Accumulation of the labdane diterpene Marrubiin in glandular trichome cells along the ontogeny of Marrubium vulgare plants

The content of the diterpene Marrubiin was assessed by GC-FID in leaves of Marrubium vulgare plants along their ontogeny. Maximum accumulation occurred just before flowering time and in fully expanded leaves. After feeding the plants with radio labeled [³H]-geranyl geranyl diphosphate, up to 70% of the radioactivity was recovered in HPLC-Rt coincidental with authentic Marrubiin, which was also characterized by GC-EIMS, thus confirming that the biosynthesis of Marrubiin proceeds through the 1-deoxy-D-xylulose-5-phosphate pathway. The major accumulation of radioactivity occurred in glandular trichome cells, and the product remained stable throughout.     

Biosynthesis of (−)-ent-kaurenoic acid in Smallanthus sonchifolius and its effect against microbial biofilms

The biosynthetic pathway of (–)-ent-kaurenoic acid (1) was investigated by incorporation of 1-d-¹³C-glucose in Smallanthus sonchifolius (Asteraceae) plantlets. The ¹³C-enrichment pattern indicated that methylerythritol-4-phosphate (MEP) pathway is the biosynthetic pathway involved in diterpenoid biosynthesis. Our studies in S. sonchifolius reinforce that the biosynthesis of different classes of terpenes should not be compartmentalized into cytosol and plastids. Additionally, (–)-ent-kaurenoic acid showed antimicrobial activity against Staphylococcus aureus biofilm.     

Phytochemical investigation of Eremostachys moluccelloides Bunge (Lamiaceae)

Phytochemical investigation of the aerial parts of Eremostachys moluccelloides Bunge led to the identification of a new diterpene, 2β,14-dihydroxy −11-formyl- 12-carboxy-13-des-isopropyl-13-hydroxymethyl-abieta-8,11,13- triene- 16(17)- lactone (1), along with the known compounds 12, 18-dicarboxy-14-hydroxy-13-des -isopropyl-13-hydroxymethyl- abieta-8,11,13-triene-16(17)-lactone (2), 5-hydroxy-3′,4′,7-trimethoxyflavone (3), 5-hydroxy-4’,7-dimethoxyflavone (4), luteolin-7-O-β-glucoside (5), verbascoside (6), luteolin 7-O-(6″-O-β-D-apiofuranosyl) -β-D-glucopyranoside (7), chlorogenic acid (8), echinacoside (9), apigenin-7-O-β-D-glucoside (10), p-coumaric acid (11), vanillic acid (12), apigenin-7-O-(6″-E-p-coumaroyl)-β-D-glucopyranoside (13), apigenin-7-O-(3″,6″-E-p-dicoumaroyl)-β-glucoside (14), lamalbide (15), 6β-hydroxy-7-epi-loganin (16), phloyoside II (17) The structures were elucidated on the basis of 1D and 2D NMR spectroscopy, UV, MS and by comparison with compounds previously reported in the literature. Compounds 1–4, 8, 9, 11, 12, 14 have not been reported previously from any species within the genus Eremostachys. Compounds 1–14, 17 were obtained from this species for the first time. The chemotaxonomic significance of the isolated compounds is discussed.     

Diterpenes from the leaves of Croton zambesicus

Two new trachylobane- and one isopimarane-type diterpenoids: ent-18-hydroxy-trachyloban-3-one; ent-trachyloban-3-one; isopimara-7,15-dien-3beta-ol, were isolated from the leaves of Croton zambesicus, together with trans-phytol, beta-sitosterol, alpha-amyrin and stigmasterol. The structures were determined by extensive NMR techniques and X-ray analysis. The cytotoxicity of these compounds has been evaluated on cancer and non-cancer cell-lines.     

Investigation of the importance of the C-2 oxygen function in the transformation of stemodin analogues by Rhizopus oryzae ATCC 11145

A new stemodinoside, stemodin-alpha-L-arabinofuranoside (5), was isolated from the plant Stemodia maritima. Incubation of stemodin (2) with Rhizopus oryzae ATCC 11145 gave 2 alpha,7 beta,13(S)-trihydroxystemodane (17) and 2 alpha,3 beta,13(S),16 alpha-tetrahydroxystemodane (18) whilst stemodinone (8) afforded 6 alpha,13(S)-dihydroxystemodan-2-one (19). The bioconversion of 2 beta,13(S)-dihydroxystemodane (10) by the fungus yielded 2 beta,7 beta,13(S)-trihydroxystemodane (20) whereas stemod-12-en-2-one (9) provided 7 beta,17-dihydroxystemod-12-en-2-one (21). The results provide useful information about the relationship between the functional groups of the substrates and their potential for bioconversion.     

Pseudopterosin biosynthesis—pathway elucidation,enzymology, and a proposed production method for anti-inflammatory metabolites from<Emphasis Type="Italic"> Pseudopterogorgia elisabethae</Emphasis>

The pseudopterosins are a family of diterpene pentosides isolated from the marine octocoral, Pseudopterogorgia elisabethae. These compounds possess non-steroidal anti-inflammatory and analgesic properties which have been shown to be greater than the industry standard, indomethacin. In our investigations, we are interested in examining the biosynthesis and enzymology of these compounds for the development of a biotechnological production method. We have isolated the pseudopterosin diterpene cyclase product, elisabethatriene, using a radioactivity-guided isolation. This has provided us with an assay to isolate the diterpene cyclase enzyme. The amino acid sequence of the purified diterpene cyclase will facilitate cloning and expression of the gene in a suitable host. In addition, we have identified over 25 novel diterpenes from one of our collections of P. elisabethae. Several of these compounds appear to be involved in pseudopterosin biosynthesis and are presently being evaluated as potential intermediates. These compounds have also been evaluated for anti-inflammatory activity and some possess greater activity than that of the pseudopterosins. We therefore propose a production method utilizing a combination of recombinant enzyme technology and synthetic methods/biocatalysis in order to produce one or more anti-inflammatory metabolites in P. elisabethae.     

Synthesis and characterisation of Pd(II) allyl complexes derived from the diterpene carvone

A series of cationic allyl complexes of Pd(II) derived from the diterpene carvone have been synthesised and characterised using the chelating ligands, bipyridine, 1,8-phenanthroline, neocuproin, S,S (-)-Chiraphos and R (+)-Binap as co-ligands. These complexes can be readily converted to new organic products in which one C---H bond of the allyl methyl has been substituted. The structure of a bipyridyl complex as its tetraphenyl borate salt has been determined via X-ray diffraction. 2-D NOESY studies on the Chiraphos and Binap complexes are reported. The Binap, but not the Chiraphos, complex reveals η³-η³η³ isomerisation at ambient temperature.     

Diterpene esters of aristolochic acids from Aristolochia pubescens

From the acetone and ethanol extracts of the tubercula of Aristolochia pubescens, two diterpene esters of aristolochic acids were isolated, together with 23 known compounds. The structures of the compounds were determined on the basis of spectroscopic analysis.     

Honatisine, a novel diterpenoid alkaloid, and six known alkaloids from Delphinium honanense and their cytotoxic activity

A novel diterpene alkaloid named honatisine (1) has been isolated from the whole plants of Delphinium honanense, along with six known alkaloids, siwanine E (2), isoatisine (3), atisine (4), delcorinine (5), uraphine (6), and nordhagenine A (7). Their structures were deduced on the basis of their spectral data. All of them were evaluated by a SRB assay for their cytotoxicity, and compound 1 showed a significant cytotoxic activity (IC(50) =3.16 μM) against the MCF-7 cell line.     

Changes in carotenoids, tocopherols and diterpenes during drought and recovery, and the biological significance of chlorophyll loss in Rosmarinus officinalis plants

Two-year-old rosemary (Rosmarinus officinalis L.) plants were subjected to severe stress by exposure to prolonged drought during a Mediterranean summer. Severely stressed plants recovered completely after the autumn rainfalls although the relative water content remained below 35% for 3 months and the chlorophyll content of leaves was reduced by up to 85% during the drought. In severe stress: (i) α-tocopherol increased 9-fold per g dry weight and 20-fold per unit of chlorophyll; (ii) lutein and β-carotene contents decreased on a dry-weight basis, but an 80% increase in lutein and constant levels of β-carotene were observed on a chlorophyll basis; (iii) there were transient and sustained increases in the de-epoxidation state of the xanthophyll cycle; and (iv) the highly oxidised abietane diterpene isorosmanol increased 8-fold as a result of the oxidation of carnosic acid. With the autumn rainfalls, water status, α-tocopherol and violaxanthin recovered first and the levels of photosynthetic pigments and abietane diterpenes increased later. The photoprotection conferred by the xanthophyll cycle and the antioxidant function of tocopherols, lutein and diterpenes may help to avoid irreversible damage in severe drought, making possible the recovery of functional membranes after the autumn rainfalls. Besides, chlorophyll loss reduces the amount of photons absorbed by leaves, which enhances the photoprotective and antioxidant capacity of leaves per amount of photons absorbed, since the ratios of xanthophylls, α-tocopherol and abietane diterpenes to chlorophyll increase. Received: 12 July 1999 / Accepted: 25 November 1999