Teugin, a neo-clerodane diterpenoid from Teucrium fragile

doi:10.1016/0031-9422(81)80125-2

Phytochemistry

Volume 20, Issue 9, 1981, Pages 2259-2261

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Abstract

From the aerial part of Teucrium fragile a new neo-clerodane diterpenoid, teugin, has been isolated. Its structure, 15,16-epoxy- 2β,6β-dihydroxy-neo-cleroda-3,13(16),14-triene-18,19:20,12S-diolide, was established mainly by spectroscopic means.

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The methylene protons at C-19 had an AB spin system. The pro-19S diastereotopic proton of this group (δ 3.92) was also ω-coupled (4J = 2.0 Hz) with the H-6β proton, indicating an α-axial orientation for C-19 (Bruno et al., 1981; Esquivel et al., 1986; Stapel., 1980). In the 1H NMR the pro-19R proton resonated at δ 4.30 which is in agreement with the lack of a substituent at C-7 position in this compound (Herz, 1977; Zdero et al., 1989; Esquivel et al., 1988).
The surface exudates of the leaves of Dodonaea angustifolia from Ngong forest population (6 km from Nairobi city center, Kenya) demonstrated antimicrobial activity against Gram-negative (Escherichia coli), Gram-positive (Staphylococcus aureus and Bacillus pumilus) bacteria and the fungus Sacchromyces cerevisiae. Chromatographic separation of the exudates yielded eight methylated flavonoids; 5-hydroxy-3, 4′,7-trimethoxyflavone (1), 3,5-dihydroxy-4′,7-dimethoxyflavone (2), santin (3), kumatakenin (4), rhamnocitrin (5), isokaempferide (6), 3,4′,5,7, tetrahydroxy-6-methoxyflavone (7), pinocembrin (8); two clerodanes, dodonic acid (9) and 2β-hydroxyhardwickiic acid (10) and one labdane; (ent-3β,8α)-15,16-epoxy-13(16),14-labdadiene-3,8-diol (11) diterpenoids. The flavonoid aglycones; 6, 7 and the clerodane diterpenoids; 9 and 10 and labdane diterpenoid, 11 were isolated for the first time from this plant species. The structures of the isolated compounds were identified using ultraviolet (UV), mass spectroscopy (MS), one dimension (1D) and two dimension (2D) nuclear magnetic resonance (NMR) spectroscopy and by comparison of the spectral data with literature. The quercetin derivative, 3,4′,5-trihydroxy-3′,7-dimethoxyflavone (12) showed broad spectrum antibacterial activities against E. coli and B. pumilus with minimum inhibition concentration (MIC) values less than 31.25 μg/well and against S. aureus with MIC below 62.5 μg/well. This compound showed poor antifungal activity against S. cerevisiae (MIC < 500 μg/well). Good antifungal activities were observed for 5,4′-dihydroxy-7-methoxyflavanone (13) and hautriwaic acid lactone (14) against S. cerevisiae with MIC values less than 7.8 μg/well. The most active antifungal compound was 5,7-dihydro-3,4′,6-trimethoxyflavone (3, santin) with an MIC value less than 3.9 μg/well against S. cerevisiae. The rest of the compounds exhibited weak to moderate activities. For comprehensive structure activity relationship studies (SAR), hautriwaic acid lactone (14), hautriwaic acid (15), penduletin (16) isolated from the surface exudates of D. angustifolia from Voi (200 km from Mombasa city center, Kenya) and 12 and 13 from Senecio roseiflorus isolated earlier were included in the bioassays.
Neo-Clerodane diterpenoids from the leaf exudate of Dodonaea angustifolia
2010, Phytochemistry Letters
Citation Excerpt :
The corresponding carbon signals for the lactone moieties appeared at δC 169.3 and 174.2 for CO, δC 71.7 and 70.2 for oxymethylenes and δC 135.8, 138.4, 134.3 and 143.9 for C-3, C-4, C-13 and C-14, respectively. The pro-19S diastereotopic proton was ω-coupled (4J = 2.0 Hz) with the H-6β proton, indicating α-axial orientation for C-19 (Bruno et al., 1981; Esquivel et al., 1986a,b; Stapel et al., 1980). The COSY spectrum clearly indicated that the proton at δ 7.14 (t, J = 1.5 Hz), assigned to H-14, was coupled with the oxymethylene protons at C-15.
Phytochemical investigation of the leaf surface exudate of Dodonaea angustifolia L.f. yielded two new neo-clerodane diterpenes, neo-clerodan-3,13-dien-16,15:18,19-diolide (mkapwanin) and 15-methoxy-neo-clerodan-3,13-dien-16,15:18,19-diolide (15-methoxymkapwanin). In addition, ten known compounds were identified. The structures were determined on the basis of spectroscopic evidence. This additional chemical information could contribute towards solving the taxonomical controversy that exists between Dodonaea angustifolia and Dodonaea viscosa Jacq., which are morphologically similar.
Antifeedant activity of neo-clerodane diterpenoids from Teucrium arduini
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Chemical and biological evaluation of genus teucrium
2000, Studies in Natural Products Chemistry
The genus Teucrium is represented by about 300 species in the world and 27 species in Turkey, 8 of them being endemic.
Teucrium species are rich source of neo-clerodane diterpenoids. Although several furanoid diterpenes with the neo-clerodane skeleton have been isolated from many plants, the genus Teucrium is the most abundant natural source of these compounds, therefore Teucrium species are accepted as chemotaxonomic markers for neo-clerodanes. Chemical investigations on this genus showed that some of the species also contain rearranged neo-clerodane or abietane diterpenes, sesquiterpenes, triterpenes and steroids. Flavonoids and aromatic compounds, although not as abundant as in the genus Salvia from the same family, are also found in the genus Teucrium. In this review, general chemical properties of neo-clerodanes isolated from Teucrium species are given with their stereochemical studies.
Teucrium species have been used for more than 2000 years as medicinal plants. They showed diuretic, diaphoretic, antiseptic and antipyretic activities. Antifeedant activities of some species previously studied against Spodeptera littoralis were presented herein. Teucrium species are used as hypoglycemic agents in North Africa and Saudi Arabia. They also possess antispasmolitic activity and used in the treatment of stomach aches. Some of the Teucrium extracts exhibited central nervous system depressant action.
Neo-clerodane and languidulane diterpenoids from Salvia sousae and S. karwinskii
1997, Phytochemistry
The new languidulane diterpenoid isosalvisousolide has been isolated from the aerial parts of Salvia sousae, besides the known neoclerodane diterpenoids salviarin, 1(10)-dehydrosalviarin and 10β-hydroxysalviarin. The flavones jaceosidin, cirsiliol and cirsilineol and oleanolic acid were also obtained from the same source. From S. karwinskii, 1(10)-dehydrosalviarin was the sole neoclerodane isolated. The structure of these compounds were established by spectroscopic means.
Neo-clerodane diterpenes from Teucrium species
1992, Phytochemistry
Nineteen already known neo-clerodane diterpenoids have been isolated from the aerial parts of Teucrium montbretii subsp. montbretii, T. belion and T. massiliense. In addition, the latter species provided a new substance, teumassin, whose structure of 19-acetoxy-4α, 18;15, 16-diepoxy-2β-hydroxy-6-oxo-neo-cleroda-13(16), 14-dien-20, 12S-olide was established by spectroscopic means and by its transformation into a previously described compound.

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Teugin, a neo-clerodane diterpenoid from Teucrium fragile

Abstract

Tetrahedron Letters

J. Org. Chem.

Heterocycles

J. Chem. Soc. Perkin Trans. 1

Planta Med.

J. Org. Chem.