane) and Heck coupling (using palladium acetate/triethylamine/triphenylantimony/dichloroethane) for the synthesis of 5-aryl-2,4-pentadienoic acids, esters and amides in moderate to good yields. The natural product piperine and pipergualamine has been synthesized via the above route. Mechanistic and theoretical studies (via AM1 calculations) provide a useful insight into the mechanism of the present halodecarboxylation reaction, suggesting an ionic pathway involving the attack of the halogenium ion across the carbon–carbon double bond, triggering the elimination of carbon dioxide.

Binding of the pepper alkaloid piperine to bovine beta-lactoglobulin: circular dichroism spectroscopy and molecular modeling study.

Abstract: The pepper alkaloid piperine is a nontoxic, natural dietary compound with a broad range of physiological activity. The present work is the first demonstration of its interaction with a mammalian protein. Circular dichroism (CD) spectroscopy was used to reveal and analyze the binding of piperine to a lipocalin protein. Induced CD spectra measured in pH 7.7 phosphate buffer at 37 degrees C demonstrated reversible, non-covalent association of piperine with bovine beta-lactoglobulin (BLG), the major whey protein in milk. The binding parameters (K(a) approximately 8 x 10(4) M(-1), n = 0.8) determined from the CD titration data showed no significant differences between the piperine binding properties of the two main genetic variants of BLG (A and B). The vanishing extrinsic CD signal obtained upon acidification of the piperine-BLG sample solution (Tanford transition) suggested that the ligand binds in the central hydrophobic cavity of the beta-barrel. The cavity binding concept was further supported by a CD displacement experiment using palmitic acid, the well-known hydrophobic ligand of BLG. Molecular docking calculations showed that piperine can be efficiently accommodated within the calyx of BLG. Additional molecular modeling calculations indicated that the beta-barrel of human tear lipocalin, human serum retinol binding protein, and human neutrophil gelatinase associated lipocalin might also accommodate a piperine molecule.

Mass spectra and organic analysis—II

Abstract: The mass spectra of a number of phenyl ethers in which the oxygen atom forms part of a heterocyclic ring have been measured. There is a strong tendency for stable aromatic heterocyclic ions to be formed without ring fission, although other fragmentation processes occur in the reduced compounds, these frequently involving ring fission and subsequent recyclization. Evidence for the existence of the dehydrotropylium and dehydrobenzene ions is presented. It is suggested that ions that are stabilized by the operation of the so-called “ortho-effect” are generally cyclic, and derivatives of one of these ions, the dioxymethylene ions of mass 122, have been examined.

Terpenoids—LXII : The constitution of agarospirol, a sesquiterpenoid with a new skeleton☆

Abstract: Degradative studies and physical measurements supported by an unambiguous synthesis of the derived ketone (XVa) have led to the assignment of a novel spiro-skeleton to agarospirol (Ia), a sesquiterpene alcohol isolated from the essential oil of infected agarwood (Aquilaria agallocha Roxb.). The corresponding carbon skeleton (VI) has been named agarospirane. Agarospirol is the second spiro-terpenoid to be isolated from Nature. The most probable stereochemistry of agarospirol appears to be as in XXXIX.