Croton é um gênero de Euphorbiaceae com cerca de 1300 espécies, amplamente distribuídas em regiões tropicais do Novo e Velho Mundos. Várias espécies há muito tempo desempenham papel importante nos usos tradicionais de plantas medicinais na África, Ásia e América do Sul. Tais usos incluem tratamento de câncer, constipação intestinal, diarréia e outros problemas digestivos, diabetes, feridas externas, febre, hipercolesterolemia, hipertensão, inflamação, vermes intestinais, malária, dor, úlceras e obesidade. Várias espécies de Croton têm um látex vermelho que contém, em algumas espécies, pró-antocianidinas e/ou alcalóides. Os alcalóides de Croton são a taspina ou substâncias relacionadas a benzilisoquinolinas. Os diterpenos são muito comuns em Croton, correspondendo a clerodanos, cembranóides, halimanos, cauranos, labdanos, ésteres do forbol, traquilobanos e sarcopetalanos. Algumas espécies são aromáticas, devido à presença de óleos voláteis. Representantes de novas classes de substâncias (fenilbutanóides, alcalóides glutarimidínicos e diterpenos sarcopetalanos) têm sido isoladas de espécies de Croton. Enquanto laticíferos têm sido descritos em espécies de Croton, até o momento não há estudos anatômicos sobre estruturas secretoras de óleos voláteis. Parece haver afinidades químicas no gênero relacionadas à geografia, agrupando espécies com (i) cauranos e/ou labdanos, (ii) traquilobanos e (iii) alcalóides. Os ensaios farmacológicos freqüentemente vêm corroborando os usos tradicionais de espécies de Croton. Grande parte dos ensaios farmacológicos trata do clerodano trans-desidrocrotonina, envolvendo uma grande diversidade de efeitos, incluindo hipolipidêmico, hipoglicêmico, antiestrogênico e anticâncer. Efeitos citotóxicos também vêm sendo observados em ensaios com alcalóides (taspina) e com diterpenóides secocaurenos, labdanos e cembranóides. Vários outros efeitos de substâncias de Croton têm sido relatados, incluindo anti-hipertensivos, antiinflamatórios, antimaláricos, antimicrobianos, antiespasmódicos, antiulcerogênicos, antivirais e mio-relaxantes.Croton is a genus of Euphorbiaceae comprising around 1,300 species, widespread in tropical regions of the Old and New Worlds. Several species have a long role in the traditional use of medicinal plants in Africa, Asia and South America. Popular uses include treatment of cancer, constipation, diabetes, digestive problems, dysentery, external wounds, fever, hypercholesterolemia, hypertension, inflammation, intestinal worms, malaria, pain, ulcers and weight-loss. Several species of Croton have a red sap, in some species containing proanthocyanidins and/or alkaloids. The latter may be taspine or some of several benzylisoquinoline-like compounds. Diterpenes are very common in Croton, corresponding to clerodanes, cembranoid, halimanes, kauranes, labdanes, phorbol esters, trachylobanes and sarcopetalanes. Some species are aromatic due to the possession of volatile oils. Representatives of new classes of compounds (phenylbutanoids, glutarimide alkaloids, sarcopetalane diterpen...
Propolis is a hive product containing chiefly beeswax and plant-derived substances such as resin and volatile compounds. Propolis has been used as an antiseptic and wound healer since ancient times and interest for the product has increased recently. Probably few plant species contribute as major resin sources. Green propolis derives mainly from vegetative apices ofBaccharis dracunculifolia(alecrim plants). However, wide variation detected in the chemical composition suggests contributions from alternative resin plant sources. Predominant components of the resin of green propolis are cinnamic acids, chiefly compounds bearing prenyl groups. Terpenoid compounds, such as sesqui, di and pentacyclic triterpenoids, have been detected in many, but not all, samples investigated. Propolis research has uncovered potentialities of substances previously isolated from plants and has detected constituents of plant origin that would hardly be known otherwise.
Structures are suggested for new substances never before seen in any kind of propolis. This is the first report of 3,4,2',3'-tetrahydroxychalcone and a flavone C-glycoside in a propolis sample.
Propolis, a honeybee product, has gained popularity as a food and alternative medicine. Its constituents have been shown to exert pharmacological effects, such as anti-microbial, anti-inflammatory and anticancer. Shoot apices of Baccharis dracunculifolia (alecrim plant, Asteraceae) have been pointed out as sources of resin for green propolis. The present work aimed (i) to observe the collecting behavior of bees, (ii) to test the efficacy of histological analysis in studies of propolis botanical origin and (iii) to compare the chemistries of alecrim apices, resin masses and green propolis. Bee behavior was observed, and resin and propolis were microscopically analyzed by inclusion in methacrylate. Ethanol extracts of shoot apices, resin and propolis were analyzed by gas chromatography/mass spectroscopy. Bees cut small fragments from alecrim apices, manipulate and place the resulting mass in the corbiculae. Fragments were detected in propolis and identified as alecrim vestiges by detection of alecrim structures. Prenylated and non-prenylated phenylpropanoids, terpenoids and compounds from other classes were identified. Compounds so far unreported for propolis were identified, including anthracene derivatives. Some compounds were found in propolis and resin mass, but not in shoot apices. Differences were detected between male and female apices and, among apices, resin and propolis. Alecrim apices are resin sources for green propolis. Chemical composition of alecrim apices seems to vary independently of season and phenology. Probably, green propolis composition is more complex and unpredictable than previously assumed.
Total phenolic contents, antioxidant activity and chemical composition of propolis samples from three localities of Minas Gerais state (southeast Brazil) were determined. Total phenolic contents were determined by the Folin–Ciocalteau method, antioxidant activity was evaluated by DPPH, using BHT as reference, and chemical composition was analyzed by GC/MS. Propolis from Itapecerica and Paula Cândido municipalities were found to have high phenolic contents and pronounced antioxidant activity. From these extracts, 40 substances were identified, among them were simple phenylpropanoids, prenylated phenylpropanoids, sesqui- and diterpenoids. Quantitatively, the main constituent of both samples was allyl-3-prenylcinnamic acid. A sample from Virginópolis municipality had no detectable phenolic substances and contained mainly triterpenoids, the main constituents being α- and β-amyrins. Methanolic extracts from Itapecerica and Paula Cândido exhibited pronounced scavenging activity towards DPPH, indistinguishable from BHT activity. However, extracts from Virginópolis sample exhibited no antioxidant activity. Total phenolic substances, GC/MS analyses and antioxidant activity of samples from Itapecerica collected monthly over a period of 1 year revealed considerable variation. No correlation was observed between antioxidant activity and either total phenolic contents or contents of artepillin C and other phenolic substances, as assayed by CG/MS analysis.
Seven bee pollen samples (C1-C7) with different palynological sources were harvested from Pindamonhangaba municipality (Southeast Brazil). Methanol extracts of untreated samples (control), samples frozen at -18 °C and samples frozen and then dried were analyzed by HPLC/PAD/ESI/MS/MS. Flavonoid diglycosides of quercetin, kaempferol, isorhamnetin and patuletin were detected, together with hydroxycinnamic acid amide derivatives, such as N',N'',N'''-tris-p-feruloylspermidine and N',N'',N'''-tris-p-coumaroylspermidine. Distinct phenolic profiles characterized the analyzed samples, but no differences were noted as resulting from different treatments. Total phenolic contents determined with the Folin-Ciocalteau reagent ranged from 1.7 to 2.2%. Antioxidant activities above 75%, based on the DPPH method, were observed for all extracts, not correlated with total phenolic contents. Among samples from the same origin, those frozen were more active than samples untreated (control), and the samples frozen and then dried were the most active.
Propolis is a complex honeybee product with resinous aspect, containing plant exudates and beeswax. Their color, texture, and chemical composition vary, depending on the location of the hives and local flora. The most studied Brazilian propolis is the green (alecrim-do-campo) type, which contains mainly prenylated phenylpropanoids and caffeoylquinic acids. Other types of propolis are produced in Brazil, some with red color, others brown, grey, or black. The aim of the present work was to determine the chemical profiles of alcohol and chloroform extracts of eight samples of propolis, corresponding to six Brazilian regions. Methanol and chloroform extracts were obtained and analyzed by HPLC/DAD/ESI/MS and GC/MS. Two chemical profiles were recognized among the samples analyzed: (1) black Brazilian propolis, characterized chiefly by flavanones and glycosyl flavones, stemming from Picos (Piauí state) and Pirenópolis (Goiás state); (2) green Brazilian propolis, characterized by prenylated phenylpropanoids and caffeoylquinic acids, stemming from Cabo Verde (Bahia state), Lavras and Mira Bela (Minas Gerais state), Pariquera-Açu and Bauru (São Paulo state), and Ponta Grossa (Paraná state). The present work represents the first report of prenylated flavonoids in Brazilian propolis and schaftoside (apigenin-8-C-glucosyl-6-C-arabinose) in green propolis.
Enaminoketones and esters are gaining increased interest, particularly cyclic-β-enaminoesters, which are known as important intermediates for the synthesis of heterocycles and natural products, because the enantioselective preparation of highly functionalized compounds is of central importance in synthetic chemistry. Enaminones are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. Enaminoketones and enaminonitriles have proven to be versatile building blocks for the synthesis of various heterocycles such as pyridine, pyrimidine and pyrrole derivatives. Enaminones systems have "enone" character, and may act as acceptors in both 1,2 and 1,4-additions. In this way the enaminone serves as a scaffold for annulation, and can gain access to systems such as pyrroles indolizidines, quinolizidines and perhydroindoles, all of which are common motifs in alkaloid structures. Enaminones are frequently employed as building blocks for the preparation of a variety of bicyclic compounds of biological interest and have been recently recognized as potential anticonvulsant compounds. Since a large number of developments in the use of enaminones in heterocyclic synthesis have occurred, a review of the recent developments in the synthetic approaches, covering the literature since 1995 until 2004, to these interesting molecules and their useful chemical transformations and biological activity can be considered of considerable value.J. Heterocyclic Chem., 41, 461 (2004).Enaminoketones. Introduction.The term enaminone was introduced by Greenhill to define the enamine of a 1,3-diketone, β-ketoester or similar 1,3-difunctional reagents, and is used to indicate any compound containing the conjugated system N-C=C-C=O . Enaminones are versatile synthetic intermediates that combine the ambident nucleophilicity of enamines with the ambident eletrophilicity of enones. The chemistry of the enaminocarbonyl group 1 is potentially an area of considerable scope when one considers that there are present in this moiety, three nucleophilic sites (a, c and e) and two electrophilic sites (b and d)  (Figure 1).Theorically, primary and secondary acyclic enaminones can exist in three tautomeric forms: ketamino form, iminoenol form and oxoimino form . There is also evidence that cyclic enaminones exist primarily in the enaminoketo form. A study of cyclic enaminoketones shows that these compounds have a significant steric fator in the six-membered ring. The six-membered ring enaminoketones are only slightly stronger bases than the saturated amines, whereas five-and-seven membered rings are much stronger bases than saturated amines. This has been attributed to a large steric strain present in six-membered enaminoketones .β-Aminoenones or enaminoketones can exist in four conformations owing to restricted rotations around the C=C double and C-C=O single bonds . Enaminones with primary or secondary amino groups can exist in both Z-and E-forms. If there is a...
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