Neoclerodane and Labdane Diterpenoids from Plectranthus ornatus

Abstract

Three new diterpenoids, a neoclerodane and two labdane derivatives, have been isolated from an acetone extract of Plectranthus ornatus. The structures of these compounds (plectrornatins A-C, 1-3, respectively) were established mainly by spectroscopic means, particularly by 1D and 2D NMR studies and, in the case of the neoclerodane 1, by an X-ray diffraction analysis. Compounds 1 and 3 showed moderate antimicrobial activity against five Candida species and selected Gram negative and Gram positive bacteria strains.

Miscellaneous Diterpenes from the Aerial Parts of Plectranthus ornatus Codd

“…It is worthy of notice that both structures of 2 and 4 were also supported by comparison of the 1 H and 13 C NMR data of these with those reported to the rearranged (4→2)-abeo-clerodane diterpenes. 22 The relative stereochemistry of 4, as depicted in Figure 3, was defined by NOESY and literature data, 16,18 which was similar to compound 2. Thus, the structure of compound 4, a new (4→2)-abeo-clerodane diterpene, was established and named as ornatin D.…”

“…The chromatographic fractionation of the n-hexane extract from the aerial parts of P. ornatus was performed, leading to the isolation of five new diterpenes which were designated as ornatins A-E (1-5), as well as the known diterpenes: coleon R (6), 14 ent-3a-hydroxycleroda-4(18), 13E-dien-15-oic acid (7), 15 plectrornatin A (8), 16 labd-13-en-8β-hydroxy-15-oic acid (9), 17 11-acetoxy-2-oxo-entcleroda-3,13E-dien-15-oic acid (10) 18 and ent-11R-acetoxy-2-oxocleroda-3,13E-dien-15-oic acid (11). 16 Compound Tables 1 and 2) of 1 were similar to those reported for the diterpenes 11-acetoxyneoclerodane, which were previously isolated of the P. ornatus.…”

“…The observed NOE's for Me-20 with Me-17 and Me-11' (methyl of the acetoxyl group) confirmed the a-position inferred for both AcO-11' and Me-17 ( Figure 3), also in agreement with the stereochemistry reported previously for 11R* diterpenes from P. ornatus. 16,18 , H-11'). The 13 C NMR spectrum exhibited 22 carbon signals, which in accordance with the DEPT 135 and HSQC spectra were defined as six methyls, four methylenes, five monohydrogenated and seven non-hydrogenated carbons, including an olefinic carbon d C 160.6 (C-13), two rid carboxyls d C 180.3 (C-3) and d C 171.6 (C-15), one of which a,β-unsaturated, and an acetoxyl moiety d C 170.9 (C-11').…”

Diterpenos tipo abietano isolados de Plectranthus barbatus Andrews

“…O interesse pelo estudo fitoquímico da espécie Plectranthus barbatus foi estimulado pelo amplo uso popular das folhas para tratamento de problemas digestivos 4,5 em substituição ao boldo do Chile. Espécies do gênero Plectranthus apresentam capacidade biossintética para produzir uma variedade de metabólitos secundários, destacando-se entre estes os diterpenos, inclusive alguns com propriedades biológicas comprovadas relevantes [6][7][8][9][10][11][12][13][14][15] . Barbatusina, ciclobutatusina 16 , 6β-Hidroxicarnosol 17 , barbatusol 18 , plectrina 19 , cariocal 20 , coleonon E, coleon F, plectrinona A, plectrinona B 21 , e 12,9(10→20)-abeo-abieta-8,11,13-trien-10β,11,12-triol 22 são constituintes identificados em P. barbatus, que apresentam importância farmacológica ou química.…”

“…O interesse pelo estudo fitoquímico da espécie Plectranthus barbatus foi estimulado pelo amplo uso popular das folhas para tratamento de problemas digestivos 4,5 em substituição ao boldo do Chile. Espécies do gênero Plectranthus apresentam capacidade biossintética para produzir uma variedade de metabólitos secundários, destacando-se entre estes os diterpenos, inclusive alguns com propriedades biológicas comprovadas relevantes [6][7][8][9][10][11][12][13][14][15] 21 , e 12,9(10→20)-abeo-abieta-8,11,13-trien-10β,11,12-triol 22 são constituintes identificados em P. barbatus, que apresentam importância farmacológica ou química. Por sua vez o estudo do óleo essencial da parte aérea e raízes da espécie P. barbatus apresentou α-pineno, β-felandreno, (Z)-β-ocimeno, manol e abietatrieno 23,24 .…”