Guy Ourisson

The Hopanoids: palaeochemistry and biochemistry of a group of natural products

More than 100 individual derivatives of hopane have been isolated from sedimentary organic matter of most varied origin. They are ubiquitous molecular fossils derived from cellular constituents of micro-organisms. Hopanoids are shown to be widely distributed among Bacteria and Cyanobacteria (blue-green algae). Their function in cells is probably equivalent to that of sterols in the eucaryote cell : to act as optimizers of the fluid lipid membranes. They are even probably phylogenetic precursors of sterols. In procaryotes containing no hopanoids, other mechanisms of fluidity control of biomembranes are probably operating ; they imply acyclic dior tetraterpenes (carotenoids or isomers), the molecular fossils of which are also present in sediments. These terpenes may in turn be phylogenetic precursors of hopanoids.

Distribution of hopanoid triterpenes in prokaryotes

Pentacyclic triterpenoids of the hopane family were found in about half of some 100 strains of prokaryotes belonging to diverse taxonomic groups, such a wide distribution indicating the biological significance of these compounds. Hopanoids were found in almost all the cyanobacteria and obligate methylotrophs examined, in all the purple non-sulphur bacteria studied and in many taxonomically diverse Gram-negative or Gram-positive chemohetero-trophs. They were absent in all archaebacteria and purple sulphur bacteria examined as well as in various other Gram-positive or Gram-negative genera. The C30 hopanoids, diploptene and diplopterol, are present in almost all hopanoid-containing prokaryotes. The major compounds are always the C35 bacteriohopanepolyols, which are present at a level of 0.1-2 mg per g dry weight, the most common one being bacteriohopanetetrol. Because of their structural characteristics and their influence on the properties of biological membrane models, these compounds might be the structural equivalents of the sterols found in eukaryotes.

Predictive microbial biochemistry — from molecular fossils to procaryotic membranes

Abstract Many of the complex organic molecules in geological sediments are derived from the membrane lipids of microorganisms. Their identification has led to the recognition of a new class of widespread microbial lipids, the hopanoids, surrogates of sterols in the membranes of many procaryotes. Other sedimentary lipids suggest the existence of other families of membrane lipids in microorganisms yet to be identified.

The terpenoid theory of the origin of cellular life: the evolution of terpenoids to cholesterol

Terpenoids have an apparently essential function in modern cellular membranes, reinforcing them against shear stresses. Primitive membranes could initially have been formed by simple terpenoids, and vesicles formed from these membranes may have evolved into progressively more complex units, more and more similar to protocells.

Tri- and tetraterpenoid hydrocarbons in the Messel oil shale

Abstract The high molecular weight constituents of the branched and cyclic hydrocarbon fraction of the Messel oil shale (Eocene) have been examined by high resolution gas chromatography and combined gas chromatography-mass spectrometry. The following compounds are present: perhydrolycopene (1; lycopane), together with one or more unsaturated analogues with the same skeleton; a series of 4-methylsteranes (2c) in higher abundance than their 4-desmethyl analogues; two series of pentacyclic triterpanes, one series (C27-C32) based on the hopane structure (3a-e), and the other (C27-C31) based on the 17α-H hopane structure (3a-d, 17αH); and an intact triterpene hop-17 (21)-ene [3c, Δ 17(21)]. Only two additional triterpanes were detected in minor concentrations, viz. 30-normoretane (3b, 21αH) and a C31 triterpane based on the hopane/lupane-type skeleton. The presence of these compounds suggests a significant microbial contribution to the forming sediment. Comparison of the tri- and tetraterpenoid hydrocarbons with those of the Green River Shale indicates differences in the organisms contributing to the two sediments.

Attraction of the Parasitic Mite Varroa to the Drone Larvae of Honey Bees by Simple Aliphatic Esters

An important parasitic threat to honey bees, the mite Varroa jacobsoni, is attracted to its major prey, drone larvae, by methyl and ethyl esters of straight-chain fatty acids, in particular methyl palmitate. These esters were extracted from drone larvae with n-hexane and were identified by gas chromatography-mass spectrometry. Their behavioral effect was evaluated with the use of a four-arm airflow olfactometer.

Cytotoxic components of Zingiber zerumbet, Curcuma zedoaria and C. domestica☆

Abstract One new and five known compounds, which all showed cytotoxic activity, were isolated from the rhizomes of Zingiber zerumbet . The new compound was 3″,4″- O -diacetylafzelin. The known compounds were zerumbone, zerumbone epoxide, diferuloylmethane, feruloyl- p -coumaroylmethane and di- p -coumaroylmethane. Several substituted cinnamoylmethanes were synthesized and tested for cytotoxic properties. Among these were tricinnamoylmethane and triferuloylmethane. The structures were elucidated mainly by spectroscopic methods and 13 C NMR data are given.

Comparison of the effects of inserted C40- and C50-terminally dihydroxylated carotenoids on the mechanical properties of various phospholipid vesicles

We have measured the extent of incorporation of zeaxanthin (C40) and decaprenozeaxanthin (C50) in unilamellar vesicles of dimyristoylphosphatidylcholine (n-C14) and dipalmitoylphosphatidylcholine (n-C16). The incorporation is larger when the molecular length of the carotenoid corresponds to the thickness of the phospholipid bilayer. Stereochemically pure 2,3-di-O-phytanyl-sn-glycero-1-phosphocholine was prepared by modification of the polar heads of the phospholipids of Halobacterium halobium. Vesicles of this branched-chain ether phospholipid incorporate poorly the carotenoids, whereas egg lecithin vesicles incorporate them better. Osmotic swelling and water permeability of vesicles, with or without carotenoids, were measured in a stopped-flow, light-scattering system. The reinforcing effect (lower permeability and higher rigidity) of carotenoids at 1.5 mol% incorporation into diphytanylphosphatidylcholine vesicles is comparable to that of 5 mol% cholesterol; however, carotenoids have no measurable effect on the egg lecithin vesicles. These results imply that the reinforcement of the membrane depends on a subtle adjustment of the phospholipid-carotenoid system.

Les acides ganoderiques tàz : triterpenes cytotoxiques de Ganoderma lucidum (Polyporacée)

Abstract Six new polyoxygenated lanostane acids have been isolated from Ganoderma lucidum (Polyporaceae). They contain the same terminally car☐ylated E-24 side-chain and display cytotoxic activity in vitro on hepatoma cells.

Fossil evidence for a novel series of archaebacterial lipids

coprostanol supply. Konstanz is the largest harbor city in the lake area and thousands of people either arrive at or depart from Konstanz each day during the summer. The direct disposal of feces by passenger ships was banned in 1976, but legislative measures were slow to develop; the input of human excreta from pleasure boats will only be prohibited by law in the course of 1979. A comparison of the coprostanol concentration from the uppermost sediment layer of our core with data from literature on surface sediments from marine environments (Table 2) shows that concentrations in the Konstanzer Trichter are comparable to those found in sediments in close proximity to sewage outfalls or sewage dumping zones in the New York Bight and the Clyde Estuary. The coprostanol concentrations of the sewage sludge introduced into these areas are also given for comparison. The Konstanzer Trichter levels are nonetheless still well below the extreme concentrations in the Tokyo Bay, which is known to be one of the most heavily polluted environments in the world.