Zobrazeno 1 - 10
of 121
pro vyhledávání: '"Alfredo, Usubillaga"'
Autor:
Andrés Eduardo Márquez, Alida Pérez, Luis Rojas, Rosa Aparicio, Freddy Ramos, Ysbelia Obregón, Alfredo Usubillaga
Publikováno v:
Biology, Medicine & Natural Product Chemistry, Vol 12, Iss 1, Pp 151-157 (2023)
The fraction of the neutral extraction of the leaves of Espeletia semiglobulata Cuatrec. was subjected to chromatographic separation, it yielded four ent-kaurene type diterpenoids: three known [ent-kaur-16-en-19-al (I), ent-kaur-18-nor-16-en-4-ol (II
Externí odkaz:
https://doaj.org/article/2362ec7c08d248169d05ac934373ac66
Autor:
Rosa Aparicio-Zambrano, Luis Rojas-Fermín, Judith Velasco, Alfredo Usubillaga, Marcos Sosa, Julio Rojas
Publikováno v:
Revista Peruana de Biología, Vol 26, Iss 1, Pp 095-100 (2019)
El aceite esencial de las hojas frescas de Libanothamnus neriifolius (B. ex H) Ernst., fue obtenido por el método de hidrodestilación utilizando la trampa de Clevenger, obteniendo 1.8 mL (rendimiento 0.087%). El aceite esencial se caracterizó por
Externí odkaz:
https://doaj.org/article/b57e9ac7d2034bb8be414d5d5b835d26
Publikováno v:
Avances en Química, Vol 9, Iss 1, Pp 7-13 (2014)
Allylic hydroxylation of ent-kaur-16-en-19-oic acid (1a) with SeO2 was tried using either dioxane or dichloro-methane as solvents as well as different reagent and reaction time conditions at room temperature. Oxidation of 1a in dioxane with H2O2 decr
Externí odkaz:
https://doaj.org/article/db3becbfee194869a6cfaf3c1a2a314e
Autor:
Alfredo Usubillaga
Publikováno v:
Natural Resources and Sustainable Development, Vol 11, Iss 1, Pp 1-10 (2021)
4-keto steroidal alkaloids are C-27 substances that have a C-4 carbonyl on their steroidal frame, which makes them different from other steroidal alkaloids. Thus far they have only been found in two South American Solanum trees, which contain them in
Autor:
Alexis Peña, Libia Alarcón, José Gregorio Baptista, Rosa Aparicio, Thayded Villasmil, Alfredo Usubillaga
Publikováno v:
Avances en Química, Vol 7, Iss 3, Pp 187-192 (2012)
Espeletia nana Cuatrec is a resinous plant, member of the Espeletiinae Subtribe. It is a small size frailejón, 25cm high, found at Páramo Ortiz, Trujillo State, Venezuela. Leaves and roots were separately extracted with a 3:1 mixture of hexane-diet
Externí odkaz:
https://doaj.org/article/d3dffd26c9784b869264343df864e71b
Publikováno v:
Revista de la Facultad de Farmacia.
The genus Carramboa (family Asteraceae) comprises seven species, among which is the Carramboa tachirensis (Aristeg.) (Cuatrec.), species endemic to the Andean paramos. In this paper we prepared an extract of n-hexane: diethyl ether (3:1) from dried l
Autor:
Julia Bruno-Colmenarez, Graciela Díaz De Delgado, Alexis Peña, Libia Alarcon, Alfredo Usubillaga, Paulino Delgado-Méndez
Publikováno v:
Avances en Química, Vol 6, Iss 2, Pp 16-20 (2011)
Ent-15α-hydroxy-kaur-16-en-19-oic acid, C20H30O3, isolated from the leaves of Coespeletia moritziana, is reported in this work. This compound crystallizes in the monoclinic system, space group C2 and unit cell parameters a=19.7509 (5), b=10.5126 (3)
Externí odkaz:
https://doaj.org/article/d869d8e4a75346dc854bf150c2b231fb
Publikováno v:
Avances en Química, Vol 5, Iss 1, Pp 45-49 (2010)
Analysis of kaurenic acids present in Espeletiopsis angustifolia Cuatrec. from the Venezuelan Andes. Leaves of Espeletiopsis angustifolia were collected at paramo of San José de Acequias (Mérida State) at 2870 m.a.s.l. The dried leaves were minced
Externí odkaz:
https://doaj.org/article/bed7399574944650b6ea842fedf8cedf
Publikováno v:
Avances en Química, Vol 2, Iss 3, Pp 3-8 (2007)
The allylic oxidation of ent-kaurenic acid, ent-kaurenic acid methyl ester, and ent-kaurenol with SeO2/H2O2 is presented. The reaction was run in dioxan solution at room temperature stirring for 4 hours. About 0.3 mmol of substrate was treated with 1
Externí odkaz:
https://doaj.org/article/ccfa614864354417866470b5fdda6527
Autor:
Luis Rojas-Fermín, Elio Sanoja, Judith Velasco, Alfredo Usubillaga, Jesús E. Velásquez, Rosa Aparicio
Publikováno v:
Bionatura. 4:908-912
This work presents a comparative study of the chemical composition of the essential oils obtained from two varieties of Centrolobium paraense (orinocense EO o and paraense EO p) from Venezuela. GC analyzed the oils, and the constituents were identifi